Electrode controllable single code channel time grating displacement sensor, absolute displacement measurement system and measurement method

Abstract

The invention discloses an electrode controllable single code channel time grating displacement sensor, an absolute displacement measuring system and a measuring method.The sensor comprises a fixed ruler base body, a movable ruler base body and a multiplexer, the fixed ruler base body, the movable ruler base body and the multiplexer are installed in parallel, a gap is kept between the fixed ruler base body and the movable ruler base body, a column of exciting electrodes are arranged on the surface of the fixed ruler base body, and a column of sensing electrodes are arranged on the surface of the movable ruler base body; different excitation electrodes and induction electrodes are selected through a multiplexer, excitation electrode A / B mode grouping and induction electrode A / B mode grouping are formed respectively, the excitation electrode A group and the induction electrode A group are matched to generate a first measurement signal, the excitation electrode B group and the induction electrode B group are matched to generate a second measurement signal, and the excitation electrode A group and the induction electrode B group have different periods. An absolute displacement value can be synthesized by using the difference between the two groups of signals. According to the sensor, absolute displacement value measurement in a full-scale range can be realized under different periodic signals, and accumulated errors of a traditional incremental sensor are thoroughly eliminated.

Description

Technical Field

[0001] This invention relates to the field of measurement and sensing technology, specifically to an electrode-controllable single-track time-grid displacement sensor, an absolute displacement measurement system, and a measurement method. Background Technology

[0002] Precision displacement measurement is one of the core technologies in modern manufacturing, CNC machine tools, robotics, and automated equipment. Traditional precision linear displacement measurement mainly relies on grating sensors such as optical gratings, magnetic gratings, and capacitive gratings, all of which use spatially evenly divided grating lines as the measurement reference. To improve measurement accuracy and resolution, precise scribing processes and high-precision electronic subdivision technology are required for manufacturing. However, the stringent manufacturing process and complex subdivision circuitry lead to problems such as high sensor cost and poor anti-interference capabilities.

[0003] In recent years, domestic research and development has yielded time-grating displacement sensors with time reference as the core. The early proposed time-grating displacement sensor based on alternating electric field (patent number: 201110145967.5) and the subsequent developed "electric field-type time-grating linear displacement sensor based on single-row multilayer structure" (patent number: 201410102437.6) both use high-frequency clock pulses as the reference and achieve precise displacement measurement through the alternating electric field between parallel capacitor plates, thereby simplifying the mechanical structure of traditional sensors.

[0004] However, both of the above-mentioned electric field time grating sensors use the principle of incremental counting, which has inherent cumulative error. Furthermore, the sensor can only identify the relative displacement within one measurement cycle and cannot directly obtain absolute displacement information across the entire measurement range when powered on, thus limiting its use in scenarios such as fully closed-loop control systems that require absolute position sensing. 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 an electrode-controllable single-track time grating displacement sensor that can achieve high precision and full-range absolute displacement measurement.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: An electrode-controllable single-track time-grid displacement sensor includes a fixed-scale base and a movable-scale base, which are mounted parallel to each other with a gap between them. The sensor also includes a multiplexer. A row of excitation electrodes is disposed on the surface of the fixed-scale base facing the movable-scale base. The multiplexer selects different excitation electrodes to form two conductive groups: excitation electrode group A and excitation electrode group B. A row of sensing electrodes is disposed on the surface of the movable-scale base facing the fixed-scale base. The multiplexer selects different sensing electrodes to form two conductive groups: sensing electrode group A and sensing electrode group B. The excitation electrode group A can cooperate with the sensing electrode group A to generate a first measurement signal, and the excitation electrode group B can cooperate with the sensing electrode group B to generate a second measurement signal. The first and second measurement signals have different periods and are used to synthesize an absolute displacement value.

[0007] In this invention, by generating two signals with different periods, a physical basis is provided for subsequent fusion calculation of absolute displacement, fundamentally solving the problems of cumulative error and inability to directly obtain absolute position in incremental sensors in the background technology. Furthermore, the adoption of a "single code track" design overcomes the limitations of traditional absolute sensors that require multiple code tracks or complex structures, significantly reducing the sensor's size and improving its compactness and robustness.

[0008] As an optimization, in the A-type grouping of the excitation electrodes, each adjacent 4n2 excitation electrodes form a pair of electrodes, resulting in N pairs of electrodes, where n2 = N-1 and n2 ≥ 1. For integers n1 from 0 to N-1: the excitation electrodes n1×4n2+1 to n1×4n2+n2 are connected as excitation phase A1, the excitation electrodes n1×4n2+n2+1 to n1×4n2+2n2 are connected as excitation phase B1, the excitation electrodes n1×4n2+2n2+1 to n1×4n2+3n2 are connected as excitation phase C1, and the excitation electrodes n1×4n2+3n2+1 to n1×4n2+4n2 are connected as excitation phase D1. In the B-mode grouping of the excitation electrodes, each adjacent 4n4 excitation electrodes form a pair, resulting in N-1 pairs, where n4=N and n4≥2. For n3, which is an integer from 0 to N-2: excitation electrodes n3×4n4+1 to n3×4n4+n4 are connected as A2 excitation phase, excitation electrodes n3×4n4+n4+1 to n3×4n4+2n4 are connected as B2 excitation phase, excitation electrodes n3×4n4+2n4+1 to n3×4n4+3n4 are connected as C2 excitation phase, and excitation electrodes n3×4n4+3n4+1 to n3×4n4+4n4 are connected as D2 excitation phase. The number of excitation electrodes in the excitation phase of the excitation electrode grouping method A differs from the number of excitation electrodes in the excitation phase of the excitation electrode grouping method B. This ensures that the spatial period of the electric field generated by the two grouping methods A and B has a fixed and known difference, providing a guarantee for the fusion of coarse and fine measurement data.

[0009] As an optimization, in the A-type grouping of the sensing electrodes, the size of a single sensing electrode in the measurement direction is the same as the total size occupied by the 2(N-1) excitation electrodes and their intervals on the fixed-length substrate. Each pair of adjacent sensing electrodes forms a pair of electrodes, forming M pairs of electrodes. For n5, which is an integer from 0 to M-1, the n5th and n5+2th sensing electrodes are connected to form the A1 sensing group, and the n5+1th and n5+3th sensing electrodes are connected to form the B1 sensing group. In the B-type grouping of the induction electrodes, the size of a single induction electrode in the measurement direction is the same as the total size occupied by the 2N excitation electrodes and their spacing on the fixed-length substrate. Each pair of adjacent induction electrodes forms a pair, resulting in M ​​pairs. For n6, an integer from 0 to M-1, the n6th and n6+2th induction electrodes are connected to form induction group A2, and the n6+1th and n6+3th induction electrodes are connected to form induction group B2. This cross-connection method forms the induction groups, enabling the generation of two signals with equal amplitude and opposite phase at the output, laying the foundation for the subsequent subtraction circuit to synthesize a differential signal with extremely strong anti-interference capability.

[0010] As an optimization, the multiplexer is either an induction electrode multiplexer or an excitation electrode multiplexer.

[0011] As an optimization, the excitation electrode in the excitation electrode is rectangular in shape, and the induction electrode in the induction electrode is double sinusoidal in shape.

[0012] An absolute displacement measurement system includes a displacement sensor, a subtraction circuit, a shaping circuit, and an FPGA signal processing system. The displacement sensor is the electrode-controllable single-code-channel time-grid displacement sensor described above. The signal input terminal of the subtraction circuit is electrically connected to the sensing electrode of the sensor. It is used to synthesize the traveling wave signal output by the sensing electrode into a first differential sinusoidal traveling wave signal Uo1 when the multiplexer is turned on in mode B and the sensing electrode is grouped in mode B. It is also used to synthesize the traveling wave signal output by the sensing electrode into a second differential sinusoidal traveling wave signal Uo2 when the multiplexer is turned on in mode A and the sensing electrode is grouped in mode A. The signal input terminal of the shaping circuit is electrically connected to the signal output terminal of the subtraction circuit. It is used to shape the first differential sinusoidal traveling wave signal Uo1 and the same frequency reference sinusoidal signal Ur into the first square wave signal, and to shape the second differential sinusoidal traveling wave signal Uo2 and the same frequency reference sinusoidal signal Ur into the second square wave signal. The signal input terminal of the FPGA signal processing system is electrically connected to the signal output terminal of the shaping circuit. The FPGA signal processing system includes a precise angular displacement calculation module, a coarse displacement calculation module, and an absolute displacement calculation module. The precise angular displacement calculation module calculates the precise displacement value based on the first square wave signal. The coarse displacement calculation module calculates the coarse displacement value based on the first and second square wave signals. The absolute displacement calculation module is used to synthesize the absolute displacement value from the precise and coarse displacement values. Through the signal chain of subtraction circuit-shaping circuit-FPGA, efficient and reliable conversion and processing from analog signal to digital signal is achieved, ensuring the real-time performance and accuracy of the measurement.

[0013] An absolute displacement measurement method based on the above-described absolute displacement measurement system includes the following steps: (1) Control the multiplexer to turn on the excitation electrode B mode group and the induction electrode B mode group, and turn off the excitation electrode A mode group and the induction electrode A mode group. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the turned-on excitation electrode B mode group. Through the coupling electric field, two sinusoidal traveling wave signals with a phase difference of 180° are induced on the induction electrode B mode group. The first sinusoidal traveling wave signal and the second sinusoidal traveling wave signal are combined into the first differential sinusoidal traveling wave signal Uo1 through the subtraction circuit. The first differential sinusoidal traveling wave signal Uo1 and a reference sinusoidal signal Ur with the same frequency are shaped into the first square wave. (2) Control the multiplexer to switch to the mode group of excitation electrode A and the mode group of induction electrode A, and disconnect the mode group of excitation electrode B and the mode group of induction electrode B. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the mode group of excitation electrode A. Through the coupling electric field, induce two sinusoidal traveling wave signals with a phase difference of 180° and a fourth sinusoidal traveling wave signal on the mode group of induction electrode A. Combine the third sinusoidal traveling wave signal and the fourth sinusoidal traveling wave signal into a second differential sinusoidal traveling wave signal Uo2 through the subtraction circuit. Shape the second differential sinusoidal traveling wave signal Uo2 and a reference sinusoidal signal Ur with the same frequency into a second square wave. (3) Using the FPGA signal processing system, the first differential sinusoidal traveling wave signal Uo1 in the first square wave is compared with a reference sinusoidal signal Ur of the same frequency, and the fine displacement value is calculated based on the comparison result; the second differential sinusoidal traveling wave signal Uo2 in the second square wave is compared with a reference sinusoidal signal Ur of the same frequency, and the comparison result is compared with the result of the comparison of the first square wave again, and the coarse displacement value is calculated based on the comparison result; the absolute displacement value is synthesized and output based on the fine displacement value and the coarse displacement value.

[0014] As an optimization, the four sinusoidal excitation signals in step (1) are applied to the excitation phases A2, B2, C2 and D2 of the excitation electrode group B, respectively, and the four sinusoidal excitation signals in step (2) are applied to the excitation phases A1, B1, C1 and D1 of the excitation electrode group A, respectively.

[0015] As an optimization, in step (3), the phase difference of the phase comparison process is characterized by interpolation high-frequency clock pulse counting.

[0016] Compared to existing technologies, this invention dynamically switches electrode groups on a single code channel using a multiplexer, forming two measurement modes with different electrical cycles on a single physical code channel. By fusing the measurement signals from the two modes, the absolute displacement value across the entire range can be directly calculated, completely eliminating the cumulative error of incremental sensors. The design employs a single code channel structure, achieving absolute measurement through electronic switching rather than physically adding code channels. This not only reduces the difficulty and cost of manufacturing but also significantly improves the sensor's robustness and environmental tolerance. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the present invention; Figure 2 This is a schematic diagram of the A-type grouping of the excitation electrode and the sensing electrode in this invention; Figure 3 This is a schematic diagram of the B-mode grouping of the excitation electrode and the sensing electrode in this invention; Figure 4 This is a flowchart of the absolute displacement measurement process in this invention. Detailed Implementation

[0018] 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.

[0019] like Figure 1As shown, the electrode-controllable single-track time-grid displacement sensor in this specific embodiment includes a fixed-scale base 11 and a movable-scale base 21. The fixed-scale base 11 and the movable-scale base 21 are installed parallel to each other with a gap between them. It also includes a multiplexer. A row of excitation electrodes is disposed on the surface of the fixed-scale base facing the movable-scale base. The multiplexer selects different excitation electrode pieces 12 from all the excitation electrodes, forming a conductive excitation electrode group A and a conductive excitation electrode group B. A row of sensing electrodes is disposed on the surface of the movable-scale base 21 facing the fixed-scale base 11. The multiplexer selects different sensing electrode pieces 22 from all the sensing electrodes, forming a conductive sensing electrode group A and a conductive sensing electrode group B. The excitation electrode group A can cooperate with the sensing electrode group A to generate a first measurement signal, and the excitation electrode group B can cooperate with the sensing electrode group B to generate a second measurement signal. The first measurement signal and the second measurement signal have different periods and are used to synthesize an absolute displacement value. The excitation electrode has a rectangular shape, and the induction electrode has a double sine shape, which is a closed curve formed by the sine curve of the sin(x) function in the interval [0,π] symmetrical about the X-axis. In the A-type grouping of induction electrodes, the induction electrodes are arranged linearly at equal intervals along the moving scale base, and each induction electrode has the same size. In the B-type grouping of induction electrodes, the induction electrodes are arranged linearly at equal intervals along the moving scale base, and each induction electrode has the same size. The center distance between the A-type and B-type groupings of induction electrodes is l. In addition, the multiplexer can be an induction electrode multiplexer or an excitation electrode multiplexer.

[0020] In the A-type grouping of the excitation electrodes, each adjacent 4n2 excitation electrodes form a pair of electrodes, resulting in N pairs of electrodes, where n2 = N-1 and n2 ≥ 1. For integers n1 from 0 to N-1: the excitation electrodes from n1×4n2+1 to n1×4n2+n2 are connected as excitation phase A1, the excitation electrodes from n1×4n2+n2+1 to n1×4n2+2n2 are connected as excitation phase B1, the excitation electrodes from n1×4n2+2n2+1 to n1×4n2+3n2 are connected as excitation phase C1, and the excitation electrodes from n1×4n2+3n2+1 to n1×4n2+4n2 are connected as excitation phase D1. In the B-mode grouping of the excitation electrodes, each adjacent 4n4 excitation electrodes form a pair, resulting in N-1 pairs, where n4=N and n4≥2. For n3, which is an integer from 0 to N-2: excitation electrodes n3×4n4+1 to n3×4n4+n4 are connected as A2 excitation phase, excitation electrodes n3×4n4+n4+1 to n3×4n4+2n4 are connected as B2 excitation phase, excitation electrodes n3×4n4+2n4+1 to n3×4n4+3n4 are connected as C2 excitation phase, and excitation electrodes n3×4n4+3n4+1 to n3×4n4+4n4 are connected as D2 excitation phase. The number of excitation electrodes in the excitation phase of the excitation electrode group A is different from the number of excitation electrodes in the excitation phase of the excitation electrode group B.

[0021] In the A-type grouping of the induction electrodes, the size of a single induction electrode in the measurement direction is the same as the total size occupied by the 2(N-1) excitation electrodes and their intervals on the fixed-length substrate. Each pair of adjacent induction electrodes forms a pair of electrodes, forming M pairs of electrodes. For n5, which is an integer from 0 to M-1, the n5th and n5+2th induction electrodes are connected to form the A1 induction group, and the n5+1th and n5+3th induction electrodes are connected to form the B1 induction group. In the B-mode grouping of the induction electrodes, the size of a single induction electrode in the measurement direction is the same as the total size occupied by the 2N excitation electrodes and their intervals on the fixed-length substrate. Each pair of adjacent induction electrodes forms a pair of electrodes, resulting in M ​​pairs of electrodes. For n6, which is an integer from 0 to M-1, the n6th and n6+2th induction electrodes are connected to form the A2 induction group, and the n6+1th and n6+3th induction electrodes are connected to form the B2 induction group.

[0022] like Figure 2 As shown, in (a), red represents the A1 excitation phase, blue represents the B1 excitation phase, green represents the C1 excitation phase, and black represents the D1 excitation phase. Each excitation phase contains four excitation electrodes. In (b), the colored areas represent the corresponding sensing electrode assemblies. Figure 3 As shown, in (a), red represents the A2 excitation phase, blue represents the B2 excitation phase, green represents the C2 excitation phase, and black represents the D2 excitation phase. Each excitation phase contains 5 excitation electrodes. In (b), the colored parts are the corresponding sensing electrode components.

[0023] An absolute displacement measurement system includes a displacement sensor, a subtraction circuit, a shaping circuit, and an FPGA signal processing system. The displacement sensor is the electrode-controllable single-code-channel time-grid displacement sensor described above. The signal input terminal of the subtraction circuit is electrically connected to the sensing electrode of the sensor. It is used to synthesize the traveling wave signal output by the sensing electrode into a first differential sinusoidal traveling wave signal Uo1 when the multiplexer is turned on in mode B and the sensing electrode is grouped in mode B. It is also used to synthesize the traveling wave signal output by the sensing electrode into a second differential sinusoidal traveling wave signal Uo2 when the multiplexer is turned on in mode A and the sensing electrode is grouped in mode A. The signal input terminal of the shaping circuit is electrically connected to the signal output terminal of the subtraction circuit. It is used to shape the first differential sinusoidal traveling wave signal Uo1 and the same frequency reference sinusoidal signal Ur into the first square wave signal, and to shape the second differential sinusoidal traveling wave signal Uo2 and the same frequency reference sinusoidal signal Ur into the second square wave signal. The signal input terminal of the FPGA signal processing system is electrically connected to the signal output terminal of the shaping circuit. The FPGA signal processing system includes a fine angular displacement calculation module, a coarse displacement calculation module, and an absolute displacement calculation module. The fine angular displacement calculation module calculates the fine displacement value based on the first square wave signal. The coarse displacement calculation module calculates the coarse displacement value based on the first square wave signal and the second square wave signal. The absolute displacement calculation module is used to synthesize the absolute displacement value based on the fine displacement value and the coarse displacement value.

[0024] like Figure 4 As shown, an absolute displacement measurement method based on the above-described absolute displacement measurement system includes the following steps: (1) Control the multiplexer to turn on the excitation electrode B mode group and the induction electrode B mode group, and turn off the excitation electrode A mode group and the induction electrode A mode group. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the turned-on excitation electrode B mode group. The sinusoidal excitation signal is coupled to the electric field between the excitation electrode B mode group and the induction electrode B mode group. The coupled electric field induces two sinusoidal traveling wave signals with a phase difference of 180° on the induction electrode B mode group. The first sinusoidal traveling wave signal and the second sinusoidal traveling wave signal are combined into the first differential sinusoidal traveling wave signal Uo1 by the subtraction circuit. The first differential sinusoidal traveling wave signal Uo1 and a reference sinusoidal signal Ur with the same frequency are shaped into the first square wave. (2) Control the multiplexer to switch to the mode group of excitation electrode A and the mode group of induction electrode A, and disconnect the mode group of excitation electrode B and the mode group of induction electrode B. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the mode group of excitation electrode A. The sinusoidal excitation signal is coupled to the electric field between the mode group of excitation electrode A and the mode group of induction electrode A. The coupled electric field induces two sinusoidal traveling wave signals with a phase difference of 180° and a fourth sinusoidal traveling wave signal on the mode group of induction electrode A. The third sinusoidal traveling wave signal and the fourth sinusoidal traveling wave signal are combined into a second differential sinusoidal traveling wave signal Uo2 by the subtraction circuit. The second differential sinusoidal traveling wave signal Uo2 and a reference sinusoidal signal Ur with the same frequency are shaped into a second square wave. (3) Using the FPGA signal processing system, the first differential sinusoidal traveling wave signal Uo1 in the first square wave is compared with a reference sinusoidal signal Ur of the same frequency, and the fine displacement value is calculated based on the comparison result; the second differential sinusoidal traveling wave signal Uo2 in the second square wave is compared with a reference sinusoidal signal Ur of the same frequency, and the comparison result is compared with the result of the comparison of the first square wave again, and the coarse displacement value is calculated based on the comparison result; the absolute displacement value is synthesized and output based on the fine displacement value and the coarse displacement value.

[0025] In step (1), the four sinusoidal excitation signals are applied to the excitation phases A2, B2, C2 and D2 of the excitation electrode group B, respectively. In step (2), the four sinusoidal excitation signals are applied to the excitation phases A1, B1, C1 and D1 of the excitation electrode group A, respectively.

[0026] In step (3), the phase difference of the phase comparison process is characterized by interpolation high-frequency clock pulse counting, and the corresponding displacement value is obtained after calculation and transformation.

[0027] 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. An electrode-controllable single-track time-grid displacement sensor, comprising a fixed-scale base and a movable-scale base, wherein the fixed-scale base and the movable-scale base are installed parallel to each other and have a gap between them, characterized in that: It also includes a multiplexer, wherein a row of excitation electrodes is provided on the side surface of the fixed scale base facing the moving scale base. Through the multiplexer, different excitation electrode pieces among all excitation electrodes are selected to form a conductive excitation electrode group A and an excitation electrode group B. A row of sensing electrodes is provided on the side surface of the moving scale base facing the fixed scale base. Through the multiplexer, different sensing electrode pieces among all sensing electrodes are selected to form a conductive sensing electrode group A and a sensing electrode group B. The excitation electrode group A can cooperate with the sensing electrode group A to generate a first measurement signal, and the excitation electrode group B can cooperate with the sensing electrode group B to generate a second measurement signal. The first measurement signal and the second measurement signal have different periods and are used to synthesize an absolute displacement value.

2. The electrode-controllable single-track time-grid displacement sensor according to claim 1, characterized in that: In the A-type grouping of the excitation electrodes, each adjacent 4n2 excitation electrodes form a pair of electrodes, resulting in N pairs of electrodes, where n2 = N-1 and n2 ≥ 1. For integers n1 from 0 to N-1: the excitation electrodes from n1×4n2+1 to n1×4n2+n2 are connected as excitation phase A1, the excitation electrodes from n1×4n2+n2+1 to n1×4n2+2n2 are connected as excitation phase B1, the excitation electrodes from n1×4n2+2n2+1 to n1×4n2+3n2 are connected as excitation phase C1, and the excitation electrodes from n1×4n2+3n2+1 to n1×4n2+4n2 are connected as excitation phase D1. In the B-mode grouping of the excitation electrodes, each adjacent 4n4 excitation electrodes form a pair, resulting in N-1 pairs, where n4=N and n4≥2. For n3, which is an integer from 0 to N-2: excitation electrodes n3×4n4+1 to n3×4n4+n4 are connected as A2 excitation phase, excitation electrodes n3×4n4+n4+1 to n3×4n4+2n4 are connected as B2 excitation phase, excitation electrodes n3×4n4+2n4+1 to n3×4n4+3n4 are connected as C2 excitation phase, and excitation electrodes n3×4n4+3n4+1 to n3×4n4+4n4 are connected as D2 excitation phase. The number of excitation electrodes in the excitation phase of the excitation electrode group A is different from the number of excitation electrodes in the excitation phase of the excitation electrode group B.

3. The electrode-controllable single-track time-grid displacement sensor according to claim 2, characterized in that: In the A-type grouping of the induction electrodes, the size of a single induction electrode in the measurement direction is the same as the total size occupied by the 2(N-1) excitation electrodes and their intervals on the fixed-length substrate. Each pair of adjacent induction electrodes forms a pair of electrodes, forming M pairs of electrodes. For n5, which is an integer from 0 to M-1, the n5th and n5+2th induction electrodes are connected to form the A1 induction group, and the n5+1th and n5+3th induction electrodes are connected to form the B1 induction group. In the B-mode grouping of the induction electrodes, the size of a single induction electrode in the measurement direction is the same as the total size occupied by the 2N excitation electrodes and their intervals on the fixed-length substrate. Each pair of adjacent induction electrodes forms a pair of electrodes, resulting in M ​​pairs of electrodes. For n6, which is an integer from 0 to M-1, the n6th and n6+2th induction electrodes are connected to form the A2 induction group, and the n6+1th and n6+3th induction electrodes are connected to form the B2 induction group.

4. The electrode-controllable single-track time-grid displacement sensor according to claim 1, characterized in that: The multiplexer is either an induction electrode multiplexer or an excitation electrode multiplexer.

5. The electrode-controllable single-track time-grid displacement sensor according to claim 1, characterized in that: The excitation electrode has a rectangular shape, and the induction electrode has a double sine-shaped shape.

6. An absolute displacement measurement system, characterized in that: It includes a displacement sensor, a subtraction circuit, a shaping circuit, and an FPGA signal processing system. The displacement sensor is the electrode-controllable single-code-channel time-grid displacement sensor as described in any one of claims 1 to 4. The signal input terminal of the subtraction circuit is electrically connected to the sensing electrode of the sensor. It is used to synthesize the traveling wave signal output by the sensing electrode into a first differential sinusoidal traveling wave signal Uo1 when the multiplexer is turned on in mode B and the sensing electrode is grouped in mode B. It is also used to synthesize the traveling wave signal output by the sensing electrode into a second differential sinusoidal traveling wave signal Uo2 when the multiplexer is turned on in mode A and the sensing electrode is grouped in mode A. The signal input terminal of the shaping circuit is electrically connected to the signal output terminal of the subtraction circuit. It is used to shape the first differential sinusoidal traveling wave signal Uo1 and the same frequency reference sinusoidal signal Ur into the first square wave signal, and to shape the second differential sinusoidal traveling wave signal Uo2 and the same frequency reference sinusoidal signal Ur into the second square wave signal. The signal input terminal of the FPGA signal processing system is electrically connected to the signal output terminal of the shaping circuit. The FPGA signal processing system includes a fine angular displacement calculation module, a coarse displacement calculation module, and an absolute displacement calculation module. The fine angular displacement calculation module calculates the fine displacement value based on the first square wave signal. The coarse displacement calculation module calculates the coarse displacement value based on the first square wave signal and the second square wave signal. The absolute displacement calculation module is used to synthesize the absolute displacement value based on the fine displacement value and the coarse displacement value.

7. An absolute displacement measurement method based on the absolute displacement measurement system of claim 6, characterized in that: Includes the following steps: (1) Control the multiplexer to turn on the excitation electrode B mode group and the induction electrode B mode group, and turn off the excitation electrode A mode group and the induction electrode A mode group. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the turned-on excitation electrode B mode group. Through the coupling electric field, two sinusoidal traveling wave signals with a phase difference of 180° are induced on the induction electrode B mode group. The first sinusoidal traveling wave signal and the second sinusoidal traveling wave signal are combined into the first differential sinusoidal traveling wave signal Uo1 through the subtraction circuit. The first differential sinusoidal traveling wave signal Uo1 and a reference sinusoidal signal Ur with the same frequency are shaped into the first square wave. (2) Control the multiplexer to switch to the mode group of excitation electrode A and the mode group of induction electrode A, and disconnect the mode group of excitation electrode B and the mode group of induction electrode B. Apply four sinusoidal excitation signals with the same frequency and equal amplitude and phase difference of 90° to the mode group of excitation electrode A. Through the coupling electric field, induce two sinusoidal traveling wave signals with a phase difference of 180° and a fourth sinusoidal traveling wave signal on the mode group of induction electrode A. Combine the third sinusoidal traveling wave signal and the fourth sinusoidal traveling wave signal into a second differential sinusoidal traveling wave signal Uo2 through the subtraction circuit. Shape the second differential sinusoidal traveling wave signal Uo2 and a reference sinusoidal signal Ur with the same frequency into a second square wave. (3) Through the FPGA signal processing system, the first differential sinusoidal traveling wave signal Uo1 in the first square wave is compared with a reference sinusoidal signal Ur of the same frequency, and the precise displacement value is calculated based on the comparison result. The second differential sinusoidal traveling wave signal Uo2 in the second square wave is compared with a reference sinusoidal signal Ur of the same frequency. The phase comparison result is then compared with the result of the phase comparison of the first square wave. The coarse displacement value is calculated based on the phase comparison result. The absolute displacement value is synthesized and output based on the precise displacement value and the coarse displacement value.

8. The absolute displacement measurement method according to claim 7, characterized in that: In step (1), the four sinusoidal excitation signals are applied to the excitation phases A2, B2, C2 and D2 of the excitation electrode group B, respectively. In step (2), the four sinusoidal excitation signals are applied to the excitation phases A1, B1, C1 and D1 of the excitation electrode group A, respectively.

9. The absolute displacement measurement method according to claim 7, characterized in that: In step (3), the phase difference of the phase comparison process is characterized by interpolation high-frequency clock pulse counting.

Images