A system and method for estimating a mechanical load on an actuator for elastography

Abstract

A system (100) for determining a load profile of an actuator (124) for elastography. The system (100) is configured to generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal, apply the actuator driving waveform to the actuator (124), determine a first value of a component of an electrical characteristic, determine a second value of the component of the electrical characteristic, and determine the load profile of the actuator (124) based on the first value and second value of the component of the electrical characteristic, the load profile relating values of the component of the electrical characteristic to values of the mechanical load on the actuator (124). The load profile is used to determine a load which is used to adapt signals applied to the actuator.

Description

[0001] A SYSTEM AND METHOD FOR ESTIMATING A MECHANICAL LOAD ON AN ACTUATOR

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a system for estimating loading on an actuator, and particularly, but not necessarily exclusively, mechanical loading on a piezoelectric actuator. The disclosure has particular application to actuators of devices for evaluating one or more mechanical properties of a sample material such as biological tissue.

[0004] BACKGROUND

[0005] Breast cancer is a significant global health concern, with breast-conserving surgeries comprising a substantial portion of treatment approaches. However, incomplete tumour removal during these procedures remains a persistent challenge, leading to increased patient distress, prolonged recovery times, and substantial financial burdens on healthcare systems. Existing methods for ensuring complete tumour removal often lack the necessary precision and efficiency to adequately address this issue.

[0006] Quantitative micro-elastography (QME) has emerged as an imaging technique for improving the accuracy of tumour margin assessment during surgical procedures. This technology offers the potential for real-time, high-resolution imaging of tissue microstructure and mechanical properties. However, the implementation of QME in clinical settings, particularly in handheld devices, presents unique challenges related to force measurement and control.

[0007] It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

[0008] SUMMARY

[0009] In some embodiments of the present disclosure, there is provided a system. The system is a system for determining loading of a piezoelectric actuator. The system comprises at least one processor. The system comprises memory. The memory stores computer-executable instructions. When executed by the at least one processor, the computer-executable instructions cause the at least one processor to generate a driving waveform to drive the piezoelectric actuator. When executed by the at least one processor, the computer-executable instructions cause the at least one processor to modulate, at a predetermined frequency, the driving waveform, with a modulating signal having a predetermined characteristic. The modulation may cause a value of at least one electrical parameter of the piezoelectric actuator to change in accordance with a variation profile that is related to applied load, when the modulating signal having the predetermined characteristic is applied at the predetermined frequency. The variation profile may be a linear profile. That is, the modulation may cause a value of at least one electrical parameter of the piezoelectric actuator to change linearly with applied load when the modulating signal having the predetermined characteristic is applied at the predetermined frequency. The variation profile may be substantially linear. That is, the modulation may cause a value of at least one electrical parameter of the piezoelectric actuator to change substantially linearly with applied load when the modulating signal having the predetermined characteristic is applied at the predetermined frequency. The variation profde may take another form (e.g. quadratic, exponential etc.). When executed by the at least one processor, the computer-executable instructions cause the at least one processor to measure voltage and current outputs from the piezoelectric actuator. When executed by the at least one processor, the computer-executable instructions cause the at least one processor to determine a loading of the piezoelectric actuator based on at least one of the measured voltage and current outputs.

[0010] In some embodiments of the present disclosure, there is provided a system for determining loading of a piezoelectric actuator. The system may comprise: at least one processor; and memory storing computerexecutable instructions that, when executed by the at least one processor, cause the at least one processor to: generate a driving waveform to drive the piezoelectric actuator; modulate, at a predetermined frequency, the driving waveform, with a modulating signal having a predetermined characteristic, the modulation causing a value of at least one electrical parameter of the piezoelectric actuator to change substantially linearly with applied load when the modulating signal having the predetermined characteristic is applied at the predetermined frequency; measure voltage and current outputs from the piezoelectric actuator; and determine a loading of the piezoelectric actuator based on at least one of the measured voltage and current outputs.

[0011] The at least one electrical parameter may comprise current output.

[0012] The at least one electrical parameter may comprise at least one of: capacitance, phase and resonant frequency.

[0013] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal.

[0014] The predetermined characteristic of the modulating signal may be that an amplitude of the modulating signal is small compared to the driving waveform.

[0015] The modulating signal may have an amplitude of around 1% of that of the driving waveform.

[0016] The modulating signal may be about lOOmVpp. The modulating signal may be a sinusoidal waveform.

[0017] The predetermined frequency may be between about 80kHz and about 100kHz. The predetermined frequency may be one of: about 89550 Hz; and about 89450 Hz.

[0018] The loading of the piezoelectric actuator may be determined using at least one of: a machine learning model; a database; a mathematical model; a feedback protocol; a feedforward protocol; and signal processing. The computer-executable instructions, when executed by the at least one processor, may be further configured to cause the at least one processor to measure a phase of the piezoelectric actuator.

[0019] The piezoelectric actuator may be disposed within a device.

[0020] The computer-executable instructions, when executed by the at least one processor, may be further configured to filter at least one of the voltage and current outputs through a lock-in amplifier.

[0021] The system may further comprise a control system, the at least one processor and the memory forming part of the control system.

[0022] The computer-executable instructions, when executed by the at least one processor, may be further configured to cause the at least one processor perform a preliminary step of determining pre-loading of the piezoelectric actuator.

[0023] The preliminary step may comprise: sequentially imposing at least two loads of different known magnitudes on the piezoelectric actuator; for each of the at least two loads, generating the driving waveform to drive the piezoelectric actuator, and modulating, at the predetermined frequency, the driving waveform with the modulating signal having the predetermined characteristic; measuring the voltage and current outputs from the piezoelectric actuator when the at least two loads are imposed; determining variation of the at least one electrical parameter of the piezoelectric actuator when the at least two loads are imposed; and determining a pre-loading of the piezoelectric actuator.

[0024] The determined loading of the piezoelectric actuator may include or make allowance for the determined pre-loading.

[0025] In some embodiments, there is provided a system for determining pre-loading of a piezoelectric actuator of a device for evaluating a mechanical property of a sample material, the piezoelectric actuator being configured to induce vibrations on a portion of the device to modulate a signal produced by or in association with the portion of the device. The system may comprise: at least one processor; and memory storing computer-executable instructions that, when executed by the at least one processor, cause the at least one processor to: generate a driving waveform to drive the piezoelectric actuator; modulate, at a predetermined frequency, the driving waveform with a modulating signal having a predetermined characteristic, wherein the predetermined frequency and the predetermined characteristic of the modulating signal are selected based on being such that at least one electrical parameter of the piezoelectric actuator varies substantially linearly with applied load when the modulating signal having the predetermined characteristic is applied at the predetermined frequency; sequentially impose at least two loads of different known magnitudes on the piezoelectric actuator; measure the voltage and current outputs from the piezoelectric actuator; determine variation of the at least one electrical parameter of the piezoelectric actuator when the at least two loads are imposed; and determine a pre-loading of the piezoelectric actuator. In some embodiments, there is provided a method comprising generating a driving waveform to drive the piezoelectric actuator; modulating, at a predetermined frequency, the driving waveform, with a modulating signal having a predetermined characteristic, the modulation causing a value of at least one electrical parameter of the piezoelectric actuator to change substantially linearly with applied load when the modulating signal having the predetermined characteristic is applied at the predetermined frequency; measuring voltage and current outputs from the piezoelectric actuator; and determining a loading of the piezoelectric actuator based on at least one of the measured voltage and current outputs.

[0026] In some embodiments of the present disclosure, there is provided a system for determining a load profile of an actuator. The system may be configured to generate a modulated driving waveform, the modulated driving waveform being a driving waveform that is modulated with a modulating signal. The system may be configured to apply the modulated driving waveform to the actuator. The system may be configured to determine a value of an electrical characteristic associated with the actuator while: the modulated driving waveform is applied to the actuator; and a first known load is applied to the actuator. The system may be configured to determine a value of the electrical characteristic associated with the actuator while: the modulated driving waveform is applied to the actuator; and a second known load is applied to the actuator. The second known load may be different to the first known load. The system may be configured to determine the load profile of the actuator based on the determined values of the electrical characteristic associated with the actuator, the load profile relating values of the electrical characteristic to estimates of the load on the actuator.

[0027] The actuator may be a piezoelectric actuator.

[0028] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal.

[0029] The driving waveform may be parameterised by a driving waveform frequency, a driving waveform amplitude and a driving waveform shape.

[0030] The modulating signal may be parameterised by a modulating waveform frequency, a modulating waveform amplitude, and a modulating waveform shape.

[0031] The modulating waveform amplitude may be small compared to the driving waveform amplitude. The modulating waveform amplitude may be about 1% of the driving waveform amplitude. The modulating waveform amplitude may be less than 2% of the driving waveform amplitude. The modulating waveform shape may be sinusoidal. The modulating waveform frequency may be associated with a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be within 20% of a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be between about 80kHz and about 100kHz. The modulating waveform frequency may be about 89550 Hz or about 89450 Hz. Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator, thereby generating a filtered output.

[0032] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator, thereby generating a second filtered output.

[0033] The electrical parameter signal may be filtered at the modulating waveform frequency.

[0034] The system may comprise a lock-in amplifier. The electrical parameter signal may be an input of the lock-in amplifier. The filtered output may be an output of the lock-in amplifier.

[0035] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator may comprise calculating a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator.

[0036] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator may comprise calculating: a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator.

[0037] The electrical parameter signal may be a voltage signal that changes with actuation of the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator. The system may comprise a current-to-voltage converter circuit that converts measurements of current across the actuator while the modulated driving waveform is applied to the actuator.

[0038] The voltage signal may be related to a strain across at least part of the actuator. The system may comprise at least one strain gauge operably connected to the actuator, the voltage signal being determined using measurements of the voltage across the one or more strain gauge while the modulated driving waveform is applied to the actuator. Each strain gauge may be fixedly connected to the actuator.

[0039] The modulating signal may be about lOOmVpp.

[0040] The load profile may be determined based on: the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator; and the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator.

[0041] The load profile may be a mathematical model. The mathematical model may relate values of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator to estimates of the load on the actuator. The value of the electrical characteristic may be an input of the mathematical model. The mathematical model may be a linear model, such that values of the electrical characteristic are linearly related to estimates of the load on the actuator.

[0042] The load profile may be a machine learning model, a lookup table, or a database.

[0043] The system may comprise a signal generator. The signal generator may generate the modulated driving waveform.

[0044] The system may comprise a device. The system may be configured to change a value of a control parameter associated with operation of the device, in response to the determined load profile. The system may be configured to control operation of the device based at least in part on the determined load profile. The device may comprise a housing. At least part of the actuator may be housed within the housing. The device may be a QME device.

[0045] In some embodiments of the present disclosure, there is provide a method for determining a load profile of an actuator. The method may comprise generating a modulated driving waveform, the modulated driving waveform being a driving waveform that is modulated with a modulating signal. The method may comprise applying the modulated driving waveform to the actuator. The method may comprise determining a value of an electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and a first known load is applied to the actuator. The method may comprise determining a value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator; and a second known load is applied to the actuator. The second known load may be different to the first known load. The method may comprise determining the load profile of the actuator based on the determined values of the electrical characteristic associated with the actuator, the load profile relating values of the electrical characteristic to estimates of the load on the actuator.

[0046] The actuator may be a piezoelectric actuator.

[0047] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal.

[0048] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal.

[0049] The driving waveform may be parameterised by a driving waveform frequency, a driving waveform amplitude and a driving waveform shape.

[0050] The modulating signal may be parameterised by a modulating waveform frequency, a modulating waveform amplitude, and a modulating waveform shape.

[0051] The modulating waveform amplitude may be small compared to the driving waveform amplitude. The modulating waveform amplitude may be about 1% of the driving waveform amplitude. The modulating waveform amplitude may be less than 2% of the driving waveform amplitude. The modulating waveform shape may be sinusoidal. The modulating waveform frequency may be associated with a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be within 20% of a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be between about 80kHz and about 100kHz. The modulating waveform frequency may be about 89550 Hz or about 89450 Hz.

[0052] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator, thereby generating a filtered output.

[0053] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator, thereby generating a second filtered output.

[0054] The electrical parameter signal may be fdtered at the modulating waveform frequency. The filtered output may be an output of a lock-in amplifier. Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator may comprise calculating a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator.

[0055] Determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator may comprise calculating a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator.

[0056] The electrical parameter signal may be a voltage signal that changes with actuation of the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator.

[0057] A current-to-voltage converter circuit may convert measurements of current across the actuator while the modulated driving waveform is applied to the actuator.

[0058] The voltage signal may be related to a strain across at least part of the actuator. The voltage signal may be determined using measurements of the voltage across one or more strain gauge that is operatively connected to the actuator, while the modulated driving waveform is applied to the actuator. Each strain gauge may be fixedly connected to the actuator.

[0059] The modulating signal may be about lOOmVpp.

[0060] The load profile may be determined based on: the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the first known load is applied to the actuator; and the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator and the second known load is applied to the actuator.

[0061] The load profile may be a mathematical model. The mathematical model may relate values of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator to estimates of the load on the actuator. The value of the electrical characteristic may be an input of the mathematical model. The mathematical model may be a linear model, such that values of the electrical characteristic are linearly related to estimates of the load on the actuator.

[0062] The load profile may be a machine learning model, a lookup table, or a database.

[0063] A signal generator may generate the modulated driving waveform.

[0064] The method may further comprise changing a value of a control parameter associated with operation of a device, in response to the determined load profde. The method may further comprise controlling operation of a device based at least in part on the determined load profile. The device may comprise a housing. At least part of the actuator may be housed within the housing. The device may be a QME device.

[0065] In some embodiments, there is provided a system for determining a value of an electrical parameter associated with an actuator. The system may be configured to generate a modulated driving waveform, the modulated driving waveform being a driving waveform that is modulated with a modulating signal. The system may be configured to apply the modulated driving waveform to the actuator. The system may be configured to determine the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator.

[0066] The system may be further configured to determine an estimate of the load on the actuator based on the value of the electrical characteristic.

[0067] The actuator may be a piezoelectric actuator.

[0068] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal. The driving waveform may be parameterised by a driving waveform frequency, a driving waveform amplitude and a driving waveform shape.

[0069] The modulating signal may be parameterised by a modulating waveform frequency, a modulating waveform amplitude and a modulating waveform shape. The modulating waveform amplitude may be small compared to the driving waveform amplitude. The modulating waveform amplitude may be about 1% of the driving waveform amplitude. The modulating waveform amplitude may be less than 2% of the driving waveform amplitude. The modulating waveform shape may be sinusoidal. The modulating waveform frequency may be associated with a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be within 20% of a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be between about 80kHz and about 100kHz. The modulating waveform frequency may be about 89550 Hz or about 89450 Hz. Determining the value of the electrical characteristic associated with the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator, thereby generating a filtered output. The electrical parameter signal may be filtered at the modulating waveform frequency.

[0070] The system may comprise a lock-in amplifier. The electrical parameter signal may be an input of the lock-in amplifier. The filtered output may be an output of the lock-in amplifier.

[0071] Determining the value of the electrical characteristic associated with the actuator may comprise calculating: a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic.

[0072] The electrical parameter signal may be a voltage signal that changes with actuation of the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator.

[0073] The system may comprise a current-to-voltage converter circuit that converts measurements of current across the actuator while the modulated driving waveform is applied to the actuator.

[0074] The voltage signal may be related to a strain across at least part of the actuator. The system may comprise at least one strain gauge operably connected to the actuator, the voltage signal being determined using measurements of the voltage across the one or more strain gauge while the modulated driving waveform is applied to the actuator. Each strain gauge may be fixedly connected to the actuator.

[0075] The modulating signal may be about lOOmVpp.

[0076] The estimate of the load on the actuator may be determined using a mathematical model. The mathematical model may relate values of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator to estimates of the load on the actuator. The value of the electrical characteristic may be an input of the mathematical model. The mathematical model may be a linear model, such that values of the electrical characteristic are linearly related to estimates of the load on the actuator.

[0077] The estimate of the load on the actuator may be determined using at least one of a machine learning model, a lookup table and a database. The mathematical model, machine learning model, lookup table or database, may be determined, at least in part, based on values of the electrical characteristic determined with known loads applied to the actuator.

[0078] The system may comprise a signal generator. The signal generator may generate the modulated driving waveform. The system may further comprise a user interface. The system may be configured to display a graphical output, using the user interface, based on the determined estimate of the load on the actuator. The graphical output may be indicative of the estimate of the load on the actuator.

[0079] The system may comprise a device. The system may be configured to change a value of a control parameter associated with operation of the device, in response to the estimate of the load on the actuator satisfying one or more load criterion. The system may be configured to control operation of the device based at least in part on the value of the electrical characteristic. The device may comprise a housing. At least part of the actuator may be housed within the housing. The device may be a QME device.

[0080] In some embodiments of the present disclosure, there is provided a method for determining a value of an electrical parameter associated with an actuator. The method may comprise generating a modulated driving waveform, the modulated driving waveform being a driving waveform that is modulated with a modulating signal. The method may comprise applying the modulated driving waveform to the actuator. The method may comprise determining the value of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator.

[0081] The method may further comprise determining an estimate of the load on the actuator based on the value of the electrical characteristic.

[0082] The actuator may be a piezoelectric actuator.

[0083] The driving waveform may be modulated with the modulating signal by summing the driving waveform and the modulating signal.

[0084] The driving waveform may be parameterised by a driving waveform frequency, a driving waveform amplitude and a driving waveform shape.

[0085] The modulating signal is parameterised by a modulating waveform frequency, a modulating waveform amplitude and a modulating waveform shape.

[0086] The modulating waveform amplitude may be small compared to the driving waveform amplitude. The modulating waveform amplitude may be about 1% of the driving waveform amplitude. The modulating waveform amplitude may be less than 2% of the driving waveform amplitude. The modulating waveform shape may be sinusoidal. The modulating waveform frequency may be associated with a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be within 20% of a resonant frequency of a mechanical system comprising the actuator. The modulating waveform frequency may be between about 80kHz and about 100kHz. The modulating waveform frequency may be about 89550 Hz or about 89450 Hz.

[0087] Determining the value of the electrical characteristic associated with the actuator may comprise filtering an electrical parameter signal that is associated with the actuator while the modulated driving waveform is applied to the actuator, thereby generating a filtered output. The electrical parameter signal may be filtered at the modulating waveform frequency. The filtered output may be an output of a lock-in amplifier.

[0088] Determining the value of the electrical characteristic associated with the actuator may comprise calculating: a phase of the electrical parameter signal, at the modulating waveform frequency; and / or an amplitude of the electrical parameter signal, at the modulating waveform frequency; using the filtered output. The phase and / or amplitude of the electrical parameter signal, at the modulating waveform frequency, may be the value of the electrical characteristic.

[0089] The electrical parameter signal may be a voltage signal that changes with actuation of the actuator. The voltage signal may be related to a measurement of current across the actuator while the modulated driving waveform is applied to the actuator.

[0090] The method may comprise converting measurements of current across the actuator while the modulated driving waveform is applied to the actuator.

[0091] The voltage signal may be related to a strain across at least part of the actuator. The voltage signal may be determined using measurements of the voltage across one or more strain gauge attached to the actuator, while the modulated driving waveform is applied to the actuator. Each strain gauge is fixedly connected to the actuator.

[0092] The modulating signal may be about lOOmVpp.

[0093] The estimate of the load on the actuator may be determined using a mathematical model. The mathematical model may relate values of the electrical characteristic associated with the actuator while the modulated driving waveform is applied to the actuator to estimates of the load on the actuator. The value of the electrical characteristic may be an input of the mathematical model. The mathematical model may be a linear model, such that values of the electrical characteristic are linearly related to estimates of the load on the actuator.

[0094] The estimate of the load on the actuator may be determined using at least one of a machine learning model, a lookup table and a database. The mathematical model, machine learning model, lookup table or database, may be determined, at least in part, based on values of the electrical characteristic determined with known loads applied to the actuator.

[0095] A signal generator may generate the modulated driving waveform.

[0096] The method may further comprise determining a graphical output using the determined estimate of the load on the actuator; and displaying the graphical output, using a user interface. The graphical output may be indicative of the estimate of the load on the actuator. The method may further comprise changing a value of a control parameter associated with operation of a device, in response to the estimate of the load on the actuator satisfying one or more load criterion. The method may further comprise controlling operation of a device based at least in part on the value of the electrical characteristic. The device may comprise a housing. At least part of the actuator may be housed within the housing. The device may be a QME device.

[0097] In some embodiments of the present disclosure, there is provided a system for determining a load profile of an actuator. The system may be configured to: generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; apply the actuator driving waveform to the actuator; determine a first value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the first value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a first known mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; determine a second value of the component of the electrical characteristic, the second value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a second known mechanical load that is different to the first known mechanical load is applied to the actuator; and determined based at least in part on the value of the parameter of the interrogation signal; and determine the load profile of the actuator based on the first value and second value of the component of the electrical characteristic, the load profile relating values of the component of the electrical characteristic to values of the mechanical load on the actuator.

[0098] The system may be configured to determine the load profile of the actuator based on the first known load and the second known load. The system may be configured to determine the load profile of the actuator based on the first known load, the first value of the component of the electrical characteristic, the second known load and the second value of the component of the electrical characteristic.

[0099] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be a sinusoidal waveform. Generating the actuator driving waveform may comprise modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain. The actuator driving waveform may have frequency components from both the primary driving waveform and the interrogation signal. The interrogation signal may be sinusoidal. An amplitude of the interrogation signal may be less than an amplitude of the primary driving waveform. A frequency of the interrogation signal may be greater than a frequency of the primary driving waveform. The frequency of the interrogation signal may be associated with a resonant frequency of a device comprising the actuator. Determining the first value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the first known mechanical load are simultaneously applied to the actuator.

[0100] At least one sensor may be operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise a voltage output. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component. The filtered output may comprise a voltage. That is, the filtered output may comprise a voltage output. The first value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the fdtered output. The first value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The first value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0101] At least one current measurement circuit may be operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current. The at least one current measurement circuit may comprise a current-to-voltage conversion circuit (CVCC). The output of the at least one current measurement circuit may comprise a voltage. That is, the output of the at least one current measurement circuit may comprise a voltage output. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component. The fdtered output may comprise a voltage. That is, the filtered output may comprise a voltage output. The first value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The first value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The first value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0102] Determining the second value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the second known mechanical load are simultaneously applied to the actuator.

[0103] At least one sensor may be operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise a voltage output. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a second filtered output comprising a second in-phase component and a second quadrature component. The second filtered output may comprise a voltage. That is, the second filtered output may comprise a voltage output. The second value of the component of the electrical characteristic may comprise a magnitude of the second in- phase component of the second filtered output. The second value of the component of the electrical characteristic may comprise a magnitude of the second quadrature component of the second fdtered output. The second value of the component of the electrical characteristic may comprise a phase calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise an amplitude calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise at least one of: a magnitude of the second in-phase component of the second fdtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

[0104] At least one current measurement circuit is operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current. The at least one current measurement circuit may comprise a current-to-voltage conversion circuit (CVCC). The output of the at least one current measurement circuit may comprise a voltage. That is, the output of the at least one current measurement circuit may comprise a voltage output. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a second filtered output comprising a second in-phase component and a second quadrature component. The second filtered output may comprise a voltage. That is, the second fdtered output may comprise a voltage output. The second value of the component of the electrical characteristic may comprise a magnitude of the second in-phase component of the second filtered output. The second value of the component of the electrical characteristic may comprise a magnitude of the second quadrature component of the second fdtered output. The second value of the component of the electrical characteristic may comprise a phase calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise an amplitude calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise at least one of: a magnitude of the second in-phase component of the second fdtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

[0105] The load profile may be a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator. The mathematical model may be a liner model.

[0106] The actuator may be a piezoelectric actuator.

[0107] In some embodiments of the present disclosure, there is provided a method for determining a load profile of an actuator. The method may comprise: generating an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; applying the actuator driving waveform to the actuator; determining a first value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the first value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a first known mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; determining a second value of the component of the electrical characteristic, the second value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a second known mechanical load that is different to the first known mechanical load is applied to the actuator; and determined based at least in part on the value of the parameter of the interrogation signal; and determining the load profile of the actuator based on the first value and second value of the component of the electrical characteristic, the load profile relating values of the component of the electrical characteristic to values of the mechanical load on the actuator.

[0108] The method may comprise determining the load profile of the actuator based on the first known load and the second known load. The method may comprise determining the load profile of the actuator based on the first known load, the first value of the component of the electrical characteristic, the second known load and the second value of the component of the electrical characteristic.

[0109] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be a sinusoidal waveform. Generating the actuator driving waveform may comprise modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain. The actuator driving waveform may have frequency components from both the primary driving waveform and the interrogation signal. The interrogation signal may be sinusoidal. An amplitude of the interrogation signal may be less than an amplitude of the primary driving waveform. A frequency of the interrogation signal may be greater than a frequency of the primary driving waveform. The frequency of the interrogation signal may be associated with a resonant frequency of a device comprising the actuator.

[0110] Determining the first value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the first known mechanical load are simultaneously applied to the actuator.

[0111] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise an output voltage. The filtered output may comprise a voltage. The filtered output may comprise an output voltage. The first value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The first value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output.

[0112] The first value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0113] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component. The at least one current measurement circuit may comprise a CVCC. The output of the at least one current measurement circuit may comprise a voltage. That is, the output of the at least one current measurement circuit may comprise an output voltage. The filtered output may comprise a voltage. The filtered output may comprise an output voltage. The first value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The first value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The first value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The first value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0114] Determining the second value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the second known mechanical load are simultaneously applied to the actuator.

[0115] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a second filtered output comprising a second in phase component and a second quadrature component. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise an output voltage. The second filtered output may comprise a voltage. The second filtered output may comprise an output voltage. The second value of the component of the electrical characteristic may comprise a magnitude of the second in-phase component of the second filtered output. The second value of the component of the electrical characteristic may comprise a magnitude of the second quadrature component of the second filtered output. The second value of the component of the electrical characteristic may comprise a phase calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise an amplitude calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

[0116] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a second filtered output comprising a second in-phase component and a second quadrature component. The at least one current measurement circuit may comprise a CVCC. The output of the at least one current measurement circuit may comprise a voltage. That is, the output of the at least one current measurement circuit may comprise an output voltage. The second fdtered output may comprise a voltage. The second filtered output may comprise an output voltage. The second value of the component of the electrical characteristic may comprise a magnitude of the second in-phase component of the second fdtered output. The second value of the component of the electrical characteristic may comprise a magnitude of the second quadrature component of the second filtered output. The second value of the component of the electrical characteristic may comprise a phase calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise an amplitude calculated using the second in-phase component and the second quadrature component. The second value of the component of the electrical characteristic may comprise at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

[0117] The load profile may be mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator. The mathematical model may be a linear model.

[0118] The actuator may be a piezoelectric actuator.

[0119] In some embodiments of the present disclosure, there is provided a system for determining an estimate of an unknown mechanical load applied to an actuator. The system may be configured to: generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; apply the actuator driving waveform to the actuator; determine a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; and determine an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

[0120] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be a sinusoidal waveform. Generating the actuator driving waveform may comprise modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain. The actuator driving waveform may have frequency components from both the primary driving waveform and the interrogation signal. The interrogation signal may be sinusoidal. An amplitude of the interrogation signal may be less than an amplitude of the primary driving waveform. A frequency of the interrogation signal may be greater than a frequency of the primary driving waveform. The frequency of the interrogation signal may be associated with a resonant frequency of a device comprising the actuator.

[0121] Determining the value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the unknown mechanical load are simultaneously applied to the actuator.

[0122] At least one sensor may be operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise an output voltage. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component. The filtered output may comprise a voltage. The filtered output may comprise an output voltage. The value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the fdtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0123] At least one current measurement circuit may be operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current. The at least one current measurement circuit may comprise a CVCC. The output of the at least one current measurement circuit may comprise a voltage. In particular, the output of the at least one current measurement circuit may comprise an output voltage. The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component. The filtered output may comprise a voltage. The fdtered output may comprise an output voltage. The value of the component of the electrical characteristic may comprise a magnitude of the in- phase component of the filtered output. The value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0124] The load profile may be a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator. The mathematical model may be a linear model. The load profile may be the load profile determined as above.

[0125] The actuator may comprise a piezoelectric actuator.

[0126] In some embodiments of the present disclosure, there is provided a method for determining an estimate of an unknown mechanical load applied to an actuator. The method may comprise: generating an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; applying the actuator driving waveform to the actuator; determining a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; and determining an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

[0127] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be a sinusoidal waveform. Generating the actuator driving waveform may comprise modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain. The actuator driving waveform may have frequency components from both the primary driving waveform and the interrogation signal. The interrogation signal may be sinusoidal. An amplitude of the interrogation signal may be less than an amplitude of the primary driving waveform. A frequency of the interrogation signal may be greater than a frequency of the primary driving waveform. The frequency of the interrogation signal may be associated with a resonant frequency of a device comprising the actuator. Determining the value of the component of the electrical characteristic may comprise filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the unknown mechanical load are simultaneously applied to the actuator.

[0128] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component. The at least one sensor may comprise a strain gauge. The output of the at least one sensor may comprise a voltage. That is, the output of the at least one sensor may comprise an output voltage. The filtered output may comprise a voltage. The filtered output may comprise an output voltage. The value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

[0129] The parameter of the interrogation signal may be a frequency of the interrogation signal. Filtering the electrical parameter signal may comprise filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component. The at least one current measurement circuit may comprise a CVCC. The output of the at least one current measurement circuit may comprise a voltage. In particular, the output of the at least one current measurement circuit may comprise an output voltage. The value of the component of the electrical characteristic may comprise a magnitude of the in-phase component of the filtered output. The value of the component of the electrical characteristic may comprise a magnitude of the quadrature component of the filtered output. The value of the component of the electrical characteristic may comprise a phase calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise an amplitude calculated using the in-phase component and the quadrature component. The value of the component of the electrical characteristic may comprise at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component. The load profile may be a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator. The mathematical model may be a linear model. The load profde may be the load profile determined as above.

[0130] The actuator may comprise a piezoelectric actuator.

[0131] In some embodiments of the present disclosure, there is provided a quantitative micro- elastography (QME) system. The QME system may comprise an optical system. The optical system may comprise a source of electromagnetic radiation and a detector for detecting electromagnetic radiation. The QME system may comprise a sensing layer. The source and detector may be in optical communication with the sensing layer. The source may emit electromagnetic radiation that is directed through an optical interface of the sensing layer. The detector may detect a portion of the electromagnetic radiation that is emitted by the source, directed through the optical interface and backscattered by a material external to the QME system. The QME system may comprise a mechanical system. The mechanical system may comprise a piezoelectric actuator that is configured to be actuated to apply a force on a mechanical interface of the sensing layer such that the force is transmitted to the material via the mechanical interface of the sensing layer. The QME system may be configured to generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal. The QME system may be configured to apply the actuator driving waveform to the actuator. The QME system may be configured to determine a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator. The value of the component of the electrical characteristic may be associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator. The value of the component of the electrical characteristic may be determined based at least in part on a value of a parameter of the interrogation signal. The QME system may be configured to determine an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

[0132] The QME system may be further configured to change a value of an operating parameter of the QME system based on the determined estimate of the unknown mechanical load.

[0133] Changing the value of the operating parameter may stop a QME imaging process of the QME system. Changing the value of the operating parameter may stop the application of the actuator driving waveform to the actuator. Changing the value of the operating parameter may cause an alarm to activate.

[0134] A frequency of the interrogation signal may be associated with a resonant frequency of the QME system.

[0135] A frequency of the interrogation signal may be within a threshold range that contains a resonant frequency of the mechanical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0136] Notwithstanding any other forms which may fall within the scope of the systems and methods as set forth in the Summary, specific embodiments will now be described, by way of example only, with reference to accompanying drawings in which:

[0137] Figure 1 is a block diagram of a system, according to some embodiments;

[0138] Figure 2 is a block diagram of a part of the system, according to some embodiments;

[0139] Figure 3 is a block diagram of a part of the system, according to some embodiments;

[0140] Figure 4 is a schematic diagram of a strain gauge, according to some embodiments;

[0141] Figure 5 is a perspective view of an actuator with a number of connected strain gauges, according to some embodiments;

[0142] Figure 6 is a process flow diagram of a method, according to some embodiments;

[0143] Figure 7 is a process flow diagram of another method, according to some embodiments;

[0144] Figure 8 is a block diagram of a system of an experiment, according to some embodiments;

[0145] Figure 9 shows a number of pieces of equipment of the experiment, according to some embodiments;

[0146] Figure 10 shows a number of results of the experiment, according to some embodiments; and Figure 11 shows results of the experiment, according to some embodiments.

[0147] DETAILED DESCRIPTION

[0148] Specific embodiments of the disclosed embodiments will now be described by way of example only. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the disclosed system or method. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to pertaining to the present disclosure. In the drawings, it should be understood that like reference numbers refer to like parts.

[0149] Quantitative micro-elastography (QME) is an advanced imaging technique used to quantify the mechanical properties, such as stiffness or elasticity, of biological tissue at a microscopic level. It builds on principles of elastography, where tissue deformation in response to applied forces is measured, and combines it with high-resolution optical imaging to generate quantitative strain and elasticity maps. These maps reveal the mechanical properties of tissues with micrometre-scale spatial resolution. QME is therefore particularly useful in biomedical applications like tumour characterisation.

[0150] In QME devices, an actuator is used to generate precise and reproduceable vibrations or compressions, which are transmitted to the tissue being studied. That is, an actuator is used to apply mechanical forces to the tissue. By manipulating the tissue in a controlled manner, the actuator facilitates the measurement of tissue deformation in response to the applied forces. The resulting data on tissue displacement and strain are then used to quantify the mechanical properties, such as stiffness and elasticity, with high spatial resolution. This integration of an actuator allows a QME device to provide detailed and accurate assessments of tissue biomechanics, enhancing, for example, tumour characterisation capabilities.

[0151] A QME device can use a piezoelectric actuator as the actuator that generates the vibrations or compressions. Piezoelectric actuators operate based on the piezoelectric effect, where a material generates an electric charge in response to applied mechanical stress, or conversely, changes shape when an electric field is applied. In a QME device, a piezoelectric actuator can deliver fine-tuned vibrations or compressions with high accuracy and repeatability, enabling detailed measurement of tissue deformation and elasticity.

[0152] A piezoelectric actuator responds quickly to changes in electrical input signals and can generate small, controlled forces enabling the micro-scale measurements of QME. Accurate calibration of the piezoelectric actuator ensures that the mechanical forces applied to the tissue are known, consistent and reproduceable.

[0153] In use, an electrical signal is applied to the piezoelectric actuator of a QME device (e.g. via an amplifier) to induce mechanical motion in the piezoelectric actuator. In particular, a signal generator generates an electrical signal in the form of a driving waveform. The driving waveform is applied to the actuator. The driving waveform may be a voltage waveform that is applied to the actuator. The driving waveform may be a current waveform that is applied to the actuator. The driving waveform is parameterised by a number of waveform parameters. These parameters include frequency, amplitude and waveform shape. The driving waveform may take a number of waveform shapes, such as that of a sine wave, square wave, triangle wave or sawtooth wave. The driving waveform causes the piezoelectric actuator to expand or contract, thereby creating mechanical motion or force.

[0154] A mechanical preloading force is applied on the piezoelectric actuator, in use. The mechanical preloading force may be the force applied to the actuator by a user of the device that initially positions the device on the tissue sample. The mechanical preloading force can be applied to the actuator by the user moving the device with respect to the tissue sample, such that the device and tissue sample are brought into contact. The extent of this contact, and, specifically, the extent to which the user pushes the device against the tissue sample, results in the application of the mechanical preloading force on the piezoelectric actuator. In some embodiments, a mechanical preload element of an actuator assembly comprising the piezoelectric actuator can provide the mechanical preloading force. During an initial setup of a QME device, this mechanical preloading force can be precisely applied using an external apparatus, or measured precisely, to enable an initial baselining of the applied mechanical force.

[0155] The mechanical preloading force is the initial mechanical load applied before dynamic stress is introduced. Precise control of this mechanical preloading force can assist in avoiding the introduction of measurement errors. Variation in this preload can lead to inaccurate assessments of tissue elasticity and stiffness. The piezoelectric actuator also applies a precise mechanical load on the tissue under analysis, in use. The tissue responds to the applied mechanical load by deforming. In QME, the deformation of the tissue is monitored using optical coherence tomography (OCT) imaging techniques. That is, real-time depth or cross-sectional images of the tissue are captured as it is being deformed. These images provide detailed information about the tissue’s structure and movement.

[0156] The images captured by OCT are used to measure the displacement and strain within the tissue sample as it deforms in response to the force applied by the actuator. The displacement data is processed to determine how much strain the tissue undergoes relative to the applied stress. By comparing the tissue deformation to the applied force, mechanical properties of the tissue, such as elasticity, stiffness and strain distribution can be quantified. These measured mechanical properties can be used to assess one or more characteristics of the tissue. For example, stiffer tissue may indicate the presence of a tumour or fibrosis, while more elastic tissue could indicate healthy or normal tissue conditions.

[0157] Receiving feedback from the piezoelectric actuator during operation can enable more accurate force control and higher QME image quality. It will be understood that receiving feedback may be considered analogous to determining data associated with the operation of the piezoelectric actuator. Tissue properties such as stiffness and elasticity are highly sensitive to the magnitude and precision of the force applied to the tissue using the actuator. Slight variations in applied force, or a miscalibration of the actuator, can lead to inaccurate measurements. In QME devices, this can reduce the quality of the data generated during the imaging process, thereby reducing the value of the inferences made using this data. In a practical example, this may reduce the confidence with which it can be stated that a particular point of a tissue sample is a boundary of a cancer.

[0158] One way of obtaining data associated with the operation of a piezoelectric actuator is to use one or more force sensor. For example, one or more strain gauges may be operably connected to the actuator. The resistance of the strain gauge(s) will change with a change in load on the actuator as the change in load causes a corresponding change in shape of the actuator. This change in resistance can be measured, and used to estimate the load applied to the actuator.

[0159] Another way of obtaining data associated with the operation of a piezoelectric actuator is to measure one or more electrical characteristics of the piezoelectric actuator during operation. As mentioned previously, a piezoelectric actuator generates an electric charge in response to applied mechanical stress. One or more characteristics of this electric charge can be measured, and used to determine an estimate of the applied mechanical stress (i.e. a mechanical load on the actuator). Determining an accurate estimate of the mechanical load on the actuator allows a better quality analysis of the tissue sample to be conducted, as the force applied on the tissue by the actuator is more precisely known. In QME, this can allow for the generation of higher-resolution images of the tissue sample.

[0160] The present disclosure relates to determining a mechanical load profile associated with an actuator. The present disclosure also relates to systems and methods for determining an estimate of a mechanical load on an actuator. The actuator described herein is a piezoelectric actuator. However, it will be appreciated that the system and method may also be applicable to other types of actuators. For example, the system and method may be applicable where the actuator is an electric motor.

[0161] System 100

[0162] Figure 1 shows a system 100, according to some embodiments of the present disclosure. The system 100 is a quantitative micro-elastography (QME) system 100. The system 100 enables a user to perform QME imaging of a sample material. The system 100 comprises a device 101. The device 101 may be a QME device 101 that enables the user to perform QME imaging of the sample material. The system 100 comprises a computing system 103. The computing system 103 is operably connected to the device 101. The system 100 is configured to enable the determination of one or more characteristics of a material 105.

[0163] The device 101 is a handheld device. The device 101 comprises a sensing layer 104. The sensing layer 104 has an exposed sensing surface 106. In the illustrated embodiment, the sensing surface 106 is positioned in direct contact with the material 105. The sensing layer 104 has a surface 108 that is opposite the sensing surface 106. The sensing layer 104 is deformable. The sensing layer 104 comprises, in the present embodiment, a silicone material. However, it will be appreciated that the sensing layer 104 may alternatively comprise another translucent or transparent deformable material such as a gel or an elastomer. The sensing layer 104 has, in this embodiment, a thickness of approximately 600pm to 1000pm. In other words, the thickness of the sensing layer 104 is between 600pm and 1000pm. In some embodiments, the thickness of the sensing layer 104 is about 700pm. It will be understood that the sensing layer 104 may have any other suitable thickness. For example, the sensing layer 104 may have a thickness in the range of 10pm to 3cm.

[0164] In another embodiment, the sensing surface 106 of the sensing layer 104 is in indirect contact with the material 105. For example, a thin layer comprising latex or another plastic material, such as a surgical sheath, may be positioned between the sensing surface 106 and the material 105 for preventing contamination of the material. The surgical sheath may comprise a polymeric material, such as a plastic.

[0165] The system 100 comprises an optical system 111. In the illustrated embodiment, the device 101 comprises the optical system 111. It will be appreciated however, that in some embodiments, another part of the system 100 may comprise some or all of the optical system 111. The optical system 111 comprises a source of electromagnetic radiation and a detector for detecting electromagnetic radiation. Both the source and the detector are in optical communication with the sensing layer 104. In the illustrated embodiment, the source and detector are in optical communication with the sensing layer 104 by means of optical fibres 116. The source emits electromagnetic radiation which is directed through one or more optical fibres 116 and an optical interface 117 of the sensing layer 104, at the material 105. A portion of this electromagnetic radiation is reflected by the material 105, through the optical interface 117 of the sensing layer 104, and the respective one or more optical fibres 116, and detected by the detector. For the purposes of this disclosure, reflection may be interpreted to comprise backscattered electromagnetic radiation. That is, a portion of the electromagnetic radiation directed through the optical interface 117 of the sensing layer, at the material 105, is backscattered by the material 105, through the optical interface 117 of the sensing layer 104, and the respective optical fibre 116, and detected by the detector.

[0166] The system 100 comprises a mechanical system 109. In the illustrated embodiment, the device 101 comprises the mechanical system 109. It will be appreciated however, that in some embodiments, another part of the system 100 may comprise some or all of the mechanical system 109. The mechanical system 109 comprises an actuator 124. The actuator 124 comprises a number of actuator components that are assembled to form the actuator 124. Therefore, the actuator 124 may alternatively be referred to as an actuator assembly. The actuator 124 comprises an actuator element (not shown). The actuator 124 of the illustrated system 100 is a piezoelectric actuator. The actuator element of the actuator 124 is a piezoelectric element. The actuator 124 comprises a plurality of electrodes (not shown). Each electrode is connected to the actuator element. Electrical signals may be applied to the actuator element via the electrodes.

[0167] The actuator 124 may comprise a mechanical preload element (not shown). The mechanical preload element can preload the actuator element with a preload force. The actuator 124 may comprise drive electronics. The actuator 124 comprises a housing (not shown). The housing houses at least part of the actuator element, the drive electronics and / or the mechanical preload element. The actuator 124 may be mounted to the device 101 via the housing. The mechanical system 109 comprises the actuator 124 and components of the device 101 that are mechanically connected to the actuator 124 (directly or indirectly), that influence the mechanical behaviour of the actuator 124.

[0168] The actuator 124 is configured to be actuated. The actuator 124, when actuated, applies a force on a mechanical interface 119 of the sensing layer 104. This force is generated by excitation of the actuator element. The mechanical interface 119 of the sensing layer 104 transmits this force to the material 105, thereby causing deformation of the material 105. The sensing layer 104, or a part thereof through which the actuator 124 acts, may be considered part of the actuator 124. In use, the sensing layer 104 is initially brought into contact with the material 105. As the user brings the sensing layer 104 into contact with the material 105, a preloading force is applied to the actuator 124. Subsequent to the sensing layer 104 being brought into contact with the material 105, the actuator 124 is actuated, thereby applying a force on the material 105.

[0169] As noted above, the actuator 124 of the illustrated embodiment is a piezoelectric actuator. Piezoelectric actuators are a type of transducer based on the piezoelectric effect and are used in many applications ranging from nano -indenting, micro-positioning systems, solid-state switches and medical ultrasound devices due to their ability to convert electrical energy into mechanical displacements and vice-versa. The person skilled in the art will understand that other actuators may be used without departing from the scope of the present disclosure, such as electric motors, linear actuators etc.

[0170] Variations in thickness of the sensing layer 104 can be observed, using the optical system 111. Similarly, displacement of the material 105 can be observed, again using the optical system 111. For example, displacements of portions of the material 105, such as when under compression, can be observed. These variations in the sensing layer 104 and / or displacement of the material 105 can be used to determine estimates of one or more physical characteristics of the material 105. Example physical characteristics of the material 105 that can be estimated can include material stiffness and / or tangent modulus. Other example physical characteristics of the material 105 that can be estimated can include elastic modulus, shear modulus, bulk modulus, Poisson’s ratio, viscosity, viscoelastic properties, strain distribution, stress-strain relationships, hardness and / or compliance.

[0171] The device 101 comprises a user interface 113. The user interface 113 enables a user of the system 100 to interact with the device 101. The user interface 113 may comprise one or more user interface components, such as one or more of a display device, a touch screen display, a keyboard, a mouse, a camera, a microphone, buttons, switches and lights.

[0172] The device 101 comprises a network interface 115. The network interface 115 is configured to enable the device 101 to communicate with the computing system 103. The network interface 115 may comprise a combination of network interface hardware and network interface software suitable for establishing, maintaining and facilitating communication over a relevant communications network. Examples of a suitable communications network include a cloud server network, a wired or wireless internet connection, a wireless local area network (WLAN) such as Wi-Fi (IEEE 82.15.1) or Zigbee (IEE 802.15.4), a wireless wide area network (WWAN) such as cellular 4G LTE and 5G or another cellular network connection, low power wide area networks (LPWAN) such as SigFox and Lora, Bluetooth™ or other near field radio communication, and / or physical media such as a Universal Serial Bus (USB) connection. The illustrated network interface 115 enables the device 101 to communicate with the computing system 103 over a wireless communications network. The computing system 103 may communicate with the device 101 over a wired communications network. The computing system 103 may communicate with the device 101 over both a wireless communications network and a wired communications network. That is, the computing system 103 may be operably connected to the device 101 via both a wired connection and a wireless connection.

[0173] The device 101 comprises a housing (not shown). The housing of the device 101 houses at least part of one or more components of the device 101. For example, the housing houses at least part of the actuator 124.

[0174] The computing system 103 is in communication with the device 101. The computing system 103 can be used to control the device 101. The computing system 103 processes the data generated using the device 101 to determine the estimate of the characteristic(s) of the material 105.

[0175] The computing system 103 comprises at least one processor 121. The computing system 103 comprises a memory 123. Memory 123 stores computer-executable instructions. The computer-executable instructions may be referred to as program instructions. The at least one processor 121 is operably connected to memory 123. That is, the at least one processor 121 is configured to communicate with memory 123. The computer-executable instructions are accessible by the at least one processor 121. The at least one processor 121 is configured to execute the computer-executable instructions. The at least one processor 121 may execute the computer-executable instructions to control the device 101. The at least one processor 121 may execute the computer-executable instructions to process the data generated using the device 101. The computer-executable instructions may comprise executable program code modules that are configured to be executed by the at least one processor 121.

[0176] The at least one processor 121 comprises one or more microprocessors, central processing units (CPUs), application specific instruction set processors (ASIPs), application specific integrated circuits (ASICs), tensor processing units (TPUs) or other processors capable of reading and executing computer executable instructions. The at least one processor 121 may comprise a plurality of processors. It will be appreciated that the at least one processor 121 may be a distributed processor. That is, one or more processor of the at least one processor 121 may be physically separated from one or more other processor of the at least one processor 121.

[0177] Memory 123 may comprise one or more volatile or non-volatile memory types. Memory 123 may comprise at least one of random-access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM) and flash memory. Memory 123 may comprise one or more computer-readable storage medium. A computer-readable storage medium can be any medium that can tangibly contain or store computer-executable instructions. In some examples, the storage medium is a transitory computer-readable storage medium. In some examples, the storage medium is a non-transitory computer-readable storage medium. The non-transitory computer-readable storage medium can include, but is not limited to, magnetic, optical, and / or semiconductor storages. Examples of such storage include magnetic disks, optical discs based on CD, DVD, or Blu-ray technologies, as well as persistent solid-state memory such as flash, solid state drives, and the like.

[0178] The computing system 103 comprises a user interface 125. The user interface 125 enables a user of the computing system 103 to interact with the computing system 103. The user interface 125 may comprise one or more user interface components, such as one or more of a display device, a touch screen display, a keyboard, a mouse, a camera, a microphone, buttons, switches and lights.

[0179] The computing system 103 comprises a network interface 127. The network interface 127 is configured to enable the computing system 103 to communicate with the device 101. The network interface 127 may comprise a combination of network interface hardware and network interface software suitable for establishing, maintaining and facilitating communication over a relevant communications network. The illustrated network interface 127 enables the computing system 103 to communicate with the device 101 over a wireless communications network. The network interface 127 enables the computing system 103 to communicate with the device 101 over a wired communications network. In some embodiments, the network interface 127 enables the computing system 103 to communicate with the device 101 over both a wired communications network and a wireless communications network.

[0180] As described herein, the device 101 may be connected to the computing system 103 via a wired communications network. In some embodiments, the source of electromagnetic radiation of the optical system 111 may be located at the computing system 103 rather than the device 101. That is, the computing system 103 may comprise the source of electromagnetic radiation of the optical system 111. The detector of the optical system 111 may similarly be positioned at the computing system 103. That is, the computing system 103 may comprise the detector. The optical fibres 116 may extend from the computing system 103 to the device 101 to provide optical communication between the source, detector, and the sensing layer 104. This configuration may allow the computing system 103 to house larger or more sensitive optical components while maintaining the handheld nature of the device 101. The at least one processor 121 may control both the source and detector operations from the computing system 103.

[0181] The system 100 comprises a signal processing system 139. In the illustrated embodiment, the computing system 103 comprises the signal processing system 139. It will be appreciated however, that in some embodiments, the device 101 may comprise the signal processing system 139. In some embodiments, the computing system 103 comprises part of the signal processing system 139 and the device 101 comprises part of the signal processing system 139.

[0182] The signal processing system 139 generates one or more signals. The signal processing system 139 processes input signals to generate outputs based on the input signals. The signal processing system 139 may be implemented in one of a number of forms. Figure 2 shows an example of a signal processing system 139A, according to some embodiments of the present disclosure. Figure 3 shows another example of a signal processing system 139B, according to some embodiments of the present disclosure.

[0183] Signal Processing System 139A

[0184] Figure 2 shows a signal processing system 139A of the system 100, according to some embodiments of the present disclosure. The signal processing system 139A comprises a signal generator 131. The signal generator 131 is operably connected to the actuator 124. In particular, the signal generator 131 is electrically connected to the actuator. The signal generator 131 is operably connected to the actuator 124 via a signal amplifier 132. The signal processing system 139A generates a driving waveform that is applied to the actuator 124 to actuate the actuator 124. In particular, the signal processing system 139A generates an actuator driving waveform that is applied to the actuator 124. The signal generator 131 and the signal amplifier 132 generate the actuator driving waveform. While the signal amplifier 132 is shown separately to the signal generator 131 in Figure 2, it will be appreciated that the signal generator 131 may comprise the signal amplifier 132, in some embodiments.

[0185] The signal generator 131 and the signal amplifier 132 together generate a driving waveform that is applied to the actuator 124. In particular, the signal generator 131 and the signal amplifier 132 generate the actuator driving waveform that is applied to the actuator 124. The actuator driving waveform may be formed from a plurality of waveforms. The amplifier driving waveform actuates the actuator 124. In other words, the amplifier driving waveform is configured to actuate the actuator 124. The output of the signal generator 131 is provided to the signal amplifier 132 for amplification, prior to being applied to the actuator 124. This amplified output may be the amplifier driving waveform described herein. That is, the signal amplifier 132 amplifies an input signal provided by the signal generator 131, thereby generating an amplified signal that is provided to the actuator 124.

[0186] In the illustrated embodiment, the at least one processor 121 of the computing system 103 is in communication with the signal generator 131. The signal generator 131 may be controlled by the at least one processor 121 of the computing system 103. The at least one processor 121 may, for example, define one or more of the characteristics of the signal generated by the signal generator 131. The at least one processor 121 may provide the information defining the characteristics of the signal that is to be output by the signal generator, such as frequencies, amplitudes and waveform shapes, and a signal corresponding to these characteristics can be generated by the signal generator 131. In some embodiments, the at least one processor 121 may also be in communication with the signal amplifier 132. The at least one processor 121 may define the amplification that the signal amplifier 132 is to apply to the signal output by the signal generator 131.

[0187] The signal processing system 139A comprises a sensor 141. The sensor 141 is operably connected to the actuator 124. The sensor 141 senses a characteristic of the actuator 124 and generates an output signal that is related to the sensed characteristic. The output signal may comprise an output voltage. The output signal may comprise an output current. The output signal may, for example, be a resistance of the sensor 141. The sensed characteristic may be a physical characteristic such as a shape or orientation of the actuator 124, or a component thereof, such as an actuator element of the actuator 124. The sensed characteristic may be an electrical characteristic such as a current through the actuator 124, a volage across the actuator 124, an impedance of the actuator 124 etc. In the illustrated embodiment, the sensor 141 is a current sensor 141 that senses a current through the actuator 124 in use, and generates an output voltage in response. The current sensor 141 converts an input current signal to the output signal. The output signal in the illustrated embodiment is a voltage output. In the illustrated embodiment, the current sensor 141 is in the form of a current-to-voltage conversion circuit (CVCC) 141. That is, the signal processing system 139A comprises a CVCC 141. The CVCC 141 is operably connected to the actuator 124. In the illustrated embodiment, this is an electrical connection. The CVCC 141 converts an input current signal to an output signal. The output signal is an output voltage. Thus, the CVCC 141 converts an input signal into an output voltage signal. A magnitude of the voltage signal output by the CVCC 141 is related to a magnitude of the input current signal of the CVCC 141. In some embodiments, the magnitude of the voltage signal output by the CVCC 141 is proportional to the magnitude of the input current signal.

[0188] A measurement of the current through the actuator 124 is an input of the CVCC 141. That is, the input current signal of the CVCC 141 is a signal representing measurements of the current through the actuator 124, over time. The CVCC 141 is electrically connected to the signal amplifier 132. In the illustrated embodiment, the CVCC 141 is electrically connected to the output of the signal amplifier 132. That is, the CVCC 141 is electrically connected to the input side of the actuator 124.

[0189] The CVCC 141 receives time-series measurements of the current through the actuator 124 as an input signal. The CVCC 141 generates a time-series output that is associated with the input current signal. The time-series output may be referred to as an output signal. In particular, the CVCC 141 generates a timeseries output in the form of a voltage output that is associated with the input current signal.

[0190] The signal processing system 139A comprises a filter 140. The filter 140 fdters an input signal to generate a filtered output. In particular, the filter 140 fdters the output of the sensor 141. That is, the filter

[0191] 140 fdters the output of the current measurement circuit 141. In particular, the filter 140 filters the output of the CVCC 141. In the illustrated embodiment, the filter 140 is in the form of a lock-in amplifier 140. That is, the signal processing system 139A comprises a lock-in amplifier 140. It will be appreciated that references to “lock-in amplifier 140” made herein may be substituted with references to “filter 140”. The lock-in amplifier 140 is electrically connected to the CVCC 141. In particular, the output signal of the CVCC 141 is an input signal of the lock-in amplifier 140. That is, the output voltage signal of the CVCC

[0192] 141 is the input signal of the lock-in amplifier 140. The lock-in amplifier 140 filters the input signal. In particular, the lock-in amplifier 140 fdters the input signal at the frequency of an interrogation signal from which the actuator driving waveform is constructed. That is, the lock-in amplifier 140 filters the output signal of the current measurement circuit 141 at the frequency of the modulation of the drive signal generated by the signal generator 131. The signal generator 131 and the signal amplifier 132 generate an actuator driving waveform comprising a primary driving waveform and an interrogation signal. The lock- in amplifier 140 filters its input signal based on a value of a parameter of the interrogation signal. In particular, the lock-in amplifier 140 fdters its input signal based on the frequency of the interrogation signal. The lock-in amplifier 140 filters the output of the CVCC 141 generated in response to the current through the actuator 124, while the actuator driving waveform is applied to the actuator 124. The lock-in amplifier 140 generates a filtered output, based on the input signal of the lock-in amplifier 140. In other words, the lock-in amplifier 140 generates a filtered output based on the voltage output of the CVCC 141.

[0193] The lock-in amplifier 140 may obtain reference frequency information through various means. For example, a reference signal may be provided to the lock-in amplifier 140. In some embodiments, the signal generator 131 may provide the reference signal to the lock-in amplifier 140. The reference signal may correspond to the frequency of the interrogation signal. In other embodiments, the at least one processor 121 may provide reference frequency information to the lock-in amplifier 140. The at least one processor 121 may communicate the frequency of the interrogation signal to the lock-in amplifier 140 to enable proper filtering at the desired frequency. Alternatively, the lock-in amplifier 140 may derive the reference from another source. For example, the lock-in amplifier 140 may include internal circuitry to extract the reference frequency from the input signal or may receive a separate reference signal from an external source. The reference frequency information enables the lock-in amplifier 140 to perform phase-sensitive detection and filtering at the specific interrogation frequency used in the construction of the actuator driving waveform.

[0194] The lock-in amplifier 140 may provide both amplitude and phase information in its filtered output. The filtered output may comprise an in-phase component and a quadrature component, enabling determination of both the magnitude and phase relationship of the input signal relative to the reference frequency. This amplitude and phase information may be used to determine values of one or more components of an electrical characteristic associated with the actuator 124, during use. In some embodiments, this amplitude and phase information forms values of the components of the electrical characteristic associated with the actuator 124. The signal processing system 139A may include timing and synchronisation mechanisms to coordinate the actuator driving waveform generation with the current measurement and filtering processes.

[0195] The at least one processor 121 is in communication with the lock-in amplifier 140. The at least one processor 121 may read the output of the lock-in amplifier 140 and perform certain functionality based on this output. That is, the at least one processor 121 may receive the output of the lock-in amplifier 140 and perform functionality described herein based on this output.

[0196] In some embodiments, the lock-in amplifier 140 is in communication with a user interface. The relevant user interface may display an output associated with the output of the lock-in amplifier 140. For example, the lock-in amplifier 140 may be in communication with the user interface 125 of the computing system 103. The user interface 125 may generate an output associated with the output of the lock-in amplifier 140. For example, the user interface 125 may generate a visual output indicating the value of an output of the lock-in amplifier 140. Alternatively, the at least one processor 121 may process the output of the lock-in amplifier 140 and generate output data reflecting this that is rendered on the user interface 125.

[0197] While the computing system 103 is described above to comprise the signal processing system 139A, it will be appreciated that one or more components of the signal processing system 139A may alternatively be separate components. For example, one or more of the signal generator 131, the signal amplifier 132, the current-to-voltage conversion circuit 141 and the lock-in amplifier 140 may be a component that does not form part of the computing system 103. In such a case, the relevant component can be in communication with the computing system 103 as required.

[0198] One or more of the components of the signal processing system 139A may be part of the device 101. For example, the device 101 may comprise one or more of the signal generator 131, the signal amplifier 132, the current-to-voltage conversion circuit 141 and the lock-in amplifier 140. In such a case, the relevant component can communicate with the computing system 103 as required, via the communications network(s) used for communication between the device 101 and the computing system 103.

[0199] It will be appreciated that the signal processing system 139 A may comprise one or more other components that are not illustrated in Figure 2. For example, the signal processing system 139A may comprise a digital-to-analogue converter (DAC). The DAC may be positioned between the signal generator 131 and the signal amplifier 132. In some embodiments, the device 101 may comprise the DAC and the signal amplifier 132.

[0200] Signal Processing System 139B

[0201] Figure 3 shows a signal processing system 139B of the system 100, according to some embodiments of the present disclosure. The signal processing system 139B comprises a signal generator 131. The signal generator 131 may be similar to, or the same as, the signal generator 131 described with reference to the signal processing system 139A of Figure 2. The signal generator 131 of the signal processing system 139B is operably connected to the actuator 124. In particular, the signal generator 131 is operably connected to the actuator 124 via a signal amplifier 132. The signal processing system 139B generates a driving waveform that is applied to the actuator 124 to actuate the actuator 124. In particular, the signal generator 131 generates an actuator driving waveform that is applied to the actuator 124. The signal generator 131 and the signal amplifier 132 generate the actuator driving waveform. While the signal amplifier 132 is shown separately to the signal generator 131 in Figure 3, it will be appreciated that the signal generator 131 may comprise the signal amplifier 132, in some embodiments.

[0202] The signal generator 131 and the signal amplifier 132 together generate a driving waveform that is applied to the actuator 124. In particular, the signal generator 131 and the signal amplifier 132 generate the actuator driving waveform that is applied to the actuator 124. The actuator driving waveform may be formed from a plurality of waveforms. The amplifier driving waveform actuates the actuator 124. In other words, the amplifier driving waveform is configured to actuate the actuator 124. The output of the signal generator 131 is provided to the signal amplifier 132 for amplification, prior to being applied to the actuator 124. This amplified output may be the amplifier driving waveform described herein. That is, the signal amplifier 132 amplifies an input signal provided by the signal generator 131, thereby generating an amplified signal that is provided to the actuator 124.

[0203] In the illustrated embodiment, the at least one processor 121 of the computing system 103 is in communication with the signal generator 131. The signal generator 131 may be controlled by the at least one processor 121 of the computing system 103. The at least one processor 121 may, for example, define one or more of the characteristics of the signal generated by the signal generator 131. The at least one processor 121 may provide the information defining the characteristics of the signal that is to be output by the signal generator 131, such as frequencies, amplitudes and waveform shapes, and a signal corresponding to these characteristics can be generated by the signal generator 131. In some embodiments, the at least one processor 121 may also be in communication with the signal amplifier 132. The at least one processor 121 may define the amplification that the signal amplifier 132 is to apply to the signal output by the signal generator 131.

[0204] In the illustrated embodiment, a sensor 136 is connected to the actuator 124. The sensor 136 is operably connected to the actuator 124. The sensor 136 senses a characteristic of the actuator 124 and generates an output signal that is related to the sensed characteristic. The output signal may comprise an output voltage. The output signal may comprise an output current. The output signal may, for example, be a resistance of the sensor 136. The sensed characteristic may be a physical characteristic such as a shape or orientation of the actuator 124, or a component thereof, such as an actuator element of the actuator 124. The sensed characteristic may be an electrical characteristic such as a current through the actuator 124, a volage across the actuator 124, an impedance of the actuator 124 etc. In the illustrated embodiment, the sensor 136 is in the form of a strain gauge 136. Thus, in the illustrated embodiment, a strain gauge 136 is connected to the actuator 124. In some embodiments, one or more sensor 136 is connected to the actuator 124. In some embodiments, a plurality of sensors 136 are operably connected to the actuator 124. For example, a plurality of strain gauges 136 may be connected to the actuator 124, or a component thereof. Figures 4 and 5 illustrate an embodiment of a strain gauge 136 (Figure 4) and an embodiment of the actuator 124 in which a plurality of strain gauges 136 are connected to, or form part of, the actuator 124 (Figure 5), as shown in Figure 3. The actuator 124 of Figure 5 is a piezoelectric actuator. In the embodiment of Figure 5, a number strain gauges 136 are operably connected to the actuator 124. The strain gauges 136 may, for example, be connected to an actuator element of the actuator 124. In this way, changes in shape of the actuator element may result in corresponding changes in shape of the strain gauges 136. Where a strain gauge is described to be connected to the actuator 124 herein, it will be understood that the strain gauge 136 may be connected to the actuator element of the actuator 124, or to another part of an actuator 124 that moves with the actuator element. The changes in shape of the strain gauges 136 that occur with actuation of the actuator can therefore be used to track the changes in shape of the actuator element and / or an extent of actuation of the actuator 124.

[0205] A first strain gauge 136 A is connected to the actuator 124. The first strain gauge 136A can be used to measure strain on the actuator 124 in a first direction 301. The first strain gauge 136A comprises a Wheatstone bridge circuit 303 (see Figure 4). The Wheatstone bridge circuit 303 comprises a plurality strain gauge components 305 that are electrically connected in a diamond configuration. An input voltage UEis applied across input terminals 307. The input voltage UEmay be applied via one or more components or parts of the signal processing system 139B. A voltage across output terminals 309 can be measured, with the measured output voltage UAindicating the strain across the strain gauge 136 in the first direction 301. When the first strain gauge 136A experiences deformation (e.g. with deformation of the actuator 124 during use), the resistance of one or more of the strain gauge components 305 changes. This change in resistance unbalances the Wheatstone bridge circuit 303, resulting in a non-zero output voltage that can be measured across the output terminals 309. The output voltage is related to the strain experienced by the first strain gauge 136 A. In some embodiments, the output voltage is proportional to the strain experienced by the first strain gauge 136B.

[0206] A second strain gauge 136B is also connected to the actuator 124. The second strain gauge 136B can be used to measure strain on the actuator 124 in a second direction 306. In the illustrated embodiment, the second direction 306 is orthogonal to the first direction 301. It will be appreciated that in some embodiments, the second direction 306 may be transverse to, but non-parallel with, the first direction 301. The second strain gauge 136B comprises a Wheatstone bridge circuit 303 (see Figure 4). The output voltage measured across the output terminals 309 of the Wheatstone bridge circuit 303 is related to the strain experienced by the second strain gauge 136B in the second direction 306. In some embodiments, the output voltage is proportional to the strain experienced by the second strain gauge 136B.

[0207] While not illustrated in Figure 5, it will be appreciated that at third strain gauge may be connected to the actuator 124 to measure strain on the actuator 124 in a third direction. The third direction can be orthogonal to the first direction 301 and the second direction 306. Alternatively, the third direction can be transverse to both the first direction 301 and the second direction 306 in a way that enables three-axis deformation to be measured via the first, second and third strain gauges.

[0208] The signal processing system 139B comprises a strain gauge amplifier 138. The strain gauge amplifier 138 samples the voltage across the strain gauge(s) 136, and amplifies this to generate an output voltage signal. In other words, the output voltage(s) across the strain gauge(s) 136 connected to the actuator 124 is an input of the strain gauge amplifier 138. The strain gauge amplifier 138 generates an output voltage signal based on this input voltage signal. In some embodiments, the signal processing system 139B comprises a strain gauge amplifier 138 for each strain gauge 136. In some embodiments, the strain gauges 136 share a strain gauge amplifier 138. That is, in some embodiments, the strain gauges 136 are each operably connected to a common strain gauge amplifier 138.

[0209] The signal processing system 139B comprises a filter 140. The filter 140 filters an input signal to generate a filtered output. In the illustrated embodiment, the filter 140 is in the form of a lock-in amplifier 140. That is, the signal processing system 139B comprises a lock-in amplifier 140. It will be appreciated that references to “lock-in amplifier 140” made herein may be substituted with references to “filter 140”. The lock-in amplifier 140 is electrically connected to the sensor 136. In the illustrated embodiment, the sensor 136 is in the form of the strain gauge 136, and the lock-in amplifier 140 is electrically connected to the strain gauge 136 via the strain gauge amplifier 138. Thus, the lock-in amplifier 140 is electrically connected to the strain gauge amplifier 138. The output signal of the sensor 136 forms part of the input of the lock-in amplifier 140. That is, the output of the strain gauge amplifier 138 is an input signal of the lock-in amplifier 140. The lock-in amplifier 140 filters the input signal. In particular, the lock-in amplifier 140 filters the input signal at the frequency of an interrogation signal from which the actuator driving waveform is constructed. That is, the lock-in amplifier 140 filters the input signal at the frequency of the modulation of the drive signal generated by the signal generator 131. The signal generator 131 and the signal amplifier 132 generate an actuator driving waveform comprising a primary driving waveform and an interrogation signal. The primary driving waveform is summed with the interrogation signal to form the actuator driving waveform. The lock-in amplifier 140 filters its input signal based on a value of a parameter of the interrogation signal. In particular, the lock-in amplifier 140 filters its input signal based on the frequency of the interrogation signal. The lock-in amplifier 140 filters the output of the strain gauge amplifier 138 generated in response to the voltage across the strain gauge(s) 136 connected to, or forming part of, the actuator 124, while the actuator driving waveform is applied to the actuator 124. The lock-in amplifier 140 generates a filtered output, based on the input signal of the lock-in amplifier 140. In other words, the lock-in amplifier 140 generates a filtered output based on the output of the strain gauge amplifier 138.

[0210] The lock-in amplifier 140 may obtain reference frequency information through various means. For example, a reference signal may be provided to the lock-in amplifier 140. In some embodiments, the signal generator 131 may provide the reference signal to the lock-in amplifier 140. The reference signal may correspond to the frequency of the interrogation signal. In other embodiments, the at least one processor 121 may provide reference frequency information to the lock-in amplifier 140. The at least one processor 121 may communicate the frequency of the interrogation signal to the lock-in amplifier 140 to enable proper filtering at the desired frequency. Alternatively, the lock-in amplifier 140 may derive the reference from another source. For example, the lock-in amplifier 140 may include internal circuitry to extract the reference frequency from the input signal or may receive a separate reference signal from an external source. The reference frequency information enables the lock-in amplifier 140 to perform phase-sensitive detection and filtering at the specific interrogation frequency used in the construction of the actuator driving waveform.

[0211] The lock-in amplifier 140 may provide both amplitude and phase information in its filtered output. The filtered output may comprise an in-phase component and a quadrature component, enabling determination of both the magnitude and phase relationship of the input signal relative to the reference frequency. This amplitude and phase information may be used to determine values of one or more components of an electrical characteristic associated with the actuator 124, during use. In some embodiments, this amplitude and phase information forms values of the components of the electrical characteristic associated with the actuator 124. The signal processing system 139B may include timing and synchronisation mechanisms to coordinate the actuator driving waveform generation with the current measurement and filtering processes.

[0212] The at least one processor 121 is in communication with the lock-in amplifier 140. The at least one processor 121 may read the output of the lock-in amplifier 140 and perform certain functionality based on this output. That is, the at least one processor 121 may receive the output of the lock-in amplifier 140 and perform functionality described herein based on this output.

[0213] In some embodiments, the lock-in amplifier 140 is in communication with a user interface. The relevant user interface may display an output associated with the output of the lock-in amplifier 140. For example, the lock-in amplifier 140 may be in communication with the user interface 125 of the computing system 103. The user interface 125 may generate an output associated with the output of the lock-in amplifier 140. For example, the user interface 125 may generate a visual output indicating the value of an output of the lock-in amplifier 140. Alternatively, the at least one processor 121 may process the output of the lock- in amplifier 140 and generate output data reflecting this that is rendered on the user interface 125.

[0214] While the computing system 103 is described above to comprise the signal processing system 139B, it will be appreciated that one or more components of the signal processing system 139B may alternatively be separate components. For example, one or more of the signal generator 131, the signal amplifier 132, the strain gauge amplifier 138 and the lock-in amplifier 140 may be a component that does not form part of the computing system 103. In such a case, the relevant component can be in communication with the computing system 103 as required.

[0215] One or more of the components of the signal processing system 139B may be part of the device 101. For example, the device 101 may comprise one or more of the signal generator 131, the signal amplifier 132, the strain gauge amplifier 138 and the lock-in amplifier 140. In such a case, the relevant component can communicate with the computing system 103 as required, via the communications network used for communication between the device 101 and the computing system 103.

[0216] It will be appreciated that the signal processing system 139B may comprise one or more other components that are not illustrated in Figure 3. For example, the signal processing system 139B may comprise a digital-to-analogue converter (DAC). The DAC may be positioned between the signal generator 131 and the signal amplifier 132. In some embodiments, the device 101 may comprise the DAC and the signal amplifier 132.

[0217] Actuator Load Profile Determination

[0218] An actuator load profde is a characterised relationship that correlates values of one or more components of a measurable characteristic of an actuator with mechanical loads applied to the actuator. This relationship may be established by applying known mechanical loads to the actuator while simultaneously applying the actuator driving waveform to the actuator as described herein. The actuator driving waveform is a composite waveform that is formed from a relatively lower frequency primary driving waveform and a relatively high frequency interrogation signal. The frequency component of the actuator driving waveform that is defined by the primary driving waveform drives the actuator in such a way as to enable desired functionality of the device comprising the actuator. In the present application, this may, for example, be in the context of QME system 100 in which the actuator 124 applies forces on the sample 105 via the sensing layer 104 to enable cross-sectional images of the sample 105 to be acquired. The values of one or more of the parameters defining the interrogation signal are tuned to the physical characteristics of the device comprising the actuator (in the present application, the device 101). That is, the interrogation signal is tuned to the device 101 such that the application of the actuator driving waveform to the actuator 124 causes resonance of at least part of the device 101. In other words, a frequency of the interrogation signal is associated with a resonant frequency of the device 101, or a subassembly of the device 101 (e.g. the actuator assembly or a sub-assembly of the device 101 comprising the actuator 124 such as the mechanical system 109). As a result, driving the actuator 124 with the actuator driving waveform causes vibrations within the device 101 at or near resonant frequencies of the device 101 or the relevant device sub-system. These resonant vibrations affect physical and / or electrical characteristics of components of the device 101, such as the actuator 124. Further, the effect of this resonance is influenced by the magnitude of the applied mechanical force on the actuator 124. As a result, an actuator load profile that relates values of one or more components of a measurable characteristic of the actuator 124 that is responsive to these resonant vibrations with mechanical loads applied to the actuator 124 can be determined by observing the effects of known mechanical loads on the measurable characteristic (or a component thereof). Further, the identified capability of determining the actuator load profile enables the measurable characteristic associated with the actuator 124 to be monitored while the actuator driving waveform is being applied to the actuator 124 when unknown mechanical loads are also applied to the actuator 124, and used to determine the magnitude of the unknown mechanical loads.

[0219] The load profile of the actuator may be constructed from these measurements by creating a mathematical model, lookup table, database, or machine learning model that maps the measured values of the component(s) of the electrical parameter to the corresponding known mechanical loads, thereby enabling estimation of unknown mechanical loads based on the value of a component of an electrical characteristic associated with the actuator during its operation.

[0220] For example, in piezoelectric actuators, the load profile is particularly well-defined due to the piezoelectric effect used in the operation of the piezoelectric actuator. When a mechanical load is applied to a piezoelectric actuator, the mechanical stress causes changes in crystal structure that directly affect the electrical properties of the piezoelectric actuator element. These changes are measurable as variations in capacitance, resonant frequency, phase response, and / or current draw when the actuator is electrically excited. For example, when a piezoelectric actuator experiences increased mechanical loading, its resonant frequency may shift, its electrical impedance may change, and the phase relationship between applied voltage and resulting current may vary. The values of these electrical characteristics can therefore be related to the applied mechanical loads. By applying known mechanical loads and measuring the corresponding electrical responses (i.e. the values of a component of an electrical characteristic of the actuator), a load profile can be established that relates a specific value of a component of an electrical characteristic of the actuator during use, to a magnitude of an applied mechanical load. This profile may then be used during operation to estimate unknown mechanical loads by measuring the electrical characteristics of the actuator and referencing the established relationship.

[0221] Load profiles may also apply to other types of actuators, though the specific electrical parameters and relationships may differ. Electric motors may exhibit load-dependent changes in current draw, back-EMF, and power factor as mechanical loads vary. Electromagnetic actuators such as solenoids may show variations in inductance, current rise time, and holding current requirements under different mechanical loading conditions. Pneumatic and hydraulic actuators, while primarily mechanical, may incorporate electrical sensors or control valves that exhibit load-dependent electrical characteristics. In each case, the load profile concept remains applicable by establishing relationships between measurable electrical parameters and the mechanical loads experienced by the actuator system.

[0222] The term “load profile” as used throughout this description, will be understood to refer to a relationship between values of one or more components of a measurable electrical characteristic of an actuator with mechanical loads applied to the actuator. In particular, the load profiles described herein refer to the relationship between values of a component of a measurable electrical characteristic of an actuator (such as values of the phase of the current signal of the actuator at the frequency of the interrogation signal, values of amplitude of the current signal of the actuator at the frequency of the interrogation signal etc.) with a mechanical load applied to the actuator.

[0223] Once a load profile of an actuator is known, mechanical loading on the actuator can be estimated by referring to the load profile. This is because, as described above, the load profile of an actuator relates values of a component of an electrical characteristic associated with the actuator in use to corresponding estimates of mechanical loads on the actuator.

[0224] The electrical characteristic associated with the actuator may be an electrical characteristic of the actuator during use. The electrical characteristic of the actuator may be one of a number of measurable parameters derived from filtering an electrical parameter signal of the actuator 124 at the frequency of the interrogation signal, generating a filtered output with in-phase and quadrature components. The magnitude of the in-phase component represents the portion of the signal synchronised with the reference frequency, which may vary with mechanical load as the actuator's impedance or current characteristics shift. The magnitude of the quadrature component represents the 90-degree out-of-phase portion, which may change as mechanical loading alters phase relationships within the actuator's electrical response. The phase calculated using both components (arctangent of quadrature / in-phase ratio) may be sensitive to mechanical loading in resonant conditions, where mechanical constraints produce measurable phase shifts. The amplitude calculated from both components (square root of sum of squares) represents the overall electrical response magnitude at the interrogation frequency.

[0225] Determining a Load Profile of the Actuator 124

[0226] Figure 6 shows a method 600, according to some embodiments of the present disclosure. The method 600 may be referred to as a method for determining a load profile of an actuator. The method 600 may be referred to as a method for controlling a device, based on a load profile. For the purposes of this disclosure, the actuator 124 will be referred to. However, it will be appreciated that the method 600 may be applicable to any suitable actuator.

[0227] Generate an Actuator Driving Waveform

[0228] At 602, an actuator driving waveform is generated. The signal processing system 139A, 139B generates the actuator driving waveform. In particular, the signal generator 131 generates the actuator driving waveform. That is, the output of the signal generator 131 may be considered the actuator driving waveform. The actuator driving waveform is amplified by the signal amplifier 132. Subsequent to this amplification, the amplified actuator driving waveform is applied to the actuator 124. It will be appreciated that applying the actuator driving waveform to the actuator 124 comprises applying the amplified actuator driving waveform to the actuator 124. That is, for the purposes of this disclosure, applying the actuator driving waveform to the actuator 124 is intended to comprise applying the amplified actuator driving waveform to the actuator 124, and is not intended to specifically require an unamplified actuator driving waveform to be applied to the actuator 124.

[0229] The at least one processor 121 of the computing system 103 controls one or more components of the signal processing system 139A, 139B. For example, the at least one processor 121 may control the signal generator 131. The at least one processor 121 of the computing system 103 may instruct the signal generator 131 to generate an output waveform. As described above, this may be considered the actuator driving waveform, which is amplified by the signal amplifier 132 to be applied to the actuator 124.

[0230] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be referred to simply as a driving waveform. The signal processing system 139A, 139B generates the primary driving waveform. In some embodiments, the signal generator 131 generates the primary driving waveform. The primary driving waveform is configured to drive the actuator 124 to perform the mechanical actuation required for QME. The primary driving waveform provides the fundamental excitation signal that causes the actuator 124 to apply controlled forces to the material 105 through the sensing layer 104, enabling the measurement of tissue deformation and mechanical properties using QME imaging.

[0231] The primary driving waveform is parameterised by a number of primary driving waveform parameters. That is, the primary driving waveform is defined and controlled by a set of numerical values (waveform parameters) that specify its characteristics such as frequency, amplitude, and shape.

[0232] The primary driving waveform is characterised by a primary driving waveform shape. The primary driving waveform shape may be referred to as a driving waveform shape. The primary driving waveform parameters comprise a primary driving waveform shape parameter that indicates a waveform shape of the primary driving waveform. The primary driving waveform shape parameter may be referred to as a driving waveform shape parameter. The primary driving waveform shape is the shape of the primary driving waveform. The primary driving waveform may take one of a number of waveform shapes. For example, the primary driving waveform may be a sine, triangle, square or sawtooth wave. The particular waveform shape of the primary driving waveform is controlled using the primary driving waveform shape parameter. For example, each different waveform shape may be associated with a different value of the primary driving waveform shape parameter.

[0233] The primary driving waveform is characterised by a primary driving waveform frequency. The primary driving waveform parameters comprise a primary driving waveform frequency parameter. The value of the primary driving waveform frequency parameter sets the frequency of the primary driving waveform. The primary driving waveform frequency parameter may be referred to as a driving waveform frequency parameter.

[0234] The primary driving waveform is characterised by a primary driving waveform amplitude. The primary driving waveform parameters comprise a primary driving waveform amplitude parameter. The value of the primary driving waveform amplitude parameter sets the amplitude of the primary driving waveform. The primary driving waveform amplitude parameter may be referred to as a driving waveform amplitude parameter.

[0235] The at least one processor 121 of the computing system 103 may control the values of the primary driving waveform parameters to control the features of the primary driving waveform generated by the signal processing system 139 A, 139B. That is, the at least one processor 121 of the computing system 103 may control the values of the primary driving waveform parameters to control the features of the primary driving waveform. The values of the primary driving waveform parameters may be stored in the memory 123 of the computing system 103. Alternatively, the values of the primary driving waveform parameters may be stored in memory of the signal generator 131.

[0236] In some embodiments, the primary driving waveform may be parameterised by a plurality of primary driving waveform frequencies, primary driving waveform amplitudes and / or primary driving waveform shapes. That is, the primary driving waveform may be a sum of a plurality of waveforms, each parameterised by a respective waveform frequency, amplitude and shape.

[0237] In some embodiments, the primary driving waveform may be a sinusoidal waveform. The primary driving waveform may be a sine wave having a driving waveform frequency, a driving waveform amplitude, and a sinusoidal waveform shape. The driving waveform amplitude may be referred to as an amplitude of the primary driving waveform. The driving waveform frequency may be referred to as a frequency of the primary driving waveform. The driving waveform frequency may be between 10Hz and 200Hz. The driving waveform frequency may be between 10Hz and 100Hz, 10Hz and 50Hz, 20Hz and 200Hz, 20Hz and 100Hz, 30Hz and 200Hz, 30Hz and 100Hz, 50Hz and 200Hz, 50Hz and 100Hz or 100Hz and 200Hz. The driving waveform frequency may be 10Hz, 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz, 110Hz, 120Hz, 130Hz, 140Hz, 150Hz, 160Hz, 170Hz, 180Hz, 190Hz or 200Hz. The driving waveform frequency may be less than 10Hz. The driving waveform frequency may be greater than 200Hz. The amplitude of the primary driving waveform may be between OVpp and lOVpp. The amplitude of the primary driving waveform may be between OVpp and 5Vpp, OVpp and 2.5Vpp, IVpp and lOVpp, IVpp and 5Vpp, 1.5Vpp and lOVpp, 1.5Vpp and 5Vpp, 2.5Vpp and lOVpp, 2.5Vpp and 5Vpp or 5Vpp and lOVpp. The amplitude of the primary driving waveform may be 0.5Vpp, IVpp, 1.5Vpp, 2Vpp, 2.5Vpp, 3Vpp, 3.5Vpp, 4Vpp, 4.5Vpp, 5Vpp, 5.5Vpp, 6Vpp, 6.5Vpp, 7Vpp, 7.5Vpp, 8Vpp, 8.5Vpp, 9Vpp, 9.5Vpp or lOVpp. The amplitude of the primary driving waveform may be less than 0.5Vpp. The amplitude of the primary driving waveform may be greater than lOVpp.

[0238] Actuation of the actuator 124 causes movement of a tip of the device 101. The tip of the device may comprise at least part of the sensing layer 104. Actuation of the actuator 124, may cause movement of the sensing layer 104. Actuation of the actuator 124 may cause movement of the mechanical interface 119. The extent of this movement is dependent on the amplitude of the primary driving waveform. The physical displacement amplitude of the device 101 components is related to the voltage amplitude of the primary driving waveform through the electromechanical characteristics of the actuator 124, with higher voltage amplitudes generally producing correspondingly larger mechanical displacements. Driving the actuator 124 with the actuator driving waveform therefore cause movement of at least part of the device 101. The movement of the device 101, or a part thereof, as a result of driving the actuator 124 using the actuator driving waveform may have an amplitude of between 10pm and 200pm. The amplitude of the movement may be between 10pm and 100pm, 10pm and 50pm, 20pm and 200pm, 20pm and 100pm, 30pm and 200pm, 30pm and 100pm, 50pm and 200pm, 50pm and 100pm or 100pm and 200pm. The amplitude of the movement may be 10pm, 20pm, 30pm, 40pm, 50pm, 60pm, 70pm, 80pm, 90pm, 100pm, 110pm, 120pm, 130pm, 140pm, 150pm, 160pm, 170pm, 180pm, 190pm or 200pm. The amplitude of the movement may be less than 10 pm. The amplitude of the movement may be greater than 200pm.

[0239] The actuator driving waveform is a waveform with a component part that has been modified with an interrogation signal. In particular, the actuator driving waveform is a waveform that is formed by modifying the primary driving waveform with the interrogation signal. That is, the actuator driving waveform is created by combining or altering a basic waveform with an additional interrogation signal to produce a composite waveform that contains components from both signals. The basic waveform is the primary driving waveform.

[0240] The signal processing system 139A, 139B modifies the primary driving waveform with the interrogation signal, thereby generating the actuator driving waveform. In particular, the signal generator 131 modifies the primary driving waveform with the interrogation signal, thereby generating the actuator driving waveform.

[0241] The primary driving waveform is modified with the interrogation signal by summing the primary driving waveform and the interrogation signal. In other words, the system 100 sums the primary driving waveform and the interrogation signal, thereby generating the actuator driving waveform. In particular, the signal generator 131 sums the primary driving waveform and the interrogation signal, thereby generating the actuator driving waveform. In some embodiments, the signal generator 131 performs the summation operation by adding the instantaneous values of the primary driving waveform and the interrogation signal at each point in time, creating a composite waveform that contains the characteristics of both input signals. The summation process may be implemented using analogue circuitry or through digital signal processing techniques where the discrete samples of each waveform are mathematically added together. When the primary driving waveform and the interrogation signal are summed, the resulting actuator driving waveform exhibits a time-varying amplitude that reflects the combined influence of both signals. The frequency content of the actuator driving waveform includes spectral components at the frequency of the primary driving waveform and at the frequency of the interrogation signal, enabling simultaneous excitation of the actuator 124 at both frequencies. The at least one processor 121 may control the timing and synchronisation of the summation process to ensure proper phase relationships between the primary driving waveform and the interrogation signal.

[0242] The interrogation signal is a waveform. The interrogation signal is parameterised by a number of interrogation waveform parameters. The interrogation signal is characterised by an interrogation waveform shape. That is, the interrogation waveform parameters comprise an interrogation waveform shape parameter that indicates a waveform shape of the interrogation signal. The interrogation waveform shape is the shape of the interrogation signal. The interrogation signal may take one of a number of waveform shapes. For example, the interrogation signal may be a sine, triangle, square or sawtooth wave. The particular waveform shape of the interrogation signal is controlled using the interrogation waveform shape parameter. For example, each different waveform shape may be associated with a different value of the interrogation waveform shape parameter.

[0243] The interrogation signal is characterised by an interrogation waveform frequency. The interrogation waveform parameters comprise an interrogation waveform frequency parameter. The value of the interrogation waveform frequency parameter sets the frequency of the interrogation signal. The interrogation waveform frequency parameter is tuned to a resonant frequency of at least part of the device 101. That is, the frequency of the interrogation signal is related to a resonant frequency of at least part of the device 101. The frequency of the interrogation signal may be related to a resonant frequency of the device 101. The frequency of the interrogation signal may be related to a resonant frequency of a subsystem of the device 101. The frequency of the interrogation signal may be related to a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be related to a resonant frequency of an actuator assembly comprising the actuator 124. The frequency of the interrogation signal may be related to a resonant frequency of the actuator 124. Being related to a resonant frequency of a structural component or combination thereof may involve being within a certain bounded range of that resonant frequency (e.g. within 5%, 10%, 15%, 20%, 25% or 30%). As a result of the frequency of the interrogation signal being associated with a resonant frequency of the device 101, or a subsystem thereof, application of the actuator driving waveform to the actuator 124 excites the relevant resonant mode of the device 101 or the subsystem thereof (such as the mechanical system 109), enabling functionality described herein.

[0244] The interrogation signal is characterised by an interrogation waveform amplitude. The interrogation waveform parameters comprise an interrogation waveform amplitude parameter. The value of the interrogation waveform amplitude parameter sets the amplitude of the interrogation signal.

[0245] The at least one processor 121 of the computing system 103 may control the values of the interrogation waveform parameters to control the features of the interrogation signal. The values of the interrogation waveform parameters may be stored in the memory 123 of the computing system 103. Alternatively, the values of the interrogation waveform parameters may be stored in memory of the signal generator 131.

[0246] In some embodiments, the interrogation signal may be parameterised by a plurality of interrogation waveform frequencies, interrogation waveform amplitudes and / or interrogation waveform shapes. That is, the interrogation signal may be a sum of a plurality of waveforms, each parameterised by a respective waveform frequency, amplitude and shape.

[0247] The amplitude of the interrogation signal is small compared to the amplitude of the primary driving waveform. The amplitude of the interrogation signal may be related to the amplitude of the primary driving waveform. For example, the amplitude of the interrogation signal may be proportional to the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 1% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 2% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is less than 2% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 0.5%, 3%, 4% or 5% of the amplitude of the primary driving waveform. The amplitude of the interrogation signal may be less than 10% of the amplitude of the primary driving waveform.

[0248] The shape of the interrogation signal of 602 is sinusoidal. The interrogation signal may be a 100 mVpp sine wave. The interrogation signal may be a 50 mVpp sine wave. The interrogation signal may be a 75 mVpp sine wave. The interrogation signal may be a 150 mVpp sine wave. The interrogation signal may be a 200 mVpp sine wave. The interrogation signal may be a 250 mVpp sine wave. The interrogation signal may be a 300 mVpp sine wave. The interrogation signal may be between 50 mVpp and 300 mVpp. The interrogation signal may be between 75 mVpp and 200 mVpp. The interrogation signal may be between 100 mVpp and 250 mVpp. The interrogation signal may have an amplitude in the range of 10 mVpp to 500 mVpp. It will be appreciated that in other embodiments, the shape and / or amplitude of the interrogation signal may be different.

[0249] The interrogation waveform frequency is associated with the mechanical system 109. In other words, the frequency of the interrogation signal is associated with the mechanical system 109. The frequency of the interrogation signal may be related to the resonant frequency of the mechanical system 109. In some embodiments, the frequency of the interrogation signal is proportional to the resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 20% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 15% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 10% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 25% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 30% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be substantially equal to a resonant frequency of the mechanical system 109. The resonant frequency of the mechanical system 109 may be a resonant frequency of the actuator 124. The resonant frequency may be a resonant frequency of the piezoelectric actuator element within the actuator 124. The resonant frequency may be determined by, or influenced by, the physical dimensions, material properties, and mounting configuration of the actuator 124.

[0250] In the illustrated embodiment, the frequency of the interrogation signal (i.e. the interrogation waveform frequency) is between about 80kHz and about 100kHz. In some embodiments, the frequency of the interrogation signal is about 89550 Hz. In some embodiments, the frequency of the interrogation signal is about 89450 Hz. In some embodiments, the frequency of the interrogation signal is about 85000 Hz. In some embodiments, the frequency of the interrogation signal is about 90000 Hz. In some embodiments, the frequency of the interrogation signal is about 95000 Hz. In some embodiments, the frequency of the interrogation signal is about 82000 Hz. In some embodiments, the frequency of the interrogation signal is about 87500 Hz. In some embodiments, the frequency of the interrogation signal is about 92500 Hz. In some embodiments, the frequency of the interrogation signal is about 97500 Hz. In some embodiments, the frequency of the interrogation signal is between 85kHz and 95kHz. In some embodiments, the frequency of the interrogation signal is between 88kHz and 92kHz. In some embodiments, the frequency of the interrogation signal is between 89kHz and 90kHz. The frequency of the interrogation signal may be selected based on the specific resonant characteristics of the mechanical system 109 and the actuator 124 configuration. These values can be within 20% of the resonant frequency of the mechanical system 109. These values can be within 20% of a resonant frequency of another subsystem of the device 101. These values can be within 10% of a resonant frequency of the mechanical system 109. These values can be within 10% of a resonant frequency of another subsystem of the device 101. These values can be within 5% of a resonant frequency of the mechanical system 109. These values can be within 5% of a resonant frequency of another subsystem of the device 101. These values can be within 30% of a resonant frequency of the mechanical system 109. These values can be within 30% of a resonant frequency of another subsystem of the device 101.

[0251] It will be appreciated that different mechanical systems that, for example, comprise different actuators, will have different resonant frequencies. Further, mounting the actuator 124 to other components of the device 101 in different ways will change the resonant frequency or frequencies of the mechanical system 109. These changes may also change how the resonant frequencies, or the resonance of the mechanical system 109 responds to applied mechanical loads. The frequency of the interrogation signal of the method 600 may therefore change depending on the particular actuator and / or mechanical system design that is being used.

[0252] While step 602 has been described in the context of modifying a primary driving waveform with an interrogation signal, 602 may also be described as modulating a driving waveform with a modulating signal. That is, 602 may be said to comprise generating a modulated driving waveform. The system 100 may generate the modulated driving waveform by modulating a driving waveform with a modulating signal. The term “modulating” in this context can refer to the process of combining two waveforms, where the signal generator 131 sums the driving waveform and the modulating signal in the time domain to create a composite waveform. This additive combination process is functionally equivalent to the modification described above. When described using modulation terminology, the actuator driving waveform may be referred to as a modulated driving waveform. The modulated driving waveform terminology emphasises that the original driving waveform has been altered by the addition of the modulating signal, resulting in a composite signal that exhibits characteristics of both component waveforms. The signal amplifier 132 receives this modulated driving waveform from the signal generator 131 and amplifies it before application to the actuator 124. The “interrogation signal” terminology may be replaced with “modulating signal” throughout the disclosure without departing from the scope of the disclosure, as both terms can refer to the same secondary waveform that is combined with the primary driving waveform by the signal generator 131. Similarly, the “modifying” process and the “modulating” process both describe the same technical operation performed by the signal processing system 139A, 139B to generate the composite waveform. The lock-in amplifier 140 filters the electrical response at the frequency of this secondary signal, whether it is termed the interrogation signal frequency or the modulating signal frequency. The at least one processor 121 controls this waveform combination process and the subsequent signal processing operations regardless of whether the terminology characterises the process as modification with an interrogation signal or modulation with a modulating signal. While method 600 can involve the use of the term “modulation” in the context of waveform addition, it will be appreciated that other methods of modulation could be employed to achieve similar outcomes as are described for the method 600. As described in more detail in the Alternative Embodiments section, amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM) techniques may also be suitable for creating actuator driving waveforms that enable mechanical load detection. Each of these alternative modulation approaches may require different signal generation hardware and processing techniques, but may still provide the described capability of correlating electrical characteristics with mechanical loads applied to the actuator 124.

[0253] Apply the Actuator Driving Waveform to the Actuator

[0254] At 604, the actuator driving waveform is applied to the actuator 124. The system 100 applies the actuator driving waveform to the actuator 124. In particular, the signal generator 131 may be said to apply the actuator driving waveform to the actuator 124. As described herein, the signal generator 131 provides output waveforms to the signal amplifier 132 for amplification. Applying the actuator driving waveform to the actuator 124 may comprise providing the actuator driving waveform to the signal amplifier 132 for amplification. The signal amplifier 132 amplifies the actuator driving waveform and applies the amplified driving waveform to the actuator 124. In other words, the amplified driving waveform that is generated by the signal amplifier 132 is applied to the actuator 124. Applying the actuator driving waveform to the actuator 124 may alternatively be expressed as driving the actuator 124 with the actuator driving waveform.

[0255] Application of the actuator driving waveform to the actuator 124 causes the actuator 124 to move in accordance with the primary driving waveform component, thereby moving the tip of the device 101 for use in applications such as QME imaging of the material 105. When being used, for example, in a QME system for imaging, the primary driving waveform provides the fundamental mechanical actuation that enables the device 101 to perform its intended function, such as applying controlled forces to the material 105 through the sensing layer 104 to generate tissue deformation for optical measurement.

[0256] Simultaneously, the interrogation signal component of the actuator driving waveform excites resonant modes of a sub-assembly of the device 101, such as the mechanical system 109 or components thereof, at frequencies that are typically much higher than the primary driving waveform frequency. This dual-function operation allows the system 100 to maintain normal device functionality while concurrently enabling the load estimation capabilities described herein in the method 700, as the excited resonant modes respond to mechanical loading conditions and produce detectable changes in the electrical characteristics of the actuator 124 that can be processed by the signal processing system 139A, 139B.

[0257] The step of applying the actuator driving waveform to the actuator 124 at 604 may be expressed using the alternative terminology for the actuator driving waveform that is detailed herein. For example, 604 may be described as applying the modulated driving waveform to the actuator 124. That is, 604 may altematively be described as any one of applying a modulated driving waveform generated at 602 to the actuator 124, applying a composite driving waveform generated at 602 to the actuator 124, applying a combined waveform generated at 602 to the actuator 124, applying a summed waveform generated at 602 to the actuator 124, and applying an additive waveform generated at 602 to the actuator 124. Similarly, the signal generator 131 may be described as applying any one of a modulated driving waveform, composite driving waveform, combined waveform, summed waveform, and additive waveform to the actuator 124 at 604. The signal amplifier 132 may amplify and apply the amplified modulated driving waveform, composite driving waveform, amplified combined waveform, amplified summed waveform, or amplified additive waveform to the actuator 124. The system 100 may be described as applying any of these alternative waveform designations to achieve the same technical result of simultaneous excitation at multiple frequencies for mechanical load detection purposes, with references to the actuator driving waveform being substitutable for any of the alternative terminologies mentioned herein without departing from the scope of the disclosure. Further, similar terminology may be used if 604 is expressed as driving the amplifier 124 with the actuator driving waveform.

[0258] Determine a First Value of a Component of an Electrical Characteristic Associated with the Actuator At 606, a first value of a component of an electrical characteristic associated with the actuator 124 is determined. The system 100 determines the first value of the component of the electrical characteristic associated with the actuator 124. In particular, the first value of the component of the electrical characteristic associated with the actuator 124 is determined for a time period during which a first known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. That is, at 606, the system 100 determines the first value of the component of the electrical characteristic associated with the actuator 124 while the first known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. The first known mechanical load is applied to the actuator 124 contemporaneously with the measurement of the electrical characteristic associated with the actuator 124. 606 may comprise applying the first known mechanical load to the actuator 124. The first value of the component of the electrical characteristic is related to the mechanical load on the actuator 124. That is, the value of the component of the electrical characteristic changes as the mechanical load on the actuator 124 changes, so the first value of the component of the electrical characteristic is related to the first mechanical load. The method 600 involves the use of this behaviour to determine a load profile of the actuator 124.

[0259] Determining the first value of the component of the electrical characteristic associated with the actuator 124 comprises filtering an electrical parameter signal that is associated with the actuator 124 while the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is applied to the actuator 124. The electrical parameter signal is a voltage signal that changes with actuation of the actuator 124 under mechanical load (either from a strain gauge 136 connected to the actuator 124 or from a current-to-voltage converter circuit 141 measuring current through the actuator 124), which is then filtered by a lock-in amplifier 141 at the interrogation signal frequency to produce an output voltage, this output voltage being the electrical characteristic. In particular, determining the first value of the component of the electrical characteristic associated with the actuator 124 comprises filtering an electrical parameter signal that is associated with the actuator 124 while both the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is applied to the actuator 124.

[0260] Determining a First Value of a Component of an Electrical Characteristic Associated with an Actuator 124 Connected to a Strain Gauge 136

[0261] The method 600 may be used for a system 100 that includes the signal processing system 139B of Figure 3. As described with reference to Figure 3, in some embodiments of the disclosed system 100, one or more strain gauge 136 is connected to the actuator 124. Step 606 of the method 600 will be described here for the case where one strain gauge 136 is connected to the actuator 124. However, it will be appreciated that similar implementations may be used where multiple strain gauges 136 are connected to the actuator 124.

[0262] The strain gauge 136 is connected to the actuator 124. In the illustrated embodiment, the strain gauge 136 is adhered to the actuator 124. As a result, changes in shape of the actuator 124, or a part thereof, when the actuator 124 is actuated, will cause corresponding changes in shape of the strain gauge 136. Also as described herein, a voltage across output terminals of the strain gauge 136 can be measured. The strain gauge 136 may therefore be said to provide a voltage signal that can be measured by other components. This voltage signal is the electrical parameter signal of this embodiment of the method 600. This voltage signal is filtered, with the electrical characteristic associated with the actuator 124 during use being the filtered signal.

[0263] The lock-in amplifier 140 is electrically connected to the strain gauge 136 via the strain gauge amplifier 138. The voltage across the output terminals of the strain gauge 136, after being amplified by the strain gauge amplifier 138, is an input of the lock-in amplifier 140. The lock-in amplifier 140 filters the voltage signal from the strain gauge 136 and strain gauge amplifier 138, thereby generating a filtered output. In particular, the lock-in amplifier 140 filters the voltage signal at the frequency of the interrogation signal. In this case, a reference signal of the lock-in amplifier 140 is a signal with a frequency that is the same as the interrogation signal. In other words, the reference frequency of the lock- in amplifier 140 when the lock-in amplifier 140 filters the voltage signal from the strain gauge 136 and strain gauge amplifier 138 is the frequency of the interrogation signal. The filtered output voltage signal of the lock-in amplifier 140 is the electrical characteristic for which values of a component thereof are determined.

[0264] The filtered output of the lock-in amplifier 140 comprises an in-phase output voltage. The in-phase output voltage is associated with the real part of the voltage signal of the strain gauge 136. That is, the in-phase output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is in phase with the reference signal. A magnitude of the in-phase output voltage of the lock-in amplifier 140 corresponds to a magnitude of the real part of the voltage signal that was the input of the lock-in amplifier 140 at the reference frequency. In some embodiments, the in-phase output voltage of the lock-in amplifier 140 is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0265] The filtered output of the lock-in amplifier 140 comprises a quadrature output voltage. The quadrature output voltage is associated with the imaginary part of the voltage signal of the strain gauge 136. That is, the quadrature output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is 90 degrees out of phase with the reference signal. A magnitude of the quadrature output voltage corresponds to a magnitude of the imaginary part of the voltage signal that was input to the lock-in amplifier 140 at the reference frequency. In some embodiments, the quadrature output voltage is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0266] In some embodiments, the value of the electrical characteristic is derived from one or both of the in-phase output voltage and the quadrature output voltage. For example, the phase calculated using both components (arctangent of quadrature / in-phase ratio) may be considered the component of the electrical characteristic for which a value is determined. Alternatively, the amplitude calculated from both components (square root of sum of squares) may be considered the component of the electrical characteristic for which a value is determined.

[0267] At 606, the system 100 determines the first value of the component of the electrical characteristic that is associated with the actuator 124 while the first known mechanical load is applied to the actuator 124 and the actuator drive waveform is applied to the actuator 124. Determining the first value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the strain gauge 136 while both the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock-in amplifier 140. The at least one processor 121 determines the first value of the component of the electrical characteristic based on the output voltage signal from the lock-in amplifier 140.

[0268] In some embodiments, the first value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140.

[0269] Determining the value of the electrical characteristic at 606 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 606 may comprise calculating a phase of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the value of the electrical characteristic, in some embodiments.

[0270] Determining the value of the electrical characteristic at 606 may comprise calculating an amplitude of the electrical characteristic, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 606 may comprise calculating an amplitude of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the amplitude of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the amplitude of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This amplitude is the value of the electrical characteristic, in some embodiments.

[0271] Therefore, the at least one processor 121 of the computing system 103 determines the first value of the component of the electrical characteristic at 606, using the filtered output of the lock-in amplifier 140.

[0272] The first value of the component of the electrical characteristic that is associated with the actuator 124 that is determined at 606 may be said to be associated with the first known mechanical load. This is because the application of the first known mechanical load on the actuator 124 resulted in the relevant value of the component of the electrical characteristic being determined, as the value of the component of the electrical characteristic changes with a change in applied mechanical load on the actuator 124. The first known mechanical load and the first value of the component of the electrical characteristic associated with the actuator 124 that is calculated at 606 may be stored in memory 123.

[0273] Determining the value of the component of the electrical characteristic associated with the actuator 124 at 606 (or 608) may be expressed using the alternative terminology for the actuator driving waveform that is detailed herein. 606 may alternatively be described as any one of determining the value of the component of the electrical characteristic while both the first known mechanical load is applied to the actuator and the actuator driving waveform generated at 602 is applied to the actuator 124, the composite driving waveform generated at 602 is applied to the actuator 124, the combined waveform generated at 602 is applied to the actuator 124, the summed waveform generated at 602 is applied to the actuator 124, or the additive waveform generated at 602 is applied to the actuator 124. The system 100 may be described as determining electrical characteristics under any of these alternative waveform designations without departing from the scope of the disclosure.

[0274] The value of the component of the electrical characteristic associated with the actuator 124 that is determined at 606 relates to the conditions present during the simultaneous application of the first known mechanical load and the actuator driving waveform to the actuator 124. While the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the value of the component of the electrical characteristic may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the first known mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the first value of the component of the electrical characteristic may be performed at a later time using the recorded measurements.

[0275] Determining a Second Value of the Component of the Electrical Characteristic Associated with the Actuator 124 Connected to a Strain Gauge 136

[0276] At 608, a second value of the component of the electrical characteristic associated with the actuator 124 is determined. The system 100 determines the second value of the component of the electrical characteristic that is associated with the actuator 124. In particular, the second value of the component of the electrical characteristic associated with the actuator 124 is determined for a time period during which a second known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. That is, at 608, the system 100 determines the second value of the component of the electrical characteristic that is associated with the actuator 124 while the second known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. The second known mechanical load is applied to the actuator 124 contemporaneously with the measurement of the electrical characteristic associated with the actuator 124. 608 may comprise applying the second known mechanical load to the actuator 124. The second known mechanical load is different to the first known mechanical load. As described at 606 with respect to the first value of the component of the electrical characteristic, the second value of the component of the electrical characteristic is related to the mechanical load on the actuator 124. That is, the value of the component of the electrical characteristic changes as the mechanical load on the actuator 124 changes, so the second value of the component of the electrical characteristic is related to the second mechanical load. The method 600 involves the use of this behaviour to determine a load profile of the actuator 124. At 608, the system 100 determines the second value of the component of the electrical characteristic that is associated with the actuator 124 while the second known mechanical load is applied to the actuator 124. Determining the second value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the strain gauge 136 while both the actuator driving waveform is applied to the actuator 124 and the second known mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock-in amplifier 140. The at least one processor 121 determines the second value of the component of the electrical characteristic based on the output voltage signal from the lock-in amplifier 140.

[0277] In some embodiments, the second value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140.

[0278] Determining the second value of the electrical characteristic at 608 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the second value of the electrical characteristic at 606 may comprise calculating a phase of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the fdtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the second value of the electrical characteristic, in some embodiments.

[0279] Alternatively, determining the second value of the component of the electrical characteristic may comprise determining an amplitude of the electrical characteristic, at the frequency of the interrogation signal, using the filtered output from the lock-in amplifier 140. The electrical characteristic is the output of the lock-in amplifier 140. In some embodiments, the amplitude of the electrical characteristic is the component of the electrical characteristic, and the magnitude or value of this amplitude under the second known mechanical load is the second value of the component. The system 100 may calculate the amplitude of the electrical characteristic using the in-phase output voltage and the quadrature output voltage from the lock-in amplifier 140. This amplitude is the second value of the component of the electrical characteristic, in some embodiments.

[0280] Therefore, the at least one processor 121 of the computing system 103 determines the second value of the component of the electrical characteristic at 608, using the filtered output of the lock in amplifier 140.

[0281] The second value of the component of the electrical characteristic associated with the actuator 124 that is determined at 608 may be said to be associated with the second known mechanical load. This is because the application of the second known mechanical load on the actuator 124 when the actuator driving waveform was being applied to the actuator resulted in the relevant value of the component of the electrical characteristic being determined. The second known mechanical load and the second value of the component of the electrical characteristic associated with the actuator 124 that is calculated at 606 may be stored in memory 123.

[0282] The second value of the component of the electrical characteristic associated with the actuator 124 that is determined at 608 relates to the conditions present during the simultaneous application of the second known mechanical load and the actuator driving waveform to the actuator 124. While second value of the component of the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the value of the component of the electrical characteristic component may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the second known mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the value of the component of the electrical characteristic may be performed at a later time using the recorded measurements.

[0283] The determination of different values of the component of the electrical characteristic that is associated with the actuator 124 while known mechanical loads are applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124 may be repeated for any number of known mechanical loads. For each additional known mechanical load, the strain gauge 136 experiences corresponding mechanical deformation as the actuator 124 responds to the applied mechanical load. The strain gauge amplifier 138 amplifies the resulting voltage signal from the strain gauge 136, and the lock-in amplifier 140 performs frequency -selective filtering at the interrogation signal frequency to generate in-phase and quadrature output voltages. The at least one processor 121 reads these filtered outputs from the lock-in amplifier 140 to determine the value of the component of the electrical characteristic for each loading condition. The relevant known mechanical load and the corresponding value of the component of the electrical characteristic associated with the actuator 124 that is determined at 606, 608 or an equivalent iteration of those steps in response to another mechanical known load may be stored as a data set in memory 123. The computing system 103 may accumulate multiple such data sets in memory 123, with each data set comprising a known mechanical load value and its corresponding electrical characteristic component value (e.g. in-phase output voltage, the quadrature output voltage, phase, amplitude), thereby building a comprehensive dataset for subsequent load profile determination.

[0284] Determining a First Value of a Component of an Electrical Characteristic Associated with an Actuator 124

[0285] The method 600 may be used for a system 100 that includes the signal processing system 139A of Figure 2. In some embodiments, the electrical characteristic associated with the actuator 124 while the actuator driving waveform is applied to the actuator 124 may be an electrical characteristic of the actuator 124 itself, or derived from such a characteristic without the need for additional hardware to be connected to the actuator 124.

[0286] As described with reference to Figure 2, in some embodiments of the disclosed system 100, a sensor 141 is operably connected to the actuator 124. The sensor 141 in the illustrated embodiment is a current sensor 141 that is configured to sense a current through the actuator 124, in use. The sensor 141 provides an output signal in response to the sensed current through the actuator 124. The output may be a voltage output. The output may be a current output. The output may, for example, be associated with an impedance of the sensor 141. In the present embodiment, the sensor 141 is in the form of a current-to- voltage converter circuit (CVCC) 141. That is, the system 100 of the illustrated embodiment comprises a current-to-voltage converter circuit (CVCC) 141 that is operably connected to the actuator 124. The CVCC 141 may alternatively be referred to herein as a current measurement circuit. The CVCC 141 may be electrically connected to the actuator 124. In the illustrated embodiment, the CVCC 141 is electrically connected to the input side of the actuator 124.

[0287] The CVCC 141 monitors the current through the actuator 124. In particular, the CVCC 141 monitors the current through the actuator 124 when the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is applied to the actuator 124, and generates a voltage signal in response to this current signal. This voltage signal is the output of the CVCC 141.

[0288] The lock-in amplifier 140 is electrically connected to the CVCC 141 and the voltage signal generated by the CVCC 141 is the input of the lock-in amplifier 140. The lock-in amplifier 140 filters the voltage signal, thereby generating a filtered output. In particular, the lock-in amplifier 140 filters the voltage signal at the frequency of the interrogation signal. In this case, a reference signal of the lock-in amplifier 140 is a signal with a frequency that is the same as the interrogation signal. In other words, the reference frequency of the lock-in amplifier 140 when the lock-in amplifier 140 filters the voltage signal from the CVCC 141 is the frequency of the interrogation signal. The interrogation signal may be the reference signal of the lock-in amplifier 140. The filtered output voltage signal of the lock-in amplifier 140 is the electrical characteristic for which values of a component thereof are determined.

[0289] The filtered output of the lock-in amplifier 140 comprises an in-phase output voltage. The in-phase output voltage is associated with the real part of the voltage signal of the CVCC 141. That is, the in-phase output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is in phase with the reference signal. A magnitude of the in-phase output voltage of the lock-in amplifier 140 corresponds to a magnitude of the real part of the voltage signal that was the input of the lock-in amplifier 140, at the reference frequency. In some embodiments, the in-phase output voltage of the lock-in amplifier 140 is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0290] The filtered output of the lock-in amplifier 140 comprises a quadrature output voltage. The quadrature output voltage is associated with the imaginary part of the voltage signal of the CVCC 141. That is, the quadrature output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is 90 degrees out of phase with the reference signal. A magnitude of the quadrature output voltage corresponds to a magnitude of the imaginary part of the voltage signal that was input to the lock-in amplifier 140 at the reference frequency. In some embodiments, the quadrature output voltage is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0291] In some embodiments, the value of the electrical characteristic is derived from one or both of the in-phase output voltage and the quadrature output voltage. For example, the phase calculated using both components (arctangent of quadrature / in-phase ratio) may be considered the component of the electrical characteristic for which a value is determined. Alternatively, the amplitude calculated from both components (square root of sum of squares) may be considered the component of the electrical characteristic for which a value is determined.

[0292] At 606, the system 100 determines a first value of the component of the electrical characteristic that is associated with the actuator 124 while the first known mechanical load is applied to the actuator 124 and the actuator drive waveform is applied to the actuator 124. Determining the first value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the CVCC 141 while both the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock-in amplifier 140. The at least one processor 121 determines the first value of the component of the electrical characteristic based on the output voltage signal from the lock-in amplifier 140.

[0293] In some embodiments, the first value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the first value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. Determining the first value of the electrical characteristic at 606 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the first value of the electrical characteristic at 606 may comprise calculating a phase of the voltage signal associated with the CVCC 141, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the first value of the electrical characteristic, in some embodiments.

[0294] Determining the value of the electrical characteristic at 606 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 606 may comprise calculating a phase of the voltage signal associated with the CVCC 141, at the frequency of the interrogation signal. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the value of the electrical characteristic, in some embodiments.

[0295] Determining the value of the electrical characteristic at 606 may comprise calculating an amplitude of the electrical characteristic, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 606 may comprise calculating an amplitude of the voltage signal associated with the CVCC 141, at the frequency of the interrogation signal. The system 100 calculates the amplitude of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the amplitude of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This amplitude is the value of the electrical characteristic, in some embodiments.

[0296] Therefore, the at least one processor 121 of the computing system 103 determines the first value of the component of the component of the electrical characteristic at 606, using the filtered output of the lock-in amplifier 140.

[0297] The first value of the component of the component of the electrical characteristic that is associated with the actuator 124 that is determined at 606 may be said to be associated with the first known mechanical load. This is because the application of the first known mechanical load on the actuator 124 resulted in the relevant value of the component of the electrical characteristic being determined, as the value of the component of the electrical characteristic changes with a change in applied mechanical load on the actuator 124. The first known mechanical load and the first value of the component of the component of the electrical characteristic associated with the actuator 124 that is calculated at 606 may be stored in memory 123.

[0298] Determining the first value of the component of the electrical characteristic associated with the actuator 124 at 606 may be expressed using the alternative terminology for the actuator driving waveform that is detailed herein. 606 may alternatively be described as any one of determining the first value of a component of the electrical characteristic while both the first known mechanical load and an actuator driving waveform generated at 602 is applied to the actuator 124, a composite driving waveform generated at 602 is applied to the actuator 124, a combined waveform generated at 602 is applied to the actuator 124, a summed waveform generated at 602 is applied to the actuator 124, or an additive waveform generated at 602 is applied to the actuator 124. The system 100 may be described as determining electrical characteristics under any of these alternative waveform designations without departing from the scope of the disclosure.

[0299] The first value of the component of the electrical characteristic associated with the actuator 124 that is determined at 606 relates to the conditions present during the simultaneous application of the first known mechanical load and the actuator driving waveform to the actuator 124. While the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the first value of the component of the electrical characteristic may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the first known mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the electrical characteristic value may be performed at a later time using the recorded measurements.

[0300] Determining a Second Value of the Component of the Electrical Characteristic Associated with the Actuator 124

[0301] At 608, a second value of a component of the electrical characteristic associated with the actuator 124 is determined. The system 100 determines the second value of the component of the electrical characteristic that is associated with the actuator 124. In particular, the second value of the component of the electrical characteristic associated with the actuator 124 is determined for a time period during which a second known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. That is, at 608, the system 100 determines the second value of the component of the electrical characteristic associated with the actuator 124 while the second known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. The second known mechanical load is applied to the actuator 124 contemporaneously with the measurement of the electrical characteristic associated with the actuator 124. 608 may comprise applying the second known mechanical load to the actuator 124. The second known mechanical load is different to the first known mechanical load. As described at 606 with respect to the first value of the component of the electrical characteristic, the second value of the component of the electrical characteristic is related to the mechanical load on the actuator 124. That is, the value of the component of the electrical characteristic changes as the mechanical load on the actuator 124 changes, so the second value of the component of the electrical characteristic is related to the second mechanical load. The method 600 involves the use of this behaviour to determine a load profile of the actuator 124.

[0302] At 608, the system 100 determines the second value of the component of the electrical characteristic that is associated with the actuator 124 while the second known mechanical load is applied to the actuator 124. Determining the second value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the CVCC 141 while both the actuator driving waveform is applied to the actuator 124 and the second known mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock in amplifier 140. The at least one processor 121 determines the second value of the component of the electrical characteristic based on the output voltage signal from the lock in amplifier 140.

[0303] In some embodiments, the second value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the second value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140.

[0304] Determining the second value of the electrical characteristic may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the second value of the electrical characteristic at 606 may comprise calculating a phase of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the second value of the electrical characteristic, in some embodiments.

[0305] Alternatively, determining the second value of the component of the electrical characteristic may comprise determining an amplitude of the electrical characteristic, at the frequency of the interrogation signal, using the filtered output from the lock-in amplifier 140. The electrical characteristic is the output of the lock-in amplifier 140. In some embodiments, the amplitude of the electrical characteristic is the component of the electrical characteristic, and the magnitude or value of this amplitude under the second known mechanical load is the second value of the component. The system 100 may calculate the amplitude of the electrical characteristic using the in-phase output voltage and the quadrature output voltage from the lock-in amplifier 140. This amplitude is the second value of the component of the electrical characteristic, in some embodiments.

[0306] Therefore, the at least one processor 121 of the computing system 103 determines the second value of the component of the electrical characteristic at 608, using the filtered output of the lock in amplifier 140.

[0307] The second value of the component of the electrical characteristic associated with the actuator 124 that is determined at 608 may be said to be associated with the second known mechanical load. This is because the application of the second known mechanical load on the actuator 124 when the actuator driving waveform was being applied to the actuator resulted in the relevant value of the component of the electrical characteristic being determined. The second known mechanical load and the second value of the component of the electrical characteristic associated with the actuator 124 that is calculated at 608 may be stored in memory 123.

[0308] The second value of the component of the electrical characteristic associated with the actuator 124 that is determined at 608 relates to the conditions present during the simultaneous application of the second known mechanical load and the actuator driving waveform to the actuator 124. While the second value of the component of the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the second value of the component of the electrical characteristic may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the second known mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the value of the component of the electrical characteristic may be performed at a later time using the recorded measurements.

[0309] The determination of different values of the component of the electrical characteristic that are associated with the actuator 124 while known mechanical loads are applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124 may be repeated for any number of known mechanical loads. For each additional known mechanical load, the CVCC 141 responds to the current through the actuator 124 that is influenced by the applied mechanical load. The lock-in amplifier 140 performs frequency -selective filtering at the interrogation signal frequency to generate in-phase and quadrature output voltages. The at least one processor 121 reads these filtered outputs from the lock-in amplifier 140 to determine the value of the component of the electrical characteristic for each loading condition. The relevant known mechanical load and the corresponding value of the component of the electrical characteristic associated with the actuator 124 that is determined at 606, 608 or an equivalent iteration of those steps in response to another known mechanical load may be stored as a data set in memory 123. The computing system 103 may accumulate multiple such data sets in memory 123, with each data set comprising a known mechanical load value and its corresponding electrical characteristic component value (e.g. in-phase output voltage, the quadrature output voltage, phase, amplitude), thereby building a comprehensive dataset for subsequent load profile determination.

[0310] Determine a Load Profile of the Actuator

[0311] At 610, a load profde of the actuator 124 is determined. The system 100 determines the load profile of the actuator 124. The at least one processor 121 may determine the load profile of the actuator 124. The load profile is determined based on the determined values of the component of the electrical characteristic associated with the actuator 124. The load profile relates values of the component of the electrical characteristic determined at 606 and 608 to estimates of the mechanical load on the actuator 124. The load profile of the actuator 124 may be referred to as a mechanical load profde of the actuator 124.

[0312] The load profile is a mathematical model. The mathematical model relates values of the component of the electrical characteristic to the mechanical load applied to the actuator 124, in use, when being driven by the actuator driving waveform. A particular value of the component of the electrical characteristic is an input of the mathematical model. The mathematical model is a linear model. That is, the mathematical model linearly relates values of the component of the electrical characteristic to the mechanical load on the actuator 124. Thus, the load profile of the actuator 124 is a linear load profile relating values of the component of the electrical characteristic associated with the actuator 124 to mechanical loads applied to the actuator 124. It will be appreciated that in some embodiments, the relationship between values of the component of the electrical characteristic and the applied mechanical load may not be linear.

[0313] The values of the component of the electrical characteristic and the associated mechanical loads on the actuator 124 determined at 606, 608 and other iterations of those steps if more known mechanical loads are used may be stored as a dataset in the memory 123 of the computing system 103. The dataset may comprise sets of data elements, where each set of data elements includes a determined value of the component of the electrical characteristic and its corresponding known mechanical load applied to the actuator 124. The dataset may be structured as a table, array, or database format suitable for subsequent processing by the at least one processor 121.

[0314] The at least one processor 121 determines the load profde for the actuator 124 based on the determined values of the component of the electrical characteristic and the associated mechanical loads on the actuator 124. The at least one processor 121 may determine the load profile directly from the first and second known mechanical loads and the corresponding first and second values of the component of the electrical characteristic determined at steps 606 and 608. The at least one processor 121 may calculate the relationship between the two data sets by determining how much the value of the component of the electrical characteristic changes relative to the change in mechanical load. The at least one processor 121 may establish a straight-line mathematical relationship that connects these points, enabling the processor 121 to predict mechanical loads based on electrical characteristic measurements or calculations. The at least one processor 121 may compute the parameters that define this linear relationship and store these parameters in the memory 123. Once established, the at least one processor 121 may use this linear model to estimate unknown mechanical loads by inputting a determined value of the component of the electrical characteristic when the actuator 124 was loaded with the relevant unknown mechanical load and being driven by the actuator driving waveform and calculating the corresponding mechanical load estimate indicated by the model. The linear model approach may be implemented by the at least one processor 121 when the relationship between the values of the component of the electrical characteristic and mechanical loads exhibits substantially linear behaviour over the operating range of the actuator 124. This may be the case, for example, where the component of the electrical characteristic is the in-phase output voltage. This may be the case, for example, where the electrical characteristic is the quadrature output voltage. This may be the case, for example, where the component of the electrical characteristic is a phase determined based on the in-phase output voltage and / or the quadrature output voltage. This may be the case, for example, where the component of the electrical characteristic is an amplitude determined based on the in- phase output voltage and / or the quadrature output voltage.

[0315] The at least one processor 121 may establish a curved mathematical relationship that connects the points, enabling the processor 121 to predict mechanical loads on the actuator 124 based on electrical characteristic measurements for non-linear relationships. The at least one processor 121 may compute the parameters that define this non-linear relationship and store these parameters in the memory 123. Once established, the at least one processor 121 may use this curved model to estimate unknown mechanical loads by inputting a measured values of the component of the electrical characteristic associated with the actuator 124, in use, and calculating the corresponding mechanical load estimate. The curved model approach may be implemented by the at least one processor 121 when the relationship between the values of the component of the electrical characteristic and applied mechanical loads exhibits non-linear behaviour over the operating range of the actuator 124. The curved relationship may take various mathematical forms, such as quadratic functions, exponential functions, logarithmic functions, or power functions. The at least one processor 121 may determine which type of curved relationship best fits the measured data points by analysing the pattern of change between the known mechanical loads and their corresponding value of the component of the electrical characteristic, selecting the mathematical form that provides the most accurate representation of the actuator's load-dependent behaviour.

[0316] The at least one processor 121 may use the first and second known mechanical loads and the corresponding first and second values of the component of the electrical characteristic determined at steps 606 and 608 to train a machine learning model, with the trained machine learning model serving as the load profile. The at least one processor 121 may implement various machine learning algorithms such as regression models, neural networks, support vector machines, or decision trees to learn the relationship between the values of the component of the electrical characteristic and the applied mechanical loads. The at least one processor 121 may iteratively optimise a cost function or loss function during the training process, adjusting model parameters to minimise prediction errors between the model's mechanical load estimates and the known mechanical loads in the dataset. The at least one processor 121 may use techniques such as gradient descent, backpropagation, or other optimisation algorithms to refine the model's accuracy. This machine learning approach may be particularly advantageous when the relationship between the electrical characteristic and mechanical load exhibits non-linear behaviour, as the at least one processor 121 can capture complex patterns and dependencies that may not be accurately represented by linear models. Once training is complete, the at least one processor 121 may store the trained model parameters in the memory 123, enabling real-time load estimation by inputting measured electrical characteristic values into the trained model during operation of the actuator 124.

[0317] In some embodiments, the dataset itself may be considered to be the load profde (e.g. in the form of a lookup table or database). This could be the case, for example, where a step like step 606 or 608 is performed for a large number of known loads.

[0318] The system 100 refers the load profile when being used in a relevant application in the future. For example, where the device 101 is a QME device, the system 100 may use the load profile to control operation of the QME device, or generate output data from a QME operation.

[0319] In some cases, the system 100 changes a value of a control parameter associated with operation of the device 101, based on the determined load profile. For example, a control parameter of the device 101 may indicate a maximum allowable mechanical load on the actuator 124, for the device 101 to perform a function such as QME imaging. In the case where the device 101 is a QME device, a number of control parameters may define a range of allowable mechanical loads on the actuator 124 within which the QME device can image the sample material 105 effectively. The system 100 may change a value of one or more of these control parameters based on the determined load profile. For example, the value of one or more of these parameters may be set to an estimated value of the component of the electrical characteristic, at an upper bound mechanical load, with the estimated value of the component of the electrical characteristic being determined using the load profile. As the upper bound mechanical load that can be applied to the actuator 124 before system degradation in response to that mechanical load is unacceptable is known (e.g. from design specifications of the actuator 124 of the device 101, which can indicate a maximum mechanical load that can be applied to the device 101 and / or actuator 124 while a certain device 101 function can be performed), the load profile can be used to estimate the value of the component of the electrical characteristic when the upper bound mechanical load is applied to the actuator 124. Similarly, the value of one or more of these parameters may be set to an estimated value of the component of the electrical characteristic, at a lower bound mechanical load, with the estimated value of the component of the electrical characteristic being determined using the load profile. In this way, the system 100 controls operation of the device 101 based at least in part on the determined load profile.

[0320] Unknown Mechanical Load Estimation

[0321] Once the load profile of the actuator 124 is known, unknown mechanical loads on the actuator 124 can be estimated using the load profile. Figure 7 shows a method 700, according to some embodiments of the present disclosure. The method 700 may be referred to as a method for determining a value of a component of an electrical parameter associated with an actuator. The method 700 may be referred to as a method for estimating a mechanical load on an actuator. The method 700 may be referred to as a method for controlling a device. For the purposes of this disclosure, the actuator 124 will be referred to. However, it will be appreciated that the method 700 may be applicable to any suitable actuator.

[0322] Generate an Actuator Driving Waveform

[0323] At 702, an actuator driving waveform is generated. The signal processing system 139A, 139B generates the actuator driving waveform. In particular, the signal generator 131 generates the actuator driving waveform. That is, the output of the signal generator 131 may be considered the actuator driving waveform. The actuator driving waveform is amplified by the signal amplifier 132. Subsequent to this amplification, the amplified actuator driving waveform is applied to the actuator 124. It will be appreciated that applying the actuator driving waveform to the actuator 124 comprises applying the amplified actuator driving waveform to the actuator 124. That is, for the purposes of this disclosure, applying the actuator driving waveform to the actuator 124 is intended to comprise applying the amplified actuator driving waveform to the actuator 124, and is not intended to specifically require an unamplified actuator driving waveform to be applied to the actuator 124.

[0324] The at least one processor 121 of the computing system 103 controls one or more components of the signal processing system 139A, 139B. For example, the at least one processor 121 may control the signal generator 131. The at least one processor 121 of the computing system 103 may instruct the signal generator 131 to generate an output waveform. As described above, this may be considered the actuator driving waveform, which is amplified by the signal amplifier 132 to be applied to the actuator 124.

[0325] Generating the actuator driving waveform may comprise generating a primary driving waveform. The primary driving waveform may be referred to simply as a driving waveform. The signal processing system 139A, 139B generates the primary driving waveform. In some embodiments, the signal generator 131 generates the primary driving waveform. The primary driving waveform is configured to drive the actuator 124 to perform the mechanical actuation required for QME. The primary driving waveform provides the fundamental excitation signal that causes the actuator 124 to apply controlled forces to the material 105 through the sensing layer 104, enabling the measurement of tissue deformation and mechanical properties using QME imaging.

[0326] The primary driving waveform is parameterised by a number of primary driving waveform parameters. That is, the primary driving waveform is defined and controlled by a set of numerical values (waveform parameters) that specify its characteristics such as frequency, amplitude, and shape.

[0327] The primary driving waveform is characterised by a primary driving waveform shape. The primary driving waveform shape may be referred to as a driving waveform shape. The primary driving waveform parameters comprise a primary driving waveform shape parameter that indicates a waveform shape of the primary driving waveform. The primary driving waveform shape parameter may be referred to as a driving waveform shape parameter. The primary driving waveform shape is the shape of the primary driving waveform. The primary driving waveform may take one of a number of waveform shapes. For example, the primary driving waveform may be a sine, triangle, square or sawtooth wave. The particular waveform shape of the primary driving waveform is controlled using the primary driving waveform shape parameter. For example, each different waveform shape may be associated with a different value of the primary driving waveform shape parameter.

[0328] The primary driving waveform is characterised by a primary driving waveform frequency. The primary driving waveform parameters comprise a primary driving waveform frequency parameter. The value of the primary driving waveform frequency parameter sets the frequency of the primary driving waveform. The primary driving waveform frequency parameter may be referred to as a driving waveform frequency parameter.

[0329] The primary driving waveform is characterised by a primary driving waveform amplitude. The primary driving waveform parameters comprise a primary driving waveform amplitude parameter. The value of the primary driving waveform amplitude parameter sets the amplitude of the primary driving waveform. The primary driving waveform amplitude parameter may be referred to as a driving waveform amplitude parameter.

[0330] The at least one processor 121 of the computing system 103 may control the values of the primary driving waveform parameters to control the features of the primary driving waveform generated by the signal processing system 139A, 139B. That is, the at least one processor 121 of the computing system 103 may control the values of the primary driving waveform parameters to control the features of the primary driving waveform. The values of the primary driving waveform parameters may be stored in the memory 123 of the computing system 103. Alternatively, the values of the primary driving waveform parameters may be stored in memory of the signal generator 131. In some embodiments, the primary driving waveform may be parameterised by a plurality of primary driving waveform frequencies, primary driving waveform amplitudes and / or primary driving waveform shapes. That is, the primary driving waveform may be a sum of a plurality of waveforms, each parameterised by a respective waveform frequency, amplitude and shape.

[0331] In some embodiments, the primary driving waveform may be a sinusoidal waveform. The primary driving waveform may be a sine wave having a driving waveform frequency, a driving waveform amplitude, and a sinusoidal waveform shape. The driving waveform frequency may be between 10Hz and 200Hz. The driving waveform frequency may be between 10Hz and 100Hz, 10Hz and 50Hz, 20Hz and 200Hz, 20Hz and 100Hz, 30Hz and 200Hz, 30Hz and 100Hz, 50Hz and 200Hz, 50Hz and 100Hz or 100Hz and 200Hz. The driving waveform frequency may be 10Hz, 20Hz, 30Hz, 40Hz, 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz, 110Hz, 120Hz, 130Hz, 140Hz, 150Hz, 160Hz, 170Hz, 180Hz, 190Hz or 200Hz. The driving waveform frequency may be less than 10Hz. The driving waveform frequency may be greater than 200Hz. The amplitude of the primary driving waveform may be between OVpp and lOVpp. The amplitude of the primary driving waveform may be between OVpp and 5Vpp, OVpp and 2.5Vpp, IVpp and lOVpp, IVpp and 5Vpp, 1.5Vpp and lOVpp, 1.5Vpp and 5Vpp, 2.5Vpp and lOVpp, 2.5Vpp and 5Vpp or 5Vpp and lOVpp. The amplitude of the primary driving waveform may be 0.5Vpp, IVpp, 1.5Vpp, 2Vpp, 2.5Vpp, 3Vpp, 3.5Vpp, 4Vpp, 4.5Vpp, 5Vpp, 5.5Vpp, 6Vpp, 6.5Vpp, 7Vpp, 7.5Vpp, 8Vpp, 8.5Vpp, 9Vpp, 9.5Vpp or lOVpp. The amplitude of the primary driving waveform may be less than 0.5Vpp. The amplitude of the primary driving waveform may be greater than lOVpp.

[0332] Actuation of the actuator 124 causes movement of a tip of the device 101. The tip of the device may comprise at least part of the sensing layer 104. Actuation of the actuator 124, may cause movement of the sensing layer 104. Actuation of the actuator 124 may cause movement of the mechanical interface 119. The extent of this movement is dependent on the amplitude of the primary driving waveform. The physical displacement amplitude of the device 101 components is related to the voltage amplitude of the primary driving waveform through the electromechanical characteristics of the actuator 124, with higher voltage amplitudes generally producing correspondingly larger mechanical displacements. Driving the actuator 124 with the actuator driving waveform therefore cause movement of at least part of the device 101. The movement of the device 101, or a part thereof, as a result of driving the actuator 124 using the actuator driving waveform may have an amplitude of between 10 pm and 200pm. The amplitude of the movement may be between 10pm and 100pm, 10pm and 50pm, 20pm and 200pm, 20pm and 100pm, 30pm and 200pm, 30pm and 100pm, 50pm and 200pm, 50pm and 100pm or 100pm and 200pm. The amplitude of the movement may be 10pm, 20pm, 30pm, 40pm, 50pm, 60pm, 70pm, 80pm, 90pm, 100pm, 110pm, 120pm, 130pm, 140pm, 150pm, 160pm, 170pm, 180pm, 190pm or 200pm. The amplitude of the movement may be less than 10 pm. The amplitude of the movement may be greater than 200pm. The actuator driving waveform is a waveform with a component part that has modified with an interrogation signal. In particular, the actuator driving waveform is a waveform that is formed by modifying the primary driving waveform with the interrogation signal. That is, the actuator driving waveform is created by combining or altering a basic waveform with an additional interrogation signal to produce a composite waveform that contains components from both signals. The basic waveform is the primary driving waveform.

[0333] The signal processing system 139A, 139B modifies the primary driving waveform with the interrogation signal, thereby generating the actuator driving waveform. In particular, the signal generator 131 modifies the primary driving waveform with the interrogation signal, thereby generating the actuator driving waveform.

[0334] The primary driving waveform is modified with the interrogation signal by summing the primary driving waveform and the interrogation signal. In other words, the system 100 sums the primary driving waveform and the interrogation signal, thereby generating the actuator driving waveform. In particular, the signal generator 131 sums the primary driving waveform and the interrogation signal, thereby generating the actuator driving waveform. In some embodiments, the signal generator 131 performs the summation operation by adding the instantaneous values of the primary driving waveform and the interrogation signal at each point in time, creating a composite waveform that contains the characteristics of both input signals. The summation process may be implemented using analogue circuitry or through digital signal processing techniques where the discrete samples of each waveform are mathematically added together. When the primary driving waveform and the interrogation signal are summed, the resulting actuator driving waveform exhibits a time-varying amplitude that reflects the combined influence of both signals. The frequency content of the actuator driving waveform includes spectral components at the frequency of the primary driving waveform and at the frequency of the interrogation signal, enabling simultaneous excitation of the actuator 124 at both frequencies. The at least one processor 121 may control the timing and synchronisation of the summation process to ensure proper phase relationships between the primary driving waveform and the interrogation signal.

[0335] The interrogation signal is a waveform. The interrogation signal is parameterised by a number of interrogation waveform parameters. The interrogation signal is characterised by an interrogation waveform shape. That is, the interrogation waveform parameters comprise an interrogation waveform shape parameter that indicates a waveform shape of the interrogation signal. The interrogation waveform shape is the shape of the interrogation signal. The interrogation signal may take one of a number of waveform shapes. For example, the interrogation signal may be a sine, triangle, square or sawtooth wave. The particular waveform shape of the interrogation signal is controlled using the interrogation waveform shape parameter. For example, each different waveform shape may be associated with a different value of the interrogation waveform shape parameter. The interrogation signal is characterised by an interrogation waveform frequency. The interrogation waveform parameters comprise an interrogation waveform frequency parameter. The value of the interrogation waveform frequency parameter sets the frequency of the interrogation signal.

[0336] The interrogation signal is characterised by an interrogation waveform amplitude. The interrogation waveform parameters comprise an interrogation waveform amplitude parameter. The value of the interrogation waveform amplitude parameter sets the amplitude of the interrogation signal.

[0337] The at least one processor 121 of the computing system 103 may control the values of the interrogation waveform parameters to control the features of the interrogation signal. The values of the interrogation waveform parameters may be stored in the memory 123 of the computing system 103. Alternatively, the values of the interrogation waveform parameters may be stored in memory of the signal generator 131.

[0338] In some embodiments, the interrogation signal may be parameterised by a plurality of interrogation waveform frequencies, interrogation waveform amplitudes and / or interrogation waveform shapes. That is, the interrogation signal may be a sum of a plurality of waveforms, each parameterised by a respective waveform frequency, amplitude and shape.

[0339] The amplitude of the interrogation signal is small compared to the amplitude of the primary driving waveform. The amplitude of the interrogation signal may be related to the amplitude of the primary driving waveform. For example, the amplitude of the interrogation signal may be proportional to the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 1% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 2% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is less than 2% of the amplitude of the primary driving waveform. In some embodiments, the amplitude of the interrogation signal is about 0.5%, 3%, 4% or 5% of the amplitude of the primary driving waveform. The amplitude of the interrogation signal may be less than 10% of the amplitude of the primary driving waveform.

[0340] The shape of the interrogation signal of 702 is sinusoidal. The interrogation signal may be a 100 mVpp sine wave. The interrogation signal may be a 50 mVpp sine wave. The interrogation signal may be a 75 mVpp sine wave. The interrogation signal may be a 150 mVpp sine wave. The interrogation signal may be a 200 mVpp sine wave. The interrogation signal may be a 250 mVpp sine wave. The interrogation signal may be a 300 mVpp sine wave. The interrogation signal may be between 50 mVpp and 300 mVpp. The interrogation signal may be between 75 mVpp and 200 mVpp. The interrogation signal may be between 100 mVpp and 250 mVpp. The interrogation signal may have an amplitude in the range of 10 mVpp to 500 mVpp. It will be appreciated that in other embodiments, the shape and / or amplitude of the interrogation signal may be different.

[0341] The interrogation waveform frequency is associated with the mechanical system 109. In other words, the frequency of the interrogation signal is associated with the mechanical system 109. The frequency of the interrogation signal may be related to the resonant frequency of the mechanical system 109. In some embodiments, the frequency of the interrogation signal is proportional to the resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 20% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 15% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 10% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 25% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be within 30% of a resonant frequency of the mechanical system 109. The frequency of the interrogation signal may be substantially equal to a resonant frequency of the mechanical system 109. The resonant frequency of the mechanical system 109 may be a resonant frequency of the actuator 124. The resonant frequency may be a resonant frequency of the piezoelectric actuator element within the actuator 124. The resonant frequency may be determined by, or influenced by, the physical dimensions, material properties, and mounting configuration of the actuator 124.

[0342] In the illustrated embodiment, the frequency of the interrogation signal (i.e. the interrogation waveform frequency) is between about 80kHz and about 100kHz. In some embodiments, the frequency of the interrogation signal is about 89550 Hz. In some embodiments, the frequency of the interrogation signal is about 89450 Hz. In some embodiments, the frequency of the interrogation signal is about 85000 Hz. In some embodiments, the frequency of the interrogation signal is about 90000 Hz. In some embodiments, the frequency of the interrogation signal is about 95000 Hz. In some embodiments, the frequency of the interrogation signal is about 82000 Hz. In some embodiments, the frequency of the interrogation signal is about 87500 Hz. In some embodiments, the frequency of the interrogation signal is about 92500 Hz. In some embodiments, the frequency of the interrogation signal is about 97500 Hz. In some embodiments, the frequency of the interrogation signal is between 85kHz and 95kHz. In some embodiments, the frequency of the interrogation signal is between 88kHz and 92kHz. In some embodiments, the frequency of the interrogation signal is between 89kHz and 90kHz. The frequency of the interrogation signal may be selected based on the specific resonant characteristics of the device 101, mechanical system 109 and / or the actuator 124 configuration. These values can be within 20% of the resonant frequency of the mechanical system 109. These values can be within 20% of the resonant frequency of a sub-assembly of the device 101. The sub-assembly of the device 101 may comprise the actuator 124.

[0343] It will be appreciated that different mechanical systems that, for example, comprise different actuators, will have different resonant frequencies. Further, mounting the actuator 124 to other components of the device 101 in different ways will change the resonant frequency of the mechanical system 109. The frequency of the interrogation signal of the method 700 may therefore change depending on the particular actuator and / or mechanical system design that is being used. While step 702 has been described in the context of modifying a primary driving waveform with an interrogation signal, 702 may also be described as modulating a driving waveform with a modulating signal. That is, 702 may be said to comprise generating a modulated driving waveform. The system 100 may generate the modulated driving waveform by modulating a driving waveform with a modulating signal. The term “modulating” in this context can refer to the process of combining two waveforms, where the signal generator 131 sums the driving waveform and the modulating signal in the time domain to create a composite waveform. This additive combination process is functionally equivalent to the modification described above. When described using modulation terminology, the actuator driving waveform may be referred to as a modulated driving waveform. The modulated driving waveform terminology emphasises that the original driving waveform has been altered by the addition of the modulating signal, resulting in a composite signal that exhibits characteristics of both component waveforms. The signal amplifier 132 receives this actuator driving waveform from the signal generator 131 and amplifies it before application to the actuator 124. The “interrogation signal” terminology may be replaced with “modulating signal” throughout the disclosure without departing from the scope of the disclosure, as both terms can refer to the same secondary waveform that is combined with the primary driving waveform by the signal generator 131. Similarly, the “modifying” process and the “modulating” process both describe the same technical operation performed by the signal processing system 139A, 139B to generate the composite waveform. The lock-in amplifier 140 filters the electrical response at the frequency of this secondary signal, whether it is termed the interrogation signal frequency or the modulating signal frequency. The at least one processor 121 controls this waveform combination process and the subsequent signal processing operations regardless of whether the terminology characterises the process as modification with an interrogation signal or modulation with a modulating signal.

[0344] While method 700 can involve the use of the term “modulation” in the context of waveform addition, it will be appreciated that other methods of modulation could be employed to achieve similar outcomes as are described for the method 700. As described in more detail in the Alternative Embodiments section, amplitude modulation (AM), frequency modulation (FM), or phase modulation (PM) techniques may also be suitable for creating actuator driving waveforms that enable mechanical load detection. Each of these alternative modulation approaches may require different signal generation hardware and processing techniques, but may still provide the described capability of correlating electrical characteristics with mechanical loads applied to the actuator 124.

[0345] Apply the Actuator Driving Waveform to the Actuator

[0346] At 704, the actuator driving waveform is applied to the actuator 124. The system 100 applies the actuator driving waveform to the actuator 124. In particular, the signal generator 131 may be said to apply the actuator driving waveform to the actuator 124. As described herein, the signal generator 131 provides output waveforms to the signal amplifier 132 for amplification. Applying the actuator driving waveform to the actuator 124 may comprise providing the actuator driving waveform to the signal amplifier 132 for amplification. The signal amplifier 132 amplifies the actuator driving waveform and applies the amplified driving waveform to the actuator 124. In other words, the amplified driving waveform that is generated by the signal amplifier 132 is applied to the actuator 124. It will be understood that this is applying the actuator driving waveform to the actuator 124. Applying the actuator driving waveform to the actuator 124 may alternatively be expressed as driving the actuator 124 with the actuator driving waveform.

[0347] Application of the actuator driving waveform to the actuator 124 causes the actuator 124 to move in accordance with the primary driving waveform component, thereby moving the tip of the device 101. When being used, for example, in a QME system for imaging, the primary driving waveform provides the fundamental mechanical actuation that enables the device 101 to perform its intended function, such as applying controlled forces to the material 105 through the sensing layer 104 to generate tissue deformation for optical measurement. Simultaneously, the interrogation signal component of the actuator driving waveform excites resonant modes of a sub-assembly of the device 101, such as the mechanical system 109 or components thereof, at frequencies that are typically much higher than the primary driving waveform frequency. This dual-function operation allows the system 100 to maintain normal device functionality while concurrently enabling the load estimation capabilities described herein, as the excited resonant modes respond to mechanical loading conditions and produce detectable changes in the electrical characteristics of the actuator 124 that can be processed by the signal processing system 139A, 139B.

[0348] The step of applying the actuator driving waveform to the actuator 124 at 704 may be expressed using the alternative terminology for the actuator driving waveform that is detailed herein. For example, 704 may be described as applying the modulated driving waveform to the actuator 124. That is, 704 may alternatively be described as any one of applying a modulated driving waveform generated at 702 to the actuator 124, applying a composite driving waveform generated at 702 to the actuator 124, applying a combined waveform generated at 702 to the actuator 124, applying a summed waveform generated at 702 to the actuator 124, and applying an additive waveform generated at 702 to the actuator 124. Similarly, the signal generator 131 may be described as applying any one of a modulated driving waveform, composite driving waveform, combined waveform, summed waveform, and additive waveform to the actuator 124 at 704. The signal amplifier 132 may amplify and apply the amplified modulated driving waveform, composite driving waveform, amplified combined waveform, amplified summed waveform, or amplified additive waveform to the actuator 124. The system 100 may be described as applying any of these alternative waveform designations to achieve the same technical result of simultaneous excitation at multiple frequencies for mechanical load detection purposes, with references to the actuator driving waveform being substitutable for any of the alternative terminologies mentioned herein without departing from the scope of the disclosure. Further, similar terminology may be used if 704 is expressed as driving the amplifier 124 with the actuator driving waveform. Determine a Value of a Component of an Electrical Characteristic Associated with the Actuator At 706, a value of a component of an electrical characteristic associated with the actuator 124 is determined. The system 100 determines the value of the component of the electrical characteristic associated with the actuator 124. In particular, the value of the component of the electrical characteristic associated with the actuator 124 is determined for a time period during which an unknown mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. That is, at 706, the system 100 determines the value of the component of the electrical characteristic that is associated with the actuator 124 while the first known mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. The unknown mechanical load is applied to the actuator 124 contemporaneously with the measurement of the electrical characteristic associated with the actuator 124. The value of the component of the electrical characteristic is related to the mechanical load on the actuator 124. That is, the value of the component of the electrical characteristic changes as the mechanical load on the actuator 124 changes, so the value of the component of the electrical characteristic is related to the unknown mechanical load. The method 700 involves the use of this behaviour and the load profile determined in the method 600 to enable the estimation of unknown mechanical loads that are applied to the actuator 124.

[0349] Determining the value of the component of the electrical characteristic associated with the actuator 124 comprises filtering an electrical parameter signal that is associated with the actuator 124 while the actuator driving waveform is applied to the actuator 124 and the unknown mechanical load is applied to the actuator 124. The electrical parameter signal is a voltage signal that changes with actuation of the actuator 124 under mechanical load (either from a strain gauge 136 connected to the actuator 124 or from a current-to-voltage converter circuit 141 measuring current through the actuator 124), which is then filtered by the lock-in amplifier 141 at the interrogation signal frequency to produce an output voltage, this output voltage being the electrical characteristic. In particular, determining the value of the component of the electrical characteristic associated with the actuator 124 comprises filtering an electrical parameter signal that is associated with the actuator 124 while both the actuator driving waveform is applied to the actuator 124 and the first known mechanical load is applied to the actuator 124.

[0350] Determining a Value of a Component of an Electrical Characteristic Associated with an Actuator 124 Connected to a Strain Gauge 136

[0351] The method 700 may be used for a system 100 that includes the signal processing system 139B of Figure 3. As described with reference to Figure 3, in some embodiments of the disclosed system 100, one or more strain gauge 136 is connected to the actuator 124. Step 706 of the method 700 will be described here for the case where one strain gauge 136 is connected to the actuator 124. However, it will be appreciated that similar implementations may be used where multiple strain gauges 136 are connected to the actuator 124. The strain gauge 136 is connected to the actuator 124. In the illustrated embodiment, the strain gauge 136 is adhered to the actuator 124. As a result, changes in shape of the actuator 124, or a part thereof, when the actuator 124 is actuated, will cause corresponding changes in shape of the strain gauge 136. Also as described herein, a voltage across output terminals of the strain gauge 136 can be measured. The strain gauge 136 may therefore be said to provide a voltage signal that can be measured by other components. This voltage signal is the electrical parameter signal of this embodiment of the method 700. This voltage signal is filtered, with the electrical characteristic associated with the actuator 124 during use being the filtered signal.

[0352] The lock-in amplifier 140 is electrically connected to the strain gauge 136 via the strain gauge amplifier 138. The voltage across the output terminals of the strain gauge 136, after being amplified by the strain gauge amplifier 138, is an input of the lock-in amplifier 140. The lock-in amplifier 140 filters the voltage signal from the strain gauge 136 and strain gauge amplifier 138, thereby generating a filtered output. In particular, the lock-in amplifier 140 filters the voltage signal at the frequency of the interrogation signal. In this case, a reference signal of the lock-in amplifier 140 is a signal with a frequency that is the same as the interrogation signal. In other words, the reference frequency of the lock-in amplifier 140 when the lock-in amplifier 140 filters the voltage signal from the strain gauge 136 and strain gauge amplifier 138 is the frequency of the interrogation signal. The filtered output voltage signal of the lock-in amplifier 140 is the electrical characteristic for which values of a component thereof are determined.

[0353] The filtered output of the lock-in amplifier 140 comprises an in-phase output voltage. The in-phase output voltage is associated with the real part of the voltage signal of the strain gauge 136. That is, the in-phase output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is in phase with the reference signal. A magnitude of the in-phase output voltage of the lock-in amplifier 140 corresponds to a magnitude of the real part of the voltage signal that was the input of the lock-in amplifier 140 at the reference frequency. In some embodiments, the in-phase output voltage of the lock-in amplifier 140 is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load such as the unknown mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0354] The filtered output of the lock-in amplifier 140 comprises a quadrature output voltage. The quadrature output voltage is associated with the imaginary part of the voltage signal of the strain gauge 136. That is, the quadrature output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is 90 degrees out of phase with the reference signal. A magnitude of the quadrature output voltage corresponds to a magnitude of the imaginary part of the voltage signal that was input to the lock-in amplifier 140 at the reference frequency. In some embodiments, the quadrature output voltage is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124. In some embodiments, the value of the electrical characteristic is derived from one or both of the in-phase output voltage and the quadrature output voltage. For example, the phase calculated using both components (arctangent of quadrature / in-phase ratio) may be considered the component of the electrical characteristic for which a value is determined. Alternatively, the amplitude calculated from both components (square root of sum of squares) may be considered the component of the electrical characteristic for which a value is determined.

[0355] At 706, the system 100 determines a value of a component of an electrical characteristic that is associated with the actuator 124 while the unknown mechanical load is applied to the actuator 124 and the actuator drive waveform is applied to the actuator 124. Determining the value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the strain gauge 136 while both the actuator driving waveform is applied to the actuator 124 and the unknown mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock-in amplifier 140. The at least one processor 121 determines the value of the component of the electrical characteristic based on the output voltage signal from the lock-in amplifier 140.

[0356] In some embodiments, the value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140.

[0357] Determining the value of the electrical characteristic at 706 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 706 may comprise calculating a phase of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in phase output voltage and the quadrature output voltage. This phase is the value of the electrical characteristic, in some embodiments. Determining the value of the electrical characteristic at 706 may comprise calculating an amplitude of the electrical characteristic, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 706 may comprise calculating an amplitude of the voltage signal associated with the strain gauge 136, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the amplitude of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the amplitude of the electrical parameter signal using the in phase output voltage and the quadrature output voltage. This amplitude is the value of the electrical characteristic, in some embodiments.

[0358] Therefore, the at least one processor 121 of the computing system 103 determines the value of the component of the electrical characteristic at 706, using the filtered output of the lock-in amplifier 140.

[0359] The value of the component of the electrical characteristic that is associated with the actuator 124 that is determined at 706 may be said to be associated with the unknown mechanical load. This is because the application of the unknown mechanical load on the actuator 124 resulted in the relevant value of the component of the electrical characteristic being determined, as the value of the component of the electrical characteristic changes with a change in applied mechanical load on the actuator 124. The value of the component of the electrical characteristic associated with the actuator 124 that is calculated at 706 may be stored in memory 123.

[0360] Determining the value of the component of the electrical characteristic associated with the actuator 124 at 706 may be expressed using the alternative terminology for the actuator driving waveform (and associated terminology) as has been detailed herein.

[0361] The value of the component of the electrical characteristic associated with the actuator 124 that is determined at 706 relates to the conditions present during the simultaneous application of the unknown mechanical load and the actuator driving waveform to the actuator 124. While the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the value of the component of the electrical characteristic may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the unknown mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the electrical characteristic value may be performed at a later time using the recorded measurements.

[0362] Electrical Characteristic of the Actuator 124

[0363] The method 700 may be used for a system 100 that includes the signal processing system 139A of Figure 2. In some embodiments, the electrical characteristic associated with the actuator 124 while the actuator driving waveform is applied to the actuator 124 may be an electrical characteristic of the actuator 124 itself, or derived from such an electrical characteristic without the need for additional hardware to be connected to the actuator 124.

[0364] As described with reference to Figure 2, in some embodiments of the disclosed system 100, a current-to- voltage converter circuit (CVCC) 141 is operably connected to the actuator 124. The CVCC 141 may alternatively be referred to herein as a current measurement circuit. The CVCC 141 may be electrically connected to the actuator 124. In the illustrated embodiment, the CVCC 141 is electrically connected to the input side of the actuator 124.

[0365] The CVCC 141 monitors the current through the actuator 124. In particular, the CVCC 141 monitors the current through the actuator 124 when the actuator driving waveform is applied to the actuator 124 and the unknown mechanical load is applied to the actuator 124, and generates a voltage signal in response to this current signal. This voltage signal is the output of the CVCC 141.

[0366] The lock-in amplifier 140 is electrically connected to the CVCC 141 and the voltage signal generated by the CVCC 141 is the input of the lock-in amplifier 140. The lock-in amplifier 140 filters the voltage signal, thereby generating a filtered output. In particular, the lock-in amplifier 140 filters the voltage signal at the frequency of the interrogation signal. In this case, a reference signal of the lock-in amplifier 140 is a signal with a frequency that is the same as the interrogation signal. In other words, the reference frequency of the lock-in amplifier 140 when the lock-in amplifier 140 filters the voltage signal from the CVCC 141 is the frequency of the interrogation signal. The interrogation signal may be the reference signal of the lock-in amplifier 140. The filtered output voltage signal of the lock-in amplifier 140 is the electrical characteristic for which values of a component thereof are determined.

[0367] The filtered output of the lock-in amplifier 140 comprises an in-phase output voltage. The in-phase output voltage is associated with the real part of the voltage signal of the CVCC 141. That is, the in-phase output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is in phase with the reference signal. A magnitude of the in-phase output voltage of the lock-in amplifier 140 corresponds to a magnitude of the real part of the voltage signal that was the input of the lock-in amplifier 140, at the reference frequency. In some embodiments, the in-phase output voltage of the lock-in amplifier 140 is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load such as the unknown mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124

[0368] The filtered output of the lock-in amplifier 140 comprises a quadrature output voltage. The quadrature output voltage is associated with the imaginary part of the voltage signal of the CVCC 141. That is, the quadrature output voltage represents the part of the input voltage signal of the lock-in amplifier 140 that is 90 degrees out of phase with the reference signal. A magnitude of the quadrature output voltage corresponds to a magnitude of the imaginary part of the voltage signal that was input to the lock-in amplifier 140 at the reference frequency. In some embodiments, the quadrature output voltage is the component of the electrical characteristic that is associated with the actuator 124 while a mechanical load is applied to the actuator 124 and the actuator driving waveform is applied to the actuator 124.

[0369] In some embodiments, the value of the electrical characteristic is derived from one or both of the in-phase output voltage and the quadrature output voltage. For example, the phase calculated using both components (arctangent of quadrature / in-phase ratio) may be considered the component of the electrical characteristic for which a value is determined. Alternatively, the amplitude calculated from both components (square root of sum of squares) may be considered the component of the electrical characteristic for which a value is determined.

[0370] At 706, the system 100 determines a value of a component of an electrical characteristic that is associated with the actuator 124 while the unknown mechanical load is applied to the actuator 124 and the actuator drive waveform is applied to the actuator 124. Determining the value of the component of the electrical characteristic comprises measuring and processing the voltage signal from the CVCC 141 while both the actuator driving waveform is applied to the actuator 124 and the unknown mechanical load is simultaneously applied to the actuator 124. The at least one processor 121 receives the output voltage signal from the lock-in amplifier 140. The at least one processor 121 determines the value of the component of the electrical characteristic based on the output voltage signal from the lock-in amplifier 140.

[0371] In some embodiments, the value of the component of the electrical characteristic is the magnitude of the in-phase output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is the magnitude of the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is a phase calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the phase using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. In some embodiments, the value of the component of the electrical characteristic is an amplitude calculated using the in-phase component and the quadrature component. The at least one processor 121 may calculate the amplitude using the in-phase output voltage of the output voltage signal of the lock-in amplifier 140 and the quadrature output voltage of the output voltage signal of the lock-in amplifier 140. Determining the value of the electrical characteristic at 706 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 706 may comprise calculating a phase of the voltage signal associated with the CVCC 141, at the frequency of the interrogation signal, in some embodiments. The system 100 calculates the phase of the electrical parameter signal based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical parameter signal using the in-phase output voltage and the quadrature output voltage. This phase is the first value of the electrical characteristic, in some embodiments. Determining the value of the electrical characteristic at 706 may comprise calculating a phase of the electrical parameter signal, at the frequency of the interrogation signal. In other words, determining the value of the component of the electrical characteristic at 706 may comprise determining a phase of the voltage signal output of the CVCC 141, at the frequency of the interrogation signal. The system 100 calculates the phase of the electrical characteristic based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the phase of the electrical characteristic using the in-phase output voltage and the quadrature output voltage. This phase is the value of the component of the electrical characteristic, in some embodiments.

[0372] Determining the value of the electrical characteristic at 706 may comprise calculating an amplitude of the electrical characteristic, at the frequency of the interrogation signal. In other words, determining the value of the electrical characteristic at 706 may comprise calculating an amplitude of the voltage signal output of the CVCC 141, at the frequency of the interrogation signal. The system 100 calculates the amplitude of the electrical characteristic based on the filtered output of the lock-in amplifier 140. The system 100 may calculate the amplitude of the electrical characteristic using the in-phase output voltage and the quadrature output voltage. This amplitude is the value of the component of the electrical characteristic, in some embodiments.

[0373] In some embodiments, the at least one processor 121 of the computing system 103 determines the value of the component of the electrical characteristic at 706, using the filtered output of the lock-in amplifier 140. In some embodiments, the at least one processor 121 of the computing system 103 calculates the value of the component of the electrical characteristic at 706, using the filtered output of the lock-in amplifier 140.

[0374] The value of the component of the electrical characteristic that is associated with the actuator 124 that is determined at 706 may be said to be associated with the unknown mechanical load. This is because the application of the unknown mechanical load on the actuator 124 resulted in the relevant value of the component of the electrical characteristic being determined, as the value of the component of the electrical characteristic changes with a change in applied mechanical load on the actuator 124.

[0375] Determining the value of the component of the electrical characteristic associated with the actuator 124 at 706 may be expressed using the alternative terminology for the actuator driving waveform that is detailed herein.

[0376] The value of the component of the electrical characteristic associated with the actuator 124 that is determined at 706 relates to the conditions present during the simultaneous application of the unknown mechanical load and the actuator driving waveform to the actuator 124. While the electrical characteristic is associated with these specific operating conditions, the actual determination or calculation of the value of the component of the electrical characteristic may be performed subsequently using measurements that were captured during this operation. For example, the relevant electrical parameter signal may be measured and recorded while the first known mechanical load and actuator driving waveform are applied, and the filtering, phase calculations, amplitude determinations, or other signal processing operations used to derive the electrical characteristic value may be performed at a later time using the recorded measurements.

[0377] The value of the component of the electrical characteristic associated with the actuator 124 that is calculated at 706 may be said to be associated with the unknown mechanical load.

[0378] Determine an Estimate of a Mechanical Load on the Actuator Based on the Value of the Component of the Electrical Characteristic

[0379] At 708, an estimate of the mechanical load on the actuator 124 is determined based on the value of the component of the electrical characteristic determined. The system 100 determines the estimate of the mechanical load on the actuator 124 based on the value of the component of the electrical characteristic that is associated with the actuator 124 at 706. The at least one processor 121 determines the estimate of the mechanical load on the actuator 124 using a load profile. The load profde relates values of the component of the electrical characteristic to estimates of the mechanical load on the actuator 124. In particular, the load profile relates values of the component of the electrical characteristic to estimates of the mechanical load on the actuator 124 that would induce such a value of the component of the electrical characteristic to be determined under the relevant mechanical load. The load profde may, for example, be determined as described in the method 600 herein. The at least one processor 121 determines the estimate of the mechanical load on the actuator 124 using a mathematical model of the load profde.

[0380] The mathematical model relates values of the component of the electrical characteristic to the mechanical load on the actuator 124. A particular value of the component of the electrical characteristic is an input of the mathematical model. The mathematical model is a linear model. That is, the mathematical model linearly relates values of the component of the electrical characteristic to the load on the actuator 124. It will be appreciated that in some embodiments, the relationship between values of the component of the electrical characteristic and the applied mechanical load may not be linear.

[0381] The at least one processor 121 uses the value of the component of the electrical characteristic as an input of the mathematical model. The output of the mathematical model is the estimate of the mechanical load on the actuator 124.

[0382] As described in the method 600, in some embodiments, the load profde comprises a trained machine learning model, a lookup table or a database. In these embodiments, the at least one processor 121 may refer to the relevant load profile (i.e. the machine learning model, lookup table or database) to determine the estimate of the mechanical load on the actuator 124. In each case, the value of the component of the electrical characteristic determined at 706 is used as an input of the relevant machine learning model, lookup table or database. The at least one processor 121 stores the estimate of the unknown mechanical load in memory 123.

[0383] Control Device 101 Based on the Value of the Component of the Electrical Characteristic

[0384] At 710, the system 100 controls the device 101 based on the value of the component of the electrical characteristic determined at 706. It may also be said that the system 100 controls the device 101 based on the estimate of the unknown mechanical load determined at 708. It will be appreciated that this functionality may be performed by the at least one processor 121. In some embodiments, step 708 of the method 700 may not be necessary. For example, at 710, the system 100 may compare the value of the component of the electrical characteristic determined at 706 to one or more threshold value. The system

[0385] 100 may control the device based on the comparison.

[0386] For example, the system 100 may allow the device 101 to perform a particular operation when the value of the component of the electrical characteristic determined at 706 meets an operating criterion. The operating criterion may be that the value of the component of the electrical characteristic is above a threshold value. The operating criterion may be that the value of the component of the electrical characteristic is below a threshold value. The operating criterion may be that the value of the component of the electrical characteristic is above a first threshold value and below a second threshold value.

[0387] The system 100 may deactivate the device 101 where the value of the component of the electrical characteristic does not meet the operating criterion. Worded differently, the system 100 may deactivate the device 101 where the value of the component of the electrical characteristic meets a deactivation criterion. The deactivation criterion may be that the value of the component of the electrical characteristic is above a threshold value. The deactivation criterion may be that the value of the component of the electrical characteristic is below a threshold value. The deactivation criterion may be that the value of the component of the electrical characteristic is above a first threshold value and below a second threshold value.

[0388] Controlling the device 101 may comprise changing a value of an operating parameter associated with the device 101. Therefore, the system 100 may change the value of an operating parameter of the device 101 based on the determined value of the component of the electrical characteristic. Changing the value of the operating parameter may cause the device 101 to perform a particular function, or may cause the device

[0389] 101 to stop performing a particular function. Changing the value of the operating parameter may cause the device 101 to shut down.

[0390] In some embodiments, the operating parameter is associated with a user interface of the device 101. The user interface may, for example, comprise an LED. Changing the value of the operating parameter may change the colour of the LED (e.g. from green to red). Alternatively, changing the value of the operating parameter may activate the LED or deactivate the LED.

[0391] In some embodiments, at 710 the system 100 controls the device 101 based on the estimate of the mechanical load on the actuator 124 determined at 708. It will be appreciated that this functionality may be performed by the at least one processor 121. At 710, the system 100 may compare the estimate of the mechanical load on the actuator 124 to one or more threshold value. The system 100 may control the device 101 based on the comparison.

[0392] For example, the system 100 may allow the device 101 to perform a particular operation when the estimate of the mechanical load on the actuator 124 meets an operating criterion. The operating criterion may be that the value of the estimate of the mechanical load on the actuator 124 is above a threshold value. The operating criterion may be that the value of the estimate of the mechanical load on the actuator 124 is below a threshold value. The operating criterion may be that the value of the estimate of the mechanical load on the actuator 124 is above a first threshold value and below a second threshold value.

[0393] The system 100 may deactivate the device 101 where the value of the estimate of the mechanical load on the actuator 124 does not meet the operating criterion. Worded differently, the system 100 may deactivate the device 101 where the value of the estimate of the mechanical load on the actuator 124 meets a deactivation criterion. The deactivation criterion may be that the value of the estimate of the mechanical load on the actuator 124 is above a threshold value. The deactivation criterion may be that the value of the estimate of the mechanical load on the actuator 124 is below a threshold value. The deactivation criterion may be that the value of the estimate of the mechanical load on the actuator 124 is above a first threshold value and below a second threshold value.

[0394] Controlling the device 101 may comprise changing a value of an operating parameter associated with the device 101. Therefore, the system 100 may change the value of an operating parameter of the device 101 based on the determined estimate of the mechanical load on the actuator 124. Changing the value of the operating parameter may cause the device 101 to perform a particular function, or may cause the device 101 to stop performing a particular function. Changing the value of the operating parameter may cause the device 101 to shut down.

[0395] In QME imaging applications, this load-based control functionality provides significant practical benefits for ensuring accurate measurements and protecting both the device 101 and the material 105 being examined. For example, if the estimated mechanical load on the actuator 124 exceeds an upper threshold, this may indicate that excessive force is being applied to the tissue sample, which could damage delicate biological material or compress the tissue beyond the range where accurate elasticity measurements can be obtained. In such cases, the system 100 may automatically reduce the amplitude of the primary driving waveform, activate a warning indicator on the user interface 113 or 125, or temporarily halt the QME imaging process to prevent tissue damage. Conversely, if the estimated load falls below a lower threshold, this may indicate insufficient contact between the sensing layer 104 and the material 105, resulting in poor signal quality or inaccurate elasticity measurements. The system 100 may then prompt the user to apply additional contact pressure or adjust the device positioning. Additionally, maintaining the mechanical load within an optimal range ensures that the actuator 124 operates within its linear response region, where the relationship between applied voltage and mechanical displacement remains predictable, thereby improving the accuracy and repeatability of the QME measurements used for tissue characterization and diagnostic applications.

[0396] In some embodiments, the operating parameter is associated with a user interface of the device 101. The user interface 101 may, for example, comprise an LED. Changing the value of the operating parameter may change the colour of the LED (e.g. from green to red). Alternatively, changing the value of the operating parameter may activate the LED or deactivate the LED. In some embodiments, the system 100 may display a numerical representation of the estimate of the load on the actuator 124 on a display of the user interface of the computing system 103 or the device 101.

[0397] Experimental Validation of the Methods 600, 700

[0398] An experimental method related to the system 100 is now described.

[0399] An equipment setup for a system 800 of the experimental method is shown in Figure 8 and some of the equipment used is shown in Figure 9. Some of the equipment of the setup 800 is the same as that of the system 100. In such cases, like reference numerals are used for like pieces of equipment. The signal generator 131 and signal amplifier 132 are used to excite the piezoelectric actuator in the actuator 124 under test. A wide scale frequency sweep from 0 Hz to 100 kHz was conducted to search for current variability with load at specific frequencies. Once identified, the existing driving waveform of the setup 800 was modified via summation with small signal, sinusoidal waveforms (100 mVpp - approximately 1% of the driving waveform) at the identified frequencies. A strain gauge 136 and its amplifier readout was used as a deterministic measure of load on the actuator 124. The electrical current waveform was measured under different loading conditions, converted to a voltage signal using CVCC 141 and sent to the lock-in amplifier 140 to filter its amplitude and phase at the frequency of the interrogation signal. The lock-in amplifier 140 had a 100 dB sensitivity which was suitable for the purposes of the experiment and was used in its default configuration with a 10 Hz low-pass cutoff frequency.

[0400] In the widescale frequency sweep, the system 800 ’s electrical current response to load at specific frequencies in the 80 - 100 kHz range displayed detectable linear variability. The 3 largest positive gradients 1010, 3 largest negative gradients 1012, and 3 most linear relationships 1014 are shown in Figure 10. Notably, the most sensitive responses to mechanical load were found between 89450 - 89550 Hz.

[0401] The plot showing the highest linearity as displayed by its R2value (coefficient of determination) of 0.999 is the 89550 Hz frequency, and this was used for preliminary testing. The lock-in amplifier 140 was configured to isolate the amplitude response of the system 800 at this frequency. This produced a noise- filtered amplitude output, and the linear response was plotted against load as seen in the dotted line in Figure 11.

[0402] To integrate this measure of load with the existing system 800, a 100 mVpp sine wave was summed with the existing driving waveform and the resultant signal was used to excite the actuator 124. The lock-in amplifier 140 was then used to isolate the system’s 800 response at this frequency. The behaviour of the system 800 under the modulated signal showed similar load variability with a 30 mV full scale resolution over the 1 kg range as seen in the dashed line in Figure 11. This relationship was consistent over 6 trials within 0.5% standard error. Preliminary results with stiffer and softer materials displayed minimal changes in the systems response which is a requirement of our application.

[0403] Alternative Embodiments

[0404] It will be appreciated that a number of variations may be made to the system 100 whilst still falling within the scope of the present disclosure.

[0405] The term “modulated driving waveform” is used herein in certain instances, such as in method steps 602 and 702, to refer to a driving waveform that has been combined with a modulating signal through signal addition in the time domain. This modulation technique involves summing two separate waveforms, the primary driving waveform and a smaller amplitude modulating signal, to create a composite waveform that retains characteristics of both component signals. The modulated driving waveform may therefore alternatively be referred to as a composite waveform. The modulation approach described in methods 600 and 700, by way of example, employ this additive modulation technique.

[0406] The modulation of the driving waveform with the modulating signal creates a modulated driving waveform that simultaneously contains frequency components from both the driving waveform and the modulating signal. For example, if the driving waveform is a waveform at a primary frequency for actuator operation and the modulating signal operates at a frequency associated with the actuator 124’s resonance (such as the 89450-89550 Hz range described herein), the resulting modulated driving waveform enables simultaneous excitation of the actuator 124 at both frequencies.

[0407] It will be appreciated that alternative modulation techniques may be employed in other embodiments, while still achieving the objectives of the present disclosure.

[0408] It will be appreciated that in the following alternative modulation approaches, the terms 'driving waveform' and 'modulating signal' may refer to either the primary driving waveform or the interrogation signal described in the above description, depending on the specific modulation technique employed. For example, in amplitude modulation implementations, the higher frequency interrogation signal may serve as the carrier waveform that is modulated by the lower frequency primary driving waveform, whereas in other modulation schemes the roles may be reversed. The selection of which signal serves as the carrier versus the modulating signal may depend on the specific technical requirements and frequency characteristics of the particular modulation approach. This may also be the case where relevant in the claims of the present application. For instance, amplitude modulation (AM) techniques could be used where the amplitude of the driving waveform is varied according to a modulating signal. In AM modulation, a modulating signal controls the amplitude envelope of a driving waveform, creating sidebands at frequencies above and below the driving waveform frequency. When applied to methods 600 and 700, AM modulation may require modification of the signal generator 131 to include amplitude modulation circuitry, such as a multiplier circuit or a variable gain amplifier controlled by the modulating signal. The lock-in amplifier 140 or another component may be configured to detect the amplitude variations at a modulating frequency, or alternatively, to filter at the sideband frequencies created by the AM process. The electrical characteristic measurements in steps 606 and 706 may focus on detecting changes in the amplitude modulation depth or sideband power levels, which may vary with mechanical load applied to the actuator 124. The frequency selection for the lock-in amplifier 140 may need adjustment to target either the modulating frequency directly or the specific sideband frequencies generated by the AM process. Additionally, the signal processing may require demodulation techniques to extract the load-dependent information from the amplitude-modulated signal. This may, for example, involve envelope detection or synchronous demodulation methods.

[0409] Frequency modulation (FM) or phase modulation (PM) approaches could also be implemented, where the frequency or phase of the driving waveform is varied by a modulating signal. Frequency modulation (FM) techniques could be implemented where the frequency of a driving waveform is varied according to a modulating signal, creating a frequency -modulated driving waveform with instantaneous frequency changes around the nominal driving waveform frequency. If FM modulation is applied to methods 600 and 700, the signal generator 131 may require other components such as voltage-controlled oscillator (VCO) circuitry or direct digital synthesis capabilities to adjust the driving waveform frequency based on the modulating signal amplitude. Modulating waveform frequency parameters stored in memory 123 may control the rate of frequency variation, while the modulating waveform amplitude parameters may determine the frequency deviation range. The lock-in amplifier 140, or other electronics, may need to be configured with a wider bandwidth to capture the frequency -modulated signal, or may employ frequency discriminator circuits to convert frequency variations back to amplitude variations for processing.

[0410] Phase modulation (PM) approaches could similarly be implemented where a phase of a driving waveform is varied by the modulating signal, creating phase shifts proportional to the modulating signal amplitude. PM implementation may require the signal generator 131 to include phase-shift circuitry or digital signal processing capabilities to introduce controlled phase variations. The at least one processor 121 may control both a modulating waveform frequency and amplitude parameters to determine phase modulation characteristics. For both FM and PM approaches, the electrical characteristic measurements in steps 606 and 706 may focus on detecting mechanical load-dependent changes in the modulation characteristics, such as variations in frequency deviation or phase shift sensitivity, which may correlate with mechanical loads applied to the actuator 124. For example, in some embodiments, the system 100 may use multiple modulating signals or interrogation signals at different frequencies simultaneously to generate a more complex actuator driving waveform. This can enable probing multiple resonant modes of the actuator 124 or improving the accuracy of load estimation.

[0411] In some embodiments, instead of using the lock-in amplifier 140, the system 100 may employ digital signal processing techniques, such as Fast Fourier Transform (FFT) analysis, to extract the relevant frequency components from the electrical parameter signal.

[0412] Further, the system 100 may incorporate adaptive filtering techniques to dynamically adjust the modulating signal frequency based on changes in the actuator’s resonant frequency due to temperature variations or aging effects.

[0413] The load profile determination and unknown mechanical load estimation may be performed using non-linear machine learning models, such as neural networks or support vector machines, to capture more complex relationships between the electrical characteristics and applied loads.

[0414] While the disclosed embodiments describe the use of a current-to-voltage converter circuit (CVCC) 141 for measuring current through the actuator 124 and generating an output voltage in response that is filtered by the lock-in amplifier 140, it will be appreciated that alternative current measurement methods may be employed without departing from the scope of the present disclosure. For example, current transformers may be used to measure alternating current through the actuator 124 by electromagnetic induction, providing a voltage output proportional to the measured current. Hall effect sensors may be positioned to detect the magnetic field generated by current flow through the actuator 124, generating a voltage output that corresponds to the current magnitude. Shunt resistors may be inserted in series with the actuator 124 to create a voltage drop proportional to the current, which may then be measured and amplified. Each of these alternative current measurement approaches may generate voltage signals that can be processed by the lock-in amplifier 140 in a similar manner to the output of the CVCC 141, enabling the determination of electrical characteristics associated with the actuator 124 for load estimation purposes.

[0415] While the disclosed embodiments describe the use of an interrogation signal at a specific frequency to excite a resonance mode of the device 101 (e.g. a resonance mode of the mechanical system 109, or another sub-system of the device 101 comprising the actuator 124), it will be appreciated that in some embodiments, multiple interrogation signals at different frequencies may be used simultaneously without departing from the scope of the present disclosure. The signal generator 131 may generate a composite interrogation signal comprising multiple sinusoidal components, each operating at a different frequency associated with different resonant modes of the device 101 or one or more sub-assemblies of the device 101. This multi -frequency approach may enable probing of different vibrational modes corresponding to different axes of deformation of the actuator element, or probing of the effects of mechanical load on different sub-assemblies of the device 101. Multiple lock-in amplifiers may be included in parallel to filter and analyse the electrical responses at each interrogation frequency independently. This approach may provide enhanced sensitivity to directional loading, enable discrimination between different types of mechanical stress, and improve load estimation accuracy by providing multiple independent measurements that are less susceptible to variations due to temperature changes or aging effects.

[0416] While method 600 describes determining a load profile using two known mechanical loads to establish the relationship between electrical characteristic values and applied mechanical loads, it will be appreciated that any number of known mechanical loads may be investigated without departing from the scope of the present disclosure. Using additional known mechanical loads may improve the accuracy of the determined load profile by providing more data points for establishing the relationship between electrical characteristics and applied loads. For example, three, four, five, or more different known mechanical loads may be sequentially applied to the actuator 124, with corresponding electrical characteristic measurements taken for each loading condition. This approach may be particularly beneficial when the relationship between electrical characteristics and mechanical loads is non-linear, as additional data points may enable more accurate characterisation of curved relationships such as quadratic, exponential, or other complex mathematical functions. The increased number of data points may also improve the training of machine learning models used as load profiles, enhance the resolution of lookup tables or databases, and provide better statistical confidence in the determined relationships.

[0417] Advantages

[0418] The system 100 and methods 600, 700 of the present disclosure enable more accurate estimation of the magnitude of mechanical loads applied to or with devices that comprise an actuator, such as the device 101 described herein.

[0419] By driving the actuator 124 with the actuator driving waveform that is formed from the primary driving waveform and the interrogation signal while a mechanical load is applied to the actuator 124, the system 100 is able to detect subtle changes in the actuator's 124 response that correlate with the applied mechanical loads. The modification or modulation technique involves superimposing a small-amplitude signal onto the main driving waveform, typically at a frequency associated with a resonance mode of the actuator 124, the device 101 or a sub-assembly of the device 101. This approach allows for the isolation of load-dependent changes in the actuator's 124 electrical characteristics from other variations that may occur during operation. The use of lock-in amplification or similar signal processing techniques may further improve the sensitivity of the measurements, enabling the detection of small load-induced changes that might be otherwise difficult to discern. This increased sensitivity may lead to more accurate load profiles and, consequently, more precise load estimations during actual use of the actuator 124.

[0420] The methods 600, 700 provide systematic approaches for determining a load profile of the actuator 124 without requiring additional and / or external load sensors. By applying known mechanical loads to the actuator 124 and measuring the values of one or more component of the relevant electrical characteristic, the methods 600, 700 can establish a relationship between these parameters. This approach enables the creation of a mathematical model or lookup table that relates values of components of the electrical characteristic to applied mechanical loads. The ability to determine a load profile without a large number of additional sensors may be particularly beneficial in applications where space is limited or where the introduction of external sensors could interfere with the system's 100 performance. These methods 600, 700 may enable load estimation capabilities in a wide range of devices, from precision instruments to robotic systems or agricultural equipment, potentially enhancing their control and functionality. Further, the implementation of the methods 600, 700, which involve the analysis of current and / or voltage signals associated with the actuator 124, does not require any, or substantial, modification of an existing device to be used.

[0421] The load profile determined by method 600, and the method 700 for determining an estimate of a mechanical load applied to an actuator 124 allow for real-time load estimation during operation of the device 100, which could enable more precise control and performance in applications such as quantitative micro-elastography (QME) devices. Once the load profile is established, it can be used to estimate mechanical loads on the actuator 124 during normal operation by measuring the relevant values of the component of the electrical characteristic and applying the previously determined relationship between these values and applied mechanical loads. This real-time mechanical load estimation may provide valuable feedback for a user of the device and / or device control systems, allowing for dynamic adjustments that can maintain performance under varying mechanical load conditions. In QME applications, for example, accurate knowledge of the force applied to a sample material using the device is important for interpreting material mechanical properties. The ability to estimate this force in real-time without additional sensors may improve the accuracy and reliability of QME measurements, potentially leading to better diagnostic outcomes, whist decreasing the complexity and cost of the device. Furthermore, real-time load estimation may enhance safety features in various applications by allowing systems to quickly detect and respond to unexpected loads or resistances.

[0422] While the present application refers to determining “values of a component of an electrical characteristic” associated with the actuator 124, it will be appreciated that this terminology may be simplified without departing from the scope of the present disclosure. The values determined using the signal processing system 139A, 139B, such as the magnitude of the in-phase component or quadrature component from the lock-in amplifier 140, the phase calculated using both components, or the amplitude derived from the filtered output, may alternatively be referred to simply as “values associated with the electrical characteristic” or “values of the electrical characteristic”. This simplified terminology encompasses the same measurable parameters that are used to establish the load profile and estimate mechanical loads on the actuator 124, whether these values are derived from current measurements through the CVCC 141, strain measurements from the strain gauge 136 and strain gauge amplifier 138, or other electrical parameter signals processed by the at least one processor 121 that are related to the operation of the amplifier 124. The underlying technical concept remains unchanged regardless of whether the measured values are characterised as components of an electrical characteristic or as values of the electrical characteristic itself, as both terminologies refer to the same quantifiable electrical parameters that correlate with mechanical loads applied to the actuator 124 during operation of the device 101.

[0423] The electrical characteristic is described herein as being “associated with the actuator” to indicate that this characteristic is derived from, influenced by, or measurable in connection with the operation and physical state of the actuator 124. This association encompasses electrical parameters that are directly measurable from the actuator 124 itself, such as current flow through the actuator element or voltage across its terminals, as well as electrical parameters that are indirectly related to the actuator’s operation, such as signals from sensors like the strain gauge 136 that are mechanically or electrically coupled to the actuator 124. The electrical characteristic may also include processed or derived electrical parameters, such as the filtered outputs from the lock-in amplifier 140 or calculated values like phase and amplitude determined by the at least one processor 121. The association exists because these electrical parameters change in response to the actuator's mechanical state, loading conditions, and operational parameters, making them suitable indicators of the mechanical loads applied to the actuator 124. This broad association allows the system 100 to use various types of electrical measurements and signal processing techniques to characterise the actuator's response to mechanical loading, whether through direct electrical measurements from the actuator itself or through measurements of related electrical signals that are influenced by the actuator's mechanical behaviour within the larger mechanical system 109.

[0424] While several exemplary embodiments have been presented in the detailed description, it should be appreciated that a number of variations exist. It should also be appreciated that the exemplary embodiments of the system and methods are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the disclosed system.

[0425] In the claims that follow and in the preceding description, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of ...

Claims

1. CLAIMS1. A system for determining a load profile of an actuator, the system being configured to : generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; apply the actuator driving waveform to the actuator; determine a first value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the first value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a first known mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; determine a second value of the component of the electrical characteristic, the second value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a second known mechanical load that is different to the first known mechanical load is applied to the actuator; and determined based at least in part on the value of the parameter of the interrogation signal; and determine the load profile of the actuator based on the first value and second value of the component of the electrical characteristic, the load profile relating values of the component of the electrical characteristic to values of the mechanical load on the actuator.

2. The system of claim 1, wherein generating the actuator driving waveform comprises: generating a primary driving waveform, the primary driving waveform being a sinusoidal waveform; and modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain, the actuator driving waveform having frequency components from both the primary driving waveform and the interrogation signal; wherein: the interrogation signal is sinusoidal; and an amplitude of the interrogation signal is less than an amplitude of the primary driving waveform.

3. The system of claim 1 or claim 2, wherein determining the first value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the first known mechanical load are simultaneously applied to the actuator.

4. The system of claim 3, wherein: at least one sensor is operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a fdtered output comprising an in-phase component and a quadrature component; and the first value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

5. The system of claim 3, wherein: at least one current measurement circuit is operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component; and the first value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

6. The system of any one of claims 1 to 5, wherein determining the second value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the second known mechanical load are simultaneously applied to the actuator.

7. The system of claim 6, wherein: at least one sensor is operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a second filtered output comprising a second in-phase component and a second quadrature component; and the second value of the component of the electrical characteristic comprises at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

8. The system of claim 6, wherein: at least one current measurement circuit is operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a second filtered output comprising a second in-phase component and a second quadrature component; and the second value of the component of the electrical characteristic comprises at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

9. The system of any one of claims 1 to 8, wherein the load profile is a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator.

10. The system of any one of claims 1 to 9, wherein the actuator is a piezoelectric actuator.

11. A method for determining a load profile of an actuator, the method comprising: generating an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; applying the actuator driving waveform to the actuator; determining a first value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the first value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a first known mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; determining a second value of the component of the electrical characteristic, the second value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and a second known mechanical load that is different to the first known mechanical load is applied to the actuator; and determined based at least in part on the value of the parameter of the interrogation signal; and determining the load profile of the actuator based on the first value and second value of the component of the electrical characteristic, the load profile relating values of the component of the electrical characteristic to values of the mechanical load on the actuator.

12. The method of claim 11 , wherein generating the actuator driving waveform comprises: generating a primary driving waveform, the primary driving waveform being a sinusoidal waveform; and modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain, the actuator driving waveform having frequency components from both the primary driving waveform and the interrogation signal; wherein: the interrogation signal is sinusoidal; and an amplitude of the interrogation signal is less than an amplitude of the primary driving waveform.

13. The method of claim 11 or claim 12, wherein determining the first value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the first known mechanical load are simultaneously applied to the actuator.

14. The method of claim 13, wherein: the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component; and the first value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

15. The method of claim 13, wherein: the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component; and the first value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

16. The method of any one of claims 11 to 15, wherein determining the second value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the second known mechanical load are simultaneously applied to the actuator.

17. The method of claim 16, wherein: the parameter of the interrogation signal is a frequency of the interrogation signal;filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a second filtered output comprising a second in phase component and a second quadrature component; and the second value of the component of the electrical characteristic comprises at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

18. The method of claim 16, wherein: the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a second filtered output comprising a second in-phase component and a second quadrature component; and the second value of the component of the electrical characteristic comprises at least one of: a magnitude of the second in-phase component of the second filtered output; a magnitude of the second quadrature component of the second filtered output; a phase calculated using the second in-phase component and the second quadrature component; and an amplitude calculated using the second in-phase component and the second quadrature component.

19. The method of any one of claims 11 to 18, wherein the load profile is a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator.

20. The method of any one of claims 11 to 19, wherein the actuator is a piezoelectric actuator.

21. A system for determining an estimate of an unknown mechanical load applied to an actuator, the system being configured to: generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; apply the actuator driving waveform to the actuator;determine a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; and determine an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

22. The system of claim 21, wherein generating the actuator driving waveform comprises: generating a primary driving waveform, the primary driving waveform being a sinusoidal waveform; and modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain, the actuator driving waveform having frequency components from both the primary driving waveform and the interrogation signal; wherein: the interrogation signal is sinusoidal; and an amplitude of the interrogation signal is less than an amplitude of the primary driving waveform.

23. The system of claim 21 or claim 22, wherein determining the value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the unknown mechanical load are simultaneously applied to the actuator.

24. The system of claim 23, wherein: at least one sensor is operably connected to the actuator such that an output of the at least one sensor changes in response to a change in shape of the actuator; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one sensor at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component; and the value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output;a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

25. The system of claim 23, wherein: at least one current measurement circuit is operably connected to the actuator such that the at least one current measurement circuit measures a current through the actuator and generates an output based on the measured current; the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering the output of the at least one current measurement circuit at the frequency of the interrogation signal to generate a filtered output comprising an in-phase component and a quadrature component; and the value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

26. The system of any one of claims 21 to 25, wherein the load profile is a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator.

27. The system of any one of claims 21 to 26, wherein the load profile is the load profile of any one of claims 1 to 10.

28. The system of any one of claims 21 to 27, wherein the actuator is a piezoelectric actuator.

29. A method for determining an estimate of an unknown mechanical load applied to an actuator, the method comprising: generating an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; applying the actuator driving waveform to the actuator; determining a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and a mechanical load is applied to the actuator, the value of the component of the electrical characteristic being:associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; and determining an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

30. The method of claim 29, wherein generating the actuator driving waveform comprises: generating a primary driving waveform, the primary driving waveform being a sinusoidal waveform; and modifying the primary driving waveform with the interrogation signal by summing the primary driving waveform and the interrogation signal in a time domain, the actuator driving waveform having frequency components from both the primary driving waveform and the interrogation signal; wherein: the interrogation signal is sinusoidal; and an amplitude of the interrogation signal is less than an amplitude of the primary driving waveform.

31. The method of claim 29 or claim 30, wherein determining the value of the component of the electrical characteristic comprises filtering an electrical parameter signal that is associated with the actuator while the actuator driving waveform and the unknown mechanical load are simultaneously applied to the actuator.

32. The method of claim 31, wherein: the parameter of the interrogation signal is a frequency of the interrogation signal; filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one sensor that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component; and the value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

33. The method of claim 31 , wherein: the parameter of the interrogation signal is a frequency of the interrogation signal;filtering the electrical parameter signal comprises filtering, at the frequency of the interrogation signal, an output of at least one current measurement circuit that is operably connected to the actuator, to generate a filtered output comprising an in-phase component and a quadrature component; and the value of the component of the electrical characteristic comprises at least one of: a magnitude of the in-phase component of the filtered output; a magnitude of the quadrature component of the filtered output; a phase calculated using the in-phase component and the quadrature component; and an amplitude calculated using the in-phase component and the quadrature component.

34. The method of any one of claims 29 to 33, wherein the load profile is a mathematical model that relates values of the component of the electrical characteristic to values of the mechanical load on the actuator.

35. The method of any one of claims 29 to 34, wherein the load profile is the load profile of any one of claims 11 to 20.

36. The method of any one of claims 29 to 35, wherein the actuator is a piezoelectric actuator.

37. A quantitative micro-elastography (QME) system comprising: an optical system comprising: a source of electromagnetic radiation; and a detector for detecting electromagnetic radiation; a sensing layer, the source and detector being in optical communication with the sensing layer, the source emitting electromagnetic radiation that is directed through an optical interface of the sensing layer, the detector detecting a portion of the electromagnetic radiation that is emitted by the source, directed through the optical interface and backscattered by a material external to the QME system; a mechanical system comprising a piezoelectric actuator that is configured to be actuated to apply a force on a mechanical interface of the sensing layer such that the force is transmitted to the material via the mechanical interface of the sensing layer; the QME system being configured to: generate an actuator driving waveform by modifying a primary driving waveform with an interrogation signal; apply the actuator driving waveform to the actuator; determine a value of a component of an electrical characteristic, the electrical characteristic being associated with the actuator while the actuator driving waveform is applied to the actuator and amechanical load is applied to the actuator, the value of the component of the electrical characteristic being: associated with the actuator while the actuator driving waveform is applied to the actuator and an unknown mechanical load is applied to the actuator; and determined based at least in part on a value of a parameter of the interrogation signal; and determine an estimate of the unknown mechanical load based on the value of the component of the electrical characteristic and a load profile of the actuator.

38. The QME system of claim 37, wherein the QME system is further configured to change a value of an operating parameter of the QME system based on the determined estimate of the unknown mechanical load.

39. The QME system of claim 38, wherein changing the value of the operating parameter: stops a QME imaging process of the QME system; stops the application of the actuator driving waveform to the actuator; or causes an alarm to activate.

40. The QME system of any one of claims 37 to 39, wherein a frequency of the interrogation signal is associated with a resonant frequency of the QME system.

41. The QME system of any one of claims 37 to 39, wherein a frequency of the interrogation signal is within a threshold range that contains a resonant frequency of the mechanical system.

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