A system and method for testing the temperature characteristics of piezoelectric coefficients of piezoelectric ceramics

Abstract

The present invention discloses a system and method for testing the temperature characteristics of the piezoelectric coefficient of piezoelectric ceramics, belonging to the technical field of piezoelectric coefficient testing. The system solves the problem in the prior art that the traditional piezoelectric coefficient testing system and method for piezoelectric ceramics cannot perform in-situ characterization of piezoelectric ceramics in a high-temperature environment. The present invention designs a piezoelectric coefficient temperature characteristics testing system, collects the actual temperature of the sample to be tested based on the acquired ideal temperature and the temperature sensor, uses the current output power of the heater to heat the fixture system, controls the drive device module to output a sinusoidal alternating drive voltage to the vibration table, and the vibration table applies a sinusoidal alternating force to the fixture system; converts the charges at both ends of the sample to be tested and the reference sample into a voltage signal, and calculates the piezoelectric coefficient of the sample to be tested at the corresponding temperature. The present invention effectively realizes the in-situ piezoelectric coefficient characterization of piezoelectric ceramics in a high-temperature environment and can be applied to high-temperature testing of the piezoelectric coefficient of piezoelectric ceramics.

Description

Technical Field

[0001] The present invention relates to a system and method for testing the temperature characteristics of a piezoelectric coefficient, and in particular to a system and method for testing the temperature characteristics of a piezoelectric coefficient of a piezoelectric ceramic, belonging to the technical field of piezoelectric coefficient testing. Background Art

[0002] Piezoelectric materials and sensor devices are core electronic functional materials and devices for realizing electromechanical energy conversion and coupling. They are key shared technologies that urgently need to be developed in aerospace, deep-sea exploration, intelligent equipment and other fields. With the increase in the ambient temperature of sensors and other devices, relevant research has been carried out on the temperature characteristics of the piezoelectric material performance of the core components of sensors, which mainly include the operating temperature range of piezoelectric materials, the performance failure threshold temperature and other performance related to practical applications.

[0003] At present, the most widely used piezoelectric coefficient test method is the quasi-static method. Its principle is simple to operate and has high accuracy, but it cannot characterize the high-temperature performance of piezoelectric ceramics and cannot evaluate the temperature characteristics of sample performance. The room temperature quasi-static piezoelectric coefficient test method is already very mature, and a metrological verification procedure for the test system has been formulated. However, it places the sample to be tested and the reference sample under the same alternating force field, compares the amplitude of the excitation signal generated by the sample to be tested and the reference sample, and combines the reference sample. Although the operation is simple and fast, the current mature test system based on the quasi-static method can only characterize the room-temperature performance of piezoelectric ceramics. Due to the presence of a standard piezoelectric ceramic sample in its test element for comparison and the limitations of the circuit elements therein, it cannot be placed in a high-temperature environment, and thus the piezoelectric ceramics in a high-temperature environment cannot be characterized in situ.

[0004] In summary, the existing technology is mainly aimed at measuring the piezoelectric coefficient at room temperature, but for high-temperature in-situ piezoelectric coefficient testing, it only relies on dynamic testing. It has high requirements on the size of the sample and can only characterize the change of the piezoelectric coefficient of samples of a specific size with temperature. Therefore, there is a need for a piezoelectric coefficient temperature characteristic testing system and method for piezoelectric ceramics suitable for high-temperature environments. Summary of the Invention

[0005] A brief overview of the present invention is provided below to provide a basic understanding of certain aspects of the present invention. It should be understood that this overview is not an exhaustive overview of the present invention. It is not intended to identify key or important aspects of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is simply to present certain concepts in a simplified form as a prelude to the more detailed description discussed later.

[0006] In view of this, in order to solve the problem that the traditional piezoelectric coefficient testing system and method of piezoelectric ceramics in the prior art cannot perform in-situ characterization of piezoelectric ceramics in a high-temperature environment, the present invention provides a piezoelectric coefficient temperature characteristic testing system and method of piezoelectric ceramics.

[0007] Technical solution 1 is as follows: A piezoelectric coefficient temperature characteristic testing system for piezoelectric ceramics, including a temperature control device, a temperature sensor, a heater, an FPGA main control module, an ADC analog-to-digital conversion module, a preamplifier module, a drive device module, a DAC digital-to-analog conversion module, a fixture system, a vibration table, and a computer;

[0008] The computer is connected to the FPGA main control module and the temperature control device respectively;

[0009] The temperature control device is connected to the temperature sensor and the heater respectively, the heater is connected to the fixture system, the fixture system is connected to the vibration table, and the temperature control device controls the temperature of the heater through a PID algorithm and collects the output temperature of the temperature sensor;

[0010] The FPGA main control module is connected to the ADC analog-to-digital conversion module and the DAC digital-to-analog conversion module respectively. The ADC analog-to-digital conversion module is connected to the preamplifier module and the fixture system in sequence. The DAC digital-to-analog conversion module is connected to the drive device module and the vibration table in sequence.

[0011] Furthermore, the fixture system is provided with an insulating column and a high and low temperature fixture, an electrode is provided on the outside of the fixture system, the bottom surface of the high and low temperature fixture is connected to the top surface of the insulating column, the high and low temperature fixture is used to clamp the sample to be tested, and the insulating column is used to isolate the reference sample.

[0012] Furthermore, the FPGA main control module is an FPGA main control module using an XC6SLX16 chip, the ADC analog-to-digital conversion module is an analog-to-digital conversion module using an AD7606 chip, the preamplifier module is a preamplifier module using an LF347 chip, the driver module is a driver module using an LM1875 chip, and the DAC digital-to-analog conversion module is a digital-to-analog conversion module using an AD9767DAC chip.

[0013] Technical Solution 2 is as follows: A method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic, used in a piezoelectric coefficient temperature characteristics testing system of a piezoelectric ceramic described in Technical Solution 1, comprising the following steps:

[0014] S1. Calculate the current output power of the heater based on the ideal temperature and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factors set in the PID algorithm stored in the computer;

[0015] S2. The fixture system is heated using the current output power of the heater. The drive module is controlled to output a sinusoidal alternating drive voltage to the vibration table, which applies a sinusoidal alternating force to the fixture system.

[0016] S3. Based on the amplitude of the sinusoidal alternating force and the piezoelectric equation, obtain the relationship between the charge at both ends of the test sample and the reference sample and their corresponding piezoelectric coefficients;

[0017] S4. Through the preamplifier module, the charges at both ends of the sample to be tested and the reference sample are converted into voltage signals, and the relationship between the piezoelectric coefficients of the sample to be tested and the reference sample and their corresponding voltage signal amplitudes is calculated. By substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample, the piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained.

[0018] Furthermore, in said S1, according to the test program in the computer combined with the PID algorithm, the temperature rise and fall sections are obtained by setting the temperature rise and fall conditions, and the theoretical temperature T m Corresponding to time t, we get the corresponding relationship;

[0019] The corresponding relationship is expressed as:

[0020] T m =T(t)

[0021] Where T is the temperature function;

[0022] The actual temperature T collected by the temperature sensor true Transmitted to the temperature control unit, according to the theoretical temperature T m and the actual temperature T true , get the difference ΔT between the actual temperature and the theoretical temperature;

[0023] The difference ΔT between the actual temperature and the theoretical temperature is expressed as:

[0024] ΔT=T m -T true

[0025] Combined with the control factor set in the PID algorithm, the current output power P of the heater is calculated. n ;

[0026] The current output power P of the heater n Expressed as:

[0027] P n =P n-1 +k p (ΔT n -ΔT n-1 )+k p k i ΔT n +kp k d (ΔT n -2ΔT n-1 +ΔT n-2 )

[0028] Among them, P n-1 is the output power of the heater at the previous moment, k p is the proportional control factor, its initial value is 18, k i is the integral control factor, its initial value is 1.5, k d is the differential control factor, its initial value is 0.01, ΔT n Is the difference between the current actual temperature and the theoretical temperature, ΔT n-1 The difference between the actual temperature and the theoretical temperature at the previous moment, ΔT n-2 It is the difference between the actual temperature and the theoretical temperature in the first two moments.

[0029] Furthermore, in S2, the FPGA main control module is controlled by a computer, and the voltage signal is converted by the DAC digital-to-analog conversion module to transmit the control instruction to the vibration table. When the vibration table receives the sinusoidal alternating driving voltage output by the driving device module, the vibration table applies a sinusoidal alternating force F to the fixture system.

[0030] The sinusoidal alternating force F is expressed as:

[0031] F=F0 sin(ωt)

[0032] Where F0 is the amplitude of the sinusoidal alternating force F.

[0033] Furthermore, in S3, the charge Q at both ends of the sample to be tested is calculated based on the amplitude F0 and the piezoelectric equation. s Its piezoelectric coefficient d s The relationship between the charge Q at both ends of the reference sample R and its piezoelectric coefficient d R the relationship between;

[0034] The charge Q at both ends of the sample to be tested s Its piezoelectric coefficient d s The relationship between them is expressed as:

[0035] Q s =d s F0 sin(ωt+δ s )

[0036] Among them, δ s The loss of the sample to be tested and the phase shift caused by the preamplifier module;

[0037] The charge Q across the reference sample R and its piezoelectric coefficient dR The relationship between them is expressed as:

[0038] Q R =d R F0 sin(ωt+δ R )

[0039] Among them, δ R is the loss of the reference sample and the phase shift caused by the preamplifier module.

[0040] Furthermore, in the step S4, the charges at both ends of the sample to be tested and the charges at both ends of the reference sample are converted into first voltage signals V s and the second voltage signal V R ;

[0041] The first voltage signal V s Expressed as:

[0042] V s =k s Q s =d s k s F0sin(ωt+δ s )

[0043] Among them, k s is the first conversion coefficient;

[0044] The second voltage signal V R Expressed as:

[0045] V R =k R Q R =d R k R F0sin(ωt+δ R )

[0046] Among them, k R is the second conversion coefficient;

[0047] According to the first voltage signal V s and the second voltage signal V R , and obtain the piezoelectric coefficient d of the sample to be tested s , the piezoelectric coefficient d of the reference sample R and the relationship between the corresponding voltage signal amplitude;

[0048]

[0049] Among them, V s0 is the piezoelectric coefficient d of the sample to be tested s The corresponding voltage signal amplitude, V R0is the piezoelectric coefficient d of the reference sample R The corresponding voltage signal amplitude.

[0050] The beneficial effects of the present invention are as follows: the present invention sets up a temperature control unit module consisting of a temperature control device, a temperature sensor and a heater, providing a suitable high-temperature environment for the piezoelectric coefficient test of piezoelectric ceramics; at the same time, the present invention automatically controls the output power of the heater by introducing a PID algorithm, thereby realizing heating of the sample to be tested in the fixture system; the present invention achieves temperature isolation between the sample to be tested and the reference sample by setting an insulating column in the fixture system, thereby further improving the accuracy of the overall test; the present invention realizes the coordinated linkage of the temperature control unit module and the piezoelectric coefficient test unit module composed of other devices. According to the piezoelectric coefficient temperature characteristic test method of piezoelectric ceramics of the present invention, the piezoelectric coefficient temperature spectrum of the piezoelectric ceramics can be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0052] Figure 1 The figure is a schematic diagram of the structure of a system for testing the temperature characteristics of the piezoelectric coefficient of piezoelectric ceramics;

[0053] Figure 2 The figure is a flow chart of a method for testing the temperature characteristics of the piezoelectric coefficient of a piezoelectric ceramic;

[0054] Figure 3 It is a flow chart of PID algorithm;

[0055] Figure 4 Schematic diagram of the connection between the fixture system and the vibration table;

[0056] Figure 5 It is a structural diagram of the drive device module;

[0057] Figure 6 It is a structural diagram of the DAC digital-to-analog conversion module;

[0058] Figure 7 It is a structural diagram of the preamplifier module;

[0059] Figure 8 It is a structural diagram of the ADC analog-to-digital conversion module;

[0060] Figure 9 It is a structural diagram of the FPGA master control module;

[0061] Figure 10 Schematic diagram of an embodiment of a system and method for testing the temperature characteristics of the piezoelectric coefficient of piezoelectric ceramics

[0062] Figure 11 Schematic diagram of the fixture system.

[0063] Figure numerals: 1. Temperature control device; 2. Temperature sensor; 3. Heater; 4. FPGA main control module; 5. ADC analog-to-digital conversion module; 6. Preamplifier module; 7. Drive device module; 8. DAC digital-to-analog conversion module; 9. Fixture system; 10. Vibration table; 11. Computer. DETAILED DESCRIPTION

[0064] To make the technical solutions and advantages of the embodiments of the present invention more clearly understood, exemplary embodiments of the present invention are further described in detail below with reference to the accompanying drawings. It should be noted that the embodiments described are only a portion of the embodiments of the present invention, and are not an exhaustive list of all embodiments. It should be noted that the embodiments of the present invention and the features thereof may be combined with each other unless they conflict.

[0065] Example 1: Reference Figures 1-10 The present embodiment is described in detail. A system for testing the temperature characteristics of a piezoelectric coefficient of a piezoelectric ceramic includes a temperature control device 1, a temperature sensor 2, a heater 3, an FPGA main control module 4, an ADC analog-to-digital conversion module 5, a preamplifier module 6, a driver module 7, a DAC digital-to-analog conversion module 8, a fixture system 9, a vibration table 10, and a computer 11.

[0066] The computer 11 is connected to the FPGA main control module 4 and the temperature control device 1 respectively;

[0067] The temperature control device 1 is connected to the temperature sensor 2 and the heater 3 respectively, the heater 3 is connected to the fixture system 9, and the fixture system 9 is connected to the vibration table 10. The temperature control device 1 controls the temperature of the heater 3 through the PID algorithm and collects the output temperature of the temperature sensor 2;

[0068] The FPGA main control module 4 is connected to the ADC analog-to-digital conversion module 5 and the DAC digital-to-analog conversion module 8 respectively. The ADC analog-to-digital conversion module 5 is connected to the preamplifier module 6 and the fixture system 9 in sequence. The DAC digital-to-analog conversion module 8 is connected to the drive device module 7 and the vibration table 10 in sequence.

[0069] Furthermore, the fixture system 9 is provided with an insulating column and a high and low temperature fixture, and an electrode is provided on the outside of the fixture system 9. The bottom surface of the high and low temperature fixture is connected to the top surface of the insulating column. The high and low temperature fixture is used to clamp the sample to be tested, and the insulating column is used to isolate the reference sample.

[0070] Furthermore, the FPGA main control module 4 is an FPGA main control module using the XC6SLX16 chip, the ADC analog-to-digital conversion module 5 is an analog-to-digital conversion module using the AD7606 chip, the preamplifier module 6 is a preamplifier module using the LF347 chip, the drive device module 7 is a drive device module using the LM1875 chip, and the DAC digital-to-analog conversion module 8 is a digital-to-analog conversion module using the AD9767DAC chip.

[0071] Specifically, the temperature control device 1 is connected to the computer 11 via the RS485 interface, and the FPGA main control module 4 is connected to the computer 11 via the USB interface.

[0072] refer to Figure 4 The sample to be tested and the reference sample are piezoelectric ceramics. In order to characterize the temperature characteristics of the piezoelectric coefficient of the piezoelectric ceramics, it is necessary to organically combine the temperature control unit module composed of the temperature control device 1, the temperature sensor 2 and the heater 3 with the piezoelectric coefficient test unit module composed of the other components. It is necessary to ensure the high and low temperature controllable characteristics of the ambient temperature of the sample to be tested and the high temperature resistance of the electrode, and also to isolate the ambient temperature of the sample to be tested from the ambient temperature of the reference sample to ensure the piezoelectric coefficient d R In order to ensure the stability of the electrode, the electrode is made of platinum and the insulating column is made of corundum, which not only ensures the high-temperature electrical conductivity, but also ensures the high-temperature insulation and force conduction properties.

[0073] refer to Figure 5 The drive device module 7 is a drive device module using the LM1875 chip, which has a small size, simple peripheral circuit, large output power, small harmonic distortion, and internal overload, overheating and inductive load reverse potential safety working protection;

[0074] refer to Figure 6 DAC digital-to-analog conversion module 8 is a digital-to-analog conversion module using the AD9767 chip, which is a dual-port, high-speed, dual-channel, 14-bit CMOSDAC that integrates two high-quality The AD9767 core, a reference voltage source, and digital interface circuitry are housed in a small 48-pin LQFP package. It offers excellent AC and DC performance while supporting update rates up to 125MSPS. The digital interface contains two double-buffered latches and control logic, with independent write inputs that allow data to be written to the two DAC ports independently of each other. The AD9767 chip is manufactured using an advanced, low-cost CMOS process and operates from a single 3.3V to 5V power supply, consuming 380mW.

[0075] refer to Figure 7The preamplifier module 6 is a preamplifier module using the LF347 chip. The LF347 chip has the characteristics of high input impedance, high conversion rate, low offset current, low harmonic distortion, and low noise, which are combined with the field effect transistor and bipolar type. The preamplifier module 6 is internally provided with four operational amplifiers. The reference signal and the measured signal each use two of the operational amplifiers to form a secondary amplification. Among them, the sliding resistor is used to adjust the output bias voltage, and the transistor is used for input protection.

[0076] refer to Figure 8 , ADC analog-to-digital conversion module 5 is an analog-to-digital conversion module using the AD7606 chip, which has built-in analog input clamp protection, second-order anti-aliasing filter, tracking and holding amplifier, 16-bit charge redistribution successive approximation ADC, flexible digital filter, 2.5V reference voltage source, reference voltage buffer and high-speed serial and parallel interface. The AD7606 chip is powered by a single 5V power supply and can process ±10V and ±5V true bipolar input signals. At the same time, all channels can be sampled at a throughput rate of up to 200kSPS. The input clamp protection circuit can withstand voltages of up to ±16.5V. Regardless of the sampling frequency, the analog input impedance of the AD7606 chip is 1MΩ. It uses a single power supply and has on-chip filtering and high input impedance. This does not require a driver operational amplifier and an external bipolar power supply. The 3dB bandwidth cutoff frequency of the second-order anti-aliasing filter is 22kHz. When the sampling rate is 200ksps, it has a 40dB anti-aliasing suppression characteristic. The flexible digital filter is pin-driven, which can improve the signal-to-noise ratio (SNR) and reduce the 3dB bandwidth. The AD7606 chip is manufactured using a low-power CMOS process, achieving low-power operation while maintaining high performance. Its interface is flexible and supports standard digital interfaces such as SPI, QSPI, and MICROWIRE. It can be easily integrated with various microcontrollers or DSPs. It has a built-in PGA and input range selection. The AD7606 chip integrates a programmable gain amplifier (PGA) and input range selection function, which can realize flexible adjustment of the input signal.

[0077] refer to Figure 9, FPGA master control module 4 is an FPGA master control module using the XC6SLX16 chip. The XC6SLX16 chip is a typical FPGA programmable logic device of Xilinx's Spartan-6 series. It has rich logic resources, high-density memory and DSP modules, and is suitable for high-performance computing, communications, data centers, industrial control and other fields. The Spartan-6 series FPGA programmable logic device uses 2.5D or 3D bare chip level packaging technology, which can combine multiple small chips into a large FPGA to meet high performance and low power consumption requirements. The XC6SLX16 chip has 16,000 logic units, 1,024 18×18 multipliers, 32 DSP48A1 slices, and 72 I / O pins. In addition, it is equipped with 256 distributed RAMs and 19,300 triggers, which can be used to build complex timing and combinational logic circuits. The XC6SLX16 chip uses low-power technology to help reduce the total power consumption of the system. It also supports JTAG programming and configuration. The FPGA master control module 4 is based on the XC6SLX16 chip and is also equipped with Flash memory, SDRAM memory, clock, and JTAB debug port. As the main controller, the XC6SLX16 chip works in conjunction with the ADC analog-to-digital conversion module 5 and the DAC digital-to-analog conversion module 8 to realize functions such as drive signal generation and piezoelectric signal acquisition.

[0078] refer to Figure 10In this embodiment, the piezoelectric coefficient of the piezoelectric ceramic is tested by the quasi-static method. The test conditions are input into the software operation interface built into the computer 11, which are respectively a test starting temperature of 138°C, a test maximum temperature of 550°C, a heating time of 100 minutes, a cooling target temperature of 550°C, a cooling time of 10 minutes, and a recording interval of 3°C. That is, the ideal temperature rise and fall section is 138°C-550°C. The sample to be tested is clamped on the high and low temperature fixture, and the "EXCUTE" button is clicked. The test program sends a command to the temperature control device 1 through the serial port line. The temperature control device 1 controls the output power of the heater 3 through the PID algorithm to increase the temperature from 138°C to 550°C in 100 minutes, and then maintains it at 550°C for 10 minutes. During the temperature rise and fall process, the test program collects the temperature information output by the temperature sensor in real time. Every time the temperature rises and falls by 3°C, the test program sends a command to the FP The GA main control module 4 issues an instruction, and then the voltage signal is converted through the DAC digital-to-analog conversion module 8, and a sinusoidal alternating driving voltage is applied to the vibration table 10 through the driving device module 7, so that the vibration table 10 applies a sinusoidal alternating force F to the electrode of the fixture system 9. Since the sample to be tested and the reference sample have a piezoelectric effect, their upper and lower surfaces will generate charges due to the existence of force, and the charge signal is converted into a voltage signal through the preamplifier module 6 and sent to the ADC analog-to-digital conversion module 5. The signal is collected and processed by the FPGA main control module 4, and sent to the computer 11 through the communication port for processing and calculation, and the amplitude and peak-to-peak value of the corresponding voltage signal are measured. Then, the piezoelectric coefficient d of the sample to be tested corresponding to the temperature is calculated through the amplitude and peak-to-peak value of the voltage signal generated by the sample to be tested and the reference sample, the conversion coefficient of the preamplifier circuit and the piezoelectric coefficient of the reference sample. s ,Finally, the piezoelectric coefficients at different temperatures were measured.

[0079] Example 2: Reference Figures 1-10 Detailed description of this embodiment, a method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic, used in the piezoelectric coefficient temperature characteristics testing system of the piezoelectric ceramic described in Example 1, specifically comprising the following steps:

[0080] S1. Calculate the current output power of the heater based on the ideal temperature and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factors set in the PID algorithm stored in the computer;

[0081] S2. The fixture system is heated using the current output power of the heater. The drive module is controlled to output a sinusoidal alternating drive voltage to the vibration table, which applies a sinusoidal alternating force to the fixture system.

[0082] S3. Based on the amplitude of the sinusoidal alternating force and the piezoelectric equation, obtain the relationship between the charge at both ends of the test sample and the reference sample and their corresponding piezoelectric coefficients;

[0083] S4. Through the preamplifier module, the charges at both ends of the sample to be tested and the reference sample are converted into voltage signals, and the relationship between the piezoelectric coefficients of the sample to be tested and the reference sample and their corresponding voltage signal amplitudes is calculated. By substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample, the piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained.

[0084] Furthermore, in said S1, according to the test program in the computer combined with the PID algorithm, the ideal temperature rise and fall section is obtained by setting the temperature rise and fall conditions, and the theoretical temperature T m Corresponding to time t, we get the corresponding relationship;

[0085] The corresponding relationship is expressed as:

[0086] T m =T(t)

[0087] Where T is the temperature function;

[0088] The actual temperature T collected by the temperature sensor true Transmitted to the temperature control unit, according to the theoretical temperature T m and the actual temperature T true , get the difference ΔT between the actual temperature and the theoretical temperature;

[0089] The difference ΔT between the actual temperature and the theoretical temperature is expressed as:

[0090] ΔT=T m -T true

[0091] Combined with the control factor set in the PID algorithm, the current output power P of the heater is calculated. n ;

[0092] The current output power P of the heater n Expressed as:

[0093] P n =P n-1 +k p (ΔT n -ΔT n-1 )+k p k i ΔT n +k p k d (ΔT n -2ΔT n-1 +ΔT n-2 )

[0094] Among them, P n-1 is the output power of the heater at the previous moment, k pis the proportional control factor, its initial value is 18, k i is the integral control factor, its initial value is 1.5, k d is the differential control factor, its initial value is 0.01, ΔTn is the current

[0095] The difference between the actual temperature and the theoretical temperature, ΔT n-1 The difference between the actual temperature and the theoretical temperature at the previous moment, ΔT n-2 It is the difference between the actual temperature and the theoretical temperature in the first two moments.

[0096] Specifically, refer to Figure 3 After the initial power P0 of the heater is given, during the temperature control process, the test program combined with the PID algorithm will realize self-learning, and appropriately adjust the value of the control factor according to the difference ΔT between the actual temperature and the theoretical temperature, thereby obtaining the appropriate current output power of the heater and providing temperature support for the test.

[0097] Furthermore, in S2, the FPGA main control module is controlled by a computer, and the voltage signal is converted by the DAC digital-to-analog conversion module to transmit the control instruction to the vibration table. When the vibration table receives the sinusoidal alternating driving voltage output by the driving device module, the vibration table applies a sinusoidal alternating force F to the fixture system, that is, the reference sample and the sample to be tested are both subjected to a force of F;

[0098] The sinusoidal alternating force F is expressed as:

[0099] F=F0sin(ωt)

[0100] Wherein, F0 is the amplitude of the sinusoidal alternating force F, and its frequency is usually 30Hz-200Hz.

[0101] Furthermore, in S3, the charge Q at both ends of the sample to be tested is calculated based on the amplitude F0 and the piezoelectric equation. s Its piezoelectric coefficient d s The relationship between the charge Q at both ends of the reference sample R and its piezoelectric coefficient d R the relationship between;

[0102] The charge Q at both ends of the sample to be tested s Its piezoelectric coefficient d s The relationship between them is expressed as:

[0103] Q s =d s F0 sin(ωt+δ s )

[0104] Among them, δ s The loss of the sample to be tested and the phase shift caused by the preamplifier module;

[0105] The charge Q across the reference sample R and its piezoelectric coefficient d R The relationship between them is expressed as:

[0106] Q R =d R F0 sin(ωt+δ R )

[0107] Among them, δ R is the loss of the reference sample and the phase shift caused by the preamplifier module.

[0108] Furthermore, in the step S4, the charges at both ends of the sample to be tested and the charges at both ends of the reference sample are converted into first voltage signals V s and the second voltage signal V R ;

[0109] The first voltage signal V s Expressed as:

[0110] V s =k s Q s =d s k s F0sin(ωt+δ s )

[0111] Among them, k s is the first conversion coefficient;

[0112] The second voltage signal V R Expressed as:

[0113] V R =k R Q R =d R k R F0sin(ωt+δ R )

[0114] Among them, k R is the second conversion coefficient;

[0115] According to the first voltage signal V s and the second voltage signal V R , and obtain the piezoelectric coefficient d of the sample to be tested s , the piezoelectric coefficient d of the reference sample R and the relationship between the corresponding voltage signal amplitude;

[0116]

[0117] Among them, V s0 is the piezoelectric coefficient d of the sample to be testeds The corresponding voltage signal amplitude, V R0 is the piezoelectric coefficient d of the reference sample R The corresponding voltage signal amplitude.

[0118] Specifically, the waveform signal of the voltage signal can be converted into a digital signal by the ADC conversion module 5, sent to the computer through the communication port, and processed and calculated to measure the amplitude and peak-to-peak value of the corresponding voltage signal;

[0119] The conversion coefficients are all known quantities, and the piezoelectric coefficient d of the reference sample is R The dynamic method, which is recognized as the most accurate method in the field of piezoelectric ceramics, can be used to process it into specific sizes and conduct tests to obtain specific values.

[0120] The piezoelectric coefficient d of the sample to be tested at the corresponding temperature can be obtained by the amplitude and peak-to-peak value of the voltage signal generated by the sample to be tested and the reference sample, the conversion coefficient of the preamplifier circuit and the piezoelectric coefficient of the reference sample. s .

[0121] Although the present invention has been described with respect to a limited number of embodiments, it will be apparent to those skilled in the art, having benefit of the foregoing description, that other embodiments are contemplated within the scope of the invention thus described. Furthermore, it should be noted that the language used in this specification has been selected primarily for readability and didactic purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention. Consequently, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is intended to be illustrative rather than restrictive of the scope of the invention, which is defined by the appended claims.

Claims

1. A method for testing the temperature characteristics of the piezoelectric coefficient of a piezoelectric ceramic, characterized in that: The piezoelectric coefficient temperature characteristic testing system of piezoelectric ceramics comprises a temperature control device (1), a temperature sensor (2), a heater (3), an FPGA main control module (4), an ADC analog-to-digital conversion module (5), a preamplifier module (6), a driving device module (7), a DAC digital-to-analog conversion module (8), a fixture system (9), a vibration table (10) and a computer (11); The computer (11) is connected to the FPGA main control module (4) and the temperature control device (1) respectively; The temperature control device (1) is connected to the temperature sensor (2) and the heater (3), respectively. The heater (3) is connected to the fixture system (9), and the fixture system (9) is connected to the vibration table (10). The temperature control device (1) controls the temperature of the heater (3) using a PID algorithm and collects the output temperature of the temperature sensor (2). The FPGA main control module (4) is connected to the ADC analog-to-digital conversion module (5) and the DAC digital-to-analog conversion module (8) respectively, the ADC analog-to-digital conversion module (5) is connected to the preamplifier module (6) and the fixture system (9) in sequence, and the DAC digital-to-analog conversion module (8) is connected to the driving device module (7) and the vibration table (10) in sequence; An insulating column and a high and low temperature clamp are provided in the clamp system (9), an electrode is provided on the outside of the clamp system (9), the bottom surface of the high and low temperature clamp is connected to the top surface of the insulating column, the high and low temperature clamp is used to clamp the sample to be tested, and the insulating column is used to isolate the reference sample; The method for testing the temperature characteristics of the piezoelectric coefficient of the piezoelectric ceramic comprises the following steps: S1. Calculate the current output power of the heater based on the ideal temperature and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factors set in the PID algorithm stored in the computer; S2. The fixture system is heated using the current output power of the heater. The drive module is controlled to output a sinusoidal alternating drive voltage to the vibration table, which applies a sinusoidal alternating force to the fixture system. S3. Based on the amplitude of the sinusoidal alternating force and the piezoelectric equation, obtain the relationship between the charge at both ends of the test sample and the reference sample and their corresponding piezoelectric coefficients; S4. Through the preamplifier module, the charges at both ends of the sample to be tested and the reference sample are converted into voltage signals, and the relationship between the piezoelectric coefficients of the sample to be tested and the reference sample and their corresponding voltage signal amplitudes is calculated. By substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample, the piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained.

2. The method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic according to claim 1, wherein: The FPGA main control module (4) is an FPGA main control module using an XC6SLX16 chip, the ADC analog-to-digital conversion module (5) is an analog-to-digital conversion module using an AD7606 chip, the preamplifier module (6) is a preamplifier module using an LF347 chip, the driver module (7) is a driver module using an LM1875 chip, and the DAC digital-to-analog conversion module (8) is a digital-to-analog conversion module using an AD9767DAC chip.

3. The method for testing the temperature characteristics of the piezoelectric coefficient of a piezoelectric ceramic according to claim 2, wherein: In S1, according to the test program in the computer combined with the PID algorithm, the temperature rise and fall sections are obtained by setting the temperature rise and fall conditions, and the theoretical temperature T m Corresponding to time t, we get the corresponding relationship; The corresponding relationship is expressed as: T m =T(t) Where T is the temperature function; The actual temperature T collected by the temperature sensor true Transmitted to the temperature control unit, according to the theoretical temperature T m and the actual temperature T true , get the difference ΔT between the actual temperature and the theoretical temperature; The difference ΔT between the actual temperature and the theoretical temperature is expressed as: ΔT=T m -T true Combined with the control factor set in the PID algorithm, the current output power P of the heater is calculated. n ; The current output power P of the heater n Expressed as: P n =P n-1 +k p (ΔT n -ΔT n-1 )+k p k i ΔT n +k p k d (ΔT n -2ΔT n-1 +ΔT n-2 ) Among them, P n-1 is the output power of the heater at the previous moment, k p is the proportional control factor, its initial value is 18, k i is the integral control factor, its initial value is 1.5, k d is the differential control factor, its initial value is 0.01, ΔT n Is the difference between the current actual temperature and the theoretical temperature, ΔT n-1 The difference between the actual temperature and the theoretical temperature at the previous moment, ΔT n-2 It is the difference between the actual temperature and the theoretical temperature in the first two moments.

4. The method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic according to claim 3, wherein: In S2, the FPGA main control module is controlled by a computer, and the voltage signal is converted by the DAC digital-to-analog conversion module to transmit the control instruction to the vibration table. When the vibration table receives the sinusoidal alternating driving voltage output by the driving device module, the vibration table applies a sinusoidal alternating force F to the fixture system; The sinusoidal alternating force F is expressed as: F=F0sin(ωt) Where F0 is the amplitude of the sinusoidal alternating force F.

5. The method for testing the temperature characteristics of the piezoelectric coefficient of a piezoelectric ceramic according to claim 4, wherein: In S3, the charge Q at both ends of the sample to be tested is calculated based on the amplitude F0 and the piezoelectric equation. s Its piezoelectric coefficient d s The relationship between the charge Q at both ends of the reference sample R and its piezoelectric coefficient d R the relationship between; The charge Q at both ends of the sample to be tested s Its piezoelectric coefficient d s The relationship between them is expressed as: Q s =d s F0sin(ωt+δ s ) Among them, δ s The loss of the sample to be tested and the phase shift caused by the preamplifier module; The charge Q across the reference sample R and its piezoelectric coefficient d R The relationship between them is expressed as: Q R =d R F0sin(ωt+δ R ) Among them, δ R is the loss of the reference sample and the phase shift caused by the preamplifier module.

6. The method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic according to claim 5, characterized in that: In the above S4, the charges at both ends of the sample to be tested and the charges at both ends of the reference sample are converted into first voltage signals V respectively through the preamplifier module. s and the second voltage signal V R ; The first voltage signal V s Expressed as: V s =k s Q s =d s k s F0sin(ωt+δ s ) Among them, k s is the first conversion coefficient; The second voltage signal V R Expressed as: V R =k R Q R =d R k R F0sin(ωt+δ R ) Among them, k R is the second conversion coefficient; According to the first voltage signal V s and the second voltage signal V R , and obtain the piezoelectric coefficient d of the sample to be tested s , the piezoelectric coefficient d of the reference sample R and the relationship between the corresponding voltage signal amplitude; Among them, V s0 is the piezoelectric coefficient d of the sample to be tested s The corresponding voltage signal amplitude, V R0 is the piezoelectric coefficient d of the reference sample R The corresponding voltage signal amplitude.

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