High-precision absolute type rotation angle sensor

Abstract

A high-precision absolute type rotation angle sensor is composed of a static pole plate, a movable pole plate and a signal demodulation circuit. Wherein the movable pole plate and the static pole plate are coaxially matched, and the movable pole plate can complete rotating motion relative to the static pole plate. In order to meet the requirement of high-precision absolute measurement of the rotation angle, the sensor is respectively provided with two groups of fan-shaped electrodes and special-shaped reflection polar plates which are used for accurate measurement and rough measurement and are periodically arranged on a static polar plate and a movable polar plate, and the fan-shaped electrodes and the special-shaped reflection polar plates jointly complete high-precision absolute measurement of the rotation angle in a capacitive coupling mode. The sensor has the advantages of simple structure, high precision, absolute measurement, good environmental adaptability and the like.

Description

Technical Field

[0001] The invention relates to the field of precision displacement measurement, and in particular to a high-precision absolute rotation angle sensor. Background Art

[0002] In key industrial fields such as aerospace, microelectronics, biomedicine and optics, the demand for precision rotation angle measurement equipment is growing. At the same time, how to achieve absolute angle measurement while maintaining high-precision measurement has become a goal that researchers continue to pursue. In the field of absolute rotation angle measurement, photoelectric and electromagnetic sensors are still the mainstream choices. Photoelectric rotation angle sensors are popular because of their mature technology and high precision. However, because they contain optical components inside, they have weak resistance to vibration and are sensitive to dust and oily environments, so they have high requirements for the working environment. Electromagnetic rotation angle sensors rely on electromagnetic induction for measurement. They are more sensitive to electromagnetic interference and it is difficult to ensure high accuracy in an environment with strong electromagnetic interference. In contrast, capacitive sensors are favored by researchers in the field of high-precision measurement with their non-contact measurement, simple structure, high resolution and strong anti-interference ability, and are promoted in precision measurement applications.

[0003] However, most existing capacitive rotation angle sensors use relative measurement methods. When the sensor is powered off, the absolute zero point will be lost, which cannot meet the absolute measurement requirements. This makes this type of sensor unable to meet the high-precision measurement requirements of absolute angles, greatly affecting the use scenarios of this type of sensor. Summary of the invention

[0004] In order to overcome the technical problems existing in the above-mentioned prior art, the present invention aims to provide a capacitive rotation angle sensor and a signal demodulation method which have a simple structure, high measurement accuracy and can meet the requirements of absolute measurement.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A high-precision absolute rotation angle sensor is composed of a moving electrode plate 1, a static electrode plate 2 and a signal demodulation circuit 3, wherein the moving electrode plate 1 and the static electrode plate 2 are coaxially matched and there is a certain gap in the vertical direction, and the moving electrode plate 1 can complete the rotation movement around its main axis relative to the static electrode plate 2. The signal demodulation circuit 3 and the static electrode plate 2 are electrically connected to each other to complete the signal demodulation work of the sensor to achieve high-precision absolute measurement of the rotation angle; further, in order to meet the high-precision measurement requirements of the rotation angle, the moving electrode plate 1 and the static electrode plate 2 are both provided with a periodically arranged electrode structure, including a first special-shaped primary reflection electrode 1-1 and a second special-shaped primary reflection electrode 1-2 located on the moving electrode plate 1 and a precise transmitting electrode group 2-1 located on the static electrode plate 2 corresponding to the positions of the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2. And the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2 are coaxially arranged, have the same structural features and only have a certain angle deviation in the spatial position, thereby forming a differential structure; when the moving electrode plate 1 rotates relative to the static electrode plate 2, the precise transmitting electrode group 2-1 in the direction of the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2 will form a variable capacitance group structure with the two, and the capacitance coupling between them will change with the rotational movement. By differentially demodulating the signals on the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2, the corresponding precise rotation angle information can be obtained, thereby completing the high-precision measurement of the angle; further, in order to complete the absolute measurement of the rotation angle, the moving electrode plate 1 and the static electrode plate 2 are connected to the moving electrode plate 1 and the static electrode plate 2. Another single-period arranged electrode structure is also provided on the electrode plate 2, including a third special-shaped primary reflection electrode 1-3 provided on the moving electrode plate 1 and a coarse transmitting electrode group 2-2 provided on the static electrode plate 2 and corresponding to the position of the third special-shaped primary reflection electrode 1-3; similarly, when the moving electrode plate 1 rotates, the coarse transmitting electrode group 2-2 in the direction opposite to the third special-shaped primary reflection electrode 1-3 will form a variable capacitor group structure with it, and the capacitive coupling between them will change with the rotational movement, and the coarse absolute angle information can be obtained by demodulating the signal on the third special-shaped primary reflection electrode 1-3; further, by integrating the coarse absolute angle information with the precise rotation angle information in the signal demodulation circuit 3, the high-precision absolute measurement of the rotation angle can be completed.

[0007] Preferably, in order to optimize the electrical connection mode of the sensor and reduce the complexity, and avoid the existence of lead-out cables on the moving electrode plate 1, which makes the connection mode too complicated and thus affects the movement stability of the sensor, a first annular secondary reflection electrode 1-4, a second annular secondary reflection electrode 1-5 and a third annular secondary reflection electrode 1-6 which are concentrically distributed are arranged on the moving electrode plate 1; a first annular receiving electrode 1-4 which is concentrically distributed and corresponds to the positions of the first annular secondary reflection electrode 1-4, the second annular secondary reflection electrode 1-5 and the third annular secondary reflection electrode 1-6 are arranged on the static electrode plate 2. The first annular receiving electrode 2-3, the second annular receiving electrode 2-4 and the third annular receiving electrode 2-5; and the first special-shaped primary reflection electrode 1-1, the second special-shaped primary reflection electrode 1-2 and the third special-shaped primary reflection electrode 1-3 are electrically connected to the first annular secondary reflection electrode 1-4, the second annular secondary reflection electrode 1-5 and the third annular secondary reflection electrode 1-6 on the moving electrode plate 1 and are all coaxially arranged; the first annular receiving electrode 2-3, the second annular receiving electrode 2-4 and the third annular receiving electrode 2-5 are directly electrically connected to the signal demodulation circuit 3 on the static electrode plate 2. Similarly, when the moving electrode plate 1 rotates relative to the static electrode plate 2, an invariable capacitance structure will be formed between the secondary reflection electrode and the receiving electrode, which will directly transmit the effective signal on the primary reflection electrode to the receiving electrode without introducing extra connecting cables on the moving electrode plate 1. Then, the effective signals on the first ring-shaped receiving electrode 2-3, the second ring-shaped receiving electrode 2-4 and the third ring-shaped receiving electrode 2-5 can be directly demodulated and integrated by the signal demodulation circuit 3 to obtain a high-precision absolute rotation angle and complete the corresponding precise measurement task. This greatly reduces the complexity of the electrical connection and further improves the motion stability of this type of sensor.

[0008] Preferably, the precise transmitting electrode group 2-1 located on the static electrode plate 2 is composed of N groups of transmitting electrodes, wherein four small fan-shaped electrodes of the same size and equal spacing constitute a group of transmitting electrodes, i.e., one period; and in each spatial period, the precise first transmitting electrode 2-1-1, the precise second transmitting electrode 2-1-2, the precise third transmitting electrode 2-1-3, and the precise fourth transmitting electrode 2-1-4 are respectively applied with four SPWM modulated sinusoidal wave signals generated by the signal demodulation circuit 3, and the phase of these four SPWM modulated sinusoidal waves is The bits are 0, π / 2, π and 3π / 2 respectively; compared with the precise transmitting electrode group 2-1 having N groups of transmitting electrodes, the coarse transmitting electrode group 2-2 has only one group of transmitting electrodes, that is, four coarse first transmitting electrodes 2-2-1, coarse second transmitting electrodes 2-2-2, coarse third transmitting electrodes 2-2-3 and coarse fourth transmitting electrodes 2-2-4 of the same size and equal spacing together constitute the coarse transmitting electrode group 2-2, and the same four-way SPWM modulated sinusoidal wave signals are also applied to these four transmitting electrodes.

[0009] The first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 are composed of N special-shaped envelope plates of the same size, which are arranged circumferentially with equal periods on the moving electrode plate 1, and the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 are different in spatial distribution, and there is a half-cycle angle deviation between the two in spatial position, so as to form a differential signal output. The polar coordinate equation of the upper and lower envelope lines of the special-shaped reflective plates of the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 is:

[0010]

[0011] Wherein R is the radius value of the special-shaped reflective plate, 2A is the radial width of the special-shaped reflective plate, and N is the number of periods of the emitting electrode group; when the moving plate 1 rotates around its rotation axis, the first special-shaped primary reflective plate 1-1 and the precise first emitting electrode 2-1-1, the precise second emitting electrode 2-1-2, the precise third emitting electrode 2-1-3 and the precise fourth emitting electrode 2-1-4 on each period form a variable capacitor C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because four excitation signals with different phases are applied to the transmitting electrode in each cycle, according to the corresponding equivalent circuit and the parallel plate capacitance expression Where S is the relative surface area between the moving plate and the static plate, d is the distance between the moving plate and the static plate, ε 0 , ε r are the vacuum dielectric constant and the relative dielectric constant respectively; the output signal on the first shaped primary reflector plate 1-1 is obtained:

[0012]

[0013] In the formula, U(Δθ,t) is the output signal on the first shaped primary reflector plate, Δθ is the rotation angle of the moving plate relative to the static plate, K is the voltage amplitude of the four excitation signals with different phases, ω is the angular frequency of the fundamental wave in the four excitation signals with different phases, S a , S b , S c , S d are the facing surface areas of the first shaped primary reflector plate 1-1 and the four emitting electrodes in each period, and t is the time; then, according to the upper and lower envelope polar coordinate equations of formula (1) and substituting the area integral into formula (2), the output signal of the first shaped primary reflector plate 1-1 when the moving plate 1 rotates by an angle Δθ is obtained:

[0014] U(Δθ,t)=K'sin(ωt-NΔθ) (3)

[0015] Wherein, K' is the output signal amplitude; according to the capacitor structure, the output signal U'(Δθ, t) on the first annular receiving electrode 2-3 is expressed as:

[0016] U'(Δθ,t)=K”sin(ωt-NΔθ) (4)

[0017] Where K" is the output signal amplitude; by observing the expression of the output signal, the phase of the output signal can be demodulated to complete the rotation angle Δθ Furthermore, the moving electrode plate 1 is provided with a second shaped primary reflector plate 1-2 which is half a spatial angle period different from the first shaped primary reflector plate 1-1. Therefore, a differential signal opposite to the output signal of the first annular receiving electrode 2-3 is generated on the second annular receiving electrode 2-4. By differentially amplifying the differential signal, an output signal with excellent signal-to-noise ratio can be obtained, thereby obtaining Accurate angle information within the range can complete high-precision measurement of rotation angle.

[0018] Preferably, in order to complete the absolute measurement of the rotation angle, the third shaped primary reflection electrode 1-3 is composed of a single shaped envelope electrode plate compared to the first shaped primary reflection electrode 1-1 and the second shaped primary reflection electrode 1-2; therefore, the output signal U" (Δθ,t

[0019] The expression is:

[0020] U”(Δθ,t)=K”'sin(ωt-Δθ) (5)

[0021] Wherein K'' is the output signal amplitude; and by observing the expression of the output signal, the phase of the output signal can be demodulated to complete the rough measurement of the rotation angle Δθ within the range of 2π, thereby completing the measurement of the absolute rotation angle. Further, by integrating the rough absolute rotation angle information with the precise angle information in the signal demodulation circuit 3, the corresponding high-precision absolute rotation angle information can be obtained, thereby completing the high-precision absolute measurement of the rotation angle.

[0022] The signal demodulation circuit 3 includes a differential circuit, a bandpass filter circuit, a shaping circuit, a phase detection circuit and an FPGA operation module; the four SPWM sinusoidal modulation waves with different phases generated by the FPGA operation module are applied to the precise transmitting electrode group 2-1 and the coarse transmitting electrode group 2-2 as the input signal of the sensor; the sensor differential output signal on the first annular receiving electrode 2-3 and the second annular receiving electrode 2-4 is obtained by the signal demodulation circuit 3, and the signal enters the bandpass filter circuit after differential processing through the differential circuit to eliminate the harmonic components therein and only retain the sinusoidal fundamental wave component of the SPWM sinusoidal modulation wave. Then, the signal is amplified and shaped by a shaping circuit to convert the sine fundamental wave into a square wave waveform, so that the subsequent phase detection circuit can identify and demodulate the output signal phase; similarly, the output signal on the third annular receiving electrode 2-5 is acquired by the signal demodulation circuit 3, and the corresponding phase demodulation information is obtained after the same filtering, shaping and phase detection processing; finally, the high-frequency clock pulse counting method is used in the FPGA operation module to calculate and process the demodulated phase signal, and the precise angle information and the absolute angle information are further distinguished and integrated by software, thereby realizing high-precision absolute measurement of the rotation angle.

[0023] Preferably, the moving electrode plate 1 and the static electrode plate 2 are made of printed circuit boards, and by arranging a primary reflective electrode plate and a secondary reflective electrode plate on the moving electrode plate, no signal line is led out of the moving electrode plate.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. Compared with traditional capacitive sensors, the high-precision absolute rotation angle sensor described in the present invention measures angles by utilizing capacitive coupling to demodulate the signal phase, which greatly reduces the interference of parasitic capacitance, temperature, humidity and other harsh environmental factors on angle measurement. It has high reliability and can adapt to harsh environments; it has the characteristics of high resolution, high precision, high stability, etc.

[0026] 2. The high-precision absolute rotation angle sensor described in the present invention completes the absolute measurement of the rotation angle by combining precise measurement with rough measurement. After the sensor is powered off and powered on again, the absolute zero point will not be lost, which greatly expands the application scope and application scenarios of this type of sensor.

[0027] 3. The sensor plate of the present invention is made of printed circuit board and is configured by a reflective capacitor plate. There is no signal line leading out of the moving plate. The structure is simple and compact, and it is easy to process and install.

[0028] 4. Compared with traditional rectangular and triangular plates, the high-precision absolute rotation angle sensor described in the present invention increases the facing area of ​​the capacitor plates by adopting special-shaped plates, improves the signal-to-noise ratio of the output signal, and enhances the anti-interference ability of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a three-dimensional schematic diagram of the high-precision absolute rotation angle sensor of the present invention.

[0030] Figure 2 It is a top view of the high-precision absolute rotation angle sensor of the present invention.

[0031] Figure 3 It is a schematic diagram of the moving electrode plate of the high-precision absolute rotation angle sensor of the present invention.

[0032] Figure 4 It is a schematic diagram of the static electrode plate of the high-precision absolute rotation angle sensor of the present invention.

[0033] Figure 5 The figure is a schematic diagram of the relationship between the rotation angle and the output signal phase of the high-precision absolute rotation angle sensor of the present invention.

[0034] Figure 6 It is a schematic diagram of the absolute angle determination principle of the high-precision absolute rotation angle sensor of the present invention.

[0035] Figure 7 This is a block diagram of a signal demodulation circuit for a high-precision absolute rotation angle sensor according to the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0037] like Figure 1 , Figure 2 and Figure 3As shown, a high-precision absolute rotation angle sensor of the present invention is composed of a moving electrode plate 1, a static electrode plate 2 and a signal demodulation circuit 3, wherein the moving electrode plate 1 and the static electrode plate 2 are coaxially matched, and there is a certain gap in the vertical direction, and the moving electrode plate 1 can complete the rotation movement around its main axis relative to the static electrode plate 2. The signal demodulation circuit 3 and the static electrode plate 2 are electrically connected to each other to complete the signal demodulation work of the sensor to achieve high-precision absolute measurement of the rotation angle. Further, in order to meet the high-precision measurement requirements of the rotation angle, a periodically arranged electrode structure is provided on the moving electrode plate 1 and the static electrode plate 2, including a first special-shaped primary reflection electrode 1-1 and a second special-shaped primary reflection electrode 1-2 located on the moving electrode plate 1 and a precise transmitting electrode group 2-1 located on the static electrode plate 2 corresponding to the position of the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2. And the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2 are coaxially arranged with the same structural features and only have a certain angle deviation in the spatial position, thereby forming a differential structure. When the moving electrode plate 1 rotates relative to the static electrode plate 2, the precise transmitting electrode group 2-1 in the direction opposite to the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2 will form a variable capacitance group structure with the two, and the capacitance coupling between them will change with the rotational movement. By differentially demodulating the signals on the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2, the corresponding precise rotation angle information can be obtained, thereby completing the high-precision measurement of the angle; further, in order to complete the absolute measurement of the rotation angle, another single-period arranged electrode structure is also arranged on the moving electrode plate 1 and the static electrode plate 2, including a third special-shaped primary reflection electrode 1-3 arranged on the moving electrode plate 1 and a rough transmitting electrode group 2-2 arranged on the static electrode plate 2 corresponding to the position of the third special-shaped primary reflection electrode 1-3. Similarly, when the moving electrode plate 1 rotates, the rough transmitting electrode group 2-2 in the direction of the third special-shaped primary reflective electrode 1-3 will form a variable capacitor group structure with it, and the capacitive coupling between them will change with the rotational movement, and the rough absolute angle information can be obtained by demodulating the signal on the third special-shaped primary reflective electrode 1-3. Further, by integrating the rough absolute angle information with the precise rotation angle information in the signal demodulation circuit 3, the high-precision absolute measurement of the rotation angle can be completed.

[0038] like Figure 3 and Figure 4As shown, in order to optimize the electrical connection mode of the sensor and reduce the complexity, and avoid the existence of lead-out cables on the moving electrode plate 1, which makes the connection mode too complicated and thus affects the motion stability of the sensor, a first annular secondary reflection electrode 1-4, a second annular secondary reflection electrode 1-5 and a third annular secondary reflection electrode 1-6 are arranged on the moving electrode plate 1 in a concentric manner; a first annular receiving electrode 2-3, a second annular receiving electrode 2-4 and a third annular receiving electrode 2-5 are arranged on the static electrode plate 2 in a concentric manner, which correspond to the positions of the first annular secondary reflection electrode 1-4, the second annular secondary reflection electrode 1-5 and the third annular secondary reflection electrode 1-6 respectively. In addition, the first special-shaped primary reflection electrode 1-1, the second special-shaped primary reflection electrode 1-2 and the third special-shaped primary reflection electrode 1-3 are electrically connected to the first annular secondary reflection electrode 1-4, the second annular secondary reflection electrode 1-5 and the third annular secondary reflection electrode 1-6 on the moving electrode plate 1 and are all coaxially arranged. The first annular receiving electrode 2-3, the second annular receiving electrode 2-4 and the third annular receiving electrode 2-5 are directly electrically connected to the signal demodulation circuit 3 on the static electrode plate 2. Similarly, when the dynamic electrode plate 1 rotates relative to the static electrode plate 2, an unchanged capacitance structure will be formed between the secondary reflection electrode and the receiving electrode, which will directly transmit the effective signal on the primary reflection electrode to the receiving electrode without introducing extra connection cables on the dynamic electrode plate 1. Then, the effective signals on the first annular receiving electrode 2-3, the second annular receiving electrode 2-4 and the third annular receiving electrode 2-5 can be directly demodulated and integrated by the signal demodulation circuit 3 to obtain a high-precision absolute rotation angle and complete the corresponding precise measurement task. This greatly reduces the complexity of the electrical connection and further improves the motion stability of this type of sensor.

[0039] like Figure 4As shown, preferably, the precise transmitting electrode group 2-1 located on the static electrode plate 2 is composed of N groups of transmitting electrodes, wherein four small fan-shaped electrodes of the same size and equal spacing constitute a group of transmitting electrodes, i.e., one period; and in each spatial period, the precise first transmitting electrode 2-1-1, the precise second transmitting electrode 2-1-2, the precise third transmitting electrode 2-1-3 and the precise fourth transmitting electrode 2-1-4 are respectively applied with four SPWM modulated sinusoidal wave signals generated by the signal demodulation circuit 3, and these four SPWM modulated sinusoidal waves The phases are 0, π / 2, π and 3π / 2 respectively; compared with the precise transmitting electrode group 2-1 having N groups of transmitting electrodes, the coarse transmitting electrode group 2-2 has only one group of transmitting electrodes, that is, four coarse first transmitting electrodes 2-2-1, coarse second transmitting electrodes 2-2-2, coarse third transmitting electrodes 2-2-3 and coarse fourth transmitting electrodes 2-2-4 of the same size and equal spacing together constitute the coarse transmitting electrode group 2-2, and the same four-way SPWM modulated sine wave signals are also applied to these four transmitting electrodes. Figure 3 and Figure 4 As shown, the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 are composed of N special-shaped envelope plates of the same size, which are arranged circumferentially with equal periods on the moving electrode plate 1, and the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 have differences in spatial distribution, and there is an angle deviation of half a period between the two in spatial position, so as to form a differential signal output. The polar coordinate equations of the upper and lower envelope lines of the special-shaped reflective plates on the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 are:

[0040]

[0041] Wherein R is the radius value of the special-shaped reflective plate, 2A is the radial width of the special-shaped reflective plate, and N is the number of periods of the emitting electrode group; when the moving plate 1 rotates around its rotation axis, the first special-shaped primary reflective plate 1-1 and the precise first emitting electrode 2-1-1, the precise second emitting electrode 2-1-2, the precise third emitting electrode 2-1-3 and the precise fourth emitting electrode 2-1-4 on each period form a variable capacitor C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because four excitation signals with different phases are applied to the transmitting electrode in each cycle, according to the corresponding equivalent circuit and the parallel plate capacitance expression Where S is the relative surface area between the moving plate and the static plate, d is the distance between the moving plate and the static plate, ε 0 , ε rare the vacuum dielectric constant and the relative dielectric constant respectively; the output signal on the first shaped primary reflector plate 1-1 is obtained:

[0042]

[0043] In the formula, U(Δθ,t) is the output signal on the first shaped primary reflector plate, Δθ is the rotation angle of the moving plate relative to the static plate, K is the voltage amplitude of the four excitation signals with different phases, ω is the angular frequency of the fundamental wave in the four excitation signals with different phases, S a , S b , S c , S d are the facing surface areas of the first shaped primary reflector plate 1-1 and the four emitting electrodes in each period, and t is the time; then, according to the upper and lower envelope polar coordinate equations of formula (1) and substituting the area integral into formula (2), the output signal of the first shaped primary reflector plate 1-1 when the moving plate 1 rotates by an angle Δθ is obtained:

[0044] U(Δθ,t)=K'sin(ωt-NΔθ) (3)

[0045] Wherein, K' is the output signal amplitude; according to the capacitor structure described in the present invention, the output signal U'(Δθ, t) on the first annular receiving electrode 2-3 is expressed as:

[0046] U'(Δθ,t)=K”sin(ωt-NΔθ) (4)

[0047] Where K" is the output signal amplitude. By observing the expression of the output signal, the phase of the output signal can be demodulated to complete the rotation angle Δθ Precise measurements within the range, such as Figure 5 As shown. Further, the moving electrode plate 1 is provided with a second shaped primary reflector plate 1-2 which is half a spatial angle period different from the first shaped primary reflector plate 1-1. Therefore, a differential signal opposite to the output signal of the first ring-shaped receiving electrode 2-3 is generated on the second ring-shaped receiving electrode 2-4. By differentially amplifying the differential signal, an output signal with excellent signal-to-noise ratio can be obtained, thereby obtaining Accurate angle information within the range can complete high-precision measurement of rotation angle.

[0048] like Figure 5 and Figure 6As shown, preferably, in order to complete the absolute measurement of the rotation angle, the third special-shaped primary reflection electrode 1-3 is composed of a single special-shaped envelope electrode plate compared to the first special-shaped primary reflection electrode 1-1 and the second special-shaped primary reflection electrode 1-2. Therefore, according to the above content, the output signal U" (Δθ, t) on the third annular receiving electrode 2-5 is expressed as:

[0049] U”(Δθ,t)=K”'sin(ωt-Δθ) (5)

[0050] Wherein K'' is the output signal amplitude. And by observing the expression of the output signal, the phase of the output signal can be demodulated to complete the rough measurement of the rotation angle Δθ within the range of 2π, thereby completing the measurement of the absolute rotation angle. Further, by integrating the rough absolute rotation angle information with the precise angle information in the signal demodulation circuit 3, the corresponding high-precision absolute rotation angle information can be obtained, thereby completing the high-precision absolute measurement of the rotation angle.

[0051] like Figure 7 The signal demodulation circuit 3 includes a differential circuit, a bandpass filter circuit, a shaping circuit, a phase detection circuit and an FPGA operation module; the four SPWM sinusoidal modulation waves of different phases generated by the FPGA operation module are applied to the precise transmitting electrode group 2-1 and the rough transmitting electrode group 2-2 as the input signal of the sensor. The differential output signal of the sensor on the first annular receiving electrode 2-3 and the second annular receiving electrode 2-4 is obtained by the signal demodulation circuit 3, and the signal enters the bandpass filter circuit after differential processing through the differential circuit to eliminate the harmonic components therein, and only retains the sinusoidal fundamental component of the SPWM sinusoidal modulation wave. Then, the signal is amplified and shaped by the shaping circuit to convert the sinusoidal fundamental wave into a square wave waveform, so that the subsequent phase detection circuit can identify and demodulate the output signal phase. Similarly, the output signal on the third annular receiving electrode 2-5 is obtained by the signal demodulation circuit 3, and the corresponding phase demodulation information is obtained after the same filtering, shaping and phase detection processing. Finally, the high-frequency clock pulse counting method is used in the FPGA operation module to calculate and process the demodulated phase signal, and the precise angle information and the absolute angle information are further integrated and processed by software discrimination, thereby achieving high-precision absolute measurement of the rotation angle.

Claims

1. A high-precision absolute rotation angle sensor, characterized in that: The invention is composed of a moving electrode plate (1), a static electrode plate (2) and a signal demodulation circuit (3), wherein the moving electrode plate (1) and the static electrode plate (2) are coaxially matched and have a certain gap in the vertical direction, and the moving electrode plate (1) can complete a rotational movement around its main axis relative to the static electrode plate (2); the signal demodulation circuit (3) and the static electrode plate (2) are electrically connected to each other to complete the signal demodulation work of the sensor and realize high-precision absolute measurement of the rotation angle; in order to meet the high-precision measurement requirements of the rotation angle, the moving electrode plate (1) and the static electrode plate (2) are both provided with periodically arranged electrode structures, including a first special-shaped first electrode structure located on the moving electrode plate (1) and a second special-shaped first electrode structure located on the moving electrode plate (1). The invention relates to a reflective electrode (1-1) and a second special-shaped primary reflective electrode (1-2) and a precise transmitting electrode group (2-1) located on a static electrode plate (2) and corresponding to the positions of the first special-shaped primary reflective electrode (1-1) and the second special-shaped primary reflective electrode (1-2); and the first special-shaped primary reflective electrode (1-1) and the second special-shaped primary reflective electrode (1-2) are coaxially arranged, have the same structural features and only have a certain angle deviation in spatial position, thereby forming a differential structure; when the dynamic electrode plate (1) rotates relative to the static electrode plate (2), the first special-shaped primary reflective electrode (1-1) and the second special-shaped primary reflective electrode (1-2) are opposite to each other. The precise transmitting electrode group (2-1) in the direction of 1-2) will form a variable capacitance group structure with the two, and the capacitance coupling between them will change with the rotational movement. By differentially demodulating the signals on the first special-shaped primary reflection electrode (1-1) and the second special-shaped primary reflection electrode (1-2), the corresponding precise rotation angle information is obtained, and the high-precision measurement of the angle is completed. In order to complete the absolute measurement of the rotation angle, another single-period arrangement electrode structure is also arranged on the moving electrode plate (1) and the static electrode plate (2), including a third special-shaped primary reflection electrode (1-3) arranged on the moving electrode plate (1) and a third special-shaped primary reflection electrode (1-3) arranged on the static electrode plate (2). The rough transmitting motor group (2-2) corresponds to the position of the third special-shaped primary reflection electrode (1-3); similarly, when the moving electrode plate (1) rotates, the rough transmitting electrode group (2-2) in the direction opposite to the third special-shaped primary reflection electrode (1-3) will form a variable capacitor group structure with it, and the capacitive coupling between them will change with the rotational movement, and the rough absolute angle information can be obtained by demodulating the signal on the third special-shaped primary reflection electrode (1-3); by integrating the rough absolute angle information with the precise rotation angle information in the signal demodulation circuit (3), the high-precision absolute measurement of the rotation angle is completed.

2. A high-precision absolute rotation angle sensor according to claim 1, characterized in that: In order to optimize the electrical connection mode of the sensor and reduce the complexity, and to avoid the existence of lead-out cables on the moving electrode plate (1) which would cause the connection mode to be too complicated and thus affect the motion stability of the sensor, a first annular secondary reflection electrode (1-4), a second annular secondary reflection electrode (1-5) and a third annular secondary reflection electrode (1-6) are arranged on the moving electrode plate (1); a first annular receiving electrode (2-3), a second annular receiving electrode (2-4) and a third annular receiving electrode (2-5) are arranged on the static electrode plate (2) and are respectively arranged corresponding to the positions of the first annular secondary reflection electrode (1-4), the second annular secondary reflection electrode (1-5) and the third annular secondary reflection electrode (1-6); a first special-shaped primary reflection electrode (1-1), a second special-shaped primary reflection electrode (1-2) and a third special-shaped primary reflection electrode (1-3) are arranged corresponding to the first annular secondary reflection electrode (1-4), the second annular secondary reflection electrode (1-5) and the third annular secondary reflection electrode (1-6); The reflection electrode (1-5) and the third annular secondary reflection electrode (1-6) are electrically connected to each other on the moving electrode plate (1) and are coaxially arranged; the first annular receiving electrode (2-3), the second annular receiving electrode (2-4) and the third annular receiving electrode (2-5) are directly electrically connected to the signal demodulation circuit (3) on the static electrode plate (2); when the moving electrode plate (1) rotates relative to the static electrode plate (2), an unchanged capacitance structure is formed between the secondary reflection electrode and the receiving electrode, which directly transmits the effective signal on the primary reflection electrode to the receiving electrode without introducing redundant connection cables on the moving electrode plate (1), and then directly demodulates and integrates the effective signals on the first annular receiving electrode (2-3), the second annular receiving electrode (2-4) and the third annular receiving electrode (2-5) through the signal demodulation circuit (3), thereby obtaining a high-precision absolute rotation angle and completing the corresponding precise measurement task.

3. A high-precision absolute rotation angle sensor according to claim 1, characterized in that: The precise transmitting electrode group (2-1) located on the static electrode plate (2) is composed of N groups of transmitting electrodes, wherein four small fan-shaped electrodes of the same size and equal spacing constitute a group of transmitting electrodes, i.e., a period; and in each spatial period, four SPWM modulated sinusoidal wave signals generated by a signal demodulation circuit (3) are applied to the precise first transmitting electrode (2-1-1), the precise second transmitting electrode (2-1-2), the precise third transmitting electrode (2-1-3), and the precise fourth transmitting electrode (2-1-4), respectively, and the phases of the four SPWM modulated sinusoidal waves are 0, π / 2, π, and 3π / 2, respectively; compared with the precise transmitting electrode group (2-1) having N groups of transmitting electrodes, the coarse transmitting electrode group (2-2) has only one group of transmitting electrodes, i.e., four coarse first transmitting electrodes (2-2-1), coarse second transmitting electrodes ( 2-2-2), a rough third transmitting electrode (2-2-3) and a rough fourth transmitting electrode (2-2-4) together form a rough transmitting electrode group (2-2), and the same four-channel SPWM modulated sinusoidal wave signals are also applied to the four transmitting electrodes respectively; the first special-shaped primary reflection electrode (1-1) and the second special-shaped primary reflection electrode (1-2) are composed of N special-shaped envelope plates of the same size, which are arranged in an equal periodic circumferential direction on the moving electrode plate (1), and the first special-shaped primary reflection electrode (1-1) and the second special-shaped primary reflection electrode (1-2) are different in spatial distribution, and there is an angle deviation of half a period between the two in spatial position, so as to form a differential signal output; the polar coordinate equations of the upper and lower envelope lines of the special-shaped reflection plates of the first special-shaped primary reflection electrode (1-1) and the second special-shaped primary reflection electrode (1-2) are: Wherein R is the radius value of the special-shaped reflective plate, 2A is the radial width of the special-shaped reflective plate, and N is the number of periods of the emitting electrode group; when the moving plate (1) rotates around its rotation axis, the first special-shaped primary reflective plate (1-1) and the precise first emitting electrode (2-1-1), the precise second emitting electrode (2-1-2), the precise third emitting electrode (2-1-3) and the precise fourth emitting electrode (2-1-4) on each period respectively form a variable capacitor C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because four excitation signals with different phases are applied to the transmitting electrode in each cycle, according to the corresponding equivalent circuit and the parallel plate capacitance expression Where S is the relative surface area between the moving plate and the static plate, d is the distance between the moving plate and the static plate, ε0, ε r are the vacuum dielectric constant and the relative dielectric constant respectively; the output signal on the first shaped primary reflector plate (1-1) is obtained: In the formula, U(Δθ,t) is the output signal on the first shaped primary reflector plate, Δθ is the rotation angle of the moving plate relative to the static plate, K is the voltage amplitude of the four excitation signals with different phases, ω is the angular frequency of the fundamental wave in the four excitation signals with different phases, S a , S b , S c , S d are the facing surface areas of the first shaped primary reflector plate (1-1) and the four emitting electrodes in each period, and t is the time; then, according to the upper and lower envelope polar coordinate equations of formula (1) and substituting them into formula (2) through area integration, the output signal of the first shaped primary reflector plate (1-1) when the moving plate (1) rotates by an angle Δθ is obtained: U(Δθ,t)=K'sin(ωt-NΔθ) (3) Wherein, K' is the output signal amplitude; according to the capacitor structure, the output signal U'(Δθ,t) on the first annular receiving electrode (2-3) is expressed as: U'(Δθ,t)=K”sin(ωt-NΔθ) (4) Where K" is the output signal amplitude; by observing the expression of the output signal, the phase of the output signal is demodulated to complete the rotation angle Δθ The moving electrode plate (1) is provided with a second special-shaped primary reflective electrode plate (1-2) which is half a spatial angle period different from the first special-shaped primary reflective electrode plate (1-1), so that a differential signal opposite to the output signal of the first ring-shaped receiving electrode (2-3) is generated on the second ring-shaped receiving electrode (2-4); the differential signal is differentially amplified to obtain an output signal with an excellent signal-to-noise ratio, thereby obtaining Accurate angle information within the range can complete high-precision measurement of rotation angle.

4. A high-precision absolute rotation angle sensor according to claim 3, characterized in that: The third special-shaped primary reflective electrode (1-3) is composed of a single special-shaped envelope electrode; therefore, the output signal U" (Δθ, t) on the third annular receiving electrode (2-5) is expressed as: U”(Δθ,t)=K”'sin(ωt-Δθ) (5) wherein K'' is the amplitude of the output signal; and by observing the expression of the output signal, the phase of the output signal is demodulated to complete a rough measurement of the rotation angle Δθ within the range of 2π, thereby completing the measurement of the absolute rotation angle. Furthermore, by integrating the rough absolute rotation angle information with the precise angle information in the signal demodulation circuit (3), the corresponding high-precision absolute rotation angle information is obtained, thereby completing the high-precision absolute measurement of the rotation angle.

5. The high-precision absolute rotation angle sensor according to claim 1, characterized in that: The signal demodulation circuit (3) comprises a differential circuit, a bandpass filter circuit, a shaping circuit, a phase detection circuit and an FPGA operation module; four SPWM sinusoidal modulation waves with different phases generated by the FPGA operation module are applied to the precise transmitting electrode group (2-1) and the coarse transmitting electrode group (2-2) as the input signal of the sensor; the sensor differential output signal on the first annular receiving electrode (2-3) and the second annular receiving electrode (2-4) is obtained by the signal demodulation circuit (3), and the signal enters the bandpass filter circuit after differential processing by the differential circuit to eliminate the harmonic components therein and only retain the SPWM sinusoidal modulation wave. Sine fundamental wave component; then, the signal is amplified and shaped by a shaping circuit to convert the sine fundamental wave into a square wave waveform, so that the subsequent phase detection circuit can identify and demodulate the output signal phase; similarly, the output signal on the third annular receiving electrode (2-5) is obtained by the signal demodulation circuit (3), and the corresponding phase demodulation information is obtained after the same filtering, shaping and phase detection processing; finally, the demodulated phase signal is calculated and processed by a high-frequency clock pulse counting method in the FPGA operation module, and the precise angle information and the absolute angle information are further distinguished and integrated, thereby realizing high-precision absolute measurement of the rotation angle.

6. The high-precision absolute rotation angle sensor according to claim 1, characterized in that: The moving electrode plate (1) and the static electrode plate (2) are made of printed circuit boards, and by arranging a primary reflective electrode plate and a secondary reflective electrode plate on the moving electrode plate, no signal line is led out of the moving electrode plate.

Images