Non-linear deviation detection and prevention of haptic actuators

Abstract

A method for determining and mitigating an excess outflow of an internal mass of an electromechanical transducer may include the steps of measuring a sensed signal associated with the electromechanical transducer in response to a driving signal driven by the electromechanical transducer, determining a nonlinearity value based on the sensed signal, mapping the nonlinearity value to a probability of excess outflow of the internal mass, and applying a gain to a signal path configured to generate a driving signal based on the probability.

Description

Technology Field

[0001] The present disclosure generally relates to methods, devices, or implementations for haptic devices. In particular, the embodiments disclosed herein may disclose systems and methods for detecting and preventing non-linear excursion in haptic actuators. Background Technology

[0002] Vibratory haptic transducers, such as Linear Resonant Actuators (LRAs), are widely used in portable devices, such as mobile phones, to generate vibrational feedback for the user. Various forms of vibrational haptic feedback generate different tactile sensations on the user's skin and can play increasingly larger roles in human-machine interactions for modern devices.

[0003] An LRA can be modeled as a mass-spring electro-mechanical vibration system. When driven by appropriately designed or controlled drive signals, an LRA can generate specific desired types of vibrations. For example, sharp and distinct vibration patterns for a user's finger can be used to create a sensation that mimics a mechanical button click. Accordingly, these distinct vibrations can be used as a virtual switch to replace a mechanical button.

[0004] FIG. 1 illustrates an example of a vibration haptic system of a device (100). The device (100) may include a controller (101) configured to control a signal applied to an amplifier (102). Thus, the amplifier (102) may drive a vibration actuator (e.g., a haptic transducer) (103) based on this signal. The controller (101) may be triggered by a trigger to output this signal. The trigger may include, for example, a pressure or force sensor on a screen or virtual button of the device (100).

[0005] Among the various forms of vibrational haptic feedback, tonal vibrations with a continuous duration can play an important role in notifying the user of a device of specific predefined events, such as incoming calls or messages, emergency alarms, and timer alerts. To efficiently generate tonal vibration notifications, it may be desirable to operate the haptic actuator at or near its resonant frequency.

[0006] The resonant frequency f0 of the haptic transducer can be estimated approximately as follows:

[0007] (1)

[0008] Here, C is the compliance of the spring system and M is the equivalent moving mass, which can be determined based on both the actual moving part of the haptic transducer and the mass of the portable device having the haptic transducer.

[0009] Usage conditions such as sample-to-sample variations of individual haptic transducers, variations in mobile device assembly, temporal component changes due to aging, and vibration resonance of the haptic transducers with varying intensities of gripping the device by the user can change over time.

[0010] FIG. 2 illustrates an example of a linear resonant actuator (LRA) modeled as a linear system. LRAs are nonlinear components that can behave differently depending, for example, on the applied voltage level, operating temperature, and the frequency content of the operating signal. However, these components can be modeled as linear components under specific conditions. In this example, the LRA is modeled as a third-order system having electrical and mechanical components. Specifically, Re and Le are the DC resistance and coil inductance of the coil-magnet system, respectively, and Bl is the magnetic force factor of the coil. The driving amplifier outputs a voltage waveform V(t) with an output impedance Ro. Terminal voltage V T (t) can be detected through the terminals of the haptic transducer. The mass spring system (201) moves at velocity u(t).

[0011] Haptic systems may require precise control of the movements of haptic transducers. Such control may depend on the magnetic force factor Bl, also known as the electromagnetic transfer function of the haptic transducer. Ideally, the magnetic force factor Bl can be given by the product of Bl, where B is the magnetic flux density and l is the total length of the electric conductor in the magnetic field generating the magnetic flux density B. Both the magnetic flux density B and the length l must remain constant in the ideal case where motion occurs along a single axis.

[0012] As described above, when current flows through the coil of the electromagnet, a force can be applied to the electromagnet due to the interaction between the electromagnet and the permanent magnet. The vibration actuator (103) can be mechanically mounted to the structure of the device (100) in such a way that vibrations caused by the moving mass are transmitted to the device so that they can be felt by the user. In most portable electronic devices, the vibration actuator (103) is driven by a low-output impedance amplifier (102) having a voltage waveform. However, the user can experience haptic events caused by the acceleration of the mass in the vibration actuator (103) acting on the mass of the rest of the device (100) as well as the user's hand.

[0013] For a given steady-state input voltage signal, the response of the LRA can become increasingly nonlinear as the voltage amplitude increases beyond a specific limit (typically designated as the maximum voltage level by the LRA manufacturer). This nonlinearity is generally caused by amplitude-dependent changes in the spring constant associated with the spring suspending the LRA's inner mass. This amplitude dependence is typically most pronounced at high voltage levels. Depending on the LRA's structure, sufficiently large input signals driven at or near the resonant frequency can displace the LRA's inner mass to the point of contacting the LRA's enclosure or mechanical end-stops. This behavior is generally referred to as over-excursion. When this occurs, it can negatively impact the user experience and, in some cases, cause physical damage to the LRA. Therefore, systems and methods may be required to detect and prevent such over-excursion.

[0014] According to the teachings of the present disclosure, disadvantages and problems associated with existing approaches for generating haptic waveforms for electromagnetic transducers can be reduced or eliminated.

[0015] According to embodiments of the present disclosure, a method for determining and mitigating an excess outflow of an internal mass of an electromechanical transducer may include the steps of measuring a sensed signal associated with the electromechanical transducer in response to a driving signal driven by the electromechanical transducer, determining a nonlinearity value based on the sensed signal, mapping the nonlinearity value to a probability of excess outflow of the internal mass, and applying a gain to a signal path configured to generate a driving signal based on the probability.

[0016] According to these and other embodiments of the present disclosure, a system for determining and mitigating an excess outflow of an internal mass of an electromechanical transducer may include an input configured to measure a sensed signal associated with the electromechanical transducer in response to a driving signal driven by the electromechanical transducer, and a nonlinear outflow detector configured to determine a nonlinearity value based on the sensed signal, map the nonlinearity value to a probability of excess outflow of the internal mass, and apply a gain to a signal path configured to generate a driving signal based on the probability.

[0017] The technical advantages of the present disclosure will be readily apparent to those skilled in the art from the drawings, detailed description, and claims contained herein. The purposes and advantages of the embodiments will be realized and achieved by the elements, features, and combinations specifically indicated in the claims, at least.

[0018] It should be understood that both the foregoing general description and the following detailed description are examples and illustrative and do not limit the claims set forth in this disclosure. Brief explanation of the drawing

[0019] A more complete understanding of the embodiments of the present invention and their advantages can be obtained by referring to the following description taken in connection with the accompanying drawings, wherein similar reference numerals indicate similar features: FIG. 1 illustrates an example of a vibration haptic system of a device as known in the art. FIG. 2 illustrates an example of a linear resonant actuator (LRA) modeled as a linear system as known in the art. FIG. 3 illustrates selected components of an exemplary host device according to embodiments of the present disclosure. FIG. 4 illustrates a cross-sectional view of an exemplary electromagnetic load implemented as a haptic transducer according to embodiments of the present disclosure. FIG. 5 illustrates a graph of exemplary gains that a waveform preprocessor can apply to a raw converter driving signal as a function of excess deviation probability to generate a processed converter driving signal according to embodiments of the present disclosure. Specific details for implementing the invention

[0020] The following description describes exemplary embodiments according to the present disclosure. Further exemplary embodiments and implementations will be apparent to those skilled in the art. Additionally, those skilled in the art will recognize that various equivalents may be applied in place of or in conjunction with the embodiments discussed below, and that all such equivalents should be deemed to be included in the present disclosure.

[0021] Various electronic devices or smart devices may have transducers, speakers, and acoustic output transducers, for example, any transducer for converting a suitable electric driving signal into an acoustic output such as a sound pressure wave or mechanical vibration. For example, many electronic devices may include the above speakers or loudspeakers for generating sound to provide, for example, playback of audio content, voice communication, and / or audible notifications.

[0022] These speakers or loudspeakers may include electromagnetic actuators, such as voice coil motors, which are mechanically coupled to a flexible diaphragm, for example, a conventional loudspeaker cone, or mechanically coupled to the surface of a device, such as a glass screen of a mobile device. Some electronic devices may also include acoustic output transducers capable of generating ultrasounds for use, for example, in proximity detection type applications and / or machine-to-machine communication.

[0023] Many electronic devices may additionally or alternatively include more specialized acoustic output transducers, such as haptic transducers, tailored to generate vibrations for haptic control feedback or notifications to the user. Additionally or alternatively, the electronic device may have a connector, such as a socket, for making a removable mating connection with a corresponding connector of an accessory device, and may be arranged to provide a driving signal to the connector to drive one or more of the aforementioned types of transducers of the accessory device when connected. Thus, such an electronic device will include a driving circuit for driving the transducers of the host device or the connected accessory with an appropriate driving signal. In the case of acoustic or haptic transducers, the driving signal will generally be an analog time-varying voltage signal, for example, a time-varying waveform.

[0024] FIG. 3 illustrates selected components of an exemplary host device (300) that incorporates force sensing using an electromagnetic load (301) of the host device (300) according to embodiments of the present disclosure. The host device (300) may include, but is not limited to, any other system, device, or apparatus including a mobile device, a home application, a vehicle, and / or a human-machine interface. The electromagnetic load (301) may include any suitable load having a complex impedance, including, without limitation, a haptic transducer, a loudspeaker, a microspeaker, a piezoelectric transducer, or other suitable transducer.

[0025] Referring briefly to FIG. 4, FIG. 4 illustrates a cross-sectional view of an exemplary electromagnetic load (301) implemented as a haptic transducer according to embodiments of the present disclosure. As illustrated in FIG. 4, the electromagnetic load (301) may include a moving mass (402) mechanically coupled to a housing (404) through one or more springs (406). The moving mass (402) may include a ferromagnetic material such that an alternating current flowing through a coil (408) surrounding the moving mass (402) may induce an alternating mechanical field that causes the moving mass (402) to vibrate (e.g., up and down in the direction illustrated in FIG. 4). The housing (404) may include end stops (410) configured to engage with corresponding features (412) of the moving mass (402) to limit the excursion of the moving mass (402) within the housing (404). As previously described, mechanical contact between the features (412) and the end stops (410) may cause nonlinearity between the electromagnetic signal driving the electromagnetic load (301) and the displacement or excursion of the moving mass (402) relative to the housing (404).

[0026] Referring again to FIG. 3, during operation, a signal generator (324) of the processing subsystem (305) of the host device (300) can generate a raw converter driving signal x'(t) (in some embodiments, it may be a waveform signal such as a haptic waveform signal or an audio signal). The raw converter driving signal x'(t) can be generated based on a desired playback waveform received by the signal generator (324).

[0027] The raw converter driving signal x'(t) can be received by a waveform preprocessor (326) capable of optimizing the raw converter driving signal x'(t) based on the probability of excess deviation of the moving mass of the electromagnetic load (301) to generate the processed converter driving signal x(t), as described in more detail below.

[0028] The processed converter drive signal x(t) can be amplified in turn by the amplifier (306) to generate a drive signal V(t) for driving the electromagnetic load (301). In response to the drive signal V(t), the detected terminal voltage V of the electromagnetic load (301) T (t) can be detected by a terminal voltage sensing block (307), e.g., a voltmeter, and converted into a digital representation by a first analog-to-digital converter (ADC) (303). Similarly, the detected current I(t) can be converted into a digital representation by a second ADC (304). The current I(t) is coupled to a resistor R coupled to the terminal of the electromagnetic load (301). s It can be detected through a shunt resistor (302) having.

[0029] As illustrated in FIG. 3, the processing subsystem (305) detects the terminal voltage V TIt is configured to determine the existence of nonlinearity between the electromagnetic signal driving the electromagnetic load (301) and the displacement of the moving mass (e.g., moving mass (402)) of the electromagnetic load (301) based on (t) and the detected current I(t), and to determine the probability P of excess deviation of the moving mass based on such nonlinearity.

[0030] To explain this function of the non-linear excursion detector (308), the non-linear excursion detector (308) has an inverse-EMF voltage V for the electromagnetic load (301). B (t) can be estimated. In general, the inverse-EMF voltage V B (t) may not be measured directly from outside the haptic transducer. However, the terminal voltage V measured at the terminals of the haptic transducer T (t) is V as follows B It can be related to (t):

[0031] (2)

[0032] Here, the parameters are defined as described with reference to Fig. 2. Consequently, the inverse-EMF voltage V B (t) can be estimated according to equation (2), which can be rearranged as follows.

[0033] (3)

[0034] Inverse-EMF voltage V B Since (t) can be proportional to the velocity of the moving mass of the electromagnetic load (301), the inverse-EMF voltage V B (t) can, in turn, provide estimates of these rates. Thus, the inverse-EMF voltage V B (t) can be estimated based on an equivalent electric model of the electromagnetic load (301), and such an electric model can vary depending on parameters of the host device (300) and the electromagnetic load (301), including resonant frequency and quality factor.

[0035] Since the estimates of DC resistance Re and inductance Le do not need to be precise (e.g., an error of approximately 10% or less is acceptable), fixed values ​​from offline calibration or datasheet specifications may suffice. For example, in some embodiments, the nonlinear deviation detector (308) is the inverse-EMF voltage V estimated according to the teaching of U.S. Patent Application Serial No. 16 / 559,238 filed September 3, 2019, which is incorporated herein by reference in its entirety. B (t) can be determined.

[0036] Detected current I(t) and inverse-EMF voltage V B By measuring (t), the nonlinear deviation detector (308) can estimate the internal states of the electromagnetic load (301). Distortions and other nonlinearities are detected in the current I(t), inverse-EMF voltage V B (t), or a combination of the two can be extracted. Based on the amount of nonlinearity observed for a threshold value, the nonlinear deviation detector (308) can control the processed converter drive signal x(t) to prevent excess deviation.

[0037] Referring again to FIG. 4, if the spring (406) of the electromagnetic load (301) is overstretched, the moving mass (402) may exhibit non-linear behavior with respect to the processed transducer drive signal x(t). Additionally, collisions between the moving mass (402) and the end stops (410) may also cause non-linear distortion. Thus, these two scenarios can define a non-linear behavior zone in which the electromagnetic load (301) is more likely to cause over-disengagement.

[0038] To determine the possibility or probability of excess deviation, the non-linear deviation detector (308) uses electrical measurements (e.g., terminal voltage V T (t), Detected current I(t), Inverse-EMF voltage VB The occurrence of nonlinearity can be determined using (t).

[0039] For example, in the case of a haptic playback waveform while the host device (300) is operating, if the processed converter driving signal x(t) is non-periodic, the probability P of excess deviation is the terminal voltage V T The voltage content ratio associated with (t) can be determined by comparing the current-voltage ratio associated with the detected current I(t). The voltage content ratio is the terminal voltage V T High-frequency content above a specific frequency present at (t) and terminal voltage V T It may include the ratio of low-frequency content below a specific frequency present at (t). Similarly, the current content ratio may include the ratio of high-frequency content above a specific frequency present at the detected current I(t) and low-frequency content below a specific frequency present at the detected current I(t). The mathematical difference or ratio between the current content ratio and the voltage content ratio may represent the probability P of excess deviation.

[0040] In addition to or alternatively, in addition to the comparison of the current content ratio and the voltage content ratio, the nonlinear deviation detector (308) is at the terminal voltage V while noise gating for the magnitude of the detected current I(t) is triggered. T The probability P of excess deviation can be determined based on whether noise gating for the magnitude of (t) is not triggered.

[0041] As another example, in an offline process where no haptic waveform is generated, the signal generator (324) can generate a pilot tone above the resonant frequency of the raw converter driving signal x'(t) and the electromagnetic load (301), and the nonlinear deviation detector (308) can generate the detected current I(t) and terminal voltage V TBased on (t), the total harmonic distortion (THD) of the pilot tone resulting from the electromagnetic load (301) entering a nonlinear operating region can be measured. This THD can be calculated as a function of the pilot tone and its harmonics. The nonlinear deviation detector (308) can also map the measured THD to a probability of excess deviation at specific frequencies and / or amplitudes, which can be used by the waveform preprocessor (326) to generate a processed transducer drive signal x(t).

[0042] A waveform processor (326) receives a signal indicating the probability P of over-deviation and, based thereon, can modify the raw converter driving signal x'(t) to generate a processed converter driving signal x(t) (e.g., by applying appropriate gains and / or filter responses), thereby reducing the probability P determined by the non-linear deviation detector (308) of the probability of over-deviation of the moving mass of the electromagnetic converter (301), thereby eliminating or reducing the occurrence of the moving mass (402) exceeding the rated deviation limit and / or other operating limits (e.g., limits defined by the manufacturer of the electromagnetic load). For example, FIG. 5 illustrates a graph of exemplary gains that the waveform preprocessor (326) can apply to the raw converter driving signal x'(t) as a function of the probability P of over-deviation to generate the processed converter driving signal x(t) according to embodiments of the present disclosure.

[0043] As described above, systems and methods for determining and mitigating the excess outflow of an internal mass (e.g., moving mass 402) of a haptic actuator and / or other electromagnetic load (e.g., electromagnetic load 301) may be provided, wherein the nonlinearity value of the electromagnetic load may be measured based at least on a current signal associated with the electromagnetic load (e.g., a detected current I(t)). The nonlinearity value may be mapped to a probability value (e.g., probability P) of the excess outflow of the moving mass. Additionally, the probability value may be used to determine the gain attenuation to be applied to the transducer driving signal.

[0044] As used herein, when two or more elements are referred to as being "combined" with one another, such term indicates that such two or more elements are in an electronic or mechanical communication state applicable indirectly or directly, or regardless of the presence or absence of intervening elements.

[0045] This disclosure encompasses all changes, substitutions, variations, modifications, and alterations to the exemplary embodiments of this specification that are understood by those skilled in the art. Similarly, where appropriate, the appended claims encompass all changes, substitutions, variations, modifications, and alterations to the exemplary embodiments of this specification that are understood by those skilled in the art. Furthermore, references in the appended claims to a device or system, or a component of a device or system, that is adapted, arranged, capable of, configured, enabled, operable, or operated to perform a specific function encompass that device, system, or component, regardless of whether that device, system, or component, or that specific function, is activated, turned on, or unlocked, insofar as that device, system, or component is adapted, arranged, capable, configured, enabled, operable, and operated. Accordingly, modifications, additions, or omissions may be made to the systems, devices, and methods described herein without departing from the scope of this disclosure. For example, components of systems and devices may be integrated or separated. Furthermore, the operations of the systems and devices disclosed herein may be performed by more, fewer, or different components, and the described methods may include more, fewer, or different steps. Additionally, the steps may be performed in any appropriate order. As used herein, "each" refers to each member of a set or each member of a subset of a set.

[0046] Although representative embodiments have been illustrated and described in the drawings, the principles of the present disclosure may be implemented using any technology, regardless of whether they are currently known. The present disclosure should by no means be limited to the representative embodiments and technologies illustrated in the drawings and described above.

[0047] Unless otherwise specifically noted, the parts depicted in the drawings are not necessarily drawn in a fixed proportion.

[0048] All examples and conditional expressions listed in this specification are intended for pedagogical purposes to help the reader understand the concepts contributed by the inventor to advance the content and technology of this disclosure, and should be interpreted as having no limitations on the examples and conditions specifically cited as such. Although the embodiments of this disclosure have been described in detail, it should be understood that various changes, substitutions, and modifications may be made without departing from the spirit and scope of this disclosure.

[0049] Although specific advantages have been listed above, various embodiments may include or exclude some or all of the listed advantages. Additionally, other technical advantages will be readily apparent to a person skilled in the art after reviewing the aforementioned drawings and description.

[0050] To assist any reader of any patent issued for this application and the Patent Office in interpreting the claims attached herein, the applicants wish to note that none of the attached claims or claim elements are intended to apply 35 USC §112(f) unless the words (“means for doing” or “step for doing”) are explicitly used in a particular claim.

Claims

Claim 1 A method for determining and mitigating over-excursion of an internal mass of an electromechanical transducer, comprising: measuring a sensed signal associated with the electromechanical transducer in response to a driving signal driven by the electromechanical transducer; determining a non-linearity value based on the sensed signal; mapping the non-linearity value to a probability of over-excursion of the internal mass; and applying a gain to a signal path configured to generate a driving signal based on the probability. Claim 2 A method for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein, in claim 1, the step of determining a nonlinearity value based on the detected signal comprises the step of determining a back-electromotive force associated with the electromechanical converter based on the detected signal. Claim 3 A method for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein, in claim 1, determining the nonlinearity value comprises: determining a first content ratio equal to the ratio of content present in a driving signal of a first frequency band to content present in a driving signal of a second frequency band; determining a second content ratio equal to the ratio of content present in a detected signal of the first frequency band to content present in the second frequency band; and determining the nonlinearity value based on a comparison of the first content ratio and the second content ratio. Claim 4 A method for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein, in claim 1, determining the nonlinearity value comprises: determining a first content ratio equal to the ratio of high-frequency content present in a driving signal above a specific frequency and low-frequency content present in a driving signal below the specific frequency; determining a second content ratio equal to the ratio of high-frequency content present in a detected signal above the specific frequency and low-frequency content present in a detected signal below the specific frequency; and determining the nonlinearity value based on a comparison of the first content ratio and the second content ratio. Claim 5 A method for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein, in claim 1, determining the nonlinearity value comprises determining the nonlinearity value based on the noise gating of the magnitude of the driving signal compared with the noise gating of the magnitude of the detected signal. Claim 6 A method for determining and mitigating excess displacement of an internal mass of an electromechanical converter, wherein, in claim 1, determining the nonlinearity value comprises: generating the driving signal as a pilot tone at a frequency greater than the resonance frequency of the electromechanical converter; measuring the total harmonic distortion present in the detected signal in response to the pilot tone; and determining the nonlinearity value based on the total harmonic distortion. Claim 7 A method for determining and mitigating excess deviation of an internal mass of an electromechanical converter, further comprising the step of attenuating the driving signal based on the gain in claim 1. Claim 8 A method for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein, in claim 1, the step of determining the nonlinearity value based on the detected signal includes the step of measuring the harmonic components of the detected signal, and the method further includes the step of determining the direction of the electromechanical converter based on the amplitude and phase of the harmonic components of the detected signal. Claim 9 A method for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein, in claim 1, the driving signal is a voltage signal and the detected signal is a current signal. Claim 10 In claim 1, a method for determining and mitigating excess displacement of an internal mass body of an electromechanical transducer, wherein the electromechanical transducer is one of a haptic transducer, a voice coil, and a loudspeaker. Claim 11 A system for determining and mitigating an excursion of an internal mass of an electromechanical converter, comprising: an input configured to measure a sensed signal associated with said electromechanical converter in response to a driving signal driven by said electromechanical converter; and a non-linear excursion detector, wherein the non-linear excursion detector comprises: a non-linear excursion detector configured to determine a non-linearity value based on said sensed signal, map said non-linearity value to a probability of excursion of an internal mass, and apply a gain to a signal path configured to generate said driving signal based on said probability. Claim 12 A system for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein determining a nonlinearity value based on the detected signal includes determining a back electromotive force associated with the electromechanical converter based on the detected signal. Claim 13 A system for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein determining the nonlinearity value comprises: determining a first content ratio equal to the ratio of content present in a driving signal of a first frequency band to content present in a driving signal of a second frequency band; determining a second content ratio equal to the ratio of content present in a detected signal of the first frequency band to content present in the second frequency band; and determining the nonlinearity value based on a comparison of the first content ratio and the second content ratio. Claim 14 A system for determining and mitigating an excess outflow of an internal mass of an electromechanical converter, wherein determining the nonlinearity value comprises: determining a first content ratio equal to the ratio of high-frequency content present in a driving signal above a specific frequency and low-frequency content present in a driving signal below the specific frequency; determining a second content ratio equal to the ratio of high-frequency content present in a detected signal above the specific frequency and low-frequency content present in a detected signal below the specific frequency; and determining the nonlinearity value based on a comparison of the first content ratio and the second content ratio. Claim 15 A system for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein, in claim 11, determining the nonlinearity value comprises determining the nonlinearity value based on noise gating of the magnitude of the driving signal compared with noise gating of the magnitude of the detected signal. Claim 16 A system for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein determining the nonlinearity value comprises: generating the driving signal as a pilot tone at a frequency greater than the resonant frequency of the electromechanical converter; measuring the total harmonic distortion present in the detected signal in response to the pilot tone; and determining the nonlinearity value based on the total harmonic distortion. Claim 17 In claim 11, the system for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein the nonlinear deviation detector is also configured to attenuate the driving signal based on the gain. Claim 18 A system for determining and mitigating excess deviation of an internal mass of an electromechanical converter, wherein, in claim 11, determining a nonlinearity value based on the detected signal includes measuring the harmonic components of the detected signal, and further including determining the direction of the electromechanical converter based on the amplitude and phase of the harmonic components of the detected signal. Claim 19 A system for determining and mitigating excess outflow of an internal mass of an electromechanical converter, wherein, in paragraph 11, the driving signal is a voltage signal and the detected signal is a current signal. Claim 20 In paragraph 11, the electromechanical transducer is a system for determining and mitigating excess displacement of an internal mass body of an electromechanical transducer, which is one of a haptic transducer, a voice coil, and a loudspeaker.

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