A calibration method for PVDF piezoelectric sensor based on electromagnetic force

Abstract

The present invention relates to the field of aerospace technology, and specifically discloses a calibration method for a PVDF piezoelectric sensor based on electromagnetic force, comprising: step S110, obtaining a standard force source and the transient force of the standard force source; the standard force source is obtained by calibrating the original force source of the inductor coil with an electronic balance; step S120, obtaining the transient stress waveform and peak value of the PVDF piezoelectric sensor after the transient force is loaded on the PVDF piezoelectric sensor; step S130, linearly fitting the peak value to achieve electromagnetic force calibration of the PVDF piezoelectric sensor. The method solves the problems of the existing PVDF piezoelectric sensor calibration method, such as the complicated operation process, the small adjustment range of the standard force source, the low accuracy, and the inability to truly record the transient force waveform when the pulse laser is loaded during the transient force measurement process.

Description

Technical Field

[0001] The invention relates to the field of aerospace technology, and in particular to a calibration method for a PVDF piezoelectric sensor based on electromagnetic force. Background Art

[0002] The process of laser ablation of target materials includes the stages of target material heating, melting and gasification, plasma generation when the laser intensity is strong enough, and high-temperature gas or plasma high-speed ejection to generate thrust. In laser ablation propulsion, gas, liquid and solid working fluids can be used as ablated materials. The process of laser interacting with target material and converting laser energy into aircraft power after the interaction with target material is a key process to achieve laser propulsion. However, the thrust generated by pulsed laser ablation of target material is instantaneous, and the thrust variation range is large with the change of laser parameters. So far, many working fluids have been used to study laser ablation propulsion, including pure water, metals and alloys, energetic liquid working fluids, etc. Laser propulsion has received widespread attention due to its large thrust range and excellent propulsion performance.

[0003] PVDF and its copolymers have excellent piezoelectric properties, good flexibility, easy processing, strong chemical stability, fast response time to input signals, wide range of pressure measurement, adaptability to complex working conditions, easy embedment, quick and simple operation, etc. Based on the above advantages, PVDF has broad application prospects in the field of transient force measurement.

[0004] At present, the common calibration methods for PVDF piezoelectric sensors include the Hopkinson bar method, the drop weight calibration method, and the equal cantilever beam method. There is still a lack of transient force calibration methods that are simple to operate, have a large standard force source adjustment range, and high accuracy. In the measurement process of thrust generated by laser ablation working fluid, thrust measurement methods such as the torsion pendulum method and the mechanoluminescence method cannot truly record the transient force waveform during pulse laser loading.

[0005] Therefore, it is of great significance to calibrate the PVDF piezoelectric sensor by electromagnetic force, measure the transient force of the laser ablation propulsion system based on the PVDF piezoelectric sensor, and analyze the laser ablation mechanism. Summary of the invention

[0006] In view of the above problems, the purpose of the present invention is to provide a calibration method for PVDF piezoelectric sensors based on electromagnetic force, so as to solve the problems of the existing PVDF piezoelectric sensor calibration method, such as complex operation process, small adjustment range of standard force source, low accuracy and inability to truly record the transient force waveform during pulse laser loading during transient force measurement.

[0007] The present invention provides a method for calibrating a PVDF piezoelectric sensor based on electromagnetic force, comprising:

[0008] Step S110, obtaining a standard force source and the transient force of the standard force source; the standard force source is obtained by calibrating the original force source of the inductance coil by an electronic balance;

[0009] Step S120, obtaining the transient stress waveform and peak value of the PVDF piezoelectric sensor after the transient force is loaded onto the PVDF piezoelectric sensor;

[0010] Step S130, performing linear fitting on the peak value to achieve electromagnetic force calibration of the PVDF piezoelectric sensor.

[0011] In a possible implementation, step S110 includes:

[0012] Control the output current of the programmable power supply to be adjusted to a preset current;

[0013] The steady-state reading of the electronic balance is obtained, and the standard force source of the preset current is calculated based on the reading.

[0014] In a possible implementation, the current adjustment range of the programmable power supply is 0.001-10A.

[0015] In a possible implementation, the calibration range of the electronic balance is 0.00001-10000g.

[0016] In a possible implementation, step S120 includes:

[0017] The transient stress waveform and peak value of the PVDF piezoelectric sensor are obtained through a data acquisition card or an oscilloscope.

[0018] In a possible implementation, step S130 includes:

[0019] Performing linear fitting on the peak values ​​under different standard force source conditions, and obtaining the piezoelectric coefficient of the PVDF piezoelectric sensor through the slope of the fitting line; the fitting line passes through the origin;

[0020] The transient force magnitude of laser ablation of different working fluids is obtained according to the piezoelectric coefficient of the PVDF piezoelectric sensor, thereby realizing the electromagnetic force calibration of the PVDF piezoelectric sensor.

[0021] In a possible implementation, the method further includes:

[0022] Step S140, evaluating the transient force change process generated by laser ablation of aluminum alloy according to the voltage waveform signal of the PVDF piezoelectric sensor.

[0023] In a possible implementation, the method further includes:

[0024] Adjusting energy parameters and spot parameters of the laser to ablate the aluminum alloy substrate;

[0025] The electrical signal of the PVDF piezoelectric sensor is recorded and analyzed by a charge amplifier, a data acquisition card and an industrial computer;

[0026] The transient force signal of laser ablation of aluminum alloy is collected in real time by the PVDF piezoelectric sensor, and the transient force generated by laser ablation of aluminum alloy is tested based on the obtained piezoelectric coefficient and the measured voltage peak value.

[0027] In a possible implementation, the laser is a solid laser, a semiconductor laser or a gas laser.

[0028] In a possible implementation, the energy parameter of the laser ranges from 10 mJ to 10 J.

[0029] The beneficial effects of the present invention include:

[0030] (1) The present invention can realize the characteristics of simple calibration operation of PVDF piezoelectric sensor, wide adjustment range of calibration force source, high calibration accuracy, and simplifies the calibration device.

[0031] (2) The present invention can realize rapid and accurate measurement of the transient force generated by the PVDF piezoelectric sensor on the laser ablation working fluid under vacuum and atmospheric conditions.

[0032] (3) The present invention can realize the real-time recording of the transient force waveform generated by the laser ablation working fluid, which is helpful for analyzing the mechanism of laser loading and laser ablation working fluid and has better usability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of a flow chart of a calibration method provided in an embodiment of the present invention;

[0034] Figure 2 A schematic diagram of calibrating a standard force source using an electronic balance provided in an embodiment of the present invention;

[0035] FIG3( a ) is a system diagram of a PVDF piezoelectric sensor for testing a standard force source according to an embodiment of the present invention;

[0036] FIG3( b ) is a waveform showing the voltage variation over time generated by the PVDF piezoelectric sensor provided by an embodiment of the present invention under different electromagnetic force conditions;

[0037] FIG3( c ) is a schematic diagram of a linear fit between a voltage peak value and an electromagnetic force provided by an embodiment of the present invention;

[0038] FIG4( a ) is a schematic diagram of a system for testing transient force generated by laser ablation of aluminum alloy using a PVDF piezoelectric sensor according to an embodiment of the present invention;

[0039] FIG4( b ) is a schematic diagram of a waveform of a voltage generated by a PVDF piezoelectric sensor test under a first laser energy condition varying with time provided by an embodiment of the present invention;

[0040] FIG4( c ) is a schematic diagram of a waveform of a voltage generated by a PVDF piezoelectric sensor test under a second laser energy condition varying with time provided by an embodiment of the present invention;

[0041] FIG4( d ) is a schematic diagram of a waveform of a voltage generated by a PVDF piezoelectric sensor provided in an embodiment of the present invention under a third laser energy condition varying with time;

[0042] FIG4( e) is a schematic diagram of a waveform of a voltage generated by a PVDF piezoelectric sensor provided by an embodiment of the present invention under a fourth laser energy condition varying with time;

[0043] FIG4( f) is a schematic diagram of a waveform of a voltage generated by a PVDF piezoelectric sensor provided by an embodiment of the present invention under a fifth laser energy condition varying with time;

[0044] FIG4( g) is a summary diagram of the voltage peaks output by the piezoelectric sensor under different laser spot sizes and laser energy conditions provided by an embodiment of the present invention;

[0045] Figure 5 This is a test diagram of the repeatability of the voltage signal output by the piezoelectric sensor under the same laser spot size and laser energy conditions provided by an embodiment of the present invention.

[0046] Figure 6 A comparison diagram of the voltage signals output by the piezoelectric sensor under vacuum and atmospheric conditions provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0047] The following detailed description of the embodiments of the present invention is further described in detail in conjunction with the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to exemplarily illustrate the principles of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the preferred embodiments described, and the scope of the present invention is defined by the claims.

[0048] In the description of the present invention, it should be noted that, unless otherwise specified, “plurality” means two or more than two; the terms “first”, “second”, etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; for ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0049] Figure 1A flow chart of a calibration method provided by an embodiment of the present invention is shown in FIG. Figure 1 As shown, the present invention provides a calibration method for a PVDF piezoelectric sensor based on electromagnetic force, comprising:

[0050] Step S110, obtaining a standard force source and a transient force of the standard force source;

[0051] The standard force source is obtained by calibrating the original force source of the inductance coil using an electronic balance.

[0052] In a possible implementation, step S110 includes:

[0053] Control the output current of the programmable power supply to be adjusted to a preset current;

[0054] Obtain the steady-state reading of the electronic balance, and calculate the standard force source of the preset current based on the reading.

[0055] In a possible implementation, the current adjustment range of the programmable power supply is 0.001-10A.

[0056] In a possible implementation, the calibration range of the electronic balance is 0.00001-10000 g.

[0057] Electromagnetic forces include those generated by coils made of materials such as copper coils, aluminum coils, ferrite coils and screen-printed coils.

[0058] Permanent magnet materials include neodymium iron boron, samarium cobalt, aluminum nickel cobalt, iron cobalt molybdenum and ferrite permanent magnet materials.

[0059] Figure 2 A schematic diagram of calibrating a standard force source using an electronic balance provided in an embodiment of the present invention, such as Figure 2 As shown, the calibration device of the standard force source mainly includes a programmable power supply 1, an electronic balance 2, an electromagnetic coil 3, a permanent magnet 4, an insulating pad 5, and a bracket 6. The force applied to the balance is controlled by the electrical parameters of the electromagnetic coil, thereby giving the magnitude of the electromagnetic force under different electrical parameter conditions.

[0060] Specifically, a high-precision balance is used to calibrate the electromagnetic force source. First, an electromagnetic force source calibration platform is built, the electromagnetic coil is fixed at an appropriate position inside the balance through an iron frame, the electromagnetic coil power supply line is connected, the electromagnetic coil is powered by a programmable power supply, and the electrical parameters of the electromagnetic coil are changed by adjusting the current of the programmable power supply. An insulating pad is placed on the microbalance to prevent the electromagnetic force generated by the electromagnetic coil from affecting the balance reading. A permanent magnet is placed on the pad. The magnetism generated by the electromagnetic coil is opposite to the magnetism of the permanent magnet and thus generates a repulsive force. This repulsive force will act on the high-precision balance, thereby causing the balance reading to change. Finally, the output current of the programmable power supply is changed to change the electromagnetic force generated by the electromagnetic coil on the balance, the programmable current and the corresponding balance reading are recorded, and the electromagnetic force of the standard force source under different electrical parameter conditions is given.

[0061] Step S120, obtaining a transient stress waveform and a peak value of the PVDF piezoelectric sensor after a transient force is loaded onto the PVDF piezoelectric sensor;

[0062] In a possible implementation, step S120 includes:

[0063] The transient stress waveform and peak value of the PVDF piezoelectric sensor are obtained through a data acquisition card or an oscilloscope.

[0064] Step S130, performing linear fitting on the peak value to achieve electromagnetic force calibration of the PVDF piezoelectric sensor.

[0065] In a possible implementation, step S130 includes:

[0066] The peak values ​​under different standard force source conditions are linearly fitted, and the piezoelectric coefficient of the PVDF piezoelectric sensor is obtained by the slope of the fitting line; the fitting line passes through the origin; according to the piezoelectric coefficient of the PVDF piezoelectric sensor, the transient force size of laser ablation of different working fluids is obtained to realize the electromagnetic force calibration of the PVDF piezoelectric sensor.

[0067] In a possible implementation, the material of the PVDF piezoelectric sensor includes PVDF and its composite materials.

[0068] In a possible implementation, the test platform of the PVDF piezoelectric sensor can be tested in a fully buried or semi-buried manner.

[0069] Specifically, the piezoelectric coefficient of the PVDF piezoelectric sensor is tested using a standard force source. First, a calibration platform for the PVDF piezoelectric sensor is built, the signal acquisition circuit of the PVDF piezoelectric sensor is connected, the PVDF piezoelectric sensor is placed on the loading platform, and a permanent magnet block is placed above the PVDF piezoelectric sensor. The electromagnetic coil is fixed with an iron stand, and the position is adjusted to align the electromagnetic coil with a position about 2 mm above the center of the permanent magnet. Finally, the electromagnetic coil is controlled to output a fixed electromagnetic force through a programmable power supply, and the standard force source generated by the electromagnetic coil and the permanent magnet is applied to the PVDF piezoelectric sensor, and the electrical signal of the PVDF piezoelectric sensor under different standard force source conditions is recorded. The standard electromagnetic force and the voltage peak signal of the PVDF piezoelectric sensor are linearly fitted to obtain the piezoelectric coefficient of the PVDF piezoelectric sensor.

[0070] Fig. 3(a) is a system diagram of a PVDF piezoelectric sensor for testing a standard force source provided by an embodiment of the present invention; Fig. 3(b) is a waveform of a voltage varying with time generated by a PVDF piezoelectric sensor under different electromagnetic force conditions provided by an embodiment of the present invention; Fig. 3(c) is a schematic diagram of a linear fit of a voltage peak value and an electromagnetic force provided by an embodiment of the present invention. As can be seen from Fig. 3(a), the piezoelectric coefficient testing device of the PVDF piezoelectric sensor mainly comprises a programmable power supply 1, a bracket 6 for fixing the electromagnetic coil, an electromagnetic coil 3, a permanent magnet 4, a PVDF piezoelectric sensor 10, an operating platform 11, a charge amplifier 7, a data acquisition card 8 and an industrial computer 9. By adjusting the electrical parameters of the programmable power supply, a fixed standard force can be applied to the PVDF piezoelectric sensor, and the electrical signal on the piezoelectric sensor is recorded on the test software of the industrial computer through the charge amplifier and the data acquisition card. As shown in Figure 3(b), when the current output by the programmable power supply is greater than 0.05A, the piezoelectric sensor can have an obvious response signal, and the corresponding standard force is 0.056N. When the current output by the programmable power supply is greater than 0.01A, the piezoelectric sensor has a recognizable voltage response signal (greater than one times the background noise), and the corresponding standard force is 0.011N.

[0071] Assuming the PVDF output voltage measured by the calibration system is V(t), its output current is:

[0072]

[0073] Ignoring the circuit system capacitance (about 10-12F), the total charge output by PVDF is:

[0074]

[0075] Where: t is the time of action of the transient force generated by laser irradiation on aluminum / titanium alloy on PVDF. The change of transient force on aluminum alloy over time can be measured. The corresponding relationship between the two is obtained by curve fitting using multiple groups of V(t) signals and standard force F signals measured by the calibration system:

[0076] F(t)=KV(t) (3)

[0077] Where: K is the dynamic piezoelectric coefficient to be calibrated, F(t) is the transient force signal measured by the PVDF piezoelectric film. According to formula (2) and formula (3), the transient force signal it is subjected to can be obtained by converting the V(t) signal output by the measured PVDF in the experiment. As shown in Figure 3(c), the voltage peak obtained by loading the corresponding standard force and electromagnetic standard force onto the PVDF piezoelectric sensor is linearly fitted. The fitting line passes through the origin, and the relationship between the peak voltage of the PVDF piezoelectric sensor and the standard force source is y=0.7x, and the piezoelectric coefficient of the PVDF piezoelectric sensor is 0.7. Therefore, the transient force value generated by the laser ablation working fluid can be calculated based on the voltage peak value of the tested PVDF piezoelectric sensor.

[0078] In a possible implementation, the method further includes: step S140, evaluating a transient force change process generated by laser ablation of aluminum alloy according to a voltage waveform signal of the PVDF piezoelectric sensor.

[0079] In a possible implementation, it also includes: adjusting the energy parameters and spot parameters of the laser to ablate the aluminum alloy substrate; recording and analyzing the electrical signals of the PVDF piezoelectric sensor through a charge amplifier, a data acquisition card and an industrial computer; real-time acquisition of the transient force signal of the laser ablation of the aluminum alloy through the PVDF piezoelectric sensor, and testing the transient force generated by the laser ablation of the aluminum alloy based on the obtained piezoelectric coefficient and the measured voltage peak.

[0080] In a possible implementation, the laser is a solid laser, a semiconductor laser or a gas laser.

[0081] In a possible implementation, the energy parameter of the laser ranges from 10 mJ to 10 J.

[0082] The specific environmental conditions may be vacuum, atmospheric environment, etc.

[0083] The laser can be a solid laser, a semiconductor laser, a gas laser, etc.

[0084] The diameter of the laser spot is 50 μm-10 cm.

[0085] The target material for laser ablation can be aluminum alloy, titanium alloy, carbon material, water, energetic liquid working fluid, air, etc.

[0086] Specifically, the transient force signal and the transient force peak value generated by laser ablation of aluminum alloy were tested under different laser optical parameter conditions. First, a PVDF piezoelectric sensor was arranged in a vacuum chamber, and the PVDF piezoelectric sensor was placed on a 5 mm thick aluminum alloy plate and a fixed substrate of a translation stage. Secondly, the circuit of the PVDF piezoelectric sensor was connected through a vacuum flange, and the electrical signal of the PVDF piezoelectric sensor was recorded and analyzed using a charge amplifier, a data acquisition card and an industrial computer. Finally, the energy parameters and spot parameters of the YAG laser were adjusted to ablate the aluminum alloy substrate. The PVDF piezoelectric sensor collected the transient force signal of the laser ablation of aluminum alloy in real time, and the piezoelectric coefficient and the measured voltage peak value obtained in the above steps were used to test the transient force generated by laser ablation of aluminum alloy.

[0087] The above-mentioned calibration method of PVDF piezoelectric sensor based on electromagnetic force and its application in transient force measurement generated by pulsed laser ablation are specifically carried out according to the following steps:

[0088] (1) Calibration steps of electromagnetic force standard source: Build the calibration platform of electromagnetic force standard source according to the method in technical implementation plan 1. Adjust the output current of the programmable power supply to 0.01A, 0.05A, 0.1A, 0.5A, 1.0A, 1.5A and 2.0A. Each time the current is adjusted, the electromagnetic force will exert a fixed electromagnetic force on the balance. After the balance reading stabilizes, the balance readings are recorded as 1.135g, 5.631g, 11.631g, 55.180g, 107.551g, 156.435g and 198.416g respectively. The standard forces under the corresponding electrical parameter conditions are calculated by the balance readings to be 0.011N, 0.056N, 0.116N, 0.552N, 1.075N, 1.564N and 1.984N respectively.

[0089] (2) Steps for measuring the piezoelectric coefficient of the PVDF piezoelectric sensor: Build a PVDF piezoelectric coefficient test platform according to the method in Technical Implementation Plan 2. Adjust the output current of the programmable power supply to 0..01A, 0.05A, 0.1A, 0.5A, 1.0A, 1.5A and 2.0A. Use the PVDF piezoelectric sensor test software to record the piezoelectric signal waveform under different electrical parameter conditions and read the peak voltage of the piezoelectric signal. Perform a linear fit on the voltage peak under different standard force conditions, and the fitting line passes through the origin. The piezoelectric coefficient of the PVDF piezoelectric sensor is obtained by calculating the slope of the fitting line. Therefore, by measuring the voltage signal of the PVDF piezoelectric sensor, the transient force of laser ablation of different working fluids can be obtained, thereby realizing the electromagnetic force calibration of the PVDF piezoelectric sensor.

[0090] (3) Test steps for the magnitude of transient force generated by laser ablation of aluminum alloy: Under specific environmental conditions, the aluminum alloy substrate target in the single-pulse laser ablation chamber is used, the voltage change is used to control the output energy of the YAG laser, the laser ablation spot size on the surface of the aluminum alloy plate is adjusted through the optical focusing system, and a PVDF piezoelectric sensor is used to record the voltage signal generated by ablation of aluminum alloy with different laser energies and different laser spots. The peak value of the voltage signal is read, and the magnitude of the transient force is calculated based on the piezoelectric coefficient of the PVDF piezoelectric sensor. The transient force change process generated by laser ablation of aluminum alloy is evaluated based on the voltage waveform signal of the PVDF piezoelectric sensor.

[0091] As shown in Figure 4(a), the PVDF piezoelectric sensor is used to test the transient force generated by laser ablation of aluminum alloy under vacuum conditions. The device mainly includes an optical platform, a YAG laser, a vacuum system, a three-axis translation stage and a fixed frame, an aluminum alloy substrate, a PVDF piezoelectric sensor, and a data acquisition system. Figure 4(b)-Figure 4(f) As shown in the figure, the voltage signals of the PVDF piezoelectric sensor obtained under different laser energy and different laser spot size parameters are summarized and analyzed. The laser energy is 800mJ, 500mJ, 350mJ, 150mJ and 90mJ respectively, and the laser spot size is 1.48mm 2 ,1.24mm 2 , 1.02mm 2 , 0.96mm 2 ,0.76mm 2 The experimental test of laser ablation of aluminum alloy working fluid was repeated three times for each laser energy and corresponding spot parameters. As shown in Figure 4(g), the voltage peaks under the optical parameter conditions of different laser energies and spot sizes are summarized. It can be seen that the peak voltage signal increases with the increase of laser spot and increases with the increase of laser energy. It can be seen that the transient force generated by laser ablation of aluminum alloy working fluid also increases with the increase of laser energy and spot.

[0092] Figure 5 This is a test diagram of the repeatability of the voltage signal output by the piezoelectric sensor under the same laser spot size and laser energy conditions provided by the embodiment of the present invention. 2 ) The voltage signal curve of the PVDF piezoelectric sensor is obtained when the aluminum alloy is ablated. The measurement is repeated 9 times. It can be seen from the figure that the voltage signal of the PVDF piezoelectric sensor has good repeatability under the same conditions. The maximum peak value of the voltage is about 1.23V and the minimum peak value is 1.21V. The measured value deviation of the voltage is less than 1.7%;

[0093] Figure 6A comparison diagram of the voltage signals output by the piezoelectric sensor under vacuum and atmospheric conditions provided by the embodiment of the present invention, Figure 6 It can be seen that under different atmospheric conditions, the same laser parameters (500mJ, 0.76mm 2 ) Voltage signal curve of PVDF piezoelectric sensor when ablating aluminum alloy. Under atmospheric conditions, the peak voltage signal generated by laser ablation of aluminum alloy is much greater than the peak voltage signal under vacuum conditions. This is mainly due to the larger jet resistance generated by laser ablation of aluminum alloy under atmospheric conditions, which in turn generates a greater reaction force on the PVDF piezoelectric sensor.

[0094] The present invention first uses an electronic balance to calibrate the standard force source of the inductor coil, and loads it onto the balance through the repulsive force of the electromagnetic force and the permanent magnet, so as to obtain a standard force source that changes through the current adjustment of the inductor coil. The transient force generated by the electromagnetic force source is loaded onto the PVDF piezoelectric sensor to obtain the transient stress waveform and peak value of the PVDF piezoelectric sensor. The peak value is linearly fitted to complete the calibration of the PVDF piezoelectric sensor. A single-pulse laser ablation aluminum alloy working fluid is generated by a laser in a vacuum and atmospheric environment, the laser parameters are adjusted, and the voltage change waveform of the PVDF piezoelectric sensor over time is used to record the dynamic process of pulsed laser ablation, and the transient stress measurement during pulsed laser loading can be realized based on the dependence of the monitored voltage peak value and the transient force of laser loading.

[0095] The electromagnetic force-based calibration method for PVDF piezoelectric sensors provided by the present invention has the characteristics of simple calibration operation, wide adjustment range of calibration force source, and high calibration accuracy, thereby simplifying the calibration device; it can realize rapid and accurate measurement of transient force generated by PVDF piezoelectric sensors for laser ablation working fluid under vacuum and atmospheric conditions; it can realize real-time recording of transient force waveforms generated by laser ablation working fluid, which is helpful for analyzing the mechanism of laser loading and laser ablation working fluid, and has better usability.

[0096] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A calibration method for PVDF piezoelectric sensor based on electromagnetic force, characterized in that: include: Step S110, obtaining a standard force source and the transient force of the standard force source; The standard force source is obtained by calibrating the original force source of the inductance coil using an electronic balance; Step S110, building an electromagnetic force source calibration platform, fixing the electromagnetic coil at an appropriate position inside the balance through an iron frame, connecting the power supply line of the electromagnetic coil, supplying power to the electromagnetic coil through a programmable power supply, controlling the output current of the programmable power supply to be adjusted to a preset current, obtaining the steady reading of the electronic balance, and calculating the standard force source of the preset current and the transient force of the standard force source according to the reading; Step S120, obtaining the transient stress waveform and peak value of the PVDF piezoelectric sensor after the transient force is loaded onto the PVDF piezoelectric sensor; Step S130, performing linear fitting on the peak value to achieve electromagnetic force calibration of the PVDF piezoelectric sensor; Step S140, evaluating the transient force change process generated by laser ablation of aluminum alloy according to the voltage waveform signal of the PVDF piezoelectric sensor; Step S130 includes: The peak values ​​under different standard force source conditions are linearly fitted to obtain a fitting line, and the piezoelectric coefficient of the PVDF piezoelectric sensor is obtained by the slope of the fitting line; the fitting line passes through the origin; The transient force magnitude of laser ablation of different working fluids is obtained according to the piezoelectric coefficient of the PVDF piezoelectric sensor, thereby realizing the electromagnetic force calibration of the PVDF piezoelectric sensor.

2. The calibration method according to claim 1, characterized in that: The current adjustment range of the programmable power supply is 0.001-10A.

3. The calibration method according to claim 1, characterized in that: The calibration range of the electronic balance is 0.00001-10000g.

4. The calibration method according to claim 1, characterized in that: The step S120 includes: The transient stress waveform and peak value of the PVDF piezoelectric sensor are obtained through a data acquisition card or an oscilloscope.

5. The calibration method according to claim 1, characterized in that: The step S140 further includes: Adjusting energy parameters and spot parameters of the laser to ablate the aluminum alloy substrate; The electrical signal of the PVDF piezoelectric sensor is recorded and analyzed by a charge amplifier, a data acquisition card and an industrial computer; The transient force signal of laser ablation of aluminum alloy is collected in real time by the PVDF piezoelectric sensor, and the transient force generated by laser ablation of aluminum alloy is tested based on the obtained piezoelectric coefficient and the measured voltage peak value.

6. The calibration method according to claim 5, characterized in that: The laser is a solid laser, a semiconductor laser or a gas laser.

7. The calibration method according to claim 5, characterized in that: The energy parameter of the laser is in the range of 10 mJ-10 J.

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