Capacitive angular displacement sensor based on three-phase excitation and method for measuring angular displacement

Abstract

The application discloses a kind of based on three-phase excitation's capacitance angle displacement sensor and the method for angular displacement measurement, including stator and the rotor coaxial with stator, the upper surface of the base of stator is provided with a circle of excitation electrode, including A excitation phase, B excitation phase and C excitation phase, three excitation phases are respectively used to exert three-way phase difference 120 ° of alternating current excitation signal in turn;The lower surface of the base of rotor is provided with a circle of induction electrode, including first induction group, second induction group, third induction group and fourth induction group, wherein first induction group and third induction group differential output first road wave signal, second induction group and fourth induction group differential output second road wave signal;Further include signal processing unit, for first road wave signal and second road wave signal are carried out data fusion and displacement solution, obtain angular displacement value.The application relative to prior art resolution is higher, hardware is simpler, and differential structure suppresses common-mode interference, improves signal-to-noise ratio and measurement accuracy.

Description

Technical Field

[0001] This invention relates to the field of measurement and sensing technology, specifically to a capacitive angular displacement sensor based on three-phase excitation and a method for measuring angular displacement. Background Technology

[0002] With the rapid development of precision manufacturing, aerospace, and defense industries, increasingly higher demands are being placed on the measurement accuracy and resolution of angular displacement sensors. Capacitive angular displacement sensors, due to their simple structure, high measurement accuracy, high sensitivity, and suitability for dynamic measurement, are widely used in angle positioning and monitoring fields such as industrial automation, automotive, aerospace, and military.

[0003] In recent years, domestically developed time-grating angular displacement sensors using clock pulses as the displacement measurement reference have been developed. For example, Chinese patent CN103968750A discloses an electric field-type time-grating angular displacement sensor. This sensor has a simple structure, low power consumption, low requirements for mechanical installation accuracy, and can achieve high-precision angular displacement measurement. However, these time-grating angular displacement sensors using four-phase excitation still face challenges in further improving their performance: First, four-phase excitation requires four independent excitation signal sources, resulting in relatively complex hardware circuitry and a large circuit space requirement, which is not conducive to the miniaturization and integration of the sensor. Second, the four-phase excitation sensor arranges four excitation electrodes within one cycle, resulting in a large central angle of the cycle, which limits further improvement in sensor resolution. If the resolution is improved by reducing the central angle of the cycle (i.e., reducing the central angle of the electrodes), it will increase the manufacturing difficulty; if the resolution is improved by secondary modulation, it will lead to problems such as decreased signal-to-noise ratio and crosstalk.

[0004] Therefore, further consideration needs to be given to how to improve the resolution of the angular displacement sensor while simplifying the hardware circuit. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is: how to provide a capacitive angular displacement sensor based on three-phase excitation that can simplify hardware circuits, improve resolution and have a high signal-to-noise ratio.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A capacitive angular displacement sensor based on three-phase excitation includes a stator and a rotor coaxially mounted with the stator. The upper surface of the stator base is parallel to and faces the lower surface of the rotor base with a gap. An excitation electrode is arranged around the upper surface of the stator base along its axis. The excitation electrode includes excitation phase A, excitation phase B and excitation phase C. The three excitation phases are used to apply three AC excitation signals with phases 120° out of phase.

[0008] A ring of induction electrodes is arranged around the lower surface of the rotor base along its axis. The induction electrodes include a first induction group, a second induction group, a third induction group, and a fourth induction group. The first induction group and the third induction group differentially output a first traveling wave signal, and the second induction group and the fourth induction group differentially output a second traveling wave signal.

[0009] It also includes a signal processing unit, which performs data fusion and displacement calculation on the first traveling wave signal and the second traveling wave signal to obtain the angular displacement value.

[0010] In this invention, three-phase excitation is used instead of traditional four-phase excitation, reducing the number of excitation sources from four to three. This results in simpler hardware circuitry, smaller footprint, and lower design difficulty and cost. Furthermore, three-phase excitation requires only three excitation electrodes per cycle, reducing the cycle center angle by approximately 1 / 4 compared to four-phase excitation. Under the same manufacturing conditions, this effectively improves the sensor's resolution. Simultaneously, the differential structure of the four sets of sensing electrodes effectively suppresses common-mode interference and improves the signal-to-noise ratio. The signal processing unit fuses the two traveling wave signals to further eliminate harmonic errors at specific frequencies, thereby improving measurement accuracy.

[0011] As an optimization, the excitation electrode is composed of several annular electrode plates arranged at equal intervals around the stator axis, wherein the first... A group of sector-shaped annular electrodes are connected to form the A excitation phase. A group of sector-shaped annular electrodes are connected to form the B excitation phase. A group of fan-shaped annular electrodes are connected together to form the C-excitation phase. Take all integers from 0 to M-1, where M is a positive integer, representing the number of pole pairs of the excitation electrodes. Each pair consists of three adjacent sector-shaped annular pole pieces. The three-phase excitation signals are applied to the three sets of pole pieces respectively, forming a rotating alternating electric field in the gap between the stator and rotor. The three-phase pole pieces are arranged alternately on the circumference, which helps to eliminate spatial harmonics and reduce measurement errors.

[0012] As an optimization, the sensing electrode is composed of several sensing electrode plates arranged at equal intervals around the rotor axis, wherein the first... The sensing electrodes are connected together to form the first sensing group, and the second sensing electrode... The sensing electrodes are connected together to form the second sensing group, the first... The induction electrodes are connected together to form the third induction group. The inductive electrodes are connected together to form the fourth inductive group. We take all integers from 0 to N-1, where N is a positive integer, representing the number of pole pairs of the induction electrodes. The arrangement of the four sets of induction electrodes matches the electric field distribution of the three-phase excitation electrodes, enabling stable induction of traveling wave signals.

[0013] As an optimization, the shape of the sensing electrode can be double sine, oblique cosine, square, or rhomboid. Those skilled in the art can flexibly choose according to specific accuracy requirements and manufacturing costs, thus expanding the applicability of the sensor.

[0014] As an optimization, the AC excitation signal is a sinusoidal signal with the same frequency and amplitude. The condition of the same frequency and amplitude ensures the stability and uniformity of the traveling wave signal, avoiding measurement errors caused by inconsistent amplitude or frequency differences.

[0015] As an optimization, the first traveling wave signal is obtained by subtracting the output signals of the first and third sensing groups, and the second traveling wave signal is obtained by subtracting the output signals of the second and fourth sensing groups. The two differential traveling wave signals sample displacement information from different spatial angles, providing a reliable data foundation for subsequent data fusion.

[0016] A method for measuring angular displacement using the aforementioned sensor involves applying three AC excitation signals, each 120° out of phase, to excitation phases A, B, and C. The output signals of the first and third sensing groups are differentially output to obtain a first traveling wave signal, and the output signals of the second and fourth sensing groups are differentially output to obtain a second traveling wave signal. The first and second traveling wave signals are then fused and displacement calculated to obtain the angular displacement value. This invention utilizes the characteristics of the three-phase excitation and four sets of sensing electrodes in the sensor structure to ensure high-precision and high-reliability absolute angular displacement measurement over the entire 360° range. The algorithm is simple and reliable.

[0017] As an optimization, the first and second traveling wave signals are shaped into square wave signals and then compared in phase. The angular displacement value is calculated based on the phase difference between the two square wave signals. This simplifies the hardware circuit design and reduces the difficulty of signal processing.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The sensor in this invention only requires three excitation sources. Compared with the current four-phase excitation scheme, its hardware system is simpler, reducing circuit space and lowering the difficulty and cost of circuit design.

[0020] (2) The excitation electrode of the present invention has only three excitation electrodes in one cycle. Compared with the existing four-phase excitation sensor which has four excitation electrodes in one cycle, the central angle of the cycle is reduced by about 1 / 4, thereby improving the resolution by about 1 / 4.

[0021] (3) The sensing electrodes adopt two sets of differential structures (differential between the first and third sensing groups, and differential between the second and fourth sensing groups), which increases the utilization rate of the sensing area, suppresses common-mode interference, improves the signal-to-noise ratio and measurement accuracy, and enhances environmental and industrial adaptability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the sensor structure in this invention;

[0023] Figure 2 This is a top view of the stator in this invention;

[0024] Figure 3 This is a bottom view of the rotor in this invention;

[0025] Figure 4 This is a block diagram illustrating the signal processing principle in this invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0027] The capacitive angular displacement sensor based on three-phase excitation in this specific embodiment, such as... Figure 1 As shown, it includes a stator 1 and a rotor 2 coaxially mounted with the stator 1. The upper surface of the base of the stator 1 is parallel to and directly opposite the lower surface of the base of the rotor 2, with a gap of 0.4 mm.

[0028] A ring of excitation electrodes 11 is arranged around the upper surface of the stator 1 base along its axial direction. The excitation electrodes 11 include excitation phase A, excitation phase B and excitation phase C. Excitation phase A, excitation phase B and excitation phase C are respectively connected to three sinusoidal AC excitation signals of the same frequency and equal amplitude with phases 120° apart. A ring of induction electrodes 21 is arranged around the lower surface of the rotor 2 base along its axial direction. The induction electrodes 21 include a first induction group, a second induction group, a third induction group and a fourth induction group. The first induction group and the third induction group differentially output a first traveling wave signal, and the second induction group and the fourth induction group differentially output a second traveling wave signal.

[0029] The sensor also includes a signal processing unit, which performs data fusion and displacement calculation on the first and second traveling wave signals to obtain the angular displacement value.

[0030] Stator structure: such as Figure 2 As shown, an excitation electrode 11 is arranged around the axial direction on the upper surface of the stator 1 substrate. The excitation electrode 11 is composed of several fan-shaped annular plates arranged at equal intervals around the axial direction of the stator 1. The radial height and central angle of the fan-shaped annular plates are the same. In this embodiment, the number of pole pairs M=15, and every three adjacent fan-shaped annular plates form a pole pair. The central angle of each pole pair is 24°, and there are a total of 45 fan-shaped annular plates. The inner radius of each fan-shaped annular plate is 34mm, the radial height is 12mm, the central angle of each fan-shaped annular plate is 4°, and the central angle corresponding to the interval between adjacent fan-shaped annular plates is 4°.

[0031] No. The 1st, 4th, 7th, ..., 43rd sector-shaped annular electrodes are connected by leads to form a group, constituting the A excitation phase; The 2nd, 5th, 8th, ..., 44th sector-shaped electrode plates are connected by leads to form a group, constituting the B excitation phase; Each sector-shaped annular electrode (i.e., the 3rd, 6th, 9th, ..., 45th) is connected by leads to form a group, constituting the C excitation phase. Take all integers from 0 to 14 in sequence.

[0032] Phases A, B, and C are respectively subjected to three sinusoidal AC excitation signals of the same frequency and amplitude, with a phase difference of 120°. , and , where H is the signal amplitude and ω is the angular frequency.

[0033] Rotor structure: such as Figure 3 As shown, a ring of induction electrodes 21 is arranged around the lower surface of the rotor 2 substrate along its axial direction. The induction electrodes 21 are composed of several induction plates arranged at equal intervals around the axial direction of the rotor 2. The induction plates are double sinusoidal plates. The shape of the double sinusoidal plates is a closed axisymmetric figure enclosed by two sinusoidal curves with equal amplitude and a phase difference of 180° in the interval [0, π].

[0034] In this embodiment, the number of pole pairs N=15, and each pair is formed by four adjacent double sinusoidal pole pieces, for a total of 60 double sinusoidal pole pieces. The central angle corresponding to the width of each double sinusoidal pole piece along the circumferential direction is 5°, the central angle corresponding to the interval between adjacent induction pole pieces is 1°, and the radial height is 10mm.

[0035] No. The first induction group consists of two double sinusoidal pole pieces (i.e., the 1st, 5th, 9th, ..., 57th pole pieces) connected by leads; The 2nd, 6th, 10th, ..., 58th double sinusoidal pole pieces are connected by leads to form a group, constituting the second induction group; The 3rd, 7th, 11th, ..., 59th double sinusoidal pole pieces are connected by leads to form a group, constituting the third induction group; The 4th, 8th, 12th, ..., 60th double sinusoidal pole pieces are connected by leads to form a group, constituting the fourth induction group. Take all integers from 0 to 14 in sequence.

[0036] The first and third sensing groups are differential structures, as are the second and fourth sensing groups. The output signals of the first and third sensing groups are subtracted to obtain the first traveling wave signal, and the output signals of the second and fourth sensing groups are subtracted to obtain the second traveling wave signal.

[0037] In other embodiments, the shape of the sensing electrode can also be oblique cosine, square or rhomboid, as long as the sinusoidal relationship between area change and displacement can be achieved. Those skilled in the art can choose a suitable shape according to actual needs.

[0038] Signal processing procedures: such as Figure 4 As shown, during operation, rotor 2 rotates about the axis relative to stator 1. The measurement process is as follows:

[0039] First, three sinusoidal AC excitation signals of the same frequency and amplitude with a phase difference of 120° are applied to excitation phases A, B, and C respectively. The three excitation signals are applied simultaneously to form an alternating electric field in the gap between stator 1 and rotor 2.

[0040] Due to the rotation of rotor 2, the coupling area between induction electrode 21 and excitation electrode 11 changes. After differential processing by the subtraction circuit, the output signals of the first induction group and the third induction group are used to obtain the first traveling wave signal. The output signals of the second and fourth induction groups are differentially processed by a subtraction circuit to obtain the second traveling wave signal. .

[0041] The two traveling wave signals are processed into square wave signals by shaping circuits and input to a signal processing unit (such as an FPGA or microcontroller) for phase comparison. The signal processing unit compares the phase difference between the two square wave signals and calculates the angular displacement value based on the conversion relationship between phase difference and angular displacement.

[0042] Data fusion refers to the comprehensive processing of displacement information carried by two traveling wave signals. The two traveling wave signals are shaped into square wave signals and then compared in phase. The angular displacement value is calculated based on the phase difference between the two square wave signals. Data fusion using two traveling wave signals can effectively eliminate harmonic errors at specific frequencies and further improve measurement accuracy.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the technical solutions. Those skilled in the art should understand that any modifications or equivalent substitutions to the technical solutions of the present invention without departing from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A capacitive angular displacement sensor based on three-phase excitation, comprising a stator and a rotor coaxially mounted with the stator, wherein the upper surface of the stator base is parallel to and directly opposite the lower surface of the rotor base with a gap between them, characterized in that: A ring of excitation electrodes is arranged around the upper surface of the stator matrix along its axis. The excitation electrodes include excitation phase A, excitation phase B and excitation phase C. The three excitation phases are used to apply three AC excitation signals with phases 120° apart. A ring of induction electrodes is arranged around the lower surface of the rotor base along its axis. The induction electrodes include a first induction group, a second induction group, a third induction group, and a fourth induction group. The first induction group and the third induction group differentially output a first traveling wave signal, and the second induction group and the fourth induction group differentially output a second traveling wave signal. It also includes a signal processing unit, which performs data fusion and displacement calculation on the first traveling wave signal and the second traveling wave signal to obtain the angular displacement value.

2. The capacitive angular displacement sensor based on three-phase excitation according to claim 1, characterized in that: The excitation electrode is composed of several annular electrode plates arranged at equal intervals around the stator axis, wherein the first... A group of sector-shaped annular electrodes are connected to form the A excitation phase. A group of sector-shaped annular electrodes are connected to form the B excitation phase. A group of fan-shaped annular electrodes are connected together to form the C-excitation phase. Take all integers from 0 to M-1 in sequence, where M is a positive integer representing the number of excitation electrodes.

3. The capacitive angular displacement sensor based on three-phase excitation according to claim 1, characterized in that: The sensing electrode is composed of several sensing electrode plates arranged at equal intervals around the rotor axis, wherein the first... The sensing electrodes are connected together to form the first sensing group, and the second sensing electrode... The sensing electrodes are connected together to form the second sensing group, the first... The induction electrodes are connected together to form the third induction group. The inductive electrodes are connected together to form the fourth inductive group. Take all integers from 0 to N-1 in sequence, where N is a positive integer and represents the number of pairs of the induction electrode.

4. The capacitive angular displacement sensor based on three-phase excitation according to claim 1, characterized in that: The inductive electrode is shaped as a double sine, a diagonal cosine, a square, or a rhombus.

5. The capacitive angular displacement sensor based on three-phase excitation according to claim 1, characterized in that: The AC excitation signal is a sinusoidal signal with the same frequency and amplitude.

6. The capacitive angular displacement sensor based on three-phase excitation according to claim 1, characterized in that: The first traveling wave signal is obtained by subtracting the output signal of the first sensing group from the output signal of the third sensing group, and the second traveling wave signal is obtained by subtracting the output signal of the second sensing group from the output signal of the fourth sensing group.

7. A method for measuring angular displacement using the sensor described in any one of claims 1 to 6, characterized in that: Three AC excitation signals with a phase difference of 120° are applied to the excitation phases A, B, and C respectively; the output signals of the first and third induction groups are differentially output to obtain a first traveling wave signal, and the output signals of the second and fourth induction groups are differentially output to obtain a second traveling wave signal; the first and second traveling wave signals are fused and displacement is calculated to obtain an angular displacement value.

8. The method for measuring angular displacement according to claim 7, characterized in that: The first and second traveling wave signals are shaped into square wave signals and then compared in phase. The angular displacement value is calculated based on the phase difference between the two square wave signals.

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