A rhombic piezoelectric actuator output force real-time measurement method and device

Abstract

The application provides a rhombic piezoelectric actuator output force real-time measurement method and device, the method comprises the following steps: step 1: under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is free, the ratio X1 of the output displacement of the piezoelectric actuator and the piezoelectric stack displacement is calculated; step 2: under the condition that the two ends of the rhombic piezoelectric actuator are fixed, the ratio X2 of the output force of the piezoelectric actuator and the piezoelectric stack displacement is calculated; step 3: under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is connected with a load, the time domain signal f1(t) of the output force of the rhombic piezoelectric actuator is calculated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of actuator hysteresis compensation control, and particularly relates to a rhombus piezoelectric actuator output force real-time measurement method and device. BACKGROUND

[0002] Piezoelectric materials have positive piezoelectric effect and inverse piezoelectric effect. According to different effects, piezoelectric materials can be used for actuators and sensors. Common forms for actuators include piezoelectric wafer and piezoelectric stack. The energy density of the piezoelectric stack is higher (about 4 times that of the piezoelectric wafer), which can generate larger driving force with relatively small power, but at the cost of lower output displacement. To meet the requirements of force and stroke actuation, piezoelectric stack piezoelectric actuators are usually configured with stroke amplification devices such as X-shaped, L-shaped and rhombus frames, which essentially amplify the stroke through the principle of lever. Piezoelectric actuators have the advantages of high displacement control accuracy, fast response speed, low power consumption and immunity to electromagnetic interference, and are widely used in micro-positioning and micro-control fields.

[0003] The rhombus piezoelectric actuator amplification outer frame adopts a flexible hinge configuration, which does not generate bearing-related friction and clearance, has a simple and compact structure, and has high mechanical efficiency. In recent years, it has been favored in the fields of active control rotors and antenna pointing. The current rhombus piezoelectric actuator shelf product generally only includes a piezoelectric stack and a rhombus outer frame. Some further products will paste a strain gauge on the piezoelectric stack to form a strain displacement sensor. Through a bench test of the rhombus piezoelectric actuator with one end fixed and the other end free, the relationship between the strain displacement sensor on the piezoelectric stack and the output displacement of the piezoelectric actuator can be calibrated, the piezoelectric actuator output displacement measurement sensitivity of the strain sensor is obtained, and a calibration certificate is delivered with the product.

[0004] However, the strain displacement sensor is only suitable for the output displacement of the piezoelectric actuator in the fixed-free state. Obviously, the strain gauge pasted on the piezoelectric stack essentially measures the displacement of the piezoelectric stack. When the piezoelectric actuator is in a loaded state, especially when the load stiffness is infinite, i.e. in a fixed-fixed state, the output displacement of the piezoelectric actuator is 0, while the displacement of the piezoelectric stack is obviously not 0. Therefore, the sensitivity of the strain displacement sensor obtained in the fixed-free state cannot be used for accurate measurement of the output displacement of the piezoelectric actuator in the loaded state. Therefore, in order to realize high-precision control of the displacement of the piezoelectric actuator, a displacement sensor must be additionally connected to directly measure the output displacement of the piezoelectric actuator, so as to realize displacement signal feedback closed-loop control of the piezoelectric actuator. The output displacement of the piezoelectric actuator can be measured by a non-contact displacement sensor such as a capacitive or laser type.

[0005] In addition, when the rhombic piezoelectric actuator works with load, the actuator often works in a boundary condition of one end fixed and one end connected with load. The traditional testing method of the output force of the piezoelectric actuator is to connect a force sensor in series between the piezoelectric actuator and the load. Obviously, this will increase the complexity of the force, displacement and other transmission relationships between the actuator and the load. In addition, the volume, mass and signal measurement circuit of the force sensor will also increase the complexity and cost of the device. Therefore, in practical applications, especially in the field of micro-displacement applications, there is often no force sensor in the device when the piezoelectric actuator works with load. The output force measurement and monitoring of the piezoelectric actuator are in a state of deficiency, which hinders people's understanding of the mechanical properties of the load in the actual working environment. SUMMARY

[0006] The purpose of the present application is to provide a rhombic piezoelectric actuator output force real-time measurement method and device, which does not need to connect a force sensor in the force transmission structure between the actuator and the load, and can provide real-time measurement and monitoring of the output force of the piezoelectric actuator only according to the piezoelectric stack displacement signal and the piezoelectric actuator output displacement signal.

[0007] In a first aspect, the present application provides a rhombic piezoelectric actuator output force real-time measurement method, which comprises the following steps:

[0008] Step 1: Under the condition of one end fixed and one end free of the rhombic piezoelectric actuator, calculate the ratio X1 of the piezoelectric actuator output displacement and the piezoelectric stack displacement.

[0009] Step 2: Under the boundary condition of both ends fixed of the rhombic piezoelectric actuator, calculate the ratio X2 of the piezoelectric actuator output force f1 and the piezoelectric stack displacement. block

[0010] Step 3: Under the condition of one end fixed and one end connected with load of the rhombic piezoelectric actuator, calculate the time domain signal f1(t) of the output force of the rhombic piezoelectric actuator.

[0011] Specifically, step 1 comprises the following steps:

[0012] Step 11: Under the condition of one end fixed and one end free of the rhombic piezoelectric actuator, apply an excitation voltage to obtain the stack displacement of the rhombic piezoelectric actuator under the fixed-free boundary condition.

[0013] Step 12: Calculate X1 by using the formula .

[0014] Specifically, step 2 comprises the following steps:

[0015] ​​​​Step 21: Fix one end of the rhombic piezoelectric actuator and connect the other end to a force sensor, while fixing the other end of the force sensor. Apply an excitation voltage to obtain the stacked displacement under this condition. Actuator output displacement and actuator output force f1 load ;

[0016] Step 22: Using the formula Calculate the external load stiffness k load ;

[0017] Step 23: Utilize stacked displacement Actuator output displacement Actuator output force f1 load and external load stiffness k load Combined with formula Calculate X2.

[0018] Specifically, step 3 includes:

[0019] Step 31: For the working condition where one end of the rhombic piezoelectric actuator is fixed and the other end is connected to the load, the time-domain signal Δx1(t) of the actuator output displacement and the time-domain signal Δx of the stacked displacement are acquired. pzt (t);

[0020] Step 32: Based on the output displacement time-domain signal Δx1(t) and the stacked displacement time-domain signal Δx pzt (t), using the formula Calculate the time-domain signal f1(t) of the output force of the rhombic piezoelectric actuator.

[0021] Secondly, this application provides a real-time measurement device for the output force of a rhombic piezoelectric actuator, the device comprising an X1 calculation unit, an X2 calculation unit, and a time-domain signal calculation unit, wherein:

[0022] The X1 calculation unit is used to calculate the output displacement of the piezoelectric actuator under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is free. With piezoelectric stack displacement The ratio of X1;

[0023] The X2 calculation unit is used to calculate the output force f1 of the piezoelectric actuator under the condition that both ends of the rhombic piezoelectric actuator are fixed at the boundary. block With piezoelectric stack displacement The ratio is X2;

[0024] The time-domain signal calculation unit is used to calculate the time-domain signal f1(t) of the output force of the rhombic piezoelectric actuator under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is connected to a load.

[0025] Specifically, the X1 computing unit is used for:

[0026] The rhombic piezoelectric actuator is fixed at one end and free at the other end, an excitation voltage is applied, and the stack displacement under the fixed-free boundary condition of the rhombic piezoelectric actuator is obtained The actuator output displacement

[0027] The formula is used to calculate X1.

[0028] Specifically, the X2 calculation unit is specifically configured to:

[0029] The rhombic piezoelectric actuator is fixed at one end and connected to a force sensor at the other end, and the force sensor is fixed at the other end, an excitation voltage is applied, and the stack displacement under this condition is obtained The actuator output displacement And the actuator output force f1 load ;

[0030] The formula is used to calculate the external load stiffness k load ;

[0031] The stack displacement The actuator output displacement The actuator output force f1 load And the external load stiffness k load , combined with the formula is used to calculate X2.

[0032] Specifically, the time domain signal calculation unit is specifically configured to:

[0033] For the working condition that the rhombic piezoelectric actuator is fixed at one end and connected to a load at the other end, the actuator output displacement time domain signal Δx1(t) and the stack displacement time domain signal Δx pzt (t) are obtained by collection;

[0034] According to the output displacement time domain signal Δx1(t) and the stack displacement time domain signal Δx pzt (t), the formula is used to calculate the time domain signal f1(t) of the rhombic piezoelectric actuator output force.

[0035] In summary, the present application provides a rhombic piezoelectric actuator output force real-time measurement method and device, specifically: based on the two parameters of the ratio of the actuator output displacement to the stack displacement under the fixed-free boundary condition of the rhombic piezoelectric actuator and the ratio of the actuator output force to the stack displacement under the fixed-fixed boundary condition, the piezoelectric stack displacement signal and the actuator output displacement signal measured under the working condition of the rhombic piezoelectric actuator with load are used to calculate the output force of the actuator in real time, and the time domain signal of the actuator output force is formed. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 A schematic diagram of the real-time measurement method for the output force of the rhombic piezoelectric actuator provided in this application;

[0037] Figure 2 This is an enlarged schematic diagram of the rhombic piezoelectric actuator provided in this application;

[0038] Figure 3 A comparison of the measured and calculated output force curves of the rhombic piezoelectric actuator provided in this application over time. Detailed Implementation

[0039] like Figure 2 As shown, the gray rectangular section in the middle of the rhombic piezoelectric actuator structure is a piezoelectric stack, which is fixed in the rhombic frame. The length of the piezoelectric stack changes with the excitation voltage, causing a corresponding change in the output displacement of the rhombic outer frame. Common excitation voltage waveforms include sine waves, triangular waves, and ramp waves.

[0040] Define the output displacement and piezoelectric stack displacement of the rhombic piezoelectric actuator under the boundary condition of one end fixed and the other end fixed as follows: Define the output force and piezoelectric stack displacement of the rhombic piezoelectric actuator as f1 under the condition that both ends of the piezoelectric actuator are fixed at the boundary. block , In the case where one end of the rhombic piezoelectric actuator is fixed and the other end is connected to an external load, the actuator output displacement and the stacked displacement are defined as Δx1 and Δx, respectively. pzt .definition The ratio is Define f1 block , The ratio is

[0041] Real-time Example 1

[0042] like Figure 1 As shown, this application provides a method for real-time measurement of the output force of a rhombic piezoelectric actuator, the method comprising:

[0043] Step 1: With one end of the rhombic piezoelectric actuator fixed and the other end free, calculate the output displacement of the piezoelectric actuator. With piezoelectric stack displacement The ratio of X1;

[0044] Specifically, step 1 includes:

[0045] Step 11: With one end of the rhombic piezoelectric actuator fixed and the other end free, an excitation voltage is applied to obtain the stacked displacement of the rhombic piezoelectric actuator under the fixed-free boundary conditions. Actuator output displacement

[0046] Step 12: Using the formula Calculate X1.

[0047] Step 2: Calculate the output force f1 of the piezoelectric actuator under the condition of fixed support boundary condition at both ends of the rhombic piezoelectric actuator block and the displacement of the piezoelectric stack ratio X2;

[0048] Specifically, step 2 includes:

[0049] Step 21: Let one end of the rhombic piezoelectric actuator be fixed, and the other end be connected with a force sensor, while the other end of the force sensor is fixed. Apply an excitation voltage to obtain the displacement of the stack under this condition the output displacement of the actuator and the output force f1 of the actuator load ;

[0050] Step 22: Calculate the external load stiffness k using the formula load ;

[0051] It should be noted that the external load of the actuator is the force sensor, and the external load stiffness k load is the stiffness of the force sensor. Among them, the stiffness of the force sensor is generally constant within the range of the range.

[0052] Step 23: Calculate X2 using the stack displacement the output displacement of the actuator the output force f1 of the actuator load and the external load stiffness k load , combined with the formula

[0053] It should be noted that the key point of step 2 is to convert the output force of the piezoelectric actuator under the fixed support-fixed support boundary condition which cannot be measured into the fixed support-fixed support boundary condition of the piezoelectric actuator+force sensor. By measuring the output force, output displacement and stack displacement of the actuator under this condition, and according to the stiffness of the rhombic piezoelectric actuator and the relationship between the load k load and the output force of the piezoelectric actuator under the same excitation voltage f1 load , f1 load =(k load +k a )Δx1=k load Δx1+f1, convert to the relationship of f1 load ,

[0054] Step 3: Calculate the time-domain signal f1(t) of the output force of the rhombic piezoelectric actuator under the condition of one end of the rhombic piezoelectric actuator being fixed and the other end being connected with a load. ​​

[0055] Specifically, step 3 comprises:

[0056] Step 31: For the working condition of the rhombic piezoelectric actuator with one end fixed and the other end connected to a load, the output displacement time domain signal Δx1(t) and the stack displacement time domain signal Δx pzt (t) of the actuator are collected.

[0057] Step 32: According to the output displacement time domain signal Δx1(t) and the stack displacement time domain signal Δx pzt (t), the formula is used to calculate the time domain signal f1(t) of the output force of the rhombic piezoelectric actuator.

[0058] As can be seen from the above formula for calculating the output force f1(t) of the actuator, if the measurement of the stack displacement always uses the same sensor, such as a strain gauge attached to the piezoelectric stack, the calculation result of f1(t) is independent of the sensor calibration coefficient of the stack displacement, that is, the calculation of f1(t) can also only use the voltage signal of the stack displacement sensor.

[0059] Real-time example two

[0060] The present application real-time example describes a rhombic piezoelectric actuator output force real-time measurement method in detail:

[0061] Step 1: Parameter calculation

[0062] For a rhombic piezoelectric actuator, the test is carried out under the condition of fixed support-free boundary, and a quasi-static 1Hz full-scale sinusoidal signal excitation voltage is used to obtain the peak-to-peak value of the stack displacement The peak-to-peak value of the output displacement of the actuator is:

[0063]

[0064] In the above formula, X1 can also be obtained by linear fitting of the time domain signal vs. .

[0065] The rhombic piezoelectric actuator + force sensor two-end fixed support-fixed support boundary condition is tested, a quasi-static 1Hz full-scale sinusoidal signal excitation voltage is used, and the peak-to-peak value of the stack displacement The peak-to-peak value f1(pk-pk) of the output force of the actuator load is:

[0066]

[0067] Step 2: Real-time calculation of output force

[0068] To verify this method, a non-full-scale sinusoidal excitation voltage signal was applied to the fixed-fixed boundary condition at both ends of the rhombic piezoelectric actuator + force sensor, and Δx1(t) and Δx were acquired. pzt f1(t), based on parameters X1, X2 and time-domain signals Δx1(t), Δx2(t), f1(t), f2(t), f3(t), f4(t), f5(t), f6(t), f7(t), f8(t), f9(t), f1(t), f1(t), f2 ...3(t), f4(t), f5(t), f6(t), f1(t), pzt (t), calculate f1(t) - measurement, and compare it with the time-domain signal of f1(t) measured by the force sensor, such as Figure 3 As shown, the time-domain signals of f1(t)-measurement and f1(t)-calculation are basically coincident. Based on the peak-to-peak value of f1(t)-measurement, the calculated peak-to-peak value error of f1(t)-calculation compared to the peak-to-peak value of f1(t)-measurement is 0.45%. The ratio of the point-by-point error of the two to the peak-to-peak value of f1(t)-measurement is 0.82%. This proves the accuracy of the rhombic piezoelectric actuator output force measurement method proposed in this patent.

[0069] The advantage of the real-time output force measurement method for the rhombic piezoelectric actuator proposed in this invention is that, when operating under load, there is no need to connect a force sensor in series in the force transmission path. The output force of the actuator can be calculated in real time simply by using the easily measurable output displacement of the actuator and the displacement of the piezoelectric stack. This is equivalent to connecting a force sensor for output force measurement to the rhombic piezoelectric actuator drive device under load. The designed verification test shows that the error between the calculated result of the actuator output force measurement method proposed in this patent and the measured value of the force sensor is less than 1%.

[0070] Since piezoelectric actuators are often used in the field of micro-displacement control, such as antenna pointing and optical stabilization, it is difficult to directly measure their output force when they are working under load. This invention utilizes displacement signals that are still easy to measure when working under load to realize real-time measurement of actuator output force. This can significantly enhance designers' understanding of the mechanical characteristics of actuators and loads, and support designers in optimizing the structure of loads, force transmission connection devices, etc., and selecting actuators.

[0071] In addition, the real-time actuator output force can also be used as a feedback signal in the servo closed-loop control of the piezoelectric actuator, improving the servo control effect of the piezoelectric actuator.

[0072] The basic performance parameters of a rhombic piezoelectric actuator generally include maximum free displacement and blocking force, i.e. f1 blockThe output force of the piezoelectric actuator can be measured by the method of the present application without increasing the cost of the piezoelectric actuator.

Claims

1. A rhombic piezoelectric actuator output force real-time measurement method, characterized in that, The method comprises: Step 1: Calculate the output displacement of the piezoelectric actuator under the condition of one end fixed and one end free to the piezoelectric stack displacement ratio ; Step 2: Calculate the output force of the piezoelectric actuator under the boundary condition of fixed support at both ends of the rhombic piezoelectric actuator The ratio of the piezoelectric stack displacement The ratio of the piezoelectric stack displacement ; comprising: Step 21: fix one end of the rhombus piezoelectric actuator, connect a force sensor to the other end, fix the other end of the force sensor, apply an excitation voltage, and get the displacement of the stack in this state , the actuator output displacement , and the actuator output force ; Step 22: Calculate the external stiffness using the formula ​ Step 23: Calculate the stack displacement using the stack displacement , actuator output displacement , actuator output force , and external load stiffness , in conjunction with the formula , to calculate ; Step 3: Calculate the time-domain signal of the output force of the rhombic piezoelectric actuator under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is connected to a load ; comprising: Step 31: Collect the time-domain signal of the output displacement of the piezoelectric actuator under the condition of one end fixed and one end connected to the load and the time-domain signal of the displacement of the stack ; Step 32: Based on the output displacement time domain signal and stacked displacement time domain signal Using the formula Calculate the time-domain signal of the output force of the rhombic piezoelectric actuator. .

2. The method of claim 1, wherein, Step 1 comprises: Step 11: one end of the rhombic piezoelectric actuator is fixed and the other end is free, an excitation voltage is applied, and the stack displacement of the rhombic piezoelectric actuator under the fixed-free boundary condition is obtained , actuator output displacement Step 12: Calculate using the formula .

3. A rhombic piezoelectric actuator output force real-time measuring device, characterized by, The apparatus comprises a computing unit, a computing unit and a time-domain signal computing unit, wherein: A computing unit for calculating the output displacement of the piezoelectric actuator under the condition of one end fixed and one end free of the rhombic piezoelectric actuator to the piezoelectric stack displacement ratio ; A computing unit for calculating the output force of a piezoelectric actuator under clamped-clamped boundary conditions at both ends of the rhombic piezoelectric actuator The ratio of the piezoelectric stack displacement The ratio of the piezoelectric stack displacement ; in particular for: Let rhombus piezoelectric actuator one end fixed, one end connected with a force sensor, while the force sensor the other end fixed, apply excitation voltage, get the stack displacement under this condition , actuator output displacement and actuator output force ; The external load stiffness is calculated using the formula ;​ Utilizing stack displacement , actuator output displacement , actuator output force , and external load stiffness , in conjunction with equations , to calculate ; A time domain signal calculation unit is configured to calculate a time domain signal of an output force of a rhombic piezoelectric actuator under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is connected to a load ; in particular for: The output displacement time-domain signal of the piezoelectric actuator is collected under the condition that one end of the rhombic piezoelectric actuator is fixed and the other end is connected with a load and the stacking displacement time-domain signal ; According to the output displacement time-domain signal and the stack displacement time-domain signal , the time-domain signal of the rhombic piezoelectric actuator output force is calculated by the formula .​ 4. The apparatus of claim 3, wherein, The computing unit is specifically configured to: The rhombic piezoelectric actuator is fixed at one end and free at the other end, an excitation voltage is applied, and the stacking displacement of the rhombic piezoelectric actuator under the fixed-free boundary condition is obtained , actuator output displacement Using the formula , calculate .

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