Piezoelectric coefficient temperature characteristic testing system and method of piezoelectric ceramic

Abstract

The invention discloses a piezoelectric coefficient temperature characteristic testing system and method for piezoelectric ceramics, and belongs to the technical field of piezoelectric coefficient testing. The problem that in the prior art, a traditional piezoelectric coefficient testing system and method for piezoelectric ceramics cannot carry out in-situ characterization on the piezoelectric ceramics in a high-temperature environment is solved. A piezoelectric coefficient temperature characteristic test system is designed, according to the obtained ideal temperature and the actual temperature, collected by a temperature sensor, of a sample to be tested, a clamp system is heated through the current output power of a heater, and sine alternating driving voltage is output to a vibration table by controlling a driving device module; the vibration table applies sine alternating force to the clamp system; the charges at the two ends of the to-be-measured sample and the reference sample are converted into voltage signals, and the piezoelectric coefficient of the to-be-measured sample at the corresponding temperature is obtained through calculation. According to the invention, in-situ piezoelectric coefficient characterization of the piezoelectric ceramic in a high-temperature environment is effectively realized, and the method can be applied to high-temperature testing of the piezoelectric coefficient of the piezoelectric ceramic.

Description

Technical Field

[0001] The present invention relates to a piezoelectric coefficient temperature characteristic testing system and method, in particular to a piezoelectric coefficient temperature characteristic testing system and method for piezoelectric ceramics, 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 areas of national strategic needs such as aerospace, deep-sea exploration, and intelligent equipment. 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, 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, which has the advantages of simple operation and 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 the metrological verification procedures for the test system have been formulated, but it places the sample to be tested and the reference sample in 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 known 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 the high-temperature in-situ piezoelectric coefficient test, it only stays at the dynamic method test, which 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, a piezoelectric coefficient temperature characteristic testing system and method suitable for piezoelectric ceramics in high-temperature environments is needed. Summary of the invention

[0005] A brief overview of the present invention is provided below in order 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 parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to a more detailed description discussed later.

[0006] In view of this, in order to solve the problem that the conventional 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] The first technical solution is as follows: a piezoelectric coefficient temperature characteristic test system of 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, and 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 system for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic described in technical solution 1, comprising the following steps:

[0014] S1. According to the ideal temperature obtained and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factor set in the PID algorithm stored in the computer, the current output power of the heater is calculated;

[0015] S2. The fixture system is heated by using the current output power of the heater, and a sinusoidal alternating driving voltage is output to the vibration table by controlling the drive device module, so that the vibration table applies a sinusoidal alternating force to the fixture system;

[0016] S3. According to the amplitude of the sinusoidal alternating force and the piezoelectric equation, the relationship between the charges at both ends of the sample to be tested and the reference sample and their corresponding piezoelectric coefficients is obtained respectively;

[0017] S4. The charges at both ends of the sample to be tested and the reference sample are converted into voltage signals through the preamplifier module, 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. The piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained by substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample.

[0018] Furthermore, in S1, according to the test program in the computer combined with the PID algorithm, the 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;

[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 It is 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 actual temperature and the theoretical temperature, ΔT n-1 is 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] Wherein, 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 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 produced 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 produced by the preamplifier module.

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

[0041] The first voltage signal V s It is 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 It is 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 amplitude of its corresponding voltage signal;

[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 composed of a temperature control device, a temperature sensor and a heater, so as to provide 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, so as to realize the heating of the sample to be tested in the fixture system; the present invention realizes the temperature isolation of the sample to be tested and the reference sample by setting an insulating column in the fixture system, so as to further improve 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, and 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 It is a structural schematic diagram of a piezoelectric coefficient temperature characteristic testing system of piezoelectric ceramics;

[0053] Figure 2 It 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 It is a schematic diagram of the connection relationship between the fixture system and the vibration table;

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

[0057] Figure 6 It is a structural diagram of a 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] Fig. 9 It is a structural diagram of the FPGA master control module;

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

[0062] Fig.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] In order to make the technical solutions and advantages of the embodiments of the present invention more clearly understood, the exemplary embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0065] Example 1: Reference Figure 1-Figure 10 The present embodiment is described in detail, a piezoelectric coefficient temperature characteristic testing system of a piezoelectric ceramic, specifically comprising 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 drive device 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, the fixture system 9 is connected to the vibration table 10, and 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 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 drive device module 7 is a drive device 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.

[0071] Specifically, the temperature control device 1 is connected to the computer 11 via an RS485 interface, and the FPGA main control module 4 is connected to the computer 11 via a 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 devices, so as 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 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 Stability, therefore, the electrode is made of platinum material, and the insulating column is a corundum column, which not only ensures the high-temperature 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, a simple peripheral circuit, a large output power, a small harmonic distortion, and an 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 chip is manufactured using an advanced low-cost CMOS process and is powered by a single 3.3V to 5V power supply with a power consumption of 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 is a combination of a field effect tube and a bipolar type. The preamplifier module 6 is internally provided with four operational amplifiers, and the reference signal and the measured signal each use two of the operational amplifiers to form a secondary amplification, wherein the sliding rheostat 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 a voltage 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, which can achieve 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 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 Fig. 9FPGA 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 the Spartan-6 series of Xilinx. 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 adopts low-power technology, which helps to reduce the total power consumption of the system. It also supports JTAG programming and configuration. The FPGA main control module 4 is based on the XC6SLX16 chip, and the periphery is also configured with Flash memory, SDRAM memory, clock and JTAB debugging port, etc. The XC6SLX16 chip, as the main controller, works in conjunction with the ADC analog-to-digital conversion module 5 and the DAC digital-to-analog conversion module 8 to achieve functions such as drive signal generation and piezoelectric signal acquisition.

[0078] refer to Fig.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 the test starting temperature of 138°C, the test maximum temperature of 550°C, the heating time of 100min, the cooling target temperature of 550°C, the cooling time of 10min and the 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 instructions 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 raise the temperature from 138°C to 550°C in 100min, 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 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 Figure 1-Figure 10 The present embodiment is described in detail. A method for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic is used in a system for testing the piezoelectric coefficient temperature characteristics of a piezoelectric ceramic described in Embodiment 1. Specifically, the method comprises the following steps:

[0080] S1. According to the ideal temperature obtained and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factor set in the PID algorithm stored in the computer, the current output power of the heater is calculated;

[0081] S2. The fixture system is heated by using the current output power of the heater, and a sinusoidal alternating driving voltage is output to the vibration table by controlling the drive device module, so that the vibration table applies a sinusoidal alternating force to the fixture system;

[0082] S3. According to the amplitude of the sinusoidal alternating force and the piezoelectric equation, the relationship between the charges at both ends of the sample to be tested and the reference sample and their corresponding piezoelectric coefficients is obtained respectively;

[0083] S4. The charges at both ends of the sample to be tested and the reference sample are converted into voltage signals through the preamplifier module, 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. The piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained by substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample.

[0084] Furthermore, in 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 It is 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 is 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, and then obtain the appropriate current output power of the heater to provide 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] Among them, 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 produced 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 produced by the preamplifier module.

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

[0109] The first voltage signal V s It is 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 It is 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 amplitude of its corresponding voltage signal;

[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 a specific size for testing 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 according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, 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 illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

Claims

1. A piezoelectric coefficient temperature characteristic testing system for piezoelectric ceramics, characterized in that: It 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 drive 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), the fixture system (9) is connected to the vibration table (10), and the temperature control device (1) controls the temperature of the heater (3) through 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 drive device module (7) and the vibration table (10) in sequence.

2. A piezoelectric coefficient temperature characteristic testing system for piezoelectric ceramics according to claim 1, characterized in that: An insulating column and a high and low temperature clamp are arranged in the clamp system (9), an electrode is arranged outside 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.

3. A piezoelectric coefficient temperature characteristic testing system for piezoelectric ceramics according to claim 2, characterized in that: 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.

4. A method for testing the temperature characteristics of piezoelectric coefficients of piezoelectric ceramics, characterized in that: A system for testing the temperature characteristics of a piezoelectric coefficient of a piezoelectric ceramic according to any one of claims 1 to 3, comprising the following steps: S1. According to the ideal temperature obtained and the actual temperature of the sample to be tested collected by the temperature sensor, combined with the control factor set in the PID algorithm stored in the computer, the current output power of the heater is calculated; S2. The fixture system is heated by using the current output power of the heater, and a sinusoidal alternating driving voltage is output to the vibration table by controlling the drive device module, so that the vibration table applies a sinusoidal alternating force to the fixture system; S3. According to the amplitude of the sinusoidal alternating force and the piezoelectric equation, the relationship between the charges at both ends of the sample to be tested and the reference sample and their corresponding piezoelectric coefficients is obtained respectively; S4. The charges at both ends of the sample to be tested and the reference sample are converted into voltage signals through the preamplifier module, 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. The piezoelectric coefficient of the sample to be tested at the corresponding temperature is obtained by substituting the voltage signal amplitude and the known piezoelectric coefficient of the reference sample.

5. A method for testing the piezoelectric coefficient temperature characteristics of piezoelectric ceramics according to claim 4, characterized in that: In S1, according to the test program in the computer combined with the PID algorithm, the 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; 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 It is 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 actual temperature and the theoretical temperature, ΔT n-1 is 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.

6. A method for testing the temperature characteristics of piezoelectric coefficients of piezoelectric ceramics according to claim 5, characterized in that: 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) Wherein, F0 is the amplitude of the sinusoidal alternating force F.

7. A method for testing the temperature characteristics of piezoelectric coefficients of piezoelectric ceramics according to claim 6, characterized in that: 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 produced 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 produced by the preamplifier module.

8. A method for testing the piezoelectric coefficient temperature characteristics of piezoelectric ceramics according to claim 7, characterized in that: In S4, the charges at both ends of the sample to be tested and the charges at both ends of the reference sample are respectively converted into first voltage signals V s and the second voltage signal V R ; The first voltage signal V s It is 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 It is 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 amplitude of its corresponding voltage signal; 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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