A large range high-precision variable capacitance displacement sensor

Abstract

The application discloses a large-range high-precision variable-capacitance displacement sensor, which comprises two core components of a moving electrode plate and a static electrode plate. The moving electrode plate above the static electrode plate can move in the horizontal direction. The static electrode plate comprises transmitting electrodes and two groups of receiving electrodes for accurate measurement, and the moving electrode plate comprises two groups of corresponding reflecting electrodes. In the movement of the moving electrode plate, the signal phase is demodulated through capacitive coupling, so that the high-precision displacement measurement is completed. The sensor has the advantages of high resolution, simple structure, high precision, good environmental adaptability and the like under the requirement of considering the large range.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precision displacement measurement, and particularly relates to a large-range high-precision variable-capacitance displacement sensor. BACKGROUND

[0002] At present, higher requirements are put forward for precision displacement measurement devices in important industrial fields such as aerospace, microelectronics, biomedicine and optics. At the same time, how to meet the requirements of large range and high precision has become the goal of researchers. At present, in the measurement of high-precision large-range displacement, photoelectric and electromagnetic sensors still occupy a dominant position. Among them, photoelectric displacement sensors are widely used due to their mature technology and high precision. However, due to the presence of optical devices inside, the anti-vibration ability is poor, and it is sensitive to dust and oil pollution environment, and the working environment requirement is high. The electromagnetic magnetic grid displacement sensor measures through electromagnetic induction, but it is sensitive to electromagnetic interference and difficult to achieve high-precision measurement in a harsh electromagnetic environment. In contrast, capacitive displacement sensors have the advantages of non-contact measurement, simple structure, high resolution and strong anti-interference ability in the field of high-precision displacement measurement, and have been popularized and applied by researchers in the field of precision measurement.

[0003] However, the existing capacitive displacement sensor mostly adopts the method of directly measuring the micro-capacitance to complete the displacement measurement. Due to the electrical characteristics of the capacitive structure itself, the resolution and precision of this type of sensor will be greatly reduced in the case of large range, and will be disturbed by environmental factors such as parasitic capacitance, temperature and humidity, thereby reducing the accuracy of the capacitive displacement sensor. This type of sensor cannot meet the common requirements of large range and high precision, greatly affecting the use scene of this type of sensor. SUMMARY

[0004] In order to overcome the technical problems existing in the prior art, the present application aims to provide a capacitive displacement sensor and signal demodulation method with simple structure, clear signal demodulation method, high measurement precision, and can meet the requirements of large range and high precision.

[0005] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0006] The utility model provides a large range high accuracy variable capacitance displacement sensor, including two parts of dynamic plate 1 and static plate 2, wherein dynamic plate 1 is located on the top of static plate 2, and dynamic plate 1 can move in the horizontal direction relative to static plate 2, in order to satisfy the measurement of high accuracy displacement, both plates are provided with the electrode structure with periodic arrangement, including the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2 in the horizontal direction on dynamic plate 1 and the transmitting electrode group 2-1 on static plate 2, and the adjacent heteromorphic envelope petal-shaped plate of first heteromorphic petal-shaped first level reflecting plate 1-1 and second heteromorphic petal-shaped first level reflecting plate 1-2 has the interval in the horizontal direction, thereby forming the differential structure, when dynamic plate 1 moves in the horizontal direction relative to static plate 2, the capacitance coupling between the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2 and the transmitting electrode group 2-1 opposite above the transmitting electrode group 2-1 changes, and the measurement of displacement is completed through the differential demodulation of the signal on the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2.

[0007] In order to optimize the wiring mode of the sensor, avoid the existence of lead cable on dynamic plate 1 and avoid the influence of cable on the stability of the sensor, the outer side of the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2 is respectively provided with the first rectangular second level reflecting plate 1-3 and the second rectangular second level reflecting plate 1-4, the two sides of the transmitting electrode group 2-1 are respectively provided with the first receiving electrode 2-2 and the second receiving electrode 2-3 opposite to the positions of the first rectangular second level reflecting plate 1-3 and the second rectangular second level reflecting plate 1-4 respectively, wherein the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2 are electrically connected with the first rectangular second level reflecting plate 1-3 and the second rectangular second level reflecting plate 1-4 on dynamic plate 1 respectively, when dynamic plate 1 moves in the horizontal direction relative to static plate 2, the first rectangular second level reflecting plate 1-3 and the second rectangular second level reflecting plate 1-4 opposite above the first receiving electrode 2-2 and the second receiving electrode 2-3 form the capacitance structure between the first receiving electrode 2-2 and the second receiving electrode 2-3 respectively, the signal on the first heteromorphic petal-shaped first level reflecting plate 1-1 and the second heteromorphic petal-shaped first level reflecting plate 1-2 is conducted to the first receiving electrode 2-2 and the second receiving electrode 2-3 on static plate 2 respectively, and the first receiving electrode 2-2 and the second receiving electrode 2-3 are connected with the peripheral signal demodulation circuit 3, the differential signal on the first receiving electrode 2-2 and the second receiving electrode 2-3 is demodulated through the peripheral signal demodulation circuit 3, thereby the distance of dynamic plate 1 moving relative to static plate 2 can be measured, and the measurement of high accuracy displacement is completed.

[0008] The emitting electrode group 2-1 located on the static electrode plate 2 is composed of N groups of small rectangular electrode plates with the same size and equal spacing, and four small rectangular electrode plates are taken as a group, i.e. a period, and the equal periods are arranged on the static electrode plate 2; and in each spatial period, four SPWM modulated sinusoidal waves generated by the signal excitation circuit in the peripheral signal demodulation circuit 3 are respectively applied to the four emitting electrodes, i.e. the first emitting electrode 2-1-1, the second emitting electrode 2-1-2, the third emitting electrode 2-1-3 and the fourth emitting electrode 2-1-4, and the phases of the four SPWM modulated sinusoidal waves are 0, π / 2, π and 3π / 2 respectively.

[0009] The peripheral signal demodulation circuit 3 includes a signal excitation circuit, a differential circuit, a band-pass filter circuit, a shaping circuit, a phase discrimination circuit and a displacement operation module; in the signal excitation circuit, four SPWM modulated sinusoidal waves with different phases are generated by the FPGA control; the sinusoidal waves are applied to the emitting electrode group 2-1 as input signals of the sensor; the differential output signals of the sensor on the first receiving electrode 2-2 and the second receiving electrode 2-3 are acquired by the peripheral signal demodulation circuit 3, and after the differential processing by the differential circuit, the signals enter the band-pass filter circuit to eliminate the harmonic components and only retain the sinusoidal fundamental wave components 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 form, so as to facilitate the phase discrimination circuit to identify the phase of the output signal; similarly, the reference signal generated by the FPGA also undergoes the same filtering and shaping processing; the processed output signal and the reference signal are compared in phase by the phase discrimination circuit; finally, the high-frequency clock pulse counting method is adopted in the FPGA to calculate and process the demodulated phase signal, so as to realize the measurement of high-precision displacement.

[0010] The first and second irregular petal-shaped primary reflector plates 1-1 and 1-2 are composed of N f identical irregular envelope petal-shaped plates, which are arranged in equal periods on the dynamic electrode plate 1, and the first and second irregular petal-shaped primary reflector plates 1-1 and 1-2 are different in spatial distribution, and the difference between them in the horizontal direction is half the length of a spatial period, so as to form a differential signal output.

[0011] The upper and lower envelope equations of the irregular petal-shaped plate on the dynamic electrode plate 1 are as follows:

[0012]

[0013] wherein L is the length of the irregular petal-shaped plate, 2A is the width of the irregular petal-shaped plate, and the length of each period of the emitting electrode group 2-1 is L / N fi.e. the length of each transmitting electrode a = L / 4N f ; when the moving electrode plate 1 moves in the horizontal direction, the first irregular petal-shaped primary reflector plate 1-1 forms a variable capacitance C with the first, second, third and fourth transmitting electrodes 2-1-1, 2-1-2, 2-1-3 and 2-1-4 in each period a (Δx), C b (Δx), C c (Δx), C d (Δx); since each transmitting electrode in each period is applied with four-phase excitation signals with different phases, according to the corresponding equivalent circuit and parallel-plate capacitance expression where S is the relative surface area between the moving electrode plate and the static electrode plate, and d is the distance between the moving electrode plate and the static electrode plate; the output signal on the first irregular petal-shaped primary reflector plate 1-1 is obtained as:

[0014]

[0015] where K is the voltage amplitude of the four-phase excitation signals with different phases, ω is the angular frequency of the fundamental wave in the four-phase excitation signals with different phases, S a , S b , S c , S d are the opposite surface areas of the first irregular petal-shaped primary reflector plate 1-1 and the four transmitting electrodes in each period, respectively, and t is time; then, according to the upper and lower envelope line equations of formula (1) and by area integration into formula (2), the output signal of when the moving electrode plate (1) moves in the horizontal direction by Δx is obtained as:

[0016]

[0017] where a is the length of the irregular envelope petal-shaped plate on the first irregular petal-shaped primary reflector plate 1-1; similarly, the output signal on the first rectangular-shaped secondary reflector plate 1-2 which is electrically connected to the first irregular petal-shaped primary reflector plate 1-1 is also shown in formula (3), when the moving electrode plate 1 moves in the horizontal direction relative to the static electrode plate 2, the first rectangular-shaped secondary reflector plate 1-3 opposite the first receiving electrode 2-2 forms a capacitance structure with the first receiving electrode 2-2, and the capacitance value does not change during the movement, so the phase of the output signal shown in formula (3) is not affected, i.e. the output signal U'(Δx, t) on the first receiving electrode 2-2 is expressed as:

[0018]

[0019] Wherein K' is the output signal amplitude; further, because the moving electrode plate (1) is provided with the second special petal-shaped first-level reflecting electrode plate 1-2 which is horizontally different from the first special petal-shaped first-level reflecting electrode plate 1-1 by a length of L / 2N f Therefore, the second receiving electrode 2-3 will generate a differential signal opposite to the output signal of the first receiving electrode 2-2.

[0020] The moving electrode plate 1 and the static electrode plate 2 are printed by a circuit board.

[0021] Compared with the prior art, the present application has the following advantages:

[0022] 1. The large-range high-precision variable-capacitance displacement sensor adopts the technical means of capacitive coupling demodulation of signal phase to complete the measurement of displacement, and through the setting of multiple-period capacitive plates, the requirement of large-range displacement measurement can be realized, and on the basis of taking into account the large range, the sensor has high resolution, high precision and high reliability.

[0023] 2. Compared with the traditional capacitive displacement sensor, the large-range high-precision variable-capacitance displacement sensor uses the capacitive coupling to demodulate the signal phase to measure the displacement, which greatly reduces the interference of parasitic capacitance, temperature, humidity and other adverse environmental factors on the displacement measurement, and has high reliability and can adapt to adverse environments.

[0024] 3. The sensor plate is printed by a circuit board, and the reflective capacitive plate is arranged, and there is no signal line leading out on the moving electrode plate, so the structure is simple and compact, and the processing and installation are convenient.

[0025] 4. Compared with the traditional rectangular and triangular plates, the large-range high-precision variable-capacitance displacement sensor uses the special petal-shaped plate to increase the directly facing area of the capacitive plate, improve the signal-to-noise ratio of the output signal, and enhance the anti-interference ability of the sensor.

[0026] 5. The large-range high-precision variable-capacitance displacement sensor uses the high-frequency clock signal generated by the FPGA module in the peripheral signal demodulation circuit to complete the demodulation of the phase information and the calculation of the displacement, so that the resolution of the sensor can also reach the nanometer level under the requirement of taking into account the large range, which greatly expands the use scene of the sensor. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a three-dimensional schematic view of the large-range high-precision capacitive displacement sensor.

[0028] Figure 2 It is a top view of the large-range high-precision capacitive displacement sensor.

[0029] Figure 3 Fig. 1 is a schematic diagram of a moving electrode plate of a large-range high-precision capacitive displacement sensor according to the present application.

[0030] Figure 4 Fig. 2 is a schematic diagram of a stationary electrode plate of a large-range high-precision capacitive displacement sensor according to the present application.

[0031] Figure 5 Fig. 3 is a block diagram of a signal demodulation system of a large-range high-precision capacitive displacement sensor according to the present application.

[0032] Figure 6 Fig. 4 is a comparison diagram of an envelope of a special-shaped reflecting electrode plate and an envelope of a full-sine petal-shaped electrode plate of a large-range high-precision capacitive sensor according to the present application.

[0033] Figure 7 Fig. 5 is a schematic diagram of a relationship between a moving distance of a moving electrode plate and a phase of an output signal of a large-range high-precision capacitive sensor according to the present application. DETAILED DESCRIPTION

[0034] The present application will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0035] As Figure 1 , Figure 2 and Figure 3The application discloses a large-range high-precision capacitive displacement sensor, which comprises a moving electrode plate 1 and a static electrode plate 2, wherein the moving electrode plate 1 is located directly above the static electrode plate 2 and can move in the horizontal direction of the static electrode plate 2. In order to meet the high-precision displacement measurement, the two electrode plates are provided with electrode structures arranged periodically, which comprises first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 arranged in the horizontal direction on the moving electrode plate 1 and a transmitting electrode group 2-1 arranged on the static electrode plate 2, and the adjacent shaped envelope petal-shaped electrode plates of the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 are spaced apart in the horizontal direction, so that a differential structure is formed. When the moving electrode plate 1 moves in the horizontal direction relative to the static electrode plate 2, the capacitive coupling between the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 and the transmitting electrode group 2-1 changes, and the displacement measurement is completed by differentially demodulating the signals on the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2. Preferably, in order to optimize the wiring mode of the sensor to a greater extent, avoid the existence of the lead cable on the moving electrode plate 1 and avoid the influence of the cable on the stability of the sensor, the application introduces first and second rectangular second-level reflection electrode plates 1-3 and 1-4 arranged on the two sides of the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 on the moving electrode plate 1, and introduces first and second receiving electrodes 2-2 and 2-3 arranged on the two sides of the transmitting electrode group 2-1 on the static electrode plate 2, wherein the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 are electrically connected with the first and second rectangular second-level reflection electrode plates 1-3 and 1-4 on the moving electrode plate 1. Similarly, when the moving electrode plate 1 moves in the horizontal direction relative to the static electrode plate 2, the first and second rectangular second-level reflection electrode plates 1-3 and 1-4 form a capacitive structure between the first and second receiving electrodes 2-2 and 2-3, and the signals on the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 are conducted to the first and second receiving electrodes 2-2 and 2-3 on the static electrode plate 2. The first and second receiving electrodes 2-2 and 2-3 are connected with a peripheral signal demodulation circuit 3, the differential signals on the first and second receiving electrodes 2-2 and 2-3 are demodulated by the peripheral signal demodulation circuit 3, and thus the distance that the moving electrode plate 1 moves relative to the static electrode plate 2 can be measured, and the high-precision displacement measurement is completed.

[0036] As Figure 4As shown, the emitter electrode group 2-1 located on the stationary electrode plate 2 is composed of N groups of small rectangular electrode plates of the same size and equal spacing, arranged in a cycle of four small rectangular electrode plates. Within each spatial cycle, four SPWM modulated sine waves generated by the signal excitation circuit in the peripheral signal demodulation circuit 3 are applied to the four emitter electrodes: the first emitter electrode 2-1-1, the second emitter electrode 2-1-2, the third emitter electrode 2-1-3, and the fourth emitter electrode 2-1-4, respectively. The phases of these four SPWM modulated sine waves are 0, π / 2, π, and 3π / 2, respectively.

[0037] like Figure 5 As shown, the peripheral signal demodulation circuit 3 includes a signal excitation circuit, a differential circuit, an active bandpass filter circuit, a shaping circuit, a phase detection circuit, and a displacement calculation module. In the signal excitation circuit, four SPWM modulated sine waves with different phases are generated by FPGA control. These sine waves are applied to the transmitting electrode group 2-1 as the input signal of the sensor. The use of FPGA not only precisely controls the phase difference of each signal, but also ensures the stability and consistency of the signal, thereby ensuring the performance and measurement accuracy of the sensor. When the relative position between the moving electrode 1 and the stationary electrode 2 changes, the capacitive coupling between the transmitting electrode group 2-1 and the first irregular petal-shaped primary reflective electrode 1-1 and the second irregular petal-shaped primary reflective electrode 1-2 changes. The differential output signal located on the first receiving electrode 2-2 and the second receiving electrode 2-3 on the stationary electrode 2 is acquired by the peripheral signal demodulation circuit 3. This signal is differentially processed by the differential circuit and then enters the bandpass filter circuit to eliminate the harmonic components and retain only the corresponding sinusoidal fundamental component of the SPWM sine modulated wave. Next, the signal is amplified and shaped by a shaping circuit, converting the sinusoidal fundamental waveform into a square wave waveform to facilitate phase identification of the output signal by the subsequent phase detector circuit. Similarly, the reference signal generated by the FPGA undergoes the same filtering and shaping process. The processed output signal and the reference signal are then compared in phase by the phase detector circuit. Finally, a high-frequency clock pulse counting method is used in the FPGA to calculate the demodulated phase signal, thereby obtaining the corresponding displacement value and achieving high-precision displacement measurement. This processing method not only improves the purity and stability of the signal but also ensures the accuracy of the displacement measurement. Through this method, the sensor can maintain efficient and accurate measurement performance in various complex environments.

[0038] like Figure 3 and Figure 6As shown, preferably, in order to reduce the interference of a large number of harmonic components in the output signal on the first receiving electrode 2-2 and the second receiving electrode 2-3, the facing area of the plate between the transmitting electrode group 2-1 and the first and second shaped petal-shaped first reflecting plate 1-1 and 1-2 is increased when the capacitive coupling is increased, the signal-to-noise ratio of the effective information in the output signal is further improved, and the measurement accuracy of the sensor is improved. Compared with the traditional triangular, rectangular and sinusoidal plate setting, the first and second shaped petal-shaped first reflecting plate 1-1 and 1-2 in the application are composed of N f equal-sized and equally-spaced shaped envelope petal-shaped plates, which are arranged in equal periods on the moving plate 1, and the first and second shaped petal-shaped first reflecting plate 1-1 and 1-2 have differences in spatial distribution, and the two differ by half the length of the spatial period in the horizontal direction, so as to form a differential signal output, and then the differential output signal conducted by the first and second rectangular-shaped second reflecting plate 1-3 and 1-4 on the first receiving electrode 2-2 and the second receiving electrode 2-3 is respectively subjected to differential signal demodulation in the peripheral signal demodulation circuit 3, so as to obtain accurate displacement information and complete the measurement of displacement. Further, the plates are printed on a circuit board.

[0039] Taking one of the two differential signals as an example, i.e., the signal on the first receiving electrode 2-2 is taken as an example. The envelope equation of the first shaped petal-shaped plate on the moving plate 1 is:

[0040]

[0041] Wherein, L is the length of the shaped petal-shaped plate, 2A is the width of the shaped petal-shaped plate, and the length of each period of the transmitting electrode group 2-1 is L / N f , i.e., the length of each transmitting electrode a = L / 4N f When the moving plate 1 moves in the horizontal direction, the shaped petal-shaped first reflecting plate 1-1 and the first, second, third and fourth transmitting electrodes 2-1-1, 2-1-2, 2-1-3 and 2-1-4 in each period form variable capacitances C a (Δx), C b (Δx), C c (Δx), C d (Δx). Since each period of the transmitting electrode applies four excitation signals with different phases, according to the equivalent circuit of the sensor, the output signal on the shaped petal-shaped first reflecting plate 1-1 is:

[0042]

[0043] In the formula, K represents the voltage amplitude of the four excitation signals with different phases, and ω represents the angular frequency of the fundamental wave among the four excitation signals with different phases. Furthermore, based on the expression for parallel plate capacitance... Where S is the relative surface area between the moving plate and the stationary plate, and d is the distance between the moving plate and the stationary plate. Simplifying equation (2), we get:

[0044]

[0045] Here S a S b S c S d Let be the surface area of ​​the first irregular petal-shaped primary reflective electrode 1-1 and the four emitting electrodes in each cycle. Then, according to the upper and lower envelope equations written in equation (1) and by substituting the area integral into equation (3), we can obtain the output signal on the first irregular petal-shaped primary reflective electrode 1-1 when the moving electrode 1 moves Δx in the horizontal direction relative to the stationary electrode 1:

[0046]

[0047] a is the length of the irregularly shaped petal-shaped primary reflective plate (1-1); similarly, the output signal of the first rectangular secondary reflective plate 1-3, which is electrically connected to the first irregularly shaped petal-shaped primary reflective plate 1-1, is also shown in equation (4). When the moving plate 1 moves horizontally relative to the stationary plate 2, a capacitor structure is formed between the first rectangular secondary reflective plate 1-3 above the first receiving electrode 2-2 and the first receiving electrode 2-2. During the movement, the capacitance value of the capacitor does not change. Therefore, it does not affect the phase of the output signal shown in equation (4). That is, the expression of the output signal U'(Δx,t) on the first receiving electrode 2-2 is:

[0048]

[0049] Where K' is the amplitude of the output signal. Furthermore, because the moving electrode 1 is provided with a length (L / 2N) that differs from the first irregularly shaped petal-shaped primary reflective electrode 1-1 in the horizontal direction by half a spatial period. f The second irregularly shaped petal-shaped primary reflective electrode 1-2, therefore, will generate a differential signal on the second receiving electrode 2-3 that is opposite to the output signal of the first receiving electrode 2-2.

[0050] like Figure 7As shown, and by observing equation (5), when the moving electrode plate 1 moves, the differential output signals on the first receiving electrode 2-2 and the second receiving electrode 2-3 will change in phase through the capacitive coupling of the emission electrode group 2-1 and the first and second shaped petal-shaped first-level reflection electrode plates 1-1 and 1-2 in each cycle, and the change is a linear change, so the displacement information can be obtained by phase discrimination of the differential output signals, the precise displacement measurement is completed, and this measurement method can expand multiple cycles of emission electrodes while ensuring that the resolution and accuracy remain unchanged to achieve the requirement of large-range displacement measurement, so that the sensor can meet the requirements of large range and high precision at the same time, complete the corresponding displacement measurement task, and greatly expand the use application scenarios of the sensor.

Claims

1. A large-range, high-precision variable capacitance displacement sensor, characterized in that: It comprises two parts: a moving electrode plate (1) and a stationary electrode plate (2). The moving electrode plate (1) is located directly above the stationary electrode plate (2), and the moving electrode plate (1) can move horizontally relative to the stationary electrode plate (2). To meet the requirements of high-precision displacement measurement, both electrodes are provided with periodically arranged electrode structures, including a first irregularly shaped petal-shaped primary reflective electrode plate (1-1) and a second irregularly shaped petal-shaped primary reflective electrode plate (1-2) located on the moving electrode plate (1) along the horizontal direction, and an emitting electrode group (2-1) located on the stationary electrode plate (2). The first irregularly shaped petal-shaped primary reflective electrode plate (1-1) and the second irregularly shaped petal-shaped primary reflective electrode plate (1-2) are arranged horizontally along the moving electrode plate (1). The adjacent irregularly shaped petal-shaped primary reflective plates (1-2) are spaced apart in the horizontal direction, thus forming a differential structure. When the moving plate (1) moves in the horizontal direction relative to the stationary plate (2), the capacitive coupling between the first irregularly shaped petal-shaped primary reflective plate (1-1) and the second irregularly shaped petal-shaped primary reflective plate (1-2) directly above the emitting electrode group (2-1) and the emitting electrode group (2-1) changes. The displacement is measured by differentially demodulating the signals on the first irregularly shaped petal-shaped primary reflective plate (1-1) and the second irregularly shaped petal-shaped primary reflective plate (1-2).

2. A large-range, high-precision variable capacitance displacement sensor according to claim 1, characterized in that: A first rectangular secondary reflector plate (1-3) and a second rectangular secondary reflector plate (1-4) are respectively disposed on the outer sides of the first irregularly shaped petal-shaped primary reflector plate (1-1) and the second irregularly shaped petal-shaped primary reflector plate (1-2); a first receiving electrode (2-2) and a second receiving electrode (2-3) are respectively disposed on both sides of the transmitting electrode group (2-1), which are respectively opposite to the positions of the first rectangular secondary reflector plate (1-3) and the second rectangular secondary reflector plate (1-4); wherein the first irregularly shaped petal-shaped primary reflector plate (1-1) and the second irregularly shaped petal-shaped primary reflector plate (1-2) are electrically connected to the first rectangular secondary reflector plate (1-3) and the second rectangular secondary reflector plate (1-4) on the moving electrode plate (1); when the moving electrode plate (1) moves horizontally relative to the stationary electrode plate (2), it is directly opposite the first receiving electrode (2-2). The first rectangular secondary reflective plate (1-3) and the second rectangular secondary reflective plate (1-4) above the second receiving electrode (2-3) form a capacitor structure with the first receiving electrode (2-2) and the second receiving electrode (2-3) respectively, so that the signals on the first irregular petal-shaped primary reflective plate (1-1) and the second irregular petal-shaped primary reflective plate (1-2) are respectively transmitted to the first receiving electrode (2-2) and the second receiving electrode (2-3) located on the stationary electrode plate (2); and the first receiving electrode (2-2) and the second receiving electrode (2-3) are connected to the peripheral signal demodulation circuit (3). After the differential signals on the first receiving electrode (2-2) and the second receiving electrode (2-3) are demodulated by the peripheral signal demodulation circuit (3), the distance of the moving electrode plate (1) relative to the stationary electrode plate (2) can be measured, and the high-precision displacement measurement is completed.

3. A large-range, high-precision variable capacitance displacement sensor according to claim 1, characterized in that: The emitter electrode group (2-1) located on the stationary electrode plate (2) is composed of N groups of small rectangular electrode plates of the same size and equal spacing. Four small rectangular electrode plates are arranged on the stationary electrode plate (2) as four emitter electrodes in one cycle. In each spatial cycle, four SPWM modulated sine waves generated by the signal excitation circuit in the peripheral signal demodulation circuit (3) are applied to the four emitter electrodes, namely the first emitter electrode (2-1-1), the second emitter electrode (2-1-2), the third emitter electrode (2-1-3), and the fourth emitter electrode (2-1-4), respectively. The phases of these four SPWM modulated sine waves are 0, π / 2, π, and 3π / 2, respectively.

4. A large-range, high-precision variable capacitance displacement sensor according to claim 3, characterized in that: The peripheral signal demodulation circuit (3) includes a signal excitation circuit, a differential circuit, a bandpass filter circuit, a shaping circuit, a phase detection circuit, and a displacement calculation module; in the signal excitation circuit, four SPWM modulated sine waves with different phases are generated by FPGA control. These sine waves are applied to the transmitting electrode group (2-1) as the input signal of the sensor; the sensor differential output signal on the first receiving electrode (2-2) and the second receiving electrode (2-3) is acquired by the peripheral signal demodulation circuit (3). After differential processing by the differential circuit, the signal enters the bandpass filter circuit to eliminate the harmonic components and retain only 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 phase detector circuit can identify the phase of the output signal; similarly, the reference signal generated by the FPGA also undergoes the same filtering and shaping process; the processed output signal and the reference signal are compared in phase by the phase detector circuit; finally, the high-frequency clock pulse counting method is used in the FPGA to calculate and process the demodulated phase signal to achieve high-precision displacement measurement.

5. A large-range, high-precision variable capacitance displacement sensor according to claim 1, characterized in that: The first irregularly shaped petal-shaped primary reflective electrode (1-1) and the second irregularly shaped petal-shaped primary reflective electrode (1-2) are made of N f It consists of two irregularly shaped petal-shaped electrodes of the same size, which are arranged periodically on the moving electrode (1). The first irregularly shaped petal-shaped primary reflective electrode (1-1) and the second irregularly shaped petal-shaped primary reflective electrode (1-2) are spatially different, and the two are separated by half a spatial period in the horizontal direction, so as to form a differential signal output.

6. A large-range, high-precision variable capacitance displacement sensor according to claim 5, characterized in that: The equations of the upper and lower envelopes of the irregular petal-shaped electrode plate located on the moving electrode plate (1) are as follows: Where L is the length of the irregular petal-shaped electrode, 2A is the width of the irregular petal-shaped electrode, and the length of each cycle of the emitting electrode group (2-1) is L / N. f That is, the length of each emitting electrode is a = L / 4N f When the moving electrode (1) moves in the horizontal direction, the irregularly shaped petal-shaped primary reflective electrode (1-1) forms a variable capacitor C with the first emitting electrode (2-1-1), the second emitting electrode (2-1-2), the third emitting electrode (2-1-3), and the fourth emitting electrode (2-1-4) in each cycle. a (Δx),C b (Δx),C c (Δx),C d (Δx); and since the emitter electrode in each cycle is subjected to four excitation signals with different phases, therefore, according to the corresponding equivalent circuit and the expression for the parallel plate capacitance... Where S is the relative surface area between the moving electrode and the stationary electrode, and d is the distance between the moving electrode and the stationary electrode; the output signal on the irregularly shaped petal-shaped primary reflective electrode (1-1) is obtained: In the formula, K represents the voltage amplitude of the four excitation signals with different phases, ω represents the angular frequency of the fundamental wave among the four excitation signals with different phases, and S... a S b S c S d These are the facing surface areas of the irregular petal-shaped primary reflective electrode (1-1) and the four emitting electrodes in each cycle, respectively, where t is time; Then, based on the upper and lower envelope equations of equation (1) and by substituting them into equation (2) through area integration, the output signal when the moving plate (1) moves Δx in the horizontal direction is obtained: Where a is the length of the irregularly shaped petal-shaped primary reflective plate (1-1); similarly, the output signal of the first rectangular secondary reflective plate (1-2), which is electrically connected to the first irregularly shaped primary reflective plate (1-1), is also shown in equation (3). When the moving plate (1) moves horizontally relative to the stationary plate (2), a capacitor structure is formed between the first rectangular secondary reflective plate (1-3) directly above the first receiving electrode (2-2) and the first receiving electrode (2-2). During the movement, the capacitance value of the capacitor does not change. Therefore, it does not affect the phase of the output signal shown in equation (3). That is, the expression of the output signal U'(Δx,t) on the first receiving electrode (2-2) is: Where K' is the output signal amplitude; further, because the moving electrode plate (1) is provided with a length L / 2N that differs from the first irregular petal-shaped primary reflective electrode plate (1-1) by half a spatial period in the horizontal direction. f The second irregular petal-shaped primary reflective electrode (1-2) will generate a differential signal on the second receiving electrode (2-3) that is opposite to the output signal of the first receiving electrode (2-2).

7. A large-range, high-precision variable capacitance displacement sensor according to claim 1, characterized in that: Both the moving electrode plate (1) and the stationary electrode plate (2) are printed on a circuit board.

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