Strong field impedance spectroscopy measurement method, system and equipment of piezoelectric material and medium

Abstract

The invention discloses a high-field impedance spectroscopy measurement method, system and device for a piezoelectric material and a medium, and relates to the technical field of high-field impedance spectroscopy measurement, and the method comprises the steps: loading a sweep frequency signal generated by a signal generator to the piezoelectric material in a high field, and reading a current signal and a current signal amplitude of the piezoelectric material; comparing the read current signal amplitude with a set current constant value, changing the voltage value of the sweep frequency signal according to a set voltage change step length when the current signal amplitude is out of an error range, and outputting the sweep frequency signal of the current frequency; and obtaining a final current signal of the piezoelectric material through the sweep frequency signal of the current frequency, fitting the final current signal to obtain an admittance circle diagram, and measuring the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram. Corresponding operation and judgment are carried out according to the relation between the current amplitude and the set current error range and the current constant value, and it is guaranteed that the measured current is kept constant all the time.

Description

Technical Field

[0001] The present invention relates to the technical field of strong field impedance spectrum measurement, and in particular to a method, system, equipment and medium for measuring strong field impedance spectrum of piezoelectric material. Background Art

[0002] Piezoelectric materials are functional materials that can convert mechanical energy into electrical energy and vice versa. They are widely used in ultrasonic testing, medical ultrasound, underwater acoustics, power ultrasound, etc. In recent years, with the rapid development and application of high-power piezoelectric devices, the characterization of the high-field power performance of piezoelectric materials has become increasingly important.

[0003] Impedance characteristic measurement is an important part of piezoelectric material performance characterization. The impedance characteristic parameters of piezoelectric materials can be characterized by measuring their impedance spectrum and phase spectrum, which are useful tools for studying the performance of piezoelectric materials and ultrasonic transducers. Currently, the performance detection of piezoelectric materials is usually completed using a commercial impedance analyzer, and its driving voltage is around 1V.

[0004] Existing commercial impedance analyzers are expensive and can only be used for constant voltage measurements. As the driving voltage increases, the impedance spectrum of the piezoelectric vibrator under constant voltage measurement conditions will produce obvious distortion or even jumps due to the nonlinear effect of the elastic coefficient of the piezoelectric vibrator under high electric fields and high vibrations. Summary of the invention

[0005] The purpose of the present invention is to address the deficiencies of the above-mentioned prior art and to provide a method, system, device and medium for measuring the strong field impedance spectrum of a piezoelectric material, so as to solve the problem in the prior art that as the driving voltage increases, the impedance spectrum of the piezoelectric vibrator under constant voltage measurement conditions will produce obvious distortion or even jump due to the nonlinear effect of the elastic coefficient of the piezoelectric vibrator under high electric field and high vibration.

[0006] The present invention specifically provides the following technical solution: a method for measuring the strong field impedance spectrum of a piezoelectric material, comprising the following steps: Loading the swept frequency signal generated by the signal generator to the piezoelectric material under the strong field, and reading the current signal and the current signal amplitude of the piezoelectric material; The read current signal amplitude is compared with the set current constant value, and when the current signal amplitude is outside the error range, the voltage value of the frequency sweep signal is changed according to the set voltage change step, and the frequency sweep signal of the current frequency is output; The final current signal of the piezoelectric material is obtained by the frequency sweep signal of the current frequency, and the admittance circle diagram is obtained by fitting the final current signal, and the strong field impedance spectrum of the piezoelectric material is measured according to the admittance circle diagram.

[0007] Preferably, after reading the current signal and the current signal amplitude of the piezoelectric material, filtering the current signal comprises the following steps: Inputting the current signal into a zero-phase filter to obtain a filtered signal without introducing additional phase delay; When obtaining the filtered signal, the signal of the current amplitude is forward filtered according to the forward coefficient to obtain an intermediate filtered signal; The reverse sequence of the intermediate filter signal is reversely filtered according to the reverse coefficient to obtain a final filter signal; wherein the values ​​of the reverse coefficient and the forward coefficient are obtained by the signal sampling rate and the cutoff frequency.

[0008] Preferably, after outputting the swept frequency signal of the current frequency, performing phase detection on the swept frequency signal comprises the following steps: Acquire a column of reference signals having the same frequency as the frequency sweep signal; The reference signal is cross-correlated with the voltage signal and current signal collected at the piezoelectric material to obtain the phase of the voltage signal and the phase of the current signal, as well as the phase difference between the voltage signal and the current signal, and the frequency of the sweep signal is adjusted by minimizing the phase difference.

[0009] Preferably, the phase difference between the voltage signal and the current signal is obtained by: .

[0010] in, are the cross-correlation values ​​of the voltage and the reference signal, and the cross-correlation values ​​of the current and the reference signal, respectively. U and I is the amplitude of the voltage and current signals, Δ φ is the phase difference, φ 1 and φ 2 are the phase of the voltage signal and the phase of the current signal respectively.

[0011] Preferably, before comparing the read current signal amplitude with the set current constant value, the following steps are also included: Use LabVIEW program in the computer to set up the current measurement unit and the judgment unit; A signal generator node is set in the current measurement unit to output a swept frequency signal of an AC voltage, and a digital oscilloscope node is set to read the amplitude of the current signal at both ends of the piezoelectric material; Add conditions in the judgment unit to judge the magnitude relationship between the current amplitude and the set current error range and the current constant value respectively.

[0012] Preferably, when the read current signal amplitude is compared with the set current constant value, if the current signal amplitude is within an error range, the current frequency sweep output is maintained and the state of the signal generator is detected.

[0013] Preferably, obtaining an admittance circle diagram by fitting the final current signal, and measuring the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram comprises the following steps: Construct a piezoelectric vibrator equivalent circuit through piezoelectric materials; The total admittance of the piezoelectric vibrator equivalent circuit is obtained through the final current signal; the specific expression is: .

[0014] .

[0015] in, Y is the admittance, I 0 is the current through the static impedance, I 1 is the current through the dynamic impedance, U is the voltage, C 0 is a pure capacitor, which is equivalent to the impedance of the piezoelectric material in static state. L 1 , C 1 and R 1 The dynamic impedance is represented by the equivalent inductance, equivalent capacitance and equivalent resistance respectively. y 0 is the static admittance, y 1 is the dynamic admittance; The conductivity G As the horizontal axis, the susceptance B As the ordinate, construct the curve of susceptance with respect to conductance and obtain the admittance circle diagram; the specific expression is: .

[0016] .

[0017] in, G is the conductivity, B is the electrical susceptance, j is an imaginary unit, is the angular frequency; The parameters of the piezoelectric material are obtained according to the admittance circle diagram, and the strong field impedance spectrum and the piezoelectric vibrator equivalent circuit parameters are measured according to the relationship that admittance is the inverse of impedance; the parameters of the piezoelectric material include dynamic resistance, dynamic capacitance, dynamic inductance and static capacitance.

[0018] The present invention provides a high-field impedance spectrum measurement system for piezoelectric materials, comprising: A data acquisition module is used to load the swept frequency signal generated by the signal generator to the piezoelectric material under the strong field, and read the current signal and the current signal amplitude of the piezoelectric material; The current feedback module is used to compare the read current signal amplitude with the set current constant value, and when the current signal amplitude is outside the error range, change the voltage value of the sweep signal according to the set voltage change step size, and output the sweep signal of the current frequency; The measuring module is used to obtain the final current signal of the piezoelectric material through the sweep frequency signal of the current frequency, obtain the admittance circle diagram through the fitting of the final current signal, and measure the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram.

[0019] The present invention provides a computer device, comprising a memory and a processor, wherein a program is stored in the memory, and when the program is executed by the processor, the processor executes the steps of a method for measuring a strong field impedance spectrum of a piezoelectric material.

[0020] The present invention provides a storage medium, which includes a stored computer program. The computer program is executed by at least one processor to enable the at least one processor to execute the steps of the above-mentioned method for measuring the strong field impedance spectrum of a piezoelectric material.

[0021] Compared with the prior art, the present invention has the following significant advantages: In the frequency sweeping process of the signal generator, the present invention performs corresponding operations and judgments according to the relationship between the collected current signal amplitude and the set current error range and the current constant value, and obtains the final current signal of the current frequency sweeping signal, which can ensure that the measured current always remains constant, and timely adjusts when the current exceeds the error range to achieve constant current measurement. The strong field impedance spectrum is measured by using the admittance circle diagram fitted by the current signal, which can ensure that the vibration amplitude near the resonant frequency is almost constant, and avoid the admittance spectrum distortion caused by elastic nonlinearity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural block diagram of the constant current measurement provided by the present invention; Figure 2 is a structural block diagram of a current feedback module provided by the present invention; Figure 3 is a comparison chart of the experimental results of the impedance measurement system provided by the present invention and a commercial impedance analyzer; wherein, Figure 3 (a) is the admittance spectrum, Figure 3 (b) is the phase spectrum; Figure 4It is a data graph measured by the strong field impedance spectrum measurement system under constant current (20mA) conditions provided by the present invention; wherein, Figure 4 (a) is the admittance spectrum, Figure 4 (b) is the current curve; Figure 5 A comparison diagram of the filtering methods provided by the present invention; Figure 6 A zero-phase signal filtering process diagram provided by the present invention; wherein, Figure 6 (a) is the forward filtering graph, Figure 6 (b) is the reverse filtering image; Figure 7 A simulated phase difference diagram provided by the present invention; Figure 8 The present invention provides an admittance circle diagram. DETAILED DESCRIPTION

[0023] The following is a clear and complete description of the technical solutions of the embodiments of the present invention in conjunction with the drawings in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0024] Due to the nonlinear effect of piezoelectric ceramics becoming stronger under high vibration, the impedance spectrum obtained by constant pressure measurement will have a jump, affecting the calculation of material parameters.

[0025] like Figure 1 to Figure 8 As shown, the present invention proposes a method, system, device and medium for measuring the strong field impedance spectrum of piezoelectric materials. The overall framework is built by LabVIEW software in a computer. The relevant parameters of the signal generator are set before the experiment (by transmitting commands and modifying voltage). After the setting is completed, the frequency sweep signal is generated and the voltage and current signals are collected, and the collected signals are filtered. In order to achieve measurement under constant current conditions, a current amplitude feedback program is added to the program, and finally, the relevant values ​​are calculated based on further analysis of the collected signals.

[0026] like Figure 1 As shown, an embodiment of the present application provides a method for measuring a strong field impedance spectrum of a piezoelectric material, comprising the following steps: Step S1: Loading a frequency sweep signal generated by a signal generator to a piezoelectric material under a strong field, and reading a current signal and a current signal amplitude of the piezoelectric material.

[0027] Relevant parameters are set for the signal generator, and a frequency sweep signal is generated according to the relevant parameters; the relevant parameters include a frequency sweep start value, a frequency sweep end value, a frequency sweep step length, a starting voltage value, and a voltage change step length.

[0028] The constant current measurement system and the constant voltage measurement system of the present invention are both written in the same program, so the signal generator used by the constant current measurement system and the signal generator used by the constant voltage measurement system are of the same model, which is the AFG1000 signal generator of Tektronix. The command set used by the instrument control module is shown in Table 1.

[0029] Table 1 Part of the SCPI command set used by the signal generator control module

[0030] The difference between the signal generator control modules of the constant current measurement system and the constant voltage measurement system is that the frequency sweeping program of the constant voltage measurement system only changes the frequency of the signal in one measurement, while the constant current measurement system needs to adjust the voltage output of the signal generator in addition to adjusting the frequency of the signal in order to adjust the current signal at both ends of the piezoelectric sample to a constant value.

[0031] When measuring the performance of piezoelectric materials using the constant current method, you only need to select the parameters such as the frequency sweep start value, end value, and frequency sweep step length of the output signal, and you can use the signal generator to generate the required frequency sweep signal. In addition, in order to meet the conditions for constant current measurement of piezoelectric materials, the starting voltage value and voltage change step length of the signal generator need to be set before measurement. The setting of the above parameters needs to be based on the parameter characteristics of the piezoelectric material to achieve the best measurement effect. The frequency sweep signal generated by the signal generator is amplified by a power amplifier, and the piezoelectric ceramic sample is loaded with the signal.

[0032] The computer transmits commands to the digital oscilloscope, and the digital oscilloscope collects voltage and current signals of the piezoelectric ceramic sample.

[0033] In the constant current measurement system, the oscilloscope-related SCPI command set used is shown in Table 2. Table 2 Part of the SCPI command set used by the digital oscilloscope control module

[0034] That is, the signal acquisition instrument used in the constant current measurement system is the MSO5074 digital oscilloscope of Puyuan Company. This oscilloscope can synchronously acquire the current and voltage signals at the same time, and ensure the authenticity of the acquired signals to ensure the accuracy of the signal phase difference and meet the requirements of piezoelectric measurement.

[0035] After reading the current signal and the current signal amplitude of the piezoelectric material, the current signal is filtered and compared by a computer, including the following steps: Step S11: input the current signal into a zero-phase filter to obtain a filtered signal without introducing additional phase delay.

[0036] The zero-phase filter is actually evolved from the IIR filter. H (z) is an IIR filter, and the signal processing process is as follows Figure 6 shown.

[0037] Step S12: When the filtered signal is obtained, the signal of the current amplitude is converted into x n Perform forward filtering to obtain the intermediate filtered signal .

[0038] Step S13: According to the reverse coefficient, the intermediate filtered signal The reverse sequence Perform reverse filtering to obtain the final filtered signal y n ; Among them, the values ​​of the reverse coefficient and the forward coefficient are obtained by the signal sampling rate and the cutoff frequency.

[0039] In the actual use of the system, special LabVIEW functions can be used to calculate the reverse coefficients and forward coefficients.

[0040] That is, during the system measurement process, the signal may be affected by various types of interference and noise, such as transmission channel loss, electromagnetic interference, etc. These interferences and noises will cause signal distortion, making the signal difficult to process. Therefore, when the data is collected into the software, the signal needs to be filtered to eliminate or reduce the noise. This system uses a zero-phase filter, which is characterized by not introducing additional phase delays during the filtering process. In other words, the zero-phase filter can pass signals with different frequency components through the filter with the same time delay without changing the signal phase relationship. Traditional filters introduce a certain phase delay in the process of processing signals, which will affect the time it takes for different signals to arrive at the output, thereby changing the phase characteristics of the signal. Such as Figure 5 As shown in the figure, compared with the signal filtered by the FIR filter, the signal output by the zero phase has almost no phase difference with the original signal, and the phase is kept stable. Therefore, a more realistic signal curve can be collected by using the zero phase filter.

[0041] Step S2: Compare the read current signal amplitude with the set current constant value, and when the current signal amplitude is outside the error range, change the voltage value of the frequency sweep signal according to the set voltage change step, and output the frequency sweep signal of the current frequency.

[0042] The current feedback module is an important part of constant current measurement. In order to achieve the measurement of constant current and constant voltage in the same set of experimental instruments, the current detection program and the current adjustment program are added to the system measurement system. Through the cooperation of these two parts of the program, it can be ensured that the current remains constant during the measurement process, thereby achieving accurate current measurement.

[0043] In the current feedback module, the impedance characteristics and frequency characteristics of piezoelectric ceramics (the piezoelectric material here is piezoelectric ceramics) play a key role. According to the impedance characteristics and frequency characteristics of piezoelectric ceramics, the impedance value of piezoelectric ceramics reaches a minimum value at the resonant frequency. Therefore, during the frequency sweep of the signal generator, the voltage value of the signal generator is changed to ensure that the current is constant during the measurement process to achieve constant current measurement. This process requires the SCPI command set related to the signal generator to drive the voltage adjustment of the signal.

[0044] The structural block diagram of the current feedback module is as follows: Figure 2 As shown in the figure, the detection process is as follows: First, input the parameters such as the initial voltage value, the frequency sweep range, the frequency sweep step, the constant current value and the voltage change step, and output the corresponding AC voltage signal according to these parameters. Then, detect the state of the signal generator, and when there is a signal generation command, detect the state of the digital oscilloscope, stop real-time acquisition, detect the digital oscilloscope to read the current value and voltage amplitude at both ends of the piezoelectric ceramic, read the waveform data, and restore the waveform, and collect it into the measurement system. Then, after the filtering program is processed, the current amplitude at both ends of the piezoelectric ceramic is obtained. After that, the collected current amplitude is compared with the set current constant value. If the collected current amplitude is within the error range, the current frequency sweep program is maintained and the program continues to run. If the collected current amplitude is outside the error range, the voltage value of the signal is changed according to the set voltage change step, and the signal of the current frequency continues to be output, and the process is repeated until the measured current amplitude is within the set current error range.

[0045] Based on the above current feedback structure diagram, the following is a design of a loop detection program, which realizes constant current measurement by writing a LabVIEW program. The specific procedure is as follows: First, create a new VI (Virtual Instrument) in LabVIEW software. Add a While loop structure in the VI interface to continuously measure and judge the current. Outside the While loop, add variables and controls to input parameters such as initial voltage value, sweep frequency range, sweep frequency step, current constant value and error constant value.

[0046] Before comparing the read current signal amplitude with the set current constant value, the following steps are also included: The current measuring unit and the judging unit are set using the LabVIEW program in the computer.

[0047] A signal generator node is set in the current measurement unit to output a swept frequency signal of an AC voltage, and a digital oscilloscope node is set to read the current signal amplitude at both ends of the piezoelectric material.

[0048] Add conditions in the judgment unit to judge the magnitude relationship between the current amplitude and the set current error range and the current constant value respectively.

[0049] That is, inside the While loop, add a signal generator node to output the AC voltage signal. Next, add a digital oscilloscope node to read the current value at both ends of the piezoelectric ceramic. Connect the output of the digital oscilloscope node to a filter program to process the collected current signal and obtain the current amplitude. Add conditional statements to determine the relationship between the current amplitude and the set current error range and current constant. If the current amplitude is within the error range, keep the current sweep program for output, continue running, and check the signal generator status.

[0050] If the current amplitude is greater than or less than the current set value, the voltage value of the signal is changed according to the set voltage change step, and the signal of the current frequency is continued to be output. Through the above loop detection program, the automation process of constant current measurement can be realized. The program will continuously measure the current, and perform corresponding operations and judgments based on the relationship between the collected current amplitude and the set current error range and current set value. In this way, it can ensure that the measured current always remains constant, and adjust in time when the current exceeds the error range to achieve accurate current measurement. It should be noted that when writing the program, it is necessary to ensure that the input and output of each node are correctly connected, and set the node parameters and the judgment conditions of the conditional statements to ensure the normal operation of the program. In addition, in order to improve the readability and maintainability of the program, appropriate comments and error handling mechanisms can be added so that problems can be discovered and fixed in time when the program runs wrong.

[0051] After the sweep frequency signal of the current frequency is output, phase detection is performed on the sweep frequency signal, including the following steps: In order to improve the accuracy of phase measurement and reduce the influence of noise, a reference signal with the same frequency as the swept frequency signal is obtained during the program writing process.

[0052] The reference signal is cross-correlated with the voltage signal and current signal collected at the piezoelectric material to obtain the phase of the voltage signal and the phase of the current signal, as well as the phase difference between the voltage signal and the current signal, and the frequency of the sweep signal is adjusted by minimizing the phase difference.

[0053] The phase difference between the voltage signal and the current signal is obtained. The specific expression is: .

[0054] in, are the cross-correlation values ​​of the voltage and the reference signal, and the cross-correlation values ​​of the current and the reference signal, respectively. U andI is the amplitude of the voltage and current signals, Δ φ is the phase difference, φ 1 and φ 2 are the phase of the voltage signal and the phase of the current signal respectively. The phase difference is Figure 7 shown.

[0055] In order to verify that the phase detection procedure can also be used in a high-frequency environment, the frequency value of the signal is changed based on the above conditions to obtain the data at different frequencies in Table 3.

[0056] Table 3 Phase difference simulation results at different frequencies

[0057] Phase detection technology has been widely used in modern communications, computers, automatic control and other fields. With the continuous advancement and development of science and technology, there are many professional phase detection circuits and phase detection algorithms at home and abroad. This system adopts a phase detection algorithm based on cross-correlation to achieve high-precision phase detection. Specifically, the cross-correlation method estimates the phase difference by calculating the cross-correlation function between the signal to be measured and the reference signal. In signal processing, the cross-correlation function is often used to measure the similarity between two signals. It can reflect information such as the phase difference, frequency difference, and time difference between the signals. Compared with other phase detection methods, the cross-correlation method has better anti-noise and anti-interference capabilities. This is because in the process of cross-correlation calculation, the errors between different positions of the signal will be averaged out, thereby reducing the impact of noise and interference on phase detection. This system adopts a phase detection algorithm based on cross-correlation, which can achieve high-precision phase detection and has good anti-interference ability and applicability.

[0058] To verify the credibility of the phase measurement program, the frequency of the two sinusoidal signals is set to 10kHz, the amplitude is 5V, and the sampling rate is 1000000Hz. To simulate the actual collected signal, a uniform white noise with an amplitude of 0.5V is added to the two signals. The phase difference between the two signals is 60°. 8000 phase data are collected. The phase difference is as follows: Figure 8 As shown, the maximum measured phase difference is 60.37°, the minimum is 58.87°, the maximum error is 0.37°, and the error is 0.62%, which meets the experimental needs.

[0059] Step S3: obtaining the final current signal of the piezoelectric material through the sweep signal of the current frequency, obtaining the admittance circle diagram through fitting the final current signal, and measuring the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram.

[0060] This step specifically includes the following steps: The piezoelectric vibrator equivalent circuit is constructed using piezoelectric materials.

[0061] The total admittance of the piezoelectric vibrator equivalent circuit is obtained through the final current signal; the specific expression is: .

[0062] .

[0063] in, Y is the admittance, I 0 is the current through the static impedance, I 1 is the current through the dynamic impedance (impedance calculated by the computer), U is the voltage, C 0 is a pure capacitor, which is equivalent to the impedance of the piezoelectric material in static state. L 1 , C 1 and R 1 The dynamic impedance is represented by the equivalent inductance, equivalent capacitance and equivalent resistance respectively. y 0 is the static admittance, y 1 is the dynamic admittance.

[0064] The conductivity G As the horizontal axis, the susceptance B As the ordinate, construct the curve of susceptance with respect to conductance and obtain the admittance circle diagram; the specific expression is: .

[0065] .

[0066] in, G is the conductivity, B is the electrical susceptance, j is an imaginary unit, is the angular frequency. The coordinates of the center of the admittance circle are , the radius is ,like Figure 8 As shown in the figure, Series resonant angular frequency, is the resonant angular frequency, Anti-resonance angular frequency.

[0067] The parameters of the piezoelectric material are obtained according to the admittance circle diagram (i.e., piezoelectric parameter calculation), and the strong field impedance spectrum is measured according to the relationship that admittance is the inverse of impedance; the parameters of the piezoelectric material include dynamic resistance, dynamic capacitance, dynamic inductance, and static capacitance.

[0068] According to the admittance circle diagram, the relevant parameters of piezoelectric materials are: (1) Dynamic resistance: .

[0069] (2) Dynamic capacitance: .

[0070] (3) Dynamic inductance: .

[0071] (4) Static capacitance: .

[0072] in, is the current conductance, is the quality factor, For any frequency, is the first frequency, is the second frequency, is the current susceptance.

[0073] Based on the above method, the present invention provides a high-field impedance spectrum measurement system for piezoelectric materials, comprising: a data acquisition module, a current feedback module and a measurement module.

[0074] Among them, the data acquisition module is used to load the swept frequency signal generated by the signal generator to the piezoelectric material under the strong field, and read the current signal and current signal amplitude of the piezoelectric material; the current feedback module is used to compare the read current signal amplitude with the set current constant value, and when the current signal amplitude is outside the error range, change the voltage value of the swept frequency signal according to the set voltage change step, and output the swept frequency signal of the current frequency; the measurement module is used to obtain the final current signal of the piezoelectric material through the swept frequency signal of the current frequency, and obtain the admittance circle diagram through the final current signal fitting, and measure the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram.

[0075] After the measurement system is built, its feasibility and stability need to be verified. Since it is impossible to use existing instruments for strong field measurements, the accuracy of the measurement system can only be verified by comparing the data of the piezoelectric vibrator measured by the measurement system under weak field with the data measured by the commercial impedance analyzer. For experimental verification, a PZT-5 long piezoelectric vibrator with a size of 40mm (length) × 6mm (width) × 2mm (height) is used as an experimental sample.

[0076] The impedance spectrum of the PZT-5 piezoelectric sample was measured at a driving voltage of 1 V using the strong field impedance spectrum measurement system constructed by the present invention and a commercial impedance analyzer. The experimental results are shown in FIG. Figure 3 (a) and Figure 3(b) is shown. By observing the measurement results, it is found that the data obtained by the measurement system is very close to the data obtained by the commercial impedance analyzer, which proves the accuracy of the measurement system. In addition, the parameter characteristics of the piezoelectric sample under weak field conditions are calculated and summarized in Table 4. By comparing with the results of the commercial impedance analyzer, it is found that the difference between the two is not significant. These differences can be mainly attributed to random errors in the data processing process.

[0077] Table 4 Parameters of the sample under weak field conditions obtained by the strong field impedance measurement system

[0078] The constant voltage method of the strong field measurement system has proved the accuracy of the data acquisition module of the measurement system, while the key point of the constant current method is that the current feedback module can operate accurately. The feasibility verification of the current feedback module can be verified by comparing the error between the current value measured during the verification experiment and the set current constant value. In the experiment, the current value is set to 20 mA, and the admittance spectrum and the corresponding current curve are shown in Figure 2. Figure 4 As shown. Figure 4 (a) and Figure 4 The measurement results of (b) show that the maximum current measured is 20.37 mA, the minimum is 19.76 mA, and the maximum absolute error is 1.85%, achieving good current stability. In addition, the calculated mechanical quality factor is 67.4.

[0079] The admittance circle of PZT5 piezoelectric material under 20 mA constant current drive is as follows Figure 8 As shown in the figure, the admittance circle of the PZT5 piezoelectric material is a complete circle, and its related equivalent circuit parameters can be calculated by the above-mentioned related formulas, as shown in Table 5.

[0080] Table 5 Equivalent circuit parameters of PZT5 under 20mA constant current drive

[0081] The present invention also provides a computer device, including a memory and a processor. The memory stores a program. When the program is executed by the processor, the processor executes the steps of a method for measuring a strong field impedance spectrum of a piezoelectric material.

[0082] According to the disclosed embodiments, a computing device may communicate with one or more external devices (e.g., keyboards, pointing devices, Bluetooth communications, etc.), or with any device (e.g., routers, modems, etc.) that enables a computing device to communicate with one or more other computing devices.

[0083] The present invention also provides a storage medium, which includes a stored computer program. The computer program is executed by at least one processor to enable the at least one processor to execute the steps of a method for measuring a strong field impedance spectrum of a piezoelectric material.

[0084] According to the disclosed embodiments, the storage medium may be a non-volatile computer-readable storage medium, such as but not limited to: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination thereof. In the present invention, the storage medium may be any tangible medium containing or storing a program that may be used by or in conjunction with an instruction execution system, apparatus, or device.

[0085] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. For technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for measuring high-field impedance spectroscopy of piezoelectric materials, characterized in that: The steps include: Loading the swept frequency signal generated by the signal generator to the piezoelectric material under the strong field, and reading the current signal and the current signal amplitude of the piezoelectric material; The read current signal amplitude is compared with the set current constant value, and when the current signal amplitude is outside the error range, the voltage value of the frequency sweep signal is changed according to the set voltage change step, and the frequency sweep signal of the current frequency is output; The final current signal of the piezoelectric material is obtained by the frequency sweep signal of the current frequency, and the admittance circle diagram is obtained by fitting the final current signal, and the strong field impedance spectrum of the piezoelectric material is measured according to the admittance circle diagram.

2. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 1, characterized in that: After reading the current signal and the current signal amplitude of the piezoelectric material, filtering the current signal comprises the following steps: Inputting the current signal into a zero-phase filter to obtain a filtered signal without introducing additional phase delay; When obtaining the filtered signal, the signal of the current amplitude is forward filtered according to the forward coefficient to obtain an intermediate filtered signal; The reverse sequence of the intermediate filter signal is reversely filtered according to the reverse coefficient to obtain a final filter signal; wherein the values ​​of the reverse coefficient and the forward coefficient are obtained by the signal sampling rate and the cutoff frequency.

3. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 1, characterized in that: After the frequency sweep signal of the current frequency is output, phase detection is performed on the frequency sweep signal, comprising the following steps: Acquire a column of reference signals having the same frequency as the frequency sweep signal; The reference signal is cross-correlated with the voltage signal and current signal collected at the piezoelectric material to obtain the phase of the voltage signal and the phase of the current signal, as well as the phase difference between the voltage signal and the current signal, and the frequency of the sweep signal is adjusted by minimizing the phase difference.

4. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 3, characterized in that: The phase difference between the voltage signal and the current signal is obtained by: ； in, are the cross-correlation values ​​of the voltage and the reference signal, and the cross-correlation values ​​of the current and the reference signal, respectively. U and I is the amplitude of the voltage and current signals, Δ φ is the phase difference, φ 1 and φ 2 are the phase of the voltage signal and the phase of the current signal respectively.

5. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 1, characterized in that: Before comparing the read current signal amplitude with the set current constant value, the method further includes the following steps: Use LabVIEW program in the computer to set up the current measurement unit and the judgment unit; A signal generator node is set in the current measurement unit to output a swept frequency signal of an AC voltage, and a digital oscilloscope node is set to read the amplitude of the current signal at both ends of the piezoelectric material; Add conditions in the judgment unit to judge the magnitude relationship between the current amplitude and the set current error range and the current constant value respectively.

6. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 1, characterized in that: When the read current signal amplitude is compared with the set current constant value, if the current signal amplitude is within the error range, the current frequency sweep output is maintained and the state of the signal generator is detected.

7. A method for measuring high-field impedance spectroscopy of a piezoelectric material as claimed in claim 1, characterized in that: The method comprises the following steps: obtaining an admittance circle diagram by fitting the final current signal, and measuring a strong field impedance spectrum of a piezoelectric material according to the admittance circle diagram: Construct a piezoelectric vibrator equivalent circuit through piezoelectric materials; The total admittance of the piezoelectric vibrator equivalent circuit is obtained through the final current signal; the specific expression is: ； ； in, Y is the admittance, I 0 is the current through the static impedance, I 1 is the current through the dynamic impedance, U is the voltage, C 0 is pure capacitance, which is equivalent to the impedance of the piezoelectric material in static state. L 1. C 1 and R 1 are equivalent inductance, equivalent capacitance and equivalent resistance for dynamic impedance respectively, y 0 is the static admittance, y 1 is the dynamic admittance; The conductivity G As the horizontal axis, the susceptance B As the ordinate, construct the curve of susceptance with respect to conductance and obtain the admittance circle diagram; the specific expression is: ； ； in, G is the conductivity, B is the electrical susceptance, j is an imaginary unit, is the angular frequency; The parameters of the piezoelectric material are obtained according to the admittance circle diagram, and the strong field impedance spectrum is measured according to the relationship that admittance is the inverse of impedance; the parameters of the piezoelectric material include dynamic resistance, dynamic capacitance, dynamic inductance and static capacitance.

8. A high-field impedance spectrum measurement system for piezoelectric materials, characterized in that: include: A data acquisition module is used to load the swept frequency signal generated by the signal generator to the piezoelectric material under the strong field, and read the current signal and the current signal amplitude of the piezoelectric material; The current feedback module is used to compare the read current signal amplitude with the set current constant value, and when the current signal amplitude is outside the error range, change the voltage value of the sweep signal according to the set voltage change step size, and output the sweep signal of the current frequency; The measuring module is used to obtain the final current signal of the piezoelectric material through the sweep frequency signal of the current frequency, obtain the admittance circle diagram through the fitting of the final current signal, and measure the strong field impedance spectrum of the piezoelectric material according to the admittance circle diagram.

9. A computer device, characterized in that: It comprises a memory and a processor, wherein a program is stored in the memory, and when the program is executed by the processor, the processor executes the steps of a method for measuring a strong field impedance spectrum of a piezoelectric material as claimed in any one of claims 1 to 7.

10. A storage medium, characterized in that: The storage medium includes a stored computer program, and the computer program is executed by at least one processor to enable the at least one processor to perform the steps of the method for measuring the strong field impedance spectrum of a piezoelectric material as claimed in any one of claims 1 to 7.

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