A dynamic adaptive closed-loop correction method for range based on capacitive displacement sensor

Abstract

The present invention provides a range dynamic adaptive closed-loop correction method based on a capacitance displacement sensor, which belongs to the field of displacement measurement technology, including: setting the initial value of the capacitance parameter of the capacitance measurement system; collecting the output code value of the capacitance measurement acquisition system at the minimum spacing, comparing the output code value with the upper limit of the effective code value, and modifying the size of the adjustable compensation capacitance value CS1 or CS2 according to the comparison result; collecting the output code value of the capacitance measurement system at the maximum spacing, calculating the difference between the output code value and the final output code value of the previous step, and modifying the size of the integral capacitance value CF according to the comparison result; and re-collecting the output code value of the capacitance measurement system at the minimum spacing. If the output code value exceeds the upper limit of the effective code value at this time, repeat the above process, and if the output code value is within the upper limit of the effective code value when returning to the minimum spacing again, the cycle is terminated and the calibration is completed. The present invention can perform adaptive correction on the capacitance displacement sensor and displacement measurement range with a long service life.

Description

Technical Field

[0001] The invention belongs to the technical field of displacement measurement, and in particular relates to a range dynamic adaptive closed-loop correction method based on a capacitive displacement sensor. Background Art

[0002] The displacement measurement range of the capacitive displacement sensor is usually between 0.05 and 10 mm, which can meet the needs of various precision measurements. In addition, the capacitive displacement sensor also has the advantages of high sensitivity, low zero drift, wide frequency response and small nonlinearity, making it an indispensable test instrument in precision production and control. The displacement output capacitance change of the capacitive displacement sensor is very weak, and its capacitance change range is often only a few pF (picofarad, 10 -12 F), or even a few fF (flying method, 10 -15 F), which places high demands on the resolution of the capacitance detection circuit. When the capacitance displacement sensor works for a long time, performance creep will occur, and the mechanical structure of the measured target will change during the long-term operation, resulting in changes in the measurement stroke and measurement accuracy uncertainty. In addition, under vacuum and atmospheric conditions, the dielectric constant changes, resulting in greater changes in the working range of the capacitance displacement sensor and changes in the effective range of the capacitance displacement sensor. Therefore, it is necessary to perform dynamic adaptive closed-loop correction of the range of the capacitance displacement sensor used in space.

[0003] The large-aperture Fast Steering Mirror (FSM) is a key component of the precision image stabilization system of the space astronomical telescope. It performs image shift compensation on the line of sight offset detected and fed back by the Fine Guide Sensor (FGS) to ensure high-quality imaging and long-term stability of the telescope's detector. The capacitive displacement sensor is used to monitor the swing angle execution results of the actuating component. By measuring at least three points simultaneously, the swing angle can be measured in real time with a measurement accuracy of milli-arcseconds. However, the effective range of the capacitive displacement sensor is very small. During the launch into orbit and long-term operation, due to the influence of vibration and structural force creep, the displacement measurement in the capacitive sensor will be different from the ground measurement result, and the change is not easy to quantify and evaluate. Therefore, it is necessary to have on-orbit range adaptive correction to ensure the function and performance of arc-second-level swing angle monitoring. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a range dynamic adaptive closed-loop correction method based on a capacitive displacement sensor, which adaptively corrects the range of a long-life capacitive displacement sensor and a capacitive measurement system, thereby solving the problem that the performance creep of the actuator and displacement measurement function and the change of the mechanical structure when the satellite is working in orbit affect the measurement accuracy of micro-displacement, and can also be used in other occasions where online range correction of the capacitive displacement sensor is required.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme:

[0006] A range dynamic adaptive closed-loop correction method based on a capacitive displacement sensor comprises the following steps:

[0007] Step 1: Use the capacitance displacement sensor to be calibrated as the detected capacitance of the differential capacitance chip, and initialize three sets of adjustable compensation capacitance values ​​CS1, adjustable compensation capacitance value CS2, and integral capacitance value CF of three differential capacitance chips;

[0008] Step 2, collecting three output code values ​​of the three piezoelectric actuators at the minimum position, and comparing the three output code values ​​with the specified code values ​​to obtain comparison results, and modifying the sizes of the three sets of adjustable compensation capacitance values ​​CS1 or adjustable compensation capacitance values ​​CS2 according to the comparison results, until the minimum position output code value is within the upper limit of the valid code value, thereby realizing the correction of the reference code value of the capacitive displacement sensor;

[0009] Step 3, collecting the output code values ​​of the three piezoelectric actuators at the maximum position, obtaining the three maximum position output code values, respectively calculating the differences between the three maximum position output code values ​​and the three output code values ​​at the minimum position in step 2, obtaining comparison results, and modifying the size of the integral capacitance value CF according to the comparison results until the three differences between the three maximum position output code values ​​and the three output code values ​​at the minimum position are within the effective dynamic code value, thereby realizing the correction of the dynamic measurement range of the capacitive displacement sensor;

[0010] Step 4: Collect the output code values ​​of the three piezoelectric actuators when they are at the minimum position. If the output code values ​​at this time exceed the upper limit of the valid code values, modify the size of the three sets of adjustable compensation capacitance values ​​CS1 or the adjustable compensation capacitance values ​​CS2 according to steps 2 and 3, and modify the size of the integral capacitance value CF until the output code values ​​are within the upper limit of the valid code values, thereby realizing dynamic adaptive closed-loop correction of the capacitive displacement sensor that needs to be corrected.

[0011] Furthermore, in the steps 2 to 4, the three output code values ​​of the capacitance measurement system at the minimum position and the output code value at the maximum position are obtained by changing the elongation of the piezoelectric actuator and correcting the output code value of the differential capacitance chip in the corresponding state.

[0012] Furthermore, in step 1, the differential capacitor chip adopts HJ3110 chip, and its output voltage The calculation formula is:

[0013] (3)

[0014] in, is the simulated magnification; is the conversion factor from capacitance to voltage; is the reference voltage; =CS2IN+CS2, =CS1IN+CS1, is the capacitance between the upper plate of the differential capacitor chip and the reference ground. It is the capacitance between the lower plate of the differential capacitor chip and the reference ground. CS1IN and CS2IN are the differential inputs of the detected capacitive displacement sensor. CS1 and CS2 are the adjustable compensation capacitor values ​​inside the HJ3110 chip, which are used to adjust the bias caused by the asymmetry of the input capacitor. CF is the integral capacitance value of the charge integrator.

[0015] Furthermore, the step 2 comprises:

[0016] The step size of the configuration value of the adjustable compensation capacitance value CS1 and the adjustable compensation capacitance value CS2 is 0.019pF; in each calibration process, one of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 is changed; the three output code values ​​at the minimum position are compared with the specified code value, if the output code value is less than the specified code value, the adjustable compensation capacitance CS1 is increased or the adjustable compensation capacitance value CS2 is reduced by one code value; if the three output code values ​​at the minimum position are greater than the specified code value, the adjustable compensation capacitance value CS1 is reduced or the adjustable compensation capacitance value CS2 is increased by one code value; if the three output code values ​​at the minimum position are within the specified code value range, the configuration of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 remains unchanged.

[0017] Furthermore, the step 3 comprises:

[0018] The step size of the configuration value of the adjustable compensation capacitor CF is 0.019pF; compare the difference between the three maximum position output code values ​​and the three output code values ​​at the minimum position in step 2 and the range of the effective dynamic code value. If the difference is less than the minimum value of the effective dynamic code value, increase the integral capacitance value CF by one code value; if the difference is greater than the maximum value of the effective dynamic code value, reduce the integral capacitance value CF by one code value; if the output code value is within the specified dynamic code value range, the configuration of the integral capacitance value CF remains unchanged.

[0019] Beneficial effects:

[0020] According to the comparison between the voltage output code value of the capacitance measurement system and the standard code value range, the present invention takes the HJ3110 chip as an example to modify the size of the adjustable compensation capacitor and the integral capacitor therein, thereby realizing the dynamic adaptive closed-loop correction of the measured capacitance displacement sensor, eliminating the hysteresis effect or creep phenomenon of the capacitance displacement sensor, and improving the measurement accuracy of the capacitance displacement sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a flow chart of a range dynamic adaptive closed-loop correction method based on a capacitive displacement sensor.

[0022] Figure 2 This is a schematic diagram of the mechanical structure of the fast swing control drive module.

[0023] Figure 3 Top view of the three-point piezoelectric-driven fast-oscillating mirror mechanism with capacitive displacement sensors.

[0024] Among them, the accompanying drawings are marked as: large-aperture fast-swing mirror mechanism 1, piezoelectric actuator 2, upper plate of capacitive displacement sensor 3, fast-swing mirror mechanism base 4, resistive strain sensor 5, piezoelectric ceramic 6, capacitive displacement sensor 7. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] The space telescope precision image stabilization system includes a fine guide sensor (FGS) module (i.e., FGS module), a fast steering mirror (FSM) mechanism, and a fast steering mirror control drive module.

[0027] The working principle of the space telescope's precision image stabilization system is as follows: when the space telescope completes pointing control, the FGS module provides the center of mass offset of the navigation star to the fast-swing mirror control drive module to control the swing of the large-aperture fast-swing mirror mechanism, thereby compensating for the space telescope's visual axis deviation and achieving optical closed-loop control.

[0028] like Figure 3As shown, piezoelectric actuator 2 is selected as the actuator of large-aperture fast-swing mirror mechanism 1. Piezoelectric actuator 2 is based on piezoelectric ceramic (PZT) and is installed through an external mechanical structure to output displacement and force. A resistance strain gauge sensor (SGS) is selected as the micro-displacement detection sensor of piezoelectric actuator 2, and a capacitive displacement sensor (CS) is selected as the swing micro-displacement detection sensor of the large-aperture fast-swing mirror mechanism. Figure 2 The figure shows the positions of the capacitive displacement sensor 7, the resistive strain sensor 5, and the piezoelectric ceramic 6. The piezoelectric ceramic 6 and the resistive strain sensor 5 are arranged in the piezoelectric actuator 2. The resistive strain sensor 5 is used to directly detect the elongation of the piezoelectric ceramic 6. The three piezoelectric ceramics 6 are transmitted to the three action points of the large-aperture fast-swing mirror mechanism 1 through the structural amplification mechanism to realize the swing of the large-aperture fast-swing mirror mechanism 1. The capacitive displacement sensor 7 is located near the piezoelectric actuator 2. The upper plate 3 of the capacitive displacement sensor is installed at the bottom of the large-aperture fast-swing mirror mechanism 1, and the lower plate of the capacitive displacement sensor is installed on the base 4 of the fast-swing mirror mechanism. Figure 3 shown.

[0029] The working principle of SGS is the conductor resistance strain effect, that is, the resistance of the metal wire will change accordingly with the size of the mechanical deformation it is subjected to. The specific detection process of SGS is to adhere the resistance strain gauge to various elastic sensitive elements, so that the change of its physical quantity is converted into the stress and strain change of the resistance strain gauge, and then converted into the change of resistance value, and finally output the voltage value through the bridge circuit. The working principle is shown in the following formula:

[0030] (1)

[0031] in, is the resistance value of the metal wire, is the metal resistivity, is the wire length, is the conductor cross-sectional area, when the conductor cross-sectional area and metal resistivity When the resistance of the metal wire is and wire length Directly proportional.

[0032] CS is a non-contact micro-displacement measurement sensor based on the principle of flat plate capacitance. The working principle is shown as follows:

[0033] (2)

[0034] in, is the sensor capacitance, is the dielectric constant, is the relative coverage area between the plates, is the distance between the plates, is the relative dielectric constant, is the dielectric constant of vacuum, which is 8.85×10fF / m.

[0035] The differential capacitor chip is used to convert the capacitance of the capacitive displacement sensor into a voltage value, and collect the voltage value through the conditioning circuit and the signal acquisition circuit. By establishing the relationship between the collected voltage value and the distance, the function of detecting micro-displacement is realized.

[0036] The fast-swing mirror control drive module controls the angle of the large-aperture fast-swing mirror mechanism 1 by changing the elongation of the three piezoelectric actuators 2. The elongation of the piezoelectric actuator 2 is measured by the SGS installed on it. Combined with the measurement of the SGS, closed-loop control of the piezoelectric actuator 2 can be achieved, and further combined with the measurement and processing of the star point by the fine guide instrument, closed-loop control of the swing angle of the large-aperture fast-swing mirror mechanism can be achieved.

[0037] In order to improve the reliability of displacement measurement, a group of capacitive displacement sensors are introduced. When the SGS creeps or fails, the measured value of the capacitive displacement sensor is used to replace the measured value of the SGS. In order to achieve this function, the capacitive displacement sensor needs to be calibrated to establish the relationship between the output code value of the capacitive displacement sensor measurement circuit and the swing mirror angle.

[0038] High-precision capacitive sensor detection usually uses a dedicated ASIC chip to convert capacitance into a voltage signal, which is called a differential capacitance chip. The HJ3110 chip is a universal differential capacitance chip with extremely low noise. It uses a modulation and demodulation capacitance detection method. After low-pass filtering and gain amplification, a voltage signal proportional to the capacitance difference is obtained. The internal capacitance parameters can be programmed and controlled by the main control chip. The capacitance detection circuit designed with the HJ3110 chip can greatly improve the design efficiency and detection performance of the circuit.

[0039] The output voltage of the HJ3110 chip for:

[0040] (3)

[0041] in, is the simulated magnification; is the conversion factor from capacitance to voltage; is the reference voltage; =CS2IN+CS2, =CS1IN+CS1, is the capacitance between the upper plate of the differential capacitor chip and the reference ground. It is the capacitance value between the lower plate of the differential capacitor chip and the reference ground. CS1IN and CS2IN are the differential inputs of the detected capacitance displacement sensor. CS1 and CS2 are the adjustable compensation capacitors inside the HJ3110 chip, which are used to adjust the bias caused by the asymmetry of the input capacitance. is the integrating capacitor of the charge integrator.

[0042] By modifying the adjustable compensation capacitance values ​​CS1, CS2 and the integral capacitance value CF in the HJ3110 chip, the output code values ​​of the capacitive displacement sensor measured at the zero position and the maximum position of the fast-swing mechanism are controlled within the standard range, so that the reference code value and the dynamic measurement range of the capacitive displacement sensor meet the specified requirements at the same time, and dynamic adaptive closed-loop correction of the capacitive displacement sensor of the large-caliber fast-swing mechanism can be achieved.

[0043] The present invention adopts the HJ3110 chip as the capacitance-voltage conversion chip of the differential capacitance sensor in the capacitance measurement system, and realizes adaptive adjustment of the displacement measurement range by adjusting the parameter program of the HJ3110 chip. By changing the elongation of the piezoelectric actuator, the output code value of the HJ3110 chip in the corresponding state is corrected, thereby realizing dynamic adaptive closed-loop correction of the capacitance displacement sensor.

[0044] like Figure 1 As shown, the capacitance displacement sensor to be calibrated is used as the detected capacitance of the HJ3110 chip. A range dynamic adaptive closed-loop calibration method based on the capacitance displacement sensor of the present invention comprises the following steps:

[0045] Step 1: Use the capacitance displacement sensor to be calibrated as the detected capacitance of the differential capacitance chip, and initialize three sets of adjustable compensation capacitance values ​​CS1, adjustable compensation capacitance value CS2, and integral capacitance value CF of three differential capacitance chips;

[0046] Step 2, collecting the output code values ​​of the capacitance measurement system when the three piezoelectric actuators are at the minimum position, and comparing the three groups of output code values ​​with the specified code values ​​to obtain comparison results, and modifying the sizes of the three groups of adjustable compensation capacitance values ​​CS1 or CS2 respectively according to the comparison results until the minimum position output code value is within the upper limit of the valid code value, thereby realizing the correction of the reference code value of the capacitive displacement sensor;

[0047] Step 3, collecting the output code values ​​of the capacitance measurement system when the three piezoelectric actuators are at the maximum position, obtaining the three maximum position output code values, respectively calculating the differences between the three output code values ​​and the final output code value at the minimum position in the previous step, and modifying the size of the integral capacitance value CF according to the comparison results until the three differences between the maximum position and the minimum position output code values ​​are within the effective dynamic code value to achieve the correction of the dynamic measurement range of the capacitive displacement sensor;

[0048] Step 4: Collect the output code value of the capacitance measurement system when the three piezoelectric actuators are at the minimum position. If the output code value exceeds the upper limit of the valid code value at this time, modify the three sets of adjustable compensation capacitance values ​​CS1 or CS2 and the integral capacitance value CF according to steps 2 and 3 until the output code value is within the upper limit of the valid code value, thereby realizing dynamic adaptive closed-loop correction of the measured capacitive displacement sensor.

[0049] Specifically, the step 2 includes:

[0050] The step size of the configuration value of the adjustable compensation capacitance value CS1 and the adjustable compensation capacitance value CS2 is 0.019pF; in each calibration process, one of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 is changed; the three output code values ​​at the minimum position are compared with the specified code value, if the output code value is less than the specified code value, the adjustable compensation capacitance CS1 is increased or the adjustable compensation capacitance value CS2 is reduced by one code value; if the three output code values ​​at the minimum position are greater than the specified code value, the adjustable compensation capacitance value CS1 is reduced or the adjustable compensation capacitance value CS2 is increased by one code value; if the three output code values ​​at the minimum position are within the specified code value range, the configuration of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 remains unchanged.

[0051] Furthermore, the step 3 comprises:

[0052] The step size of the configuration value of the adjustable compensation capacitor CF is 0.019pF; compare the difference between the three maximum position output code values ​​and the three output code values ​​at the minimum position in step 2 and the range of the effective dynamic code value. If the difference is less than the minimum value of the effective dynamic code value, increase the integral capacitance value CF by one code value; if the difference is greater than the maximum value of the effective dynamic code value, reduce the integral capacitance value CF by one code value; if the output code value is within the specified dynamic code value range, the configuration of the integral capacitance value CF remains unchanged.

Claims

1. A dynamic adaptive closed-loop calibration method for a range based on a capacitive displacement sensor, characterized in that: The steps include: Step 1: Use the capacitance displacement sensor to be calibrated as the detected capacitance of the differential capacitance chip, and initialize three sets of adjustable compensation capacitance values ​​CS1, adjustable compensation capacitance value CS2, and integral capacitance value CF of three differential capacitance chips; Step 2, collecting three output code values ​​of the three piezoelectric actuators at the minimum position, and comparing the three output code values ​​with the specified code values ​​to obtain comparison results, and modifying the sizes of the three sets of adjustable compensation capacitance values ​​CS1 or adjustable compensation capacitance values ​​CS2 according to the comparison results, until the minimum position output code value is within the upper limit of the valid code value, thereby realizing the correction of the reference code value of the capacitive displacement sensor; Step 3, collecting the output code values ​​of the three piezoelectric actuators at the maximum position, obtaining the three maximum position output code values, respectively calculating the differences between the three maximum position output code values ​​and the three output code values ​​at the minimum position in step 2, obtaining comparison results, and modifying the size of the integral capacitance value CF according to the comparison results until the three differences between the three maximum position output code values ​​and the three output code values ​​at the minimum position are within the effective dynamic code value, thereby realizing the correction of the dynamic measurement range of the capacitive displacement sensor; Step 4, collecting the output code values ​​of the three piezoelectric actuators at the minimum position. If the output code value at this time exceeds the upper limit of the valid code value, according to steps 2 and 3, modify the size of the three sets of adjustable compensation capacitance values ​​CS1 or the adjustable compensation capacitance value CS2, and modify the size of the integral capacitance value CF until the output code value is within the upper limit of the valid code value, thereby realizing dynamic adaptive closed-loop correction of the capacitive displacement sensor that needs to be corrected; In the steps 2 to 4, the three output code values ​​of the capacitance measurement system at the minimum position and the output code value at the maximum position are obtained by changing the elongation of the piezoelectric actuator and correcting the output code value of the differential capacitance chip in the corresponding state.

2. A dynamic adaptive closed-loop calibration method for a capacitive displacement sensor according to claim 1, characterized in that: In step 1, the differential capacitor chip adopts HJ3110 chip, and its output voltage The calculation formula is: （3） in, is the simulated magnification; is the conversion factor from capacitance to voltage; is the reference voltage; =CS2IN+CS2, =CS1IN+CS1, is the capacitance between the upper plate of the differential capacitor chip and the reference ground. It is the capacitance between the lower plate of the differential capacitor chip and the reference ground. CS1IN and CS2IN are the differential inputs of the detected capacitive displacement sensor. CS1 and CS2 are the adjustable compensation capacitor values ​​inside the HJ3110 chip, which are used to adjust the bias caused by the asymmetry of the input capacitor. CF is the integral capacitance value of the charge integrator.

3. A dynamic adaptive closed-loop calibration method for a capacitive displacement sensor according to claim 2, characterized in that: The step 2 comprises: The step size of the configuration value of the adjustable compensation capacitance value CS1 and the adjustable compensation capacitance value CS2 is 0.019pF; in each calibration process, one of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 is changed; the three output code values ​​at the minimum position are compared with the specified code value, if the output code value is less than the specified code value, the adjustable compensation capacitance CS1 is increased or the adjustable compensation capacitance value CS2 is reduced by one code value; if the three output code values ​​at the minimum position are greater than the specified code value, the adjustable compensation capacitance value CS1 is reduced or the adjustable compensation capacitance value CS2 is increased by one code value; if the three output code values ​​at the minimum position are within the specified code value range, the configuration of the adjustable compensation capacitance value CS1 or the adjustable compensation capacitance value CS2 remains unchanged.

4. A dynamic adaptive closed-loop calibration method for a capacitive displacement sensor according to claim 1, characterized in that: The step 3 comprises: The step size of the configuration value of the adjustable compensation capacitor CF is 0.019pF; compare the difference between the three maximum position output code values ​​and the three output code values ​​at the minimum position in step 2 and the range of the effective dynamic code value. If the difference is less than the minimum value of the effective dynamic code value, increase the integral capacitance value CF by one code value; if the difference is greater than the maximum value of the effective dynamic code value, reduce the integral capacitance value CF by one code value; if the output code value is within the specified dynamic code value range, the configuration of the integral capacitance value CF remains unchanged.

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