A piezoelectric ceramic force-position output characteristic testing device and method

Abstract

The present invention belongs to the field of piezoelectric ceramic characteristic measurement, and proposes a device and method for testing the force and position output characteristics of piezoelectric ceramics. The method test device has a built-in pressure sensor, which can obtain the external force on the piezoelectric ceramic in real time. The spring at the front end can provide a margin for the expansion and contraction of the piezoelectric ceramic while applying pressure to avoid damage to the piezoelectric ceramic. The displacement of the piezoelectric ceramic can be measured by a laser displacement sensor. The laser displacement sensor adopts a floating design to avoid the influence of deformation of structural parts and ensure that the measurement head and end are consistent with the ceramic elongation displacement. In order to ensure the force neutrality of the ceramic, the device adopts a spherical matching structure for pre-tightening. The output displacement of piezoelectric ceramics under different driving voltages and different stress states is measured. The bolt pre-tightening and the spring force application method can ensure that the ceramic is subjected to a directional load of stable size during the elongation action. The overall testing method can ensure the synchronous and precise measurement of force and position, and has the characteristics of compact structure and simple control.

Description

Technical Field

[0001] The present invention relates to the field of piezoelectric ceramic property measurement, and particularly to a test device and method for the force-position output characteristics of piezoelectric ceramics. Background Art

[0002] The dynamic stability derivative is a key parameter for the analysis and design of the stability and controllability of aircraft, and has an important impact on the control system design and flight quality of aircraft. With the continuous development of aircraft systems towards high speed and precision, the performance requirements for aircraft design are also continuously increasing. Among them, the dynamic derivatives including damping derivatives, cross derivatives, and cross-coupling derivatives generated by aircraft under ultra-high speed and large-amplitude maneuvers play a crucial guiding role in the analysis and design of aircraft shapes. For example, the cross-coupling derivative generated by the longitudinal motion of an aircraft at a large angle of attack significantly affects the stability of the aircraft. In traditional forced vibration tests, the effects of pure rotation rate and translational acceleration cannot be separated, and the combined dynamic derivative is given. Usually, some mathematical models use the combined dynamic derivative, and the predicted flight characteristics are reasonably consistent with the actual situation. However, this approximation is not applicable in all cases. For example, using rotational forced oscillation data to represent the derivative generated by a pure rotation angular rate can produce non-negligible deviations at large angles of attack. Therefore, it is necessary to determine the dynamic derivatives in the pitch, yaw, and roll directions and their coupling effects to improve the prediction effect of aircraft flight characteristics.

[0003] The multi-degree-of-freedom dynamic derivative experiment of aircraft in a high-speed wind tunnel faces the following difficulties: First, the driving element needs to drive the model to complete multi-dimensional composite excitation motion within a limited space. Second, the driving element needs to resist transient multi-dimensional loads in a complex flow field environment and output precise motion. Finally, the measurement tasks of various dynamic derivatives have different working conditions. To enhance the adaptability of the test mechanism, the driving element needs to have capabilities such as high load-bearing, high stiffness, and wide-frequency response. Conventional dynamic derivative test mechanisms are no longer applicable. The stacked piezoelectric ceramic actuator arranges piezoelectric ceramic plates in series in terms of structure and uses parallel connection between the piezoelectric ceramic plates in the circuit. It has characteristics such as fast response speed and compact structure. Moreover, the piezoelectric ceramic has a small volume, a large driving force-to-energy consumption ratio, and can efficiently convert electrical energy into mechanical energy. As an actuator for a dynamic derivative test device, it can achieve a good driving effect. However, the physical properties of piezoelectric materials themselves endow them with nonlinear characteristics such as hysteresis and creep, and their load limits in different directions are not equal. The axial load capacity is much greater than the tangential load capacity. It is necessary to ensure that the piezoelectric ceramic is axially loaded to enhance the reliability of the device. When stressed, the output displacement of the piezoelectric ceramic will relatively decrease, showing a stiffness time-varying nonlinear characteristic, which seriously affects the control accuracy of the piezoelectric ceramic actuator in practical applications. This requires testing and research on the force-bearing limits and output displacement characteristics of piezoelectric ceramics under different driving voltages and load states. Currently, commonly used piezoelectric ceramic displacement measurement devices and measurement methods do not consider the coupling relationship between the load characteristics and output displacement characteristics of piezoelectric ceramics.

[0004] The patent "Piezoelectric Ceramic Actuator Displacement Measurement Device" by Chen Shenghua et al., with the patent number CN202121375877.0, discloses a piezoelectric ceramic actuator displacement measurement device. This device uses the piezoelectric ceramic actuator to push the weak part to generate deformation, and high-precision strain gauges are pasted on the weak part of the outer frame to measure the displacement, which can greatly improve the torsional strength of the piezoelectric ceramic actuator itself. The patent "A Piezoelectric Material Voltage-Displacement Characteristic Measuring Experiment Instrument" by Pei Shixin et al., with the patent number CN201820915686.0, discloses a piezoelectric ceramic actuator displacement measurement device based on the Michelson interference principle. It controls the movement of the plane mirror by changing the working voltage of the piezoelectric material, and then measures the number of moving interference fringes to obtain the relationship between the displacement of the piezoelectric material and the applied voltage. However, the above devices do not consider the influence of external forces on the output of the ceramics and can only characterize the output of the piezoelectric ceramic under no-load conditions.

[0005] The patent "An Active Piezoelectric Ceramic Maximum Output Force Measuring Device" by Rong Weibin et al., with patent number CN201610891447.1, discloses an active piezoelectric ceramic maximum output force measuring device. This device has high stiffness, can achieve zero displacement output when the piezoelectric ceramic outputs force, and can accurately measure and calibrate the force output values at different displacement outputs. However, this device uses a high-stiffness structure to fix the displacement of the piezoelectric ceramic, ignoring the influence of external forces on the piezoelectric ceramic, and can only measure the maximum output force of the ceramic at a certain displacement, and cannot obtain the force-displacement correspondence of the piezoelectric ceramic under different external forces. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and invent a piezoelectric ceramic force-displacement output characteristic testing device and method to realize the measurement of the output displacement of the piezoelectric ceramic under different driving voltages and different stress states.

[0007] The technical solution of the present invention is as follows: A piezoelectric ceramic force-displacement output characteristic testing device includes a parallel block 1, a main body 2, a spring 4, a front-end bearing plate 5, a laser displacement sensor 7, a sensor positioning plate 8, a cantilever 9, a rear-end bearing plate 11, a pressure sensor 13, a piezoelectric ceramic 14, a moving base 15, a main body base 18, a cylindrical cover 19, an adjustable support block 20, and a force conduction stud 22; the main body base 18 is L-shaped, one side of which is fixedly connected to one end of the main body 2, and the other side is fixed to one side of the main body 2 through the adjustable support block 20; a trapezoidal groove is opened at the bottom of the main body 2, and one end of the adjustable support block 20 is located in the trapezoidal groove to support the main body 2; three cylindrical grooves of different sizes are opened inside the main body 2, a spring 4 and a front-end bearing plate 5 are installed in the first cylindrical groove, and a transverse groove is opened at the bottom of the first cylindrical groove; one end of the front-end bearing plate 5 is connected to the parallel block 1, and the parallel block 1 moves in the transverse groove; one side of the front-end bearing plate 5 is a protrusion, the spring 4 is sleeved on the protrusion, and both ends are in contact with the inner wall of the first cylindrical groove and the front-end bearing plate 5 respectively; the piezoelectric ceramic 14 is installed in the second cylindrical groove; the rear-end bearing plate 11 is installed in the third cylindrical groove; both ends of the piezoelectric ceramic 14 are in contact with the front-end bearing plate 5 and the rear-end bearing plate 11 through the moving base respectively; one end of the rear-end bearing plate 11 is connected to the pressure sensor 13 through the force conduction stud 22; the pressure sensor 13 is fixed on one side of the main body base 18; the other end of the rear-end bearing plate 11 is connected to one end of the cantilever 9; the other end of the cantilever 9 is connected to the sensor positioning plate 8; the laser displacement sensor 7 is installed on the sensor positioning plate 8; the cylindrical cover 19 is installed on the main body 2.

[0008] A piezoelectric ceramic force-displacement output characteristic testing method, based on the piezoelectric ceramic force-displacement output characteristic testing device, measures the output displacement of the piezoelectric ceramic under different driving voltages and different stress states; the specific steps are as follows:

[0009] Step 1: Assemble the piezoelectric ceramic force-displacement output characteristic test device; connect the laser displacement sensor 7 and the pressure sensor 13 to the data acquisition module; connect the data acquisition module to the upper computer, real-time controller, and power amplifier in sequence; install the piezoelectric ceramic 14 onto the piezoelectric ceramic force-displacement output characteristic test device, and apply a pre-tightening force to the piezoelectric ceramic 14; connect the power amplifier to the piezoelectric ceramic 14;

[0010] Step 2: Apply input signals of different magnitudes, frequencies, and waveforms to the piezoelectric ceramic 14 to complete the preset experiment on the piezoelectric ceramic;

[0011] Step 3: Collect the output data of the laser displacement sensor 7 and the pressure sensor 13 through the upper computer, and obtain the displacement values of the piezoelectric ceramic 14 and the corresponding pressure values under different voltages after processing the data.

[0012] The displacement values of the piezoelectric ceramic 14 and the corresponding pressure values are specifically as follows:

[0013] The laser displacement sensor 7 includes a laser, a CCD camera, and a photosensitive element; the laser emitted by the laser is incident on the surface of the measured object at a certain angle with the normal of the object surface, the reflected light and scattered light are converged and imaged by the lens at O, and finally collected by the photosensitive element;

[0014] The included angle between the incident light AB and the baseline AC is α, AO is the distance between the center of the laser and the center of the CCD camera, OE is the focal length f of the lens, D is the limit position of the reflected light imaging on the photosensitive element when the measured object is infinitely far from the baseline; DF is the displacement of the light spot deviating from the limit position on the photosensitive unit, denoted as x; △ABO∽△DOF, then there is a side length relationship:

[0015]

[0016]

[0017]

[0018] When there is a relative displacement between the measured surface and the baseline AO, x changes to x’, and the displacement value y of the piezoelectric ceramic 14 is obtained from the above conditions as:

[0019]

[0020] In the pressure sensor 13, the strain gauges are arranged as a Wheatstone bridge, and the strain gauges deflect when pressure is applied;

[0021] The magnitude of the force on both ends of the piezoelectric ceramic 14 is given by formula (5):

[0022]

[0023] Among them, ΔL represents the displacement value of the piezoelectric ceramic 14, E represents the elastic modulus of the piezoelectric ceramic 14, S represents the cross-sectional area of the piezoelectric ceramic 14, and L is the length of the piezoelectric ceramic 14.

[0024] Beneficial effects of the present invention: A test device and method for the force-displacement output characteristics of a piezoelectric ceramic are proposed to realize the measurement of the output displacement of the piezoelectric ceramic under different driving voltages and different stress states. The test device for the force-displacement output characteristics of the piezoelectric ceramic is internally provided with a pressure sensor to obtain the pressure on the piezoelectric ceramic in real time. The high-rigidity spring at the front end can provide a margin for the expansion and contraction of the piezoelectric ceramic while applying pressure, ensuring that the ceramic expands and contracts freely under a stable load. The displacement of the piezoelectric ceramic can be measured by a laser displacement sensor, which can provide high-precision data for the dynamic modeling of the piezoelectric ceramic, etc. Description of the Drawings

[0025] Figure 1 It is a schematic connection diagram of the test device for the force-displacement output characteristics of the piezoelectric ceramic of the present invention;

[0026] Figure 2 It is a flowchart of the test method for the force-displacement output characteristics of the piezoelectric ceramic of the present invention;

[0027] Figure 3 It is a structural diagram of the test device for the force-displacement output characteristics of the piezoelectric ceramic of the present invention;

[0028] Figure 4 It is a central cross-sectional view of the piezoelectric ceramic and the pressure sensor;

[0029] Figure 5 It is a structural diagram of the bottom of the main body;

[0030] Figure 6 It is a working principle diagram of the laser displacement sensor;

[0031] Figure 7 It is a working principle diagram of the pressure sensor.

[0032] In the figure: 1 - parallel block, 2 - main body, 3 - cylindrical cap set screw, 4 - spring, 5 - front end bearing plate, 6 - laser displacement sensor set screw, 7 - laser displacement sensor, 8 - sensor positioning plate, 9 - cantilever, 10 - positioning plate set screw, 11 - rear end bearing plate, 12 - cantilever set screw, 13 - pressure sensor, 14 - piezoelectric ceramic, 15 - moving base, 16 - positioning pin, 17 - main body set screw, 18 - main body base, 19 - cylindrical cap, 20 - adjustable support block, 21 - force sensor set screw, 22 - force conduction stud. Specific Embodiments

[0033] The implementation process of the present invention will be described in detail below in combination with the technical solutions and the drawings.

[0034] The piezoelectric ceramic force-position output characteristic testing device is built-in with a pressure sensor 13, which can obtain the external force on the piezoelectric ceramic 14 in real time. The front-end spring 4 can provide a margin for the expansion and contraction of the piezoelectric ceramic while applying pressure, avoiding damage to the piezoelectric ceramic 14. The displacement of the piezoelectric ceramic 14 can be measured by a laser displacement sensor 7. The laser displacement sensor 7 adopts a floating design to avoid the influence of the deformation of structural components and ensure that the measurement start and end coincide with the elongation displacement of the piezoelectric ceramic. To ensure the neutrality of the force on the piezoelectric ceramic, the piezoelectric ceramic force-position output characteristic testing device adopts a spherical mating structure for preloading. The method of bolt preloading and spring force application can ensure that the ceramic is subjected to a stable and directional load of a certain magnitude during elongation actuation. The overall testing method can ensure accurate synchronous measurement of force and position, and has the characteristics of compact structure and simple control.

[0035] The technical solution adopted in this method is as follows:

[0036] Step 1: Assemble the piezoelectric ceramic force-position output characteristic testing device; install the piezoelectric ceramic 14 on the piezoelectric ceramic force-position output characteristic testing device and apply a pre-tightening force to the piezoelectric ceramic 14.

[0037] As Figure 1 shown, the piezoelectric ceramic force-position output characteristic testing device, power amplifier, real-time controller, data acquisition device, upper computer, etc. form a piezoelectric ceramic data acquisition hardware system. The structure of the testing device is as Figure 3 、 4As shown in FIGS. 5, the parallel block 1 fixes the front-end bearing plate 5 at the front end of the main body 2 through threaded connection to ensure the perpendicularity between the front-end bearing plate 5 and the main body 2; the rear-end bearing plate 11 is in groove fit with the main body 2 to determine the perpendicularity; the moving bases 15 at both ends of the piezoelectric ceramic 14 are respectively in groove fit with the grooves in the middle of the front-end bearing plate 5 and the rear-end bearing plate 11 to ensure that the output of the ceramic measured by the pressure sensor 13 is an axial output; a trapezoidal groove is opened at the bottom of the main body 2, and it is positioned and supported in cooperation with the main body base 18 through the positioning pin 16 and the adjustable support block 20 to keep the main body in a horizontal state; the main body 2 is connected to the main body base 18 through the main body set screw 17, and different initial pre-tightening forces can be applied to the piezoelectric ceramic 14 through the main body set screw 17; the pressure sensor 13 is connected to the main body base 18 through the pressure sensor set screw 21; the rear-end bearing plate 11 is connected to the pressure sensor 13 through the force conduction stud 22, which can transmit the force received by the piezoelectric ceramic 14 to the pressure sensor in real time and can determine the position of the rear-end bearing plate 11 at the same time; the cantilever 9 is connected to the rear-end bearing plate 11 through the cantilever set screw 12; the sensor positioning plate 8 is connected to the cantilever 9 through the positioning plate set screw 10; the laser displacement sensor 7 is connected to the sensor positioning plate 8 through the laser displacement sensor set screw 6, and the laser displacement sensor 7 is fixed, and the output displacement of the piezoelectric ceramic 14 is obtained by measuring the relative distance between it and the front-end bearing plate 5; the cylindrical cover 19 is connected to the main body 2 through the cylindrical cover set screw 3 to prevent the internal components of the main body from falling out.

[0038] Step 2: Apply input signals of different magnitudes, different frequencies and different waveforms to the piezoelectric ceramic 14 to complete the preset experiment of the piezoelectric ceramic;

[0039] Step 3: Collect the output data of the laser displacement sensor 7 and the pressure sensor 13 through the upper computer, and obtain the displacement values of the piezoelectric ceramic 14 and the corresponding pressure values under different voltages after processing the data.

[0040] In summary, the force-displacement output characteristic data of the piezoelectric ceramic 14 are obtained through the piezoelectric ceramic test system.

[0041] In the laser displacement sensor 7, the laser, the CCD camera and the photosensitive element are the main components of the laser displacement sensor. As Figure 6 shown in the optical path diagram, the laser emitted by the laser enters the surface of the measured object at a certain angle with the normal of the object surface, and the reflected light and scattered light are converged and imaged by the lens at O, and finally collected by the photosensitive element;

[0042] The included angle between the incident light AB and the baseline AC is α, AO is the distance between the center of the laser and the center of the CCD camera, OE is the focal length f of the lens, D is the limit position where the reflected light forms an image on the photosensitive element when the measured object is at an infinite distance from the baseline; DF is the displacement of the light spot from the limit position on the photosensitive unit, denoted as x; △ABO∽△DOF, then there is a side length relationship:

[0043]

[0044]

[0045]

[0046] When the measured surface has a relative displacement with respect to the baseline AO, x changes to x', and from the above conditions, the displacement value y of the piezoelectric ceramic 14 is:

[0047]

[0048] In the pressure sensor 13, the strain gauges are arranged as a Wheatstone bridge, and when pressure is applied, the strain gauges deflect;

[0049] The force on both ends of the piezoelectric ceramic 14 is given by formula (5):

[0050]

[0051] Among them, ΔL represents the displacement value of the piezoelectric ceramic, E represents the elastic modulus of the piezoelectric ceramic, S represents the cross-sectional area of the piezoelectric ceramic, and L is the length of the piezoelectric ceramic.

[0052] The test device for the force-displacement output characteristics of the piezoelectric ceramic of the present invention can realize the measurement of the output displacement of the piezoelectric ceramic under different driving voltages and different stress states. The device has a compact structure and simple control, can provide high-precision data for the dynamic modeling of piezoelectric ceramics, etc., fills the gap in the existing technical field, and has great application potential.

Claims

1. A piezoelectric ceramic force-position output characteristic testing device, characterized in that The piezoelectric ceramic force-position output characteristic testing device includes a parallel block (1), a main body (2), a spring (4), a front bearing plate (5), a laser displacement sensor (7), a sensor positioning plate (8), a cantilever (9), a rear bearing plate (11), a pressure sensor (13), a piezoelectric ceramic (14), a moving base (15), a main body base (18), a cylindrical cover (19), an adjustable support block (20), and a force conduction stud (22); the main body base (18) is L-shaped, one side of which is fixedly connected to one end of the main body (2), and the other side is fixed to one side of the main body (2) through the adjustable support block (20); a trapezoidal groove is opened at the bottom of the main body (2), and one end of the adjustable support block (20) is in the trapezoidal groove to support the main body (2); three cylindrical grooves with different sizes are opened inside the main body (2), the first cylindrical groove is installed with the spring (4) and the front bearing plate (5), and a transverse groove is opened at the bottom of the first cylindrical groove; one end of the front bearing plate (5) is connected to the parallel block (1), and the parallel block (1) moves in the transverse groove; one side of the front bearing plate (5) is a protrusion, the spring (4) is sleeved on the protrusion, and the two ends are respectively in contact with the inner wall of the first cylindrical groove and the front bearing plate (5); the second cylindrical groove is installed with the piezoelectric ceramic (14); the third cylindrical groove is installed with the rear bearing plate (11); both ends of the piezoelectric ceramic (14) are in contact with the front bearing plate (5) and the rear bearing plate (11) respectively through the moving base; one end of the rear bearing plate (11) is connected to the pressure sensor (13) through the force conduction stud (22); the pressure sensor (13) is fixed on one side of the main body base (18); the other end of the rear bearing plate (11) is connected to one end of the cantilever (9); the other end of the cantilever (9) is connected to the sensor positioning plate (8); the laser displacement sensor (7) is installed on the sensor positioning plate (8); the cylindrical cover (19) is installed on the main body (2).

2. A piezoelectric ceramic force-position output characteristic testing method, characterized in that Based on the piezoelectric ceramic force-position output characteristic testing device described in claim 1, measure the output displacement of the piezoelectric ceramic under different driving voltages and different stress states; the specific steps are as follows: The first step: Assemble the piezoelectric ceramic force-position output characteristic testing device; connect the laser displacement sensor (7) and the pressure sensor (13) to the data acquisition module; the data acquisition module is sequentially connected to the upper computer, the real-time controller, and the power amplifier; install the piezoelectric ceramic (14) on the piezoelectric ceramic force-position output characteristic testing device, and apply a pre-tightening force to the piezoelectric ceramic (14); the power amplifier is connected to the piezoelectric ceramic (14). The second step: Apply input signals with different magnitudes, different frequencies, and different waveforms to the piezoelectric ceramic (14) to complete the preset experiment of the piezoelectric ceramic. The third step: Collect the output data of the laser displacement sensor (7) and the pressure sensor (13) through the upper computer, and obtain the displacement value of the piezoelectric ceramic (14) and the corresponding pressure value under different voltages after processing the data.

3. The piezoelectric ceramic force-position output characteristic testing method according to claim 2, characterized in that The displacement value of the piezoelectric ceramic (14) and the corresponding pressure value are specifically as follows: The laser displacement sensor (7) includes a laser, a CCD camera, and a photosensitive element; the laser emitted by the laser is incident on the surface of the object to be measured at a certain angle with the normal of the object surface, and the reflected light and scattered light are converged and imaged by the lens at O, and finally collected by the photosensitive element; The included angle between the incident light AB and the baseline AC is α, AO is the distance between the center of the laser and the center of the CCD camera, OE is the focal length f of the lens, D is the limit position of the reflected light imaging on the photosensitive element when the object to be measured is infinitely far from the baseline; DF is the displacement of the light spot deviating from the limit position on the photosensitive unit, denoted as x; △ABO∽△DOF, then there is a side length relationship: When the surface to be measured has a relative displacement with the baseline AO, x changes to x', and from the above conditions, the displacement value y of the piezoelectric ceramic (14) is: In the pressure sensor (13), the strain gauges are arranged as a Wheatstone bridge, and the strain gauges deflect when pressure is applied; The force magnitudes at both ends of the piezoelectric ceramic (14) are given by formula (5): Where, ΔL represents the displacement value of the piezoelectric ceramic (14), E represents the elastic modulus of the piezoelectric ceramic (14), S represents the cross-sectional area of the piezoelectric ceramic (14), and L is the length of the piezoelectric ceramic (14).

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