Piezoelectric actuator displacement self-sensing device and method based on total charge

Abstract

The invention discloses a piezoelectric actuator displacement self-sensing device and method based on total charge, and belongs to the field of micro-nano positioning and intelligent sensing. The device comprises a driving circuit, a protection circuit and a measuring circuit, a capacitance voltage dividing structure is combined with a coupling type charge amplifier, displacement sensing is achieved by measuring the total charge flowing to a piezoelectric actuator, capacitance parameters meet the condition that Cc < Cp < Cr, and the cost is remarkably reduced while the measuring precision is guaranteed. According to the method, an extended piezoelectric constitutive equation is provided, a displacement self-sensing model with a clear structure and controllable parameters is established, model simplification according to precision requirements is supported, and high-precision and high-timeliness real-time displacement estimation is realized. The method solves the problems of complex model, large calculation amount, high charge measurement cost and easy drifting in the prior art, and is suitable for the fields of micro-nano control, precise positioning, vibration suppression and the like.

Description

Technical Field

[0001] This invention relates to the field of micro-nano positioning and intelligent sensing, and in particular to a piezoelectric actuator displacement self-sensing device and method based on total charge. Background Technology

[0002] Piezoelectric actuators, with their advantages of high displacement resolution and fast response speed, are indispensable core components in micro- and nano-scale mechanisms and precision control equipment for executing physical motion. They are commonly used in micro- and nano-positioning and manipulation fields requiring precise positioning, such as micromirrors, micro- and nano-manipulated robots, and micro-servo valves. However, piezoelectric actuators exhibit nonlinear characteristics such as hysteresis and creep in their displacement response relative to the excitation voltage. In applications such as biomedicine and ultra-precision manufacturing, extremely high requirements are often placed on positioning accuracy and control of the interaction with the environment. Therefore, achieving precise measurement and control of the end-effector displacement has become a key technical challenge.

[0003] There are two technical solutions for the accurate measurement of piezoelectric actuator displacement: one is to use an external high-precision displacement sensor, the main disadvantages of which are high cost and space occupation; the other is to utilize the coexistence of piezoelectric effect and piezoelectric inverse effect, and indirectly realize displacement measurement by measuring the electrical signal related to the output displacement and the applicable displacement self-sensing model. The second technical solution, namely displacement self-sensing technology, is particularly suitable for space-constrained applications such as micro-nano operation or vibration suppression. Displacement self-sensing based on charge measurement is currently the mainstream technology, but there are still some core bottleneck problems: (1) The displacement self-sensing theoretical model describing the nonlinear dynamic behavior between output displacement, charge and excitation voltage has an inherent contradiction between its simplification and sensing accuracy: complex models have a large amount of calculation, which affects the timeliness of online sensing; excessive simplification makes it difficult to guarantee the displacement sensing accuracy. (2) The charge measurement involved in self-sensing technology has measurement errors such as charge drift, especially under quasi-static excitation conditions, the measurement error is large. In industrial applications, it is urgent to solve the measurement error compensation problem under the condition of limited charge measurement cost. Summary of the Invention

[0004] The technical problem this invention aims to solve is that existing self-sensing models generally suffer from complex structures and high computational demands, making it difficult to meet real-time displacement sensing requirements. Furthermore, the measurement bandwidth of the charge amplification circuit used for charge measurement is limited by the frequency response characteristics of the integrator network, and integral drift easily leads to charge measurement errors, further restricting the low-frequency performance and stability of displacement self-sensing. To address these problems, this invention provides a piezoelectric actuator displacement self-sensing device and method based on total charge.

[0005] The object of this invention is achieved in the following manner:

[0006] A piezoelectric actuator displacement self-sensing device based on total charge, comprising:

[0007] The drive circuit, used to provide excitation voltage to the piezoelectric actuator, includes a voltage-source drive power supply, the piezoelectric actuator, and a reference capacitor C connected in series between the negative terminal or ground of the drive power supply and the piezoelectric actuator. r ;

[0008] The protection circuit unit has its input terminal connected to the reference capacitor C. r The two ends are used to receive and clamp the reference capacitor C. r The voltage signals at both ends; the protection circuit unit includes at least one voltage follower, the input of which is protected by voltage clamping through a positive clamp and a negative clamp, and its output provides the voltage signal after following; when the displacement self-sensing device is working normally, the output voltage of the protection circuit is the same as the voltage across the reference capacitor Cr;

[0009] The measurement circuit unit includes a charge amplifier, the input of which is connected to a coupling capacitor C. c The charge amplifier is electrically connected to the output terminal of the protection circuit unit; the charge amplifier consists of a high-impedance operational amplifier and a feedback capacitor C connected in parallel between the output terminal and the inverting input terminal of the operational amplifier. f and feedback resistor R f constitute;

[0010] The operational amplifier output voltage V o With the reference capacitor C r The voltage V across the terminals r The following relationship exists between (t): .

[0011] The protection circuit unit can be omitted if the drive circuit already has overvoltage and overcurrent protection functions.

[0012] The charge amplifier is a quasi-static charge amplifier with an output voltage V. o The relationship between the total charge Q flowing to the piezoelectric actuator and the piezoelectric actuator is as follows: .

[0013] It also includes the input bias current I of the charge amplifier. b With input offset voltage V os The module that compensates for measurement errors caused by the error, and the total charge after compensation. .

[0014] A piezoelectric actuator displacement self-sensing method based on total charge, the method comprising the following steps:

[0015] Step 1: Establish the extended piezoelectric constitutive equation to decompose the electric displacement into a purely dielectric electric displacement. piezoelectric coupling electric displacement and piezoelectric induced electric displacement Decompose the strain into purely elastic strain piezoelectric coupling strain and piezoelectric induced strain And establish piezoelectric coupling electric displacement With piezoelectric induced strain piezoelectric coupling strain With piezoelectric induced electric displacement The synchronization ratio constraint relationship between them;

[0016] Step 2: Based on the extended piezoelectric constitutive equation, construct a model describing the output displacement x and driving voltage V of the piezoelectric actuator. in A displacement self-sensing model of the dynamic relationship between Q and total charge;

[0017] Step 3: Using the device described in any one of claims 1-4, acquire the driving voltage V. in Output displacement x and output voltage V o Time series data;

[0018] Step 4: Based on the model described in Step 2 and the data described in Step 3, a hybrid method of physical model and data-driven approach is used to identify parameters and obtain an accurate displacement self-sensing model.

[0019] Step 5: Convert the displacement self-sensing model, which has already undergone parameter identification, into a model driven by a driving voltage V. in and output voltage V o Input: Output: Displacement estimate The output displacement reconstruction model; during the operation of the piezoelectric actuator, the real-time measured driving voltage V in With output voltage V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

[0020] The extended piezoelectric constitutive equation is:

[0021] ,in, It is the piezoelectric coupling dielectric constant. is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient.

[0022] The displacement self-sensing model includes compensation terms for rate-dependent energy loss and rate-independent energy loss during the electrical-to-mechanical energy conversion process; the complete structural form of the displacement self-sensing model is as follows:

[0023] Where n, L, and A represent the number of layers, total thickness, and cross-sectional area of ​​the piezoelectric stack, respectively. This represents the actual excitation voltage applied to the piezoelectric actuator. , Represents the total charge. Indicates the output displacement. The parameter to be identified has the same unit as capacitance. It is a time constant. , Both m and m are parameters to be identified; It is the piezoelectric coupling dielectric constant. Here, d is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient; the second equation indicates that the charge loss corresponding to all rate-dependent energy losses is included in the calculation of the purely dielectric free charge term. The dynamic model; where the third equation represents the charge loss corresponding to rate-independent loss.

[0024] To simplify the calculations, if no losses and charge measurement errors are considered, the above displacement self-sensing model can be simplified to:

[0025] ,

[0026] The above displacement self-sensing model can be further simplified to: .

[0027] To simplify the calculation, the dynamic model of pure dielectric free charge considering rate-dependent losses and the charge loss term corresponding to rate-independent losses can be approximated. The above displacement self-sensing model can be simplified as follows:

[0028] .

[0029] The displacement self-sensing model has 3 to 9 parameters, and can be simplified by ignoring loss terms to adapt to different real-time and accuracy requirements.

[0030] The beneficial effects of this invention are as follows: The piezoelectric actuator displacement self-sensing device and method provided by this invention acquires the charge variable data generated by the piezoelectric actuator during operation by measuring the charge variable data, and obtains the self-sensing displacement by constructing a displacement self-sensing model based on the extended piezoelectric equation. The beneficial effects are reflected in two aspects: First, a piezoelectric actuator displacement self-sensing device based on total charge measurement is proposed. Its core technology is to achieve the measurement of the total charge flowing to the piezoelectric actuator through capacitive voltage division and capacitively coupled charge amplifier. Its advantage lies in ensuring measurement accuracy while effectively reducing costs, and its measurement error can be compensated by establishing an error model. Second, the proposed piezoelectric actuator displacement self-sensing method based on total charge proposes a novel extended piezoelectric constitutive equation. Based on this, a displacement self-sensing model for the piezoelectric actuator is proposed. Its advantage lies in the clear structure of the constructed displacement self-sensing model, which can be simplified or made more complex according to the required accuracy. The number of parameters to be identified ranges from a minimum of 3 to a maximum of 9, and it does not contain complex sub-models such as hysteresis operators. When implementing displacement self-sensing online, it has the advantages of low computational load and high timeliness. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the relationship between internal field variables in the extended piezoelectric constitutive equation.

[0032] Figure 2 This is a schematic diagram of a self-sensing device. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same technical meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0035] like Figure 1 and Figure 2 As shown, this invention provides a piezoelectric actuator displacement self-sensing device based on total charge. This device obtains displacement information by measuring the total charge flowing into the piezoelectric actuator in real time under the action of excitation voltage; it includes:

[0036] The drive circuit, used to provide excitation voltage to the piezoelectric actuator, includes a voltage-source drive power supply, the piezoelectric actuator, and a reference capacitor C connected in series between the negative terminal or ground of the drive power supply and the piezoelectric actuator. r ;

[0037] The protection circuit unit has its input terminal connected to the reference capacitor C. r The two ends are used to receive and clamp the reference capacitor C. rThe voltage signals at both ends; the protection circuit unit includes at least one voltage follower, the input of which is protected by voltage clamping through a positive clamp and a negative clamp, and its output provides the voltage signal after following; when the displacement self-sensing device is working normally, the output voltage of the protection circuit is the same as the voltage across the reference capacitor Cr;

[0038] The measurement circuit unit includes a charge amplifier, the input of which is connected to a coupling capacitor C. c The charge amplifier is electrically connected to the output terminal of the protection circuit unit; the charge amplifier consists of a high-impedance operational amplifier and a feedback capacitor C connected in parallel between the output terminal and the inverting input terminal of the operational amplifier. f and feedback resistor R f constitute;

[0039] The operational amplifier output voltage V o With the reference capacitor C r The voltage V across the terminals r The following relationship exists between (t): .

[0040] Wherein, the static capacitor C of the piezoelectric actuator p Reference capacitor C r and coupling capacitor C c The size relationship between them is: C c <<C p <<C r And the leakage resistance R of the reference capacitor leak_r Much smaller than the leakage resistance R of the coupling capacitor leak_c The capacitance and leakage resistance conditions ensure that the terminal voltage of the reference capacitor is only 5% or less of the excitation voltage when the piezoelectric actuator is operating normally, and ensure that almost all the total charge flowing to the piezoelectric actuator flows to the reference capacitor. The total charge Q flowing to the piezoelectric actuator is directly proportional to the output voltage Vo of the measuring circuit unit, i.e. .

[0041] The protection circuit unit can be omitted if the drive circuit already has overvoltage and overcurrent protection functions.

[0042] The charge amplifier is a quasi-static charge amplifier. When an input bias current Ib and an input offset voltage Vos are present, the output voltage of the charge amplifier will exhibit measurement errors. Total charge after measurement error compensation .

[0043] This invention provides a displacement self-sensing method for a piezoelectric actuator based on total charge, the method comprising the following steps:

[0044] Step 1: Establish the extended piezoelectric constitutive equation to decompose the electric displacement into a purely dielectric electric displacement. piezoelectric coupling electric displacement and piezoelectric induced electric displacement Decompose the strain into purely elastic strain piezoelectric coupling strain and piezoelectric induced strain And establish piezoelectric coupling electric displacement With piezoelectric induced strain piezoelectric coupling strain With piezoelectric induced electric displacement The synchronization ratio constraint relationship between them;

[0045] Step 2: Based on the extended piezoelectric constitutive equation, construct a model describing the output displacement x and driving voltage V of the piezoelectric actuator. in A displacement self-sensing model of the dynamic relationship between Q and total charge;

[0046] Step 3: Using the device, acquire the driving voltage V in Output displacement x and output voltage V o Time series data;

[0047] Step 4: Based on the model described in Step 2 and the data described in Step 3, a hybrid method of physical model and data-driven approach is used to identify parameters and obtain an accurate displacement self-sensing model.

[0048] Step 5: Convert the displacement self-sensing model, which has already undergone parameter identification, into a model driven by a driving voltage V. in and output voltage V o Input: Output: Displacement estimate The output displacement reconstruction model; during the operation of the piezoelectric actuator, the real-time measured driving voltage V in With output voltage V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

[0049] Furthermore, the extended piezoelectric constitutive equation in step 1 specifically includes:

[0050] The traditional piezoelectric constitutive equation can be derived through a two-step sequential loading process. First, the piezoelectric material is subjected to an electric field E without any mechanical action. Second, mechanical stress T is applied while the electric field remains constant.

[0051] The first step is to induce polarization in the piezoelectric material using an electric field. The electric displacement is numerically equal to the surface charge density on the electrode plates and consists of three components: first, the free charge generated by charging the vacuum capacitor under the influence of the electric field; second, the free charge induced by pure dielectric polarization in the absence of strain, which does not involve piezoelectric energy conversion; and third, the free charge induced by piezoelectric polarization accompanying piezoelectric strain, which participates in piezoelectric energy conversion. Since the first two components do not involve piezoelectric polarization and strain, and their dielectric constant is much greater than 1, they can be combined into a pure dielectric electric displacement. The last component, because it is related to electromechanical energy coupling, is defined as the piezoelectric-coupled electric displacement. To establish the connection between these components and the traditional piezoelectric equations, an electromechanical coupling coefficient is introduced. Therefore, the electric displacement can be decomposed and expressed as follows:

[0052]

[0053] Represents the vacuum permittivity. and They represent dielectric polarization intensity and dielectric constant, respectively. and These represent the piezoelectric polarization intensity and the piezoelectric constant, respectively. It is dielectric displacement. It is piezoelectric coupling electric displacement. It is the dielectric constant under constant strain, which is consistent with the definition in the traditional piezoelectric equation; It is the piezoelectric coupling dielectric constant.

[0054] It can be assumed that, under conditions of electrical short circuit and negligible electrostriction and microscopic 180° domain change, the piezoelectric coupling electric displacement The piezoelectric induced strain remains synchronized with and proportional to the piezoelectric strain. This relationship holds regardless of any nonlinearity in the piezoelectric conversion process or whether the system is in an unsteady state. This relationship can be expressed as:

[0055] (2)

[0056] In the second step, the electric field remains constant, and then stress is applied. The elastic strain of the piezoelectric material under stress consists of two parts: one is the pure elastic strain without piezoelectric polarization, and the other is the piezoelectric coupling strain accompanying piezoelectric polarization or piezoelectric energy conversion. In the direct piezoelectric effect, the latter is always synchronous and proportional to the piezoelectrically induced electric displacement. Similar to the first step, the synchronous coexistence between piezoelectric coupling strain and piezoelectrically induced electric displacement remains valid even in the presence of piezoelectric nonlinearity and system unsteadiness. Therefore, the relationship between the field variables can be expressed as:

[0057] (3)

[0058] (4)

[0059] in It is the elastic compliance constant under open-circuit conditions, which means that no free charges can migrate to the electrode surface, and therefore the electric displacement remains unchanged. It is the piezoelectric coupling elastic compliance constant. Based on the analysis of these two steps, by combining equations (1)-(4), the piezoelectric constitutive equation is extended as follows:

[0060] ,in, It is the piezoelectric coupling dielectric constant. is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient.

[0061] The displacement self-sensing model includes compensation terms for rate-dependent energy loss and rate-independent energy loss during the electrical-to-mechanical energy conversion process; the complete structural form of the displacement self-sensing model is as follows:

[0062] Where n, L, and A represent the number of layers, total thickness, and cross-sectional area of ​​the piezoelectric stack, respectively. This represents the actual excitation voltage applied to the piezoelectric actuator. , Represents the total charge. Indicates the output displacement. The parameter to be identified has the same unit as capacitance. It is a time constant. , Both m and m are parameters to be identified; It is the piezoelectric coupling dielectric constant. Here, d is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient; the second equation indicates that the charge loss corresponding to all rate-dependent energy losses is included in the calculation of the purely dielectric free charge term. The dynamic model; where the third equation represents the charge loss corresponding to rate-independent loss.

[0063] To simplify the calculations, if no losses and charge measurement errors are considered, the above displacement self-sensing model can be simplified to:

[0064] ,

[0065] The above displacement self-sensing model can be further simplified to: .

[0066] To simplify the calculation, the dynamic model of pure dielectric free charge considering rate-dependent losses and the charge loss term corresponding to rate-independent losses can be approximated. The above displacement self-sensing model can be simplified as follows:

[0067] .

[0068] The displacement self-sensing model has 3 to 9 parameters, and can be simplified by ignoring loss terms to adapt to different real-time and accuracy requirements.

[0069] Step 3 specifically includes:

[0070] Drive voltage V in It is an independent active input variable, and a continuous multi-tone signal excitation method is adopted based on the determination of the amplitude range and frequency range of the driving voltage.

[0071] Under the action of the excitation signal, the driving voltage V is synchronously acquired. in Output displacement x, output voltage V o .

[0072] Step 4 specifically includes:

[0073] Based on the displacement self-sensing model in step 2 and the driving voltage V collected in step 3 in Output displacement x Output voltage V o Based on the original data, the parameters of the displacement self-sensing model are identified by the nonlinear least squares regression algorithm, and the steady-state displacement self-sensing model of the piezoelectric actuator is obtained.

[0074] The method further includes: normalization and denoising of online data in the data used for parameter identification of the displacement self-sensing model in steps 3 and 4 above, spectral analysis, denoising, and synchronous estimation of the output displacement of the piezoelectric actuator, as well as optimization of sampling time in the modeling and estimation process.

[0075] Implementation Case 1: The piezoelectric actuator has a stacked structure, where n, L, and A represent the number of layers, total thickness, and cross-sectional area of ​​the stacked piezoelectric actuator, respectively. In step 2 of the piezoelectric actuator displacement self-sensing method, if any energy loss and charge measurement error during the electrical-to-mechanical energy conversion process are disregarded, the displacement self-sensing model simplifies to:

[0076] It can be further organized into The parameters to be identified are , and In step 3 of the piezoelectric actuator displacement self-sensing method, the driving voltage signal is set to contain at least two frequency components, and the driving voltage V is synchronously acquired. in End displacement x and output voltage V oThe original experimental data is then denoised. In step 4 of the piezoelectric actuator displacement self-sensing method, the least squares regression algorithm is used to identify three parameters to be identified in the displacement self-sensing model, thus obtaining the steady-state displacement self-sensing model of the piezoelectric actuator. In step 5 of the piezoelectric actuator displacement self-sensing method, since the self-sensing model itself is a displacement reconstruction model about the driving voltage and the output voltage, during the operation of the piezoelectric actuator, the real-time measured V... in and V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

[0077] Implementation Case 2: Taking a piezoelectric stacked actuator as the implementation object, in step 2 of the piezoelectric actuator displacement self-sensing method, to simplify the calculation, an approximate description is made of the dynamic model of pure dielectric free charge considering rate-dependent losses and the charge loss term corresponding to rate-independent losses, while ignoring charge measurement errors. The displacement self-sensing model can be simplified to...

[0078] ,

[0079] It can be further organized as follows:

[0080] The parameters to be identified are (i=1,2,3,4,5) And m, a total of 7. In step 3 of the piezoelectric actuator displacement self-sensing method, the driving voltage signal is set to contain at least 4 frequency components, and the driving voltage V is synchronously acquired. in End displacement x and output voltage V o The original experimental data was then denoised to obtain a discrete sequence V. in [k]、V o [k] and x[k] are further used to obtain the discrete sequence V through proportional relationships. p [k] and Q[k], where k is a non-negative integer representing the sampling time index. In step 4 of the piezoelectric actuator displacement self-sensing method, the seven parameters to be identified in the displacement self-sensing model are identified using a nonlinear least squares regression algorithm to obtain the steady-state displacement self-sensing model of the piezoelectric actuator. In step 5 of the piezoelectric actuator displacement self-sensing method, since the self-sensing model itself is a displacement reconstruction model about the driving voltage and the output voltage, during the operation of the piezoelectric actuator, the real-time measured V... in and V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

[0081] Implementation Case 3: Taking a piezoelectric stacked actuator as the implementation object, in step 2 of the piezoelectric actuator displacement self-sensing method, the displacement self-sensing model includes compensation terms for rate-dependent energy loss and rate-independent energy loss in the electrical-to-mechanical energy conversion process; the complete structural form of the displacement self-sensing model is as follows:

[0082] ,

[0083] The parameters to be identified are , , , , , , , And m, a total of 9. In step 3 of the piezoelectric actuator displacement self-sensing method, the driving voltage signal is set to contain at least 5 frequency components, and the sampling time step is set to T. s Synchronously acquire driving voltage V in End displacement x and output voltage V o The original experimental data was then denoised to obtain a discrete sequence V. in [k]、V o [k], x[k], and V p [k], where k is a non-negative integer representing the sampling time index. The complete structural form of the displacement self-sensing model is transformed into a discrete-time difference form: The displacement reconstruction model is obtained by sorting:

[0084] .

[0085] In step 4 of the piezoelectric actuator displacement self-sensing method, the global residual minimization is constructed as the objective function, and the physical variable V is set. in [k]、V o [k], x[k], Q d [k]、Q L The initial state of [k] is 0. Initial values ​​and possible value ranges are set for the nine parameters to be identified. A nonlinear least squares optimization algorithm, such as the Levenberg-Marquardt algorithm, is used to identify the nine parameters in the displacement self-sensing model, and the robustness of the parameter identification model is verified. If the model robustness is poor, step 2 can be returned to correct the model structure, such as merging redundant parameters, reducing the number of parameters to be identified, and lowering the risk of overfitting; or, to use a robust least squares identification algorithm in step 4, the self-sensing model can be converted into a state-space model in step 2, and process noise and measurement noise can be considered in the model; step 3 can then be returned to optimize V. in [k]、V oThe quality of the original data [k] and x[k]. In step 5 of the piezoelectric actuator displacement self-sensing method, since the self-sensing model itself is a displacement reconstruction model about the driving voltage and the output voltage, during the operation of the piezoelectric actuator, the V measured in real time will be... in and V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

[0086] Although the three specific embodiments listed all use piezoelectric stacked actuators as the implementation object, this invention patent can apply the piezoelectric actuator displacement self-sensing device and method to cantilever beam piezoelectric actuators, cylindrical piezoelectric actuators, and other structural forms of piezoelectric actuators.

[0087] The piezoelectric actuator displacement self-sensing device and method provided by this invention acquires the charge variable data generated by the piezoelectric actuator during operation by measuring the charge variable data, and obtains the self-sensing displacement by constructing a displacement self-sensing model based on the extended piezoelectric equation. The beneficial effects are reflected in two aspects: First, it proposes a piezoelectric actuator displacement self-sensing device based on total charge measurement. Its core technology is to achieve the measurement of the total charge flowing to the piezoelectric actuator through capacitive voltage division and capacitively coupled charge amplifiers. Its advantages are that it ensures measurement accuracy while effectively reducing costs, and its measurement error can be compensated by establishing an error model. Second, the proposed piezoelectric actuator displacement self-sensing method based on total charge proposes a novel extended piezoelectric constitutive equation. Based on this, it proposes a displacement self-sensing model for the piezoelectric actuator. Its advantages are that the constructed displacement self-sensing model has a clear structure, can be simplified or made more complex according to the required accuracy, and the number of parameters to be identified can range from a minimum of 3 to a maximum of 9. Furthermore, it does not contain complex sub-models such as hysteresis operators, and has the advantages of low computational load and high timeliness when implementing displacement self-sensing online.

[0088] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several changes and improvements without departing from the overall concept of the present invention, and these should also be considered within the scope of protection of the present invention.

Claims

1. A piezoelectric actuator displacement self-sensing device based on total charge, characterized in that: include The drive circuit, used to provide excitation voltage to the piezoelectric actuator, includes a voltage-source drive power supply, the piezoelectric actuator, and a reference capacitor C connected in series between the negative terminal or ground of the drive power supply and the piezoelectric actuator. r ; The protection circuit unit has its input terminal connected to the reference capacitor C. r The two ends are used to receive and clamp the reference capacitor C. r The voltage signals at both ends; the protection circuit unit includes at least one voltage follower, the input of which is protected by voltage clamping through a positive clamp and a negative clamp, and its output provides the voltage signal after following; when the displacement self-sensing device is working normally, the output voltage of the protection circuit is the same as the voltage across the reference capacitor Cr; The measurement circuit unit includes a charge amplifier, the input of which is connected to a coupling capacitor C. c The charge amplifier is electrically connected to the output terminal of the protection circuit unit; the charge amplifier consists of a high-impedance operational amplifier and a feedback capacitor C connected in parallel between the output terminal and the inverting input terminal of the operational amplifier. f and feedback resistor R f constitute; The operational amplifier output voltage V o With the reference capacitor C r The voltage V across the terminals r The following relationship exists between (t): .

2. The piezoelectric actuator displacement self-sensing device based on total charge according to claim 1, characterized in that: The protection circuit unit can be omitted if the drive circuit already has overvoltage and overcurrent protection functions.

3. The piezoelectric actuator displacement self-sensing device based on total charge according to claim 1, characterized in that: The charge amplifier is a quasi-static charge amplifier with an output voltage V. o The relationship between the total charge Q flowing to the piezoelectric actuator and the following is satisfied: .

4. The piezoelectric actuator displacement self-sensing device based on total charge according to claim 3, characterized in that: It also includes the input bias current I of the charge amplifier. b With input offset voltage V os The module that compensates for measurement errors caused by the error, and the total charge after compensation. .

5. A displacement self-sensing method for a piezoelectric actuator based on total charge, characterized in that: The method includes the following steps: Step 1: Establish the extended piezoelectric constitutive equation to decompose the electric displacement into a purely dielectric electric displacement. piezoelectric coupling electric displacement and piezoelectric induced electric displacement Decompose the strain into purely elastic strain piezoelectric coupling strain and piezoelectric induced strain And establish piezoelectric coupling electric displacement With piezoelectric induced strain piezoelectric coupling strain With piezoelectric induced electric displacement The synchronization ratio constraint relationship between them; Step 2: Based on the extended piezoelectric constitutive equation, construct a model describing the output displacement x and driving voltage V of the piezoelectric actuator. in A displacement self-sensing model of the dynamic relationship between Q and total charge; Step 3: Using the device described in any one of claims 1-4, acquire the driving voltage V. in Output displacement x and output voltage V o Time series data; Step 4: Based on the model described in Step 2 and the data described in Step 3, a hybrid method of physical model and data-driven approach is used to identify parameters and obtain an accurate displacement self-sensing model. Step 5: Convert the displacement self-sensing model, which has already undergone parameter identification, into a model driven by a driving voltage V. in and output voltage V o Input: Output: Displacement estimate The output displacement reconstruction model; during the operation of the piezoelectric actuator, the real-time measured driving voltage V in With output voltage V o The input is fed into the displacement reconstruction model, and the estimated value of the output displacement is calculated in real time. .

6. The piezoelectric actuator displacement self-sensing method based on total charge according to claim 5, characterized in that: The extended piezoelectric constitutive equation is: ,in, It is the piezoelectric coupling dielectric constant. is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient.

7. The piezoelectric actuator displacement self-sensing method based on total charge according to claim 5, characterized in that: The displacement self-sensing model includes compensation terms for rate-dependent energy loss and rate-independent energy loss during the electrical-to-mechanical energy conversion process; the complete structural form of the displacement self-sensing model is as follows: Where n, L, and A represent the number of layers, total thickness, and cross-sectional area of ​​the piezoelectric stack, respectively. This represents the actual excitation voltage applied to the piezoelectric actuator. , Represents the total charge. Indicates the output displacement. The parameter to be identified has the same unit as capacitance. It is a time constant. , Both m and m are parameters to be identified; It is the piezoelectric coupling dielectric constant. Here, d is the piezoelectric coupling elastic compliance constant, and d is the piezoelectric coefficient; the second equation indicates that the charge loss corresponding to all rate-dependent energy losses is included in the calculation of the purely dielectric free charge term. The dynamic model; where the third equation represents the charge loss corresponding to rate-independent loss.

8. The piezoelectric actuator displacement self-sensing method based on total charge according to claim 7, characterized in that: To simplify the calculations, if no losses and charge measurement errors are considered, the above displacement self-sensing model can be simplified to: ， The above displacement self-sensing model can be further simplified to: .

9. The piezoelectric actuator displacement self-sensing method based on total charge according to claim 7, characterized in that: To simplify the calculation, the dynamic model of pure dielectric free charge considering rate-dependent losses and the charge loss term corresponding to rate-independent losses can be approximated. The above displacement self-sensing model can be simplified as follows: 。 10. The piezoelectric actuator displacement self-sensing method based on total charge according to claim 5, characterized in that: The displacement self-sensing model has 3 to 9 parameters, and can be simplified by ignoring loss terms to adapt to different real-time and accuracy requirements.

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