A high-precision absolute rotation angle sensor

Abstract

A high-precision absolute rotation angle sensor comprises a static plate, a dynamic plate, and a signal demodulation circuit. The dynamic plate and the static plate are coaxially coupled and can rotate relative to the static plate. To meet the requirements for high-precision absolute measurement of rotation angles, the sensor is equipped with two sets of periodically arranged sector-shaped electrodes and a special-shaped reflective plate on the static plate and the dynamic plate, respectively, for precise and rough measurement. These two sets of electrodes, coupled together through capacitive coupling, achieve high-precision absolute measurement of rotation angles. The sensor has the advantages of simple structure, high precision, absolute measurement, and good environmental adaptability.

Description

Technical Field

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

[0002] The demand for precision rotation angle measurement equipment is growing in key industrial sectors such as aerospace, microelectronics, biomedicine, and optics. At the same time, achieving absolute angle measurement while maintaining high precision has become a persistent goal for researchers. In the field of absolute rotation angle measurement, photoelectric and electromagnetic sensors remain the mainstream choices. Photoelectric rotation angle sensors are popular due to their mature technology and high accuracy. However, due to their internal optical components, they are less resistant to vibration and sensitive to dust and oil, thus requiring a more demanding operating environment. Electromagnetic rotation angle sensors rely on electromagnetic induction for measurement, making them sensitive to electromagnetic interference and struggling to maintain high accuracy in environments with strong electromagnetic interference. In contrast, capacitive sensors, with their non-contact measurement, simple structure, high resolution, and strong anti-interference capabilities, have gained favor among researchers in the field of high-precision measurement and are gaining popularity in precision measurement applications.

[0003] However, most existing capacitive rotation angle sensors use relative measurement methods. When the sensor loses power, the absolute zero point is lost, making it unable to meet the requirements of absolute measurement. This makes these sensors unable to meet the high-precision requirements of absolute angle measurement, significantly limiting their use cases. 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 having a simple structure, high measurement accuracy and the ability to meet absolute measurement requirements.

[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 comprises a moving plate 1, a stationary plate 2, and a signal demodulation circuit 3. The moving plate 1 and the stationary plate 2 are coaxially matched and vertically spaced apart, allowing the moving plate 1 to rotate about its principal axis relative to the stationary plate 2. The signal demodulation circuit 3 is electrically connected to the stationary plate 2, thereby completing the sensor's signal demodulation and achieving high-precision absolute measurement of the rotation angle. Furthermore, to meet the requirements for high-precision measurement of the rotation angle, both the moving plate 1 and the stationary plate 2 are provided with a periodically arranged electrode structure, including a first and second shaped primary reflective electrodes 1-1 and 1-2 on the moving plate 1, and a precision transmitting electrode group 2-1 on the stationary plate 2 corresponding to the positions of the first and second shaped primary reflective electrodes 1-1 and 1-2. In addition, 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 angular deviation in spatial position, thereby forming a differential structure; when the dynamic 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 reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 will form a variable capacitor group structure with the two, and the capacitive coupling between them will change with the rotational movement. By differentially demodulating the signals on the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2, the corresponding precise rotation angle information can be obtained, thereby completing high-precision measurement of the angle; further, in order to complete the absolute measurement of the rotation angle, the dynamic electrode plate 1 and the static electrode 2 are connected to each other. Another single-period arranged electrode structure is also provided on the electrode plate 2, which includes 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 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. 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, 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 cables on the dynamic electrode plate 1, which makes the connection mode too cumbersome and thus affects the motion stability of the sensor, a concentrically distributed 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 provided on the dynamic electrode plate 1; a concentrically distributed first annular receiving electrode 1-4, a second annular secondary reflection electrode 1-5 and a third annular secondary reflection electrode 1-6 are provided on the static electrode plate 2. The first special-shaped primary reflective electrode 1-1, the second special-shaped primary reflective electrode 1-2 and the third special-shaped primary reflective electrode 1-3 are electrically connected to the first special-shaped secondary reflective electrode 1-4, the second special-shaped secondary reflective electrode 1-5 and the third special-shaped secondary reflective electrode 1-6 on the dynamic electrode plate 1 and are all coaxially arranged; the first special-shaped primary reflective electrode 1-1, the second special-shaped primary reflective electrode 1-2 and the third special-shaped primary reflective electrode 1-3 are electrically connected to the first special-shaped secondary reflective electrode 1-4, the second special-shaped secondary reflective electrode 1-5 and the third special-shaped secondary reflective electrode 1-6 on the dynamic electrode plate 1 and are all coaxially arranged; the first special-shaped primary reflective electrode 2-3, the second special-shaped primary reflective electrode 2-4 and the third special-shaped primary reflective electrode 2-5 are directly electrically connected to the signal demodulation circuit 3 on the static electrode plate 2. Similarly, when the moving plate 1 rotates relative to the static plate 2, a constant capacitance structure is formed between the secondary reflective electrode and the receiving electrode. This transmits the effective signal from the primary reflective electrode directly to the receiving electrode, eliminating the need for redundant connecting cables on the moving plate 1. The effective signals from the first, second, and third annular receiving electrodes 2-3, 2-4, and 2-5 can then be directly demodulated and integrated by the signal demodulation circuit 3 to obtain a highly accurate absolute rotation angle, completing the corresponding precise measurement task. This significantly reduces the complexity of the electrical connections and further improves the motion stability of this type of sensor.

[0008] Preferably, the precise transmitting electrode group 2-1 located on the static plate 2 is composed of N groups of transmitting electrodes, wherein four small sector-shaped electrodes of the same size and equal spacing constitute a group of transmitting electrodes, i.e., a period; and within 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 with 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 and second shaped primary reflective electrodes 1-1 and 1-2 are composed of N shaped envelope plates of equal size, which are arranged circumferentially on the dynamic electrode plate 1 with equal periods. The first and second shaped primary reflective electrodes 1-1 and 1-2 differ in spatial distribution, and there is an angular deviation of half a period between their spatial positions, thereby forming a differential signal output. The polar coordinate equations of the upper and lower envelope lines of the shaped reflective plates of the first and second shaped primary reflective electrodes 1-1 and 1-2 are:

[0010]

[0011] Where R is the radius of the special-shaped reflector plate, 2A is the radial width of the special-shaped reflector 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 reflector 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 variable capacitors C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because the transmitting electrode in each cycle is applied with four excitation signals with different phases, 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 relative dielectric constant respectively; the output signal on the first special-shaped primary reflector plate 1-1 is obtained:

[0012]

[0013] Where 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, and S a , S b , S c , S d are the facing surface areas of the first special-shaped primary reflector plate 1-1 and the four emitting electrodes in each period, and t is the time; then, according to the polar coordinate equations of the upper and lower envelopes of formula (1) and substituting the area integral into formula (2), the output signal of the first special-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 follows:

[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 special-shaped primary reflector plate 1-2 which is half a spatial angle period different from the first special-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 an excellent signal-to-noise ratio can be obtained, thereby obtaining Accurate angle information within the range can be used to complete high-precision measurement of rotation angles.

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

[0019] The expression is:

[0020] U”(Δθ,t)=K”'sin(ωt-Δθ) (5)

[0021] Where 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 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 can be obtained, 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 is differentially processed by the differential circuit and then enters the bandpass filter circuit to eliminate the harmonic components therein and only retain the sine fundamental wave component of the SPWM sinusoidal modulation wave. Then, the signal is amplified and shaped by the 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 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, greatly reducing the interference caused by harsh environmental factors such as parasitic capacitance, temperature, and humidity on angle measurement. It has high reliability and can adapt to harsh environments. It has the characteristics of high resolution, high accuracy, and high stability.

[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 then powered on again, the absolute zero point will not be lost, which greatly expands the scope of application 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 as a reflective capacitor plate. There is no signal line leading out of the moving plate, so 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 This is a three-dimensional schematic diagram of the high-precision absolute rotation angle sensor of the present invention.

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

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

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

[0033] Figure 5 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 This 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 the signal demodulation circuit of the high-precision absolute rotation angle sensor of the present invention. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 、 Figure 2 and Figure 3As shown, the present invention discloses a high-precision absolute rotation angle sensor comprising a moving plate 1, a stationary plate 2, and a signal demodulation circuit 3. The moving plate 1 and the stationary plate 2 are coaxially coupled and vertically spaced apart, enabling the moving plate 1 to rotate about its principal axis relative to the stationary plate 2. The signal demodulation circuit 3 is electrically connected to the stationary plate 2, thereby performing the sensor's signal demodulation and achieving high-precision absolute measurement of the rotation angle. Furthermore, to meet the requirements for high-precision rotation angle measurement, both the moving plate 1 and the stationary plate 2 are provided with a periodically arranged electrode structure, including a first and second shaped primary reflective electrodes 1-1 and 1-2 located on the moving plate 1, and a precision transmitting electrode group 2-1 located on the stationary plate 2 corresponding to the first and second shaped primary reflective electrodes 1-1 and 1-2. The first and second shaped primary reflective electrodes 1-1 and 1-2 are coaxially arranged and share identical structural features, differing only by a certain angular positional offset, 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 reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2 will form a variable capacitor group structure with the two, and the capacitive coupling between them will change with the rotational movement. By differentially demodulating the signals on the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2, the corresponding precise rotation angle information can be obtained, thereby completing 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 provided on the moving electrode plate 1 and the static electrode plate 2, including a third special-shaped primary reflective 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 corresponding to the position of the third special-shaped primary reflective electrode 1-3. Similarly, when the moving electrode plate 1 rotates, the coarse transmitting electrode group 2-2 facing the third shaped primary reflective electrode 1-3 forms a variable capacitor group structure with it. The capacitive coupling between them changes with the rotational motion. By demodulating the signal from the third shaped primary reflective electrode 1-3, coarse absolute angle information can be obtained. Furthermore, by integrating the coarse absolute angle information with the precise rotation angle information in the signal demodulation circuit 3, high-precision absolute measurement of the rotation angle can be achieved.

[0038] like Figure 3 and Figure 4As shown, to optimize the sensor's electrical wiring and reduce complexity, and to avoid the presence of lead cables on the moving electrode plate 1 that would complicate the wiring and thus affect the sensor's motion stability, a concentrically distributed first annular secondary reflective electrode 1-4, a second annular secondary reflective electrode 1-5, and a third annular secondary reflective electrode 1-6 are provided on the moving electrode plate 1. Concentrically distributed first annular receiving electrodes 2-3, a second annular receiving electrode 2-4, and a third annular receiving electrode 2-5 are provided on the static electrode plate 2, corresponding to the positions of the first annular secondary reflective electrode 1-4, the second annular secondary reflective electrode 1-5, and the third annular secondary reflective electrode 1-6, respectively. Furthermore, the first, second, and third shaped primary reflective electrodes 1-1, 1-2, and 1-3 are electrically connected to the first, second, and third annular secondary reflective electrodes 1-4, 1-5, and 1-6 on the moving electrode plate 1, and are all coaxially arranged. The first, second, and third annular receiving electrodes 2-3, 2-4, and 2-5 are directly electrically connected to the signal demodulation circuit 3 on the static plate 2. Similarly, when the dynamic plate 1 rotates relative to the static plate 2, a constant capacitance structure is formed between the secondary reflective electrode and the receiving electrode. This transmits the effective signal from the primary reflective electrode directly to the receiving electrode, eliminating the need for redundant connecting cables on the dynamic plate 1. Consequently, the effective signals from the first, second, and third annular receiving electrodes 2-3, 2-4, and 2-5 can be directly demodulated and integrated by the signal demodulation circuit 3 to obtain a highly accurate absolute rotation angle, completing the corresponding precise measurement task. This significantly reduces the complexity of the electrical connections 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 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 within 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, namely, the four coarse first transmitting electrodes 2-2-1, the coarse second transmitting electrodes 2-2-2, the coarse third transmitting electrodes 2-2-3, and the 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 dynamic electrode 1. In addition, 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 angular deviation of half a period between the two in spatial position, thereby forming 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] Where R is the radius of the special-shaped reflector plate, 2A is the radial width of the special-shaped reflector 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 reflector 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 variable capacitors C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because the transmitting electrode in each cycle is applied with four excitation signals with different phases, 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 rare the vacuum dielectric constant and relative dielectric constant respectively; the output signal on the first special-shaped primary reflector plate 1-1 is obtained:

[0042]

[0043] Where 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, and S a , S b , S c , S d are the facing surface areas of the first special-shaped primary reflector plate 1-1 and the four emitting electrodes in each period, and t is the time; then, according to the polar coordinate equations of the upper and lower envelopes of formula (1) and substituting the area integral into formula (2), the output signal of the first special-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 follows:

[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. Accurate measurement within the range, such as Figure 5 As shown. Furthermore, a second shaped primary reflector plate 1-2 is provided on the moving electrode plate 1, which is half the 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 an excellent signal-to-noise ratio can be obtained, thereby obtaining Accurate angle information within the range can be used to complete high-precision measurement of rotation angles.

[0048] like Figure 5 and Figure 6As shown, preferably, to achieve absolute measurement of the rotation angle, the third special-shaped primary reflective electrode 1-3, compared to the first special-shaped primary reflective electrode 1-1 and the second special-shaped primary reflective electrode 1-2, is composed of a single special-shaped envelope electrode. Therefore, based on the above, 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] 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 achieve a rough measurement of the rotation angle Δθ within a 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 can be obtained, completing the high-precision absolute measurement of the rotation angle.

[0051] like Figure 7 The signal demodulation circuit 3 comprises a differential circuit, a bandpass filter circuit, a shaping circuit, a phase detector circuit, and an FPGA operation module. Four SPWM sinusoidal modulated waves of 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 sensor input signals. The differential output signals of the sensors from the first annular receiving electrode 2-3 and the second annular receiving electrode 2-4 are captured by the signal demodulation circuit 3. After differential processing by the differential circuit, these signals enter the bandpass filter circuit to eliminate harmonic components and retain only the fundamental sine wave component of the SPWM sinusoidal modulated wave. The signal is then amplified and shaped by the shaping circuit, converting the fundamental sine wave into a square wave, facilitating subsequent phase detection and demodulation of the output signal. Similarly, the output signal from the third annular receiving electrode 2-5 is captured by the signal demodulation circuit 3 and subjected to the same filtering, shaping, and phase detection processing to obtain corresponding phase demodulation information. Finally, a 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 absolute angle information are further integrated and processed by software, thereby achieving high-precision absolute measurement of the rotation angle.

Claims

1. A high-precision absolute rotation angle sensor, characterized by: 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 the 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 a periodically arranged electrode structure, including a first special-shaped first-stage electrode structure located on the moving electrode plate (1) and a second special-shaped first-stage 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 emitting 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); 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 motion. 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 provided on the moving electrode plate (1) and the static electrode plate (2), including a third special-shaped primary reflection electrode (1-3) provided on the moving electrode plate (1) and a third special-shaped primary reflection electrode (1-3) provided on the static electrode plate (2). The coarse emitting electrode group (2-2) corresponds to the position of the third special-shaped primary reflective electrode (1-3); similarly, when the moving electrode plate (1) rotates, the coarse emitting electrode group (2-2) in the direction opposite to the third special-shaped primary reflective electrode (1-3) forms a variable capacitance group structure with it, and the capacitance coupling between them changes with the rotational movement, and the coarse absolute angle information is obtained by demodulating the signal on the third special-shaped primary reflective electrode (1-3); and the high-precision absolute measurement of the rotation angle is completed by integrating the coarse absolute angle information with the precise rotation angle information in the signal demodulation circuit (3); 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 provided 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 provided on the static electrode plate (2) and are concentrically distributed and 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); 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 provided with 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 reflecting electrode (1-5) and the third annular secondary reflecting electrode (1-6) are electrically connected to each other 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); when the moving electrode plate (1) rotates relative to the static electrode plate (2), an invariable capacitance structure is formed between the secondary reflecting electrode and the receiving electrode, which directly transmits the effective signal on the primary reflecting electrode to the receiving electrode without introducing an extra connection cable 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.

2. The 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., one period; and within each spatial period, four SPWM modulated sinusoidal wave signals generated by the 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), four coarse second transmitting electrodes ( 2-2-2), a coarse third emitting electrode (2-2-3) and a coarse fourth emitting electrode (2-2-4) together form a coarse emitting electrode group (2-2), and the same four-way SPWM modulated sinusoidal wave signal is also applied to these four emitting electrodes; the first special-shaped primary reflecting electrode (1-1) and the second special-shaped primary reflecting 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 (1), and the first special-shaped primary reflecting electrode (1-1) and the second special-shaped primary reflecting electrode (1-2) have differences in spatial distribution, and there is an angle deviation of half a period between the two in spatial position, thereby forming a differential signal output; the polar coordinate equations of the upper and lower envelope lines of the special-shaped reflecting plates of the first special-shaped primary reflecting electrode (1-1) and the second special-shaped primary reflecting electrode (1-2) are: Wherein R is the radius 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 electrode (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 variable capacitors C a (Δθ),C b (Δθ),C c (Δθ),C d (Δθ); and because the transmitting electrode in each cycle is applied with four excitation signals with different phases, 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 relative dielectric constant respectively; the output signal on the first special-shaped primary reflective electrode (1-1) is obtained: Where 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, and S a , S b , S c , S d are the facing surface areas of the first special-shaped primary reflective electrode (1-1) and the four emitting electrodes in each period, and t is the time; Then, according to the polar coordinate equations of the upper and lower envelopes of formula (1) and substituting them into formula (2) through area integration, the output signal of the first special-shaped primary reflective electrode (1-1) when the moving electrode plate (1) rotates by an angle Δθ is obtained: U(Δθ,t)=K'sin(ωt-NΔθ) (3) Where 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 reflection electrode (1-2) which is half a spatial angle period different from the first special-shaped primary reflection electrode (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 an excellent signal-to-noise ratio is obtained, thereby obtaining Accurate angle information within the range can be used to complete high-precision measurement of rotation angles.

3. The high-precision absolute rotation angle sensor according to claim 2, 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, thereby completing 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 is obtained, thereby completing the high-precision absolute measurement of the rotation angle.

4. 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 of 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 is subjected to differential processing by the differential circuit and then enters the bandpass filter 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 the shaping circuit, and the sine fundamental wave is converted 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 distinguished and integrated, thereby realizing high-precision absolute measurement of the rotation angle.

5. 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.

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