Non-contact two-degree-of-freedom angle measurement method based on spherical capacitor

Abstract

The invention discloses a non-contact two-degree-of-freedom angle measurement method based on a spherical capacitor, and the method comprises the steps: firstly fixing a drive module on a device which needs to measure the angle of a moving part, then connecting a detection capacitor with the moving part, and enabling the detection capacitor and the drive module to form a spherical differential four-quadrant capacitive sensor together; when the detection capacitors rotate in a Cartesian coordinate system along with a moving part in the equipment, the relative areas of the four measurement capacitors are subjected to differential change pairwise, and corresponding differential output capacitors are generated; constructing a relational expression between the differential output capacitance and the coordinate axis angle component when the detection capacitor is in different quadrants, then applying a sine excitation signal to the detection capacitor based on a signal detection circuit, obtaining a current signal output by each driving capacitor, converting the current signal into a voltage signal, and calculating the differential output capacitance; an angle component is then calculated based on the relational expression. The device has the characteristics of simple structure, low cost and high reliability.

Description

Technical Field

[0001] The invention belongs to the field of measurement technology, and in particular relates to a non-contact two-degree-of-freedom angle measurement method based on spherical capacitance. Background Art

[0002] At present, the stabilization mechanism of the aviation optoelectronic pod is mainly based on the universal frame structure such as "two-axis two-frame", "three-axis three-frame", "two-axis four-frame", etc. According to the generational classification of the stabilization mechanism by L3 PV Labs, the two-axis four-frame belongs to the third-generation stabilization mechanism. Although the third-generation frame structure can effectively isolate the impact of wind resistance disturbance on imaging quality, it has nonlinear friction, large frame mass and space volume, and low payload ratio.

[0003] There is a generation gap between the advanced technologies at home and abroad in the field of aviation optoelectronic pods. The fourth-generation aviation optoelectronic pods (using unconstrained drive-active follow-up gimbal structure) and the fifth-generation aviation optoelectronic pods (using parallel-active follow-up gimbal) have been maturely applied abroad; among them, the fourth-generation aviation optoelectronic pod stabilization mechanism has effectively solved the problems existing in the third-generation aviation optoelectronic pods, but the design of the fourth-generation aviation optoelectronic pods is difficult, and many core technologies have not yet been broken through in China. One of the key core difficulties is the non-contact spatial two-degree-of-freedom angle measurement technology; because by analyzing the motion characteristics and structural characteristics of the fourth-generation aviation optoelectronic pod stabilization mechanism, it can be seen that the rotation angles of its two degrees of freedom are mutually coupled, and the rotary transformers, photoelectric encoders, capacitive angle position sensors, etc. in the form of stators / rotors in the traditional framework cannot be applied to the fourth-generation aviation optoelectronic pods. Therefore, it is necessary to design a non-contact two-degree-of-freedom angle sensor to measure the spatial two-degree-of-freedom angle of its stabilization mechanism. Summary of the invention

[0004] The purpose of the present invention is to provide a non-contact two-degree-of-freedom angle measurement method based on spherical capacitance, so as to solve the current problem of spatial two-degree-of-freedom angle measurement.

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

[0006] A non-contact two-degree-of-freedom angle measurement method based on spherical capacitance, comprising:

[0007] For a device that needs to measure the angle of a moving part, first fix the driving module on the device, then connect the detection capacitor to the moving part, so that there is a gap between the detection capacitor and the driving module; wherein the detection capacitor and the driving module are both spherical structures, the centers of the detection capacitor and the driving module coincide, and are set at the origin of a Cartesian coordinate system; the driving module is divided into four mutually insulated and identically sized sector-shaped driving capacitors by the x and y axes of the coordinate system, the four driving capacitors are respectively located in four quadrants on the sphere, and together with the detection capacitor, form a spherical differential four-quadrant capacitance sensor; initially, the center of the detection capacitor is located directly above the center of the driving module;

[0008] When the detection capacitor follows the moving part in the device and rotates in the Cartesian coordinate system, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances;

[0009] A relationship between the differential output capacitance and the angle component of the coordinate axis when the detection capacitance is in different quadrants is constructed, and then a sinusoidal excitation signal is applied to the detection capacitance based on the signal detection circuit. The current signal output by each driving capacitor is obtained and converted into a voltage signal, and the differential output capacitance is solved; and then the angle component is calculated based on the relationship.

[0010] Furthermore, the relationship between the differential output capacitance and the coordinate axis angle component when the detection capacitor is in different quadrants is expressed as:

[0011]

[0012] Among them, C 13 is the differential output capacitance between the first quadrant and the third quadrant, C 24 is the differential output capacitance between the second quadrant and the fourth quadrant; ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, r is the projection circle radius of the detection capacitor, R is the curvature radius of the detection capacitor, α1 is the angular component of the detection capacitor driven by the moving part around the x-axis in the Cartesian coordinate system, and α2 is the angular component of the detection capacitor around the y-axis in the Cartesian coordinate system.

[0013] Furthermore, the signal processing circuit of the measurement method includes a driving circuit, a detection circuit and an FPGA, wherein the driving circuit is used to generate a sinusoidal excitation signal to excite the detection capacitor; the detection circuit is used to obtain four induced current signals output by four driving capacitors when the detection capacitor is excited, and convert the four induced current signals into voltage signals; the FPGA is used to perform decoupling operations to obtain angle components.

[0014] Furthermore, the driving circuit includes a 1MHz crystal oscillator, a four-frequency division circuit, a second-order integral shaping circuit and a radio frequency connector; first, the frequency division circuit divides the 1MHz signal by 4 to obtain a 250KHz square wave excitation signal; secondly, the second-order integral circuit shapes the divided 250KHz square wave signal into a 250KHz sinusoidal excitation signal; finally, the radio frequency connector applies the obtained sinusoidal excitation signal to the detection capacitor to realize the excitation of the spherical differential four-quadrant capacitance sensor.

[0015] Furthermore, the detection circuit includes four RF connectors, four T-type transimpedance amplifiers, two differential amplifier circuits and an ADC converter; first, the four T-type transimpedance amplifiers convert the four weak current signals output by the four driving capacitors into voltage signals V1, V2, V3, and V4 when the detection capacitor is excited; secondly, a differential amplifier differentially amplifies V1 and V3, and another differential amplifier differentially amplifies V2 and V4 to obtain differential voltage values ​​V respectively. 13 , V 24 ; V 13 =GC 13 , V 24 =GC 24 ; Where G is the gain of the T-type transimpedance amplifier and the differential amplifier circuit; Then, the ADC converter converts V 13 , V 24 The signal is sampled and transmitted to the FPGA.

[0016] Furthermore, the FPGA is powered from V 13 , V 24 Solve to get C 13 , C 24 After that, the decoupling operation is performed according to the following formula to obtain the angle components α1 and α2:

[0017]

[0018] A measuring device comprises a processor, a memory and a computer program stored in the memory; when the processor executes the computer program, the non-contact two-degree-of-freedom angle measurement method based on spherical capacitance is implemented.

[0019] A computer-readable storage medium stores a computer program; when the computer program is executed by a processor, the non-contact two-degree-of-freedom angle measurement method based on spherical capacitance is implemented.

[0020] Compared with the prior art, the present invention has the following technical features:

[0021] 1. The present invention is based on the spherical differential four-quadrant capacitive sensor with two degrees of freedom in space, avoiding the problems of multi-axis error accumulation and introduction of nonlinear friction.

[0022] 2. The present invention only needs one driving capacitor and one four-quadrant detection capacitor to detect the two degrees of freedom in space, with a small number of capacitors, a simple structure, low cost and high reliability.

[0023] 3. The present invention performs non-contact measurement of the two-degree-of-freedom angle in space based on the capacitance measurement principle, breaking through the technical difficulty of measuring the two-degree-of-freedom angle in space in the stabilization mechanism of the fourth-generation aviation optoelectronic pod. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the spherical differential four-quadrant capacitance sensor of the present invention;

[0025] Figure 2 This is the principle block diagram of the signal processing circuit. DETAILED DESCRIPTION

[0026] Capacitive sensors have the advantages of high dynamics, non-contact measurement, and strong environmental adaptability. If a capacitive angle sensor can be designed based on the characteristics of the capacitive sensor, it will play an important role in breaking through the key technologies in the fourth-generation aviation optoelectronic pod. The present invention provides a non-contact two-degree-of-freedom angle measurement method based on spherical capacitance, which uses the capacitance change between spherical differential four-quadrant capacitors to achieve the measurement of the spatial two-degree-of-freedom angle.

[0027] Referring to the accompanying drawings, the measuring method provided by the present invention comprises the following steps:

[0028] Step 1, for equipment that needs to measure the angle of a moving part (for example, measuring the angle of a stabilizing mechanism of an aviation optoelectronic pod), first fix the driving module on the equipment, and then connect the detection capacitor to the moving part so that there is a gap between the detection capacitor and the driving module; wherein the detection capacitor and the driving module are both spherical structures, the centers of the detection capacitor and the driving module coincide, and are set at the origin o of the Cartesian coordinate system; the driving module is divided into four mutually insulated and identically sized sector-shaped driving capacitors by the x and y axes, and the four driving capacitors are respectively located in four quadrants on the sphere, and together with the detection capacitor constitute a spherical differential four-quadrant capacitance sensor; initially, the center of the detection capacitor is located directly above the center of the driving module.

[0029] Step 2: When the detection capacitor follows the moving part in the device and rotates in the Cartesian coordinate system, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances; the driving capacitances of the first to fourth quadrants are C1 to C4 respectively, and the differential output capacitance C between the first and third quadrants is obtained. 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 .

[0030] By detecting the driving capacitors C1 and C3, the differential output capacitance C of the first and third quadrants can be obtained. 13 Similarly, by detecting the driving capacitors C2 and C4, the differential output capacitors C of the second and fourth quadrants can be obtained. 24 ; Initially, the detection capacitor and the four drive capacitors of the drive module are in a balanced state. At this time, the differential output capacitor C 13 and C 24 are all zero; when the detection capacitor follows the moving part around the axis in the Cartesian coordinate system (z represents the z-axis component of the Cartesian coordinate system. In this solution, the radial direction of the driving module is defined as the z-axis) When rotating, the detection capacitor and the four driving capacitors are unbalanced. At this time, the differential output capacitor C 13 With the shaft The spatial angle displacement of one channel is proportional to that of the other channel, while the differential output capacitance of the other channel is zero.

[0031] Therefore, when the detection capacitor rotates around an arbitrary axis in the Cartesian coordinate system, the detection capacitor and the four drive capacitors are unbalanced, and the differential output capacitance C 13 , C 24 They will change with the change of spatial angle.

[0032] Step 3, construct a relationship between the differential output capacitance and the angle component of the coordinate axis when the detection capacitor is in different quadrants, then apply a sinusoidal excitation signal to the detection capacitor based on the signal detection circuit, obtain the current signal output by each driving capacitor and convert it into a voltage signal, and then solve the differential output capacitance; then calculate the angle component based on the relationship.

[0033] According to the capacitance measurement principle, when the center of the detection capacitor moves into the first quadrant, the differential output capacitance C between the first quadrant and the third quadrant 13 And the differential output capacitance C between the second quadrant and the fourth quadrant 24 for:

[0034]

[0035] Wherein, ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, r is the radius of the projected circle of the detection capacitor, R is the radius of curvature of the detection capacitor, α1 is the angular component of the detection capacitor driven by the moving part around the x-axis in the Cartesian coordinate system, and α2 is the angular component of the detection capacitor around the y-axis in the Cartesian coordinate system.

[0036] Since the angle of the inner frame is a small range follow-up motion, the Taylor series can be used to Approximately α1, Approximately α2; thus, when the center of the detection capacitor moves to other quadrants in the Cartesian coordinate system, the differential output capacitance C 13, C 24 The expression is:

[0037]

[0038] Write equation 3 and equation 4 in the form of a matrix:

[0039]

[0040] According to equations 5 and 6, the angle components α1 and α2 are coupled to each other and cannot directly detect C. 13 , C 24 Thus, the values ​​of α1 and α2 are known. By analyzing the coupling mode of the angle components, it can be known that the coupling in C can be calculated as follows: 13 , C 24 The angle components α1 and α2 in are decoupled, and the decoupling operation is as follows:

[0041]

[0042] See attached Figure 1 In one embodiment of the present invention, the detection capacitor is a convex spherical capacitor, the driving capacitor is a four-quadrant concave spherical capacitor, the geometric center of the detection capacitor and the geometric center of the driving capacitor coincide with each other at the origin of the Cartesian coordinate system; the four driving capacitors and the detection capacitor constitute a spherical differential four-quadrant structure capacitance sensor; when the detection capacitor moves relative to the driving capacitor in the Cartesian coordinate system, the relative areas of the four measuring capacitors are driven to change differentially in pairs, generating a differential output capacitance C 13 , C 24 , by adjusting the differential output capacitance C 13 , C 24 Further processing can be used to measure the two-degree-of-freedom angle in space.

[0043] The present invention realizes a signal processing circuit based on AC excitation capacitor signal detection technology. The circuit includes three parts: a driving circuit, a detection circuit and an FPGA. The driving circuit is used to generate a sinusoidal excitation signal to excite the detection capacitor; the detection circuit is used to obtain four induced current signals output by four driving capacitors when the detection capacitor is excited, and convert the four induced current signals into voltage signals; the FPGA is used to perform decoupling operations to obtain angle components α1 and α2.

[0044] See attached Figure 2 , in one embodiment of the present invention:

[0045] The driving circuit includes a 1MHz crystal oscillator, a four-frequency division circuit, a second-order integral shaping circuit and a radio frequency connector; first, the frequency division circuit divides the 1MHz signal by four to obtain a 250KHz square wave excitation signal; second, the second-order integral circuit shapes the divided 250KHz square wave signal into a 250KHz string excitation signal V d ; Finally, the RF connector applies the obtained sinusoidal excitation signal to the detection capacitor to realize the excitation of the spherical differential four-quadrant capacitive sensor.

[0046] The detection circuit includes four RF connectors, four T-type transimpedance amplifiers, two differential amplifier circuits and an ADC converter; first, the four T-type transimpedance amplifiers convert the four weak current signals output by the four driving capacitors into voltage signals V1, V2, V3, and V4 when the detection capacitor is excited; secondly, a differential amplifier differentially amplifies V1 and V3, and another differential amplifier differentially amplifies V2 and V4 to obtain differential voltage values ​​V respectively. 13 , V 24 ; V 13 =GC 13 , V 24 =GC 24 , where G is the gain of the T-type transimpedance amplifier and the differential amplifier circuit; then, the ADC converter converts V 13 , V 24 The signal is sampled and transmitted to the FPGA.

[0047] Finally, the FPGA passes V 13 , V 24 The decoupling operation shown in equations 7 and 8 is performed to obtain the angle components α1 and α2, thereby realizing the measurement of the moving angle of the moving parts in the device in the Cartesian coordinate system.

[0048] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A non-contact two-degree-of-freedom angle measurement method based on spherical capacitance, characterized in that: include: For a device that needs to measure the angle of a moving part, first fix the driving module on the device, then connect the detection capacitor to the moving part, so that there is a gap between the detection capacitor and the driving module; wherein the detection capacitor and the driving module are both spherical structures, the centers of the detection capacitor and the driving module coincide, and are set at the origin of a Cartesian coordinate system; the driving module is divided into four mutually insulated and identically sized sector-shaped driving capacitors by the x and y axes of the coordinate system, the four driving capacitors are respectively located in four quadrants on the sphere, and together with the detection capacitor, form a spherical differential four-quadrant capacitance sensor; initially, the center of the detection capacitor is located directly above the center of the driving module; When the detection capacitor follows the moving part in the device and rotates in the Cartesian coordinate system, the relative areas between the four measurement capacitors change differentially in pairs, generating corresponding differential output capacitances; A relationship between the differential output capacitance and the angle component of the coordinate axis when the detection capacitance is in different quadrants is constructed, and then a sinusoidal excitation signal is applied to the detection capacitance based on the signal detection circuit. The current signal output by each driving capacitor is obtained and converted into a voltage signal, and the differential output capacitance is solved; and then the angle component is calculated based on the relationship.

2. The non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to claim 1, characterized in that: The relationship between the differential output capacitance and the coordinate axis angle component when the detection capacitor is in different quadrants is expressed as: Among them, C 13 is the differential output capacitance between the first quadrant and the third quadrant, C 24 is the differential output capacitance between the second quadrant and the fourth quadrant; ε is the dielectric constant of air, d0 is the gap between the driving capacitor and the detection capacitor, r is the projection circle radius of the detection capacitor, R is the curvature radius of the detection capacitor, α1 is the angular component of the detection capacitor driven by the moving part around the x-axis in the Cartesian coordinate system, and α2 is the angular component of the detection capacitor around the y-axis in the Cartesian coordinate system.

3. The non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to claim 1, characterized in that: The signal processing circuit of the measurement method includes a driving circuit, a detection circuit and an FPGA, wherein the driving circuit is used to generate a sinusoidal excitation signal to excite the detection capacitor; the detection circuit is used to obtain four induced current signals output by four driving capacitors when the detection capacitor is excited, and convert the four induced current signals into voltage signals; the FPGA is used to perform decoupling operations to obtain angle components.

4. The non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to claim 1, characterized in that: The driving circuit includes a 1MHz crystal oscillator, a four-frequency division circuit, a second-order integral shaping circuit and a radio frequency connector; first, the frequency division circuit divides the 1MHz signal by 4 to obtain a 250KHz square wave excitation signal; second, the second-order integral circuit shapes the divided 250KHz square wave signal into a 250KHz sinusoidal excitation signal; finally, the radio frequency connector applies the obtained sinusoidal excitation signal to the detection capacitor to realize the excitation of the spherical differential four-quadrant capacitance sensor.

5. The non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to claim 1, characterized in that: The detection circuit includes four RF connectors, four T-type transimpedance amplifiers, two differential amplifier circuits and an ADC converter. First, the four T-type transimpedance amplifiers convert the four weak current signals output by the four driving capacitors when the detection capacitor is excited into voltage signals V1, V2, V3, V4; secondly, a differential amplifier performs differential amplification on V1 and V3, and another differential amplifier performs differential amplification on V2 and V4 to obtain differential voltage values ​​V 13 , V 24 ; V 13 =GC 13 , V 24 =GC 24 ; Where G is the gain of the T-type transimpedance amplifier and the differential amplifier circuit; Then, the ADC converter converts V 13 , V 24 The signal is sampled and transmitted to the FPGA.

6. The non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to claim 1, characterized in that: FPGA from V 13 , V 24 Solve to get C 13 , C 24 After that, the decoupling operation is performed according to the following formula to obtain the angle components α1 and α2:

7. A measuring device comprising a processor, a memory and a computer program stored in the memory; characterized in that: When the processor executes the computer program, the non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to any one of claims 1 to 6 is implemented.

8. A computer-readable storage medium, wherein a computer program is stored in the medium; characterized in that: When the computer program is executed by a processor, the non-contact two-degree-of-freedom angle measurement method based on spherical capacitance according to any one of claims 1 to 6 is implemented.

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