An absolute planar two-dimensional time-grating displacement sensor and measurement method based on alternating electric field

Abstract

This invention discloses an absolute planar two-dimensional time-grating displacement sensor and measurement method based on an alternating electric field. Excitation signals are sequentially applied to the X-excitation pairs. When the sensing electrode generates a sensing signal, the application of excitation signals to the remaining X-excitation pairs is stopped. By processing the four electrical signals generated by the sensing group, the position of the moving scale substrate within the X-excitation pair and its displacement position within that pair are obtained, thus yielding the absolute two-dimensional time-grating displacement value of the moving scale substrate relative to the fixed scale substrate in the X direction. Similarly, the absolute two-dimensional time-grating displacement value of the moving scale substrate in the Y direction is obtained. Then, the absolute two-dimensional time-grating displacement values ​​in the XY directions are used as the coordinates of the moving scale substrate in the XY directions, thus obtaining the absolute displacement of the moving scale substrate. This invention uses a scanning method to obtain the absolute position in the XY directions to achieve planar two-dimensional absolute displacement measurement, which can reduce cumulative and random errors, improve measurement accuracy, and achieve high-precision measurement over a large range.

Description

Technical Field

[0001] This invention relates to improvements in linear displacement sensor measurement technology, specifically to an absolute planar two-dimensional time-grating displacement sensor and measurement method based on an alternating electric field, belonging to the field of planar two-dimensional displacement precision measurement sensing technology. Background Technology

[0002] Precision displacement measurement technology is widely used in various precision motion control fields such as CNC machine tools, chip manufacturing, metrology and testing, aerospace, and national defense. Existing planar two-dimensional displacement sensors can be mainly divided into three types: optical, capacitive, and inductive. Optical planar two-dimensional displacement sensors are relatively mature, but they rely heavily on ultra-precision scribing technology and have weak resistance to oil contamination and impact vibration. Capacitive planar two-dimensional time-grating sensors consist of a fixed scale and a moving scale. The dielectric constant of capacitive planar two-dimensional displacement sensors is easily affected by external environmental factors such as temperature, resulting in weak anti-interference capabilities. Currently, the developed planar two-dimensional time-grating displacement sensors are mainly incremental, which suffers from drawbacks such as cumulative error, the need for manual zeroing after power-on, and data loss after power failure.

[0003] On November 22, 2024, the applicant applied for an invention patent entitled "A self-calibration method based on a planar two-dimensional time grating sensor". The excitation electrodes are arranged in 2m rows along the upper surface of the fixed-length substrate. Each row of excitation electrodes is composed of n identical square excitation plates evenly arranged along the X-axis. The starting positions of adjacent rows of excitation electrodes are staggered by a certain distance along the X-axis. The starting positions of the excitation electrodes in odd-numbered rows along the X-axis are the same, and the starting positions of the excitation electrodes in even-numbered rows along the X-axis are the same. n = 4k1, m = 4k2.

[0004] In the excitation electrode array consisting of all odd-numbered rows of excitation electrodes, all excitation electrodes in each row are connected to form row excitation groups, thus forming m rows of row excitation groups; starting from the first row, every four rows form a cycle, which are respectively called row excitation group Y1, row excitation group Y2, row excitation group Y3 and row excitation group Y4;

[0005] In the excitation electrode array consisting of all even-numbered rows of excitation electrodes, all excitation electrodes in each column are connected to form column excitation groups, thus forming m column excitation groups; starting from the first column, every four columns form a cycle, which are respectively called column excitation group X1, column excitation group X2, column excitation group X3 and column excitation group X4;

[0006] All X1 column excitation groups and all Y1 row excitation groups are connected to form phase A excitation electrode group; all X2 column excitation groups and all Y2 row excitation groups are connected to form phase B excitation electrode group; all X3 column excitation groups and all Y3 row excitation groups are connected to form phase C excitation electrode group; and all X4 column excitation groups and all Y4 row excitation groups are connected to form phase D excitation electrode group. During operation, sinusoidal excitation voltages of equal amplitude and frequency with a phase difference of π / 2 are sequentially applied to the four phase excitation electrode groups (A, B, C, and D). By processing the output of the induction electrodes accordingly, self-calibration and displacement measurement can be achieved.

[0007] The aforementioned sensor is an incremental type, which also has drawbacks such as cumulative error, the need for manual zeroing after power-on, and data loss after power failure, so self-calibration is required. Summary of the Invention

[0008] To address the aforementioned shortcomings of existing displacement measurement methods, the present invention aims to provide an absolute planar two-dimensional time-grid displacement sensor and measurement method based on an alternating electric field. The present invention has a simple structure and achieves planar two-dimensional absolute displacement measurement by obtaining the absolute positions in the x and y directions respectively. This reduces cumulative and random errors, improves measurement accuracy, and enables high-precision measurement over a large range.

[0009] The technical solution of this invention is implemented as follows:

[0010] An absolute planar two-dimensional time-grating displacement sensor based on an alternating electric field includes a fixed-scale base and a movable-scale base. The lower surface of the movable-scale base is installed parallel to the upper surface of the fixed-scale base with a gap between them. The upper surface of the fixed-scale base has 2m rows of excitation electrodes arranged side-by-side. Each row of excitation electrodes consists of n identical square excitation plates evenly arranged along the X-axis. The distance Ie between two adjacent square excitation plates is greater than the width Le of one square excitation plate. The distance between two adjacent rows of excitation electrodes along the Y-axis is (Ie-Le) / 2. The starting positions along the X-axis are staggered by (Ie+Le) / 2. The starting positions of the excitation electrodes in odd-numbered rows are the same along the X-axis, and the starting positions of the excitation electrodes in even-numbered rows are the same along the X-axis. Where n = 4k1, m = 4k2, and k1 and k2 are both positive integers.

[0011] A sensing electrode is provided on the lower surface of the moving scale base, and the sensing electrode on the moving scale base is directly opposite the excitation electrode on the fixed scale base. The sensing electrode is composed of r sensing units arranged in a matrix, with a spacing of Ii between two adjacent sensing units. Each sensing unit is composed of four identical square sensing electrodes a, b, c, and d arranged in a 2x2 pattern. The side length of each sensing electrode is Li, and the spacing between two adjacent sensing electrodes is Ii, where Li + Ii = 2(Le + Ie). The sensing electrodes a in all sensing units are connected to form sensing group a, sensing electrodes b in all sensing units are connected to form sensing group b, sensing electrodes c in all sensing units are connected to form sensing group c, and sensing electrodes d in all sensing units are connected to form sensing group d.

[0012] In the array of excitation electrodes consisting of all odd-numbered rows of excitation electrodes, all excitation electrodes in each row are connected to form Y excitation units, thus forming m Y excitation units; starting from the first one, every four Y excitation units form a Y excitation pair stage, for a total of k2 Y excitation pair stages; the four Y excitation units in each Y excitation pair stage are called YA excitation unit, YB excitation unit, YC excitation unit and YD excitation unit respectively;

[0013] In the array of excitation electrodes consisting of all even-numbered rows of excitation electrodes, all excitation electrodes in each column are connected to form X excitation units, thereby forming n X excitation units; starting from the first one, every four X excitation units form an X excitation pair stage, for a total of k1 X excitation pair stages; the four X excitation units in each X excitation pair stage are called XA excitation unit, XB excitation unit, XC excitation unit and XD excitation unit respectively.

[0014] It also includes a driving circuit, which sequentially drives k1 X-excitation pairs and k2 Y-excitation pairs to generate excitation signals. When driving each X-excitation pair, it applies sinusoidal excitation signals of equal amplitude and frequency with phase differences of π / 2 to the XA, XB, XC, and XD excitation units respectively. When driving each Y-excitation pair, it applies sinusoidal excitation signals of equal amplitude and frequency with phase differences of π / 2 to the YA, YB, YC, and YD excitation units respectively. When the moving scale substrate is electrically coupled to the fixed scale substrate, the a, b, c, and d induction groups generate four induction signals for the X-excitation pairs and Y-excitation pairs respectively. After processing, the linear displacement of the moving scale substrate relative to the fixed scale substrate in the X-axis direction and the linear displacement in the Y-axis direction are obtained.

[0015] Let the width of the sensing unit be W, which satisfies W = 2(Li + Ii) = 4(Le + Ie).

[0016] This invention also provides a method for measuring absolute planar two-dimensional time-grating displacement based on alternating electric fields, which is implemented using the aforementioned absolute planar two-dimensional time-grating displacement sensor based on alternating electric fields; during measurement,

[0017] Excitation signals are sequentially applied to k1 X excitation pairs. When the induction electrode on the moving scale substrate generates an induction signal due to electric field coupling, the application of excitation signals to the remaining X excitation pairs is stopped. By processing the four electrical signals generated by the induction groups a, b, c, and d, the position of the moving scale substrate within the X excitation pair and its displacement position within the X excitation pair are obtained, thereby obtaining the two-dimensional absolute displacement value of the moving scale substrate relative to the fixed scale substrate in the X direction.

[0018] Excitation signals are sequentially applied to k2 Y excitation pairs. When the induction electrode on the moving scale substrate generates an induction signal due to electric field coupling, the application of excitation signals to the remaining Y excitation pairs is stopped. By processing the four electrical signals generated by the induction groups a, b, c, and d, the position of the moving scale substrate within the Y excitation pair and its displacement within the Y excitation pair are obtained, thereby obtaining the two-dimensional absolute displacement value of the moving scale substrate relative to the fixed scale substrate in the Y direction.

[0019] Then, the absolute displacement values ​​of the two-dimensional time grating in the X direction and the absolute displacement values ​​of the two-dimensional time grating in the Y direction are used as the coordinates of the moving scale base in the X and Y directions, thus obtaining the absolute displacement of the moving scale base.

[0020] Furthermore, if an excitation signal is applied to the X excitation pair from left to right, the sensing signal of the sensing group consisting of the sensing electrodes corresponding to the left column of each sensing unit is taken for calculation; if an excitation signal is applied to the X excitation pair from right to left, the sensing signal of the sensing group consisting of the sensing electrodes corresponding to the right column of each sensing unit is taken for calculation.

[0021] If the excitation signal is applied to the Y excitation pair stage from top to bottom, the sensing signal of the sensing group composed of the sensing electrodes in the upper row of each sensing unit is taken for calculation and processing; if the excitation signal is applied to the Y excitation pair stage from bottom to top, the sensing signal of the sensing group composed of the sensing electrodes in the lower row of each sensing unit is taken for calculation and processing.

[0022] The present invention can simultaneously apply excitation signals to k1 X excitation pairs and k2 Y excitation pairs; or it can apply excitation signals to k1 X excitation pairs and k2 Y excitation pairs separately.

[0023] This invention uses software control to sequentially supply excitation signals (sin+, cos+, sin-, cos-) to the excitation electrodes of the scale substrate along the X and Y directions: excitation signals are sequentially supplied from electrode X1 to electrode Xn along the X direction; and excitation signals are sequentially supplied from electrode Y1 to electrode Yn along the Y direction. When the X direction scans to the Mth channel, if the induction electrode on the moving scale substrate couples with the excitation electrode on the fixed scale substrate, an induction signal is generated and fed back to the host computer. This allows the determination of which electrode pair the moving scale substrate is located in and its displacement position within the electrode pair, thus obtaining the absolute displacement value of the two-dimensional time grating in the X direction. Similarly, when the Y direction scans to the Nth channel, if the induction electrode on the moving scale substrate couples with the excitation electrode on the fixed scale substrate, an induction signal is generated and fed back to the host computer. This allows the determination of which electrode pair the moving scale substrate is located in and its displacement position within the electrode pair, thus obtaining the absolute displacement value of the two-dimensional time grating in the Y direction. Finally, by adding the two position values, the absolute displacement value of the two-dimensional time grating can be obtained, thereby realizing the absolute displacement measurement of the planar two-dimensional time grating displacement sensor in the XOY plane.

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

[0025] 1. While ensuring sensor stability, real-time performance, and high resolution, this invention achieves integrated planar two-dimensional absolute linear displacement measurement. Compared to incremental measurement methods, this invention obtains the current absolute planar position upon power-up, offering advantages such as eliminating accumulated sensor errors, eliminating the need for manual zeroing upon power-up, and ensuring data integrity even after power failure.

[0026] 2. This absolute planar two-dimensional displacement sensor adopts a non-contact measurement method, has strong anti-interference ability, can adapt to relatively harsh working environments, and has a low cost.

[0027] 3. The sensor of this invention has a simple structure, a wide measurement range, and a wider range of applications. Attached Figure Description

[0028] Figure 1 This is a schematic diagram illustrating the correspondence between the fixed-length base and the moving-length base in Implementation 1.

[0029] Figure 2 This is a schematic diagram of the arrangement of excitation electrodes on the fixed-length substrate in Example 1.

[0030] Figure 3 This is a schematic diagram of the arrangement of the sensing units on the moving ruler substrate in Example 1.

[0031] Figure 4 for Figure 3 A schematic diagram of the structure of a single sensing unit.

[0032] Figure 5 This is a schematic diagram of the measurement method of the present invention.

[0033] Figures 6 to 9 This is a diagram showing the state of the moving scale base on the fixed scale base in other embodiments. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0035] like Figures 1 to 4 As shown, the present invention is an absolute planar two-dimensional time-grid displacement sensor based on alternating electric field, including a fixed scale base 1 and a movable scale base 2. The lower surface of the movable scale base 2 is installed parallel to the upper surface of the fixed scale base 1, with a gap of d = 1 mm.

[0036] like Figure 2 As shown, 32 rows (m=16, or k2=4) of excitation electrodes are arranged side by side on the upper surface of the fixed-length substrate 1. Each row of excitation electrodes consists of 16 identical square excitation electrode pieces 15 (n=16, or k1=4) evenly arranged along the X-axis. The distance between two adjacent square excitation electrode pieces 15 is Ie=6mm, and the width of one square excitation electrode piece 15 is Le=4mm. The distance between two adjacent rows of excitation electrodes along the Y-axis is 1mm. The starting positions of the odd-numbered rows of excitation electrodes (i.e., rows 1, 3, ..., 29, 31) along the X-axis are the same, and the starting positions of the even-numbered rows of excitation electrodes (i.e., rows 2, 4, ..., 30, 32) along the X-axis are the same. The starting positions of the odd-numbered rows of excitation electrodes along the X-axis are offset by 5mm from the starting positions of the even-numbered rows of excitation electrodes along the X-axis.

[0037] In a 16x16 excitation electrode array consisting of all even-numbered rows of excitation electrodes, all excitation electrodes (16 excitation plates) in each column are connected by excitation signal leads to form X excitation units, thus forming 16 X excitation units. Starting from the first one, every four X excitation units form an X excitation pair stage, for a total of 4 X excitation pairs stages. The four X excitation units in each X excitation pair stage are sequentially called XA excitation unit, XB excitation unit, XC excitation unit, and XD excitation unit. The 16 X excitation units are numbered sequentially along the positive X-axis as 1, 2, 3, ..., 16. Then, the 1st, 5th, 9th, and 13th X excitation units are XA excitation units, the 2nd, 6th, 10th, and 14th X excitation units are XB excitation units, the 3rd, 7th, 11th, and 15th X excitation units are XC excitation units, and the 4th, 8th, 12th, and 16th X excitation units are XD excitation units.

[0038] In a 16x16 excitation electrode array consisting of all odd-numbered rows of excitation electrodes, all excitation electrodes (16 excitation plates) in each row are connected by excitation signal leads to form Y excitation units, thus forming 16 Y excitation units. Starting from the first one, every four Y excitation units form a Y excitation pair stage, for a total of 4 Y excitation pairs stages. The four Y excitation units in each Y excitation pair stage are called YA excitation unit, YB excitation unit, YC excitation unit, and YD excitation unit, respectively. The 16 Y excitation units are numbered sequentially along the positive Y-axis as 1, 2, 3, ..., 16. Then, the 1st, 5th, 9th, and 13th Y excitation units are YA excitation units, the 2nd, 6th, 10th, and 14th Y excitation units are YB excitation units, the 3rd, 7th, 11th, and 15th Y excitation units are YC excitation units, and the 4th, 8th, 12th, and 16th Y excitation units are YD excitation units.

[0039] In this embodiment, the pole width W = 4(Le + Ie) = 40mm, there are 4 pole pairs in the X-axis direction and 4 pole pairs in the Y-axis direction.

[0040] See Figure 3 and Figure 4 The lower surface of the moving scale base is provided with a sensing electrode, which is directly opposite the excitation electrode on the fixed scale base. The sensing electrode is composed of r sensing units arranged in a matrix, with a spacing of Ii between two adjacent sensing units. Each sensing unit consists of four identical square sensing electrodes a, b, c, and d arranged in a 2x2 pattern. The side length of each sensing electrode is Li, and the spacing between two adjacent sensing electrodes is Ii, where Li + Ii = 2(Le + Ie). The sensing electrodes a in all sensing units are connected to form sensing group a, sensing electrodes b in all sensing units are connected to form sensing group b, sensing electrodes c in all sensing units are connected to form sensing group c, and sensing electrodes d in all sensing units are connected to form sensing group d.

[0041] Figure 3 In the embodiment shown, four sensing units are arranged in a 2x2 pattern on the lower surface of the moving ruler base 2, i.e., r = 4. Sensing electrodes a and c are located in the same row, and sensing electrodes a and b are located in the same column. The side length of the sensing electrodes is Li = 19 mm, and the distance between two adjacent sensing electrodes is Ii = 1 mm in the X-axis direction and Ii = 1 mm in the Y-axis direction.

[0042] The invention also includes a driving circuit, which sequentially drives four X-excitation pairs and four Y-excitation pairs to generate excitation signals. When driving each X-excitation pair, sinusoidal excitation signals of equal amplitude and frequency with sequentially phased phase differences of π / 2 are applied to the XA, XB, XC, and XD excitation units, respectively. When driving each Y-excitation pair, sinusoidal excitation signals of equal amplitude and frequency with sequentially phased phase differences of π / 2 are applied to the YA, YB, YC, and YD excitation units, respectively. When the moving scale substrate is electrically coupled relative to the fixed scale substrate, induction groups a, b, c, and d generate four induction signals Ua, Ub, Uc, and Ud for the X-excitation pairs and Y-excitation pairs, respectively. These four induction signals are processed to obtain the linear displacement of the moving scale substrate relative to the fixed scale substrate in the X-axis direction and the linear displacement in the Y-axis direction.

[0043] A coupling capacitor is formed between the sensing unit on the lower surface of the moving scale base 2 and the square excitation electrode 15 on the upper surface of the opposite fixed scale base 1. During measurement, XA is sequentially applied along the X direction. j3 XB j3 XC j3 XD j3 The excitation unit applies a sinusoidal excitation signal U A =U m sinωt、U B =U m cosωt、U C =-U m sinωt、U D =-U m cosωt, j3 takes all integers from 1 to k1 in sequence. Along the Y direction, YA is given sequentially. j4 YB j4 YC j4 YD j4 The excitation unit applies a sinusoidal excitation signal U A =U m sinωt、U B =U m cosωt、U C =-U m sinωt、U D =-U m cosωt, j4 takes all integers from 1 to k2 (equivalent to determining the position of the moving scale substrate in the XY direction by scanning in the XY direction respectively). In the embodiment, the amplitude U of the excitation signal m =5V, frequency f = 40kHz, angular frequency ω = 2πf = 8 × 10 4 π.

[0044] When the moving scale base 2 moves relative to the fixed scale base 1 along the X-axis, the induction groups a, b, c, and d generate U through electric field coupling. a U b U c U d The expression for the four induced electrical signals is:

[0045]

[0046] When the moving scale base 2 moves relative to the fixed scale base 1 along the Y-axis, the induction groups a, b, c, and d generate U through electric field coupling. a U b U c U d The expression for the four induced electrical signals is:

[0047]

[0048] In the formula, Ke is the electric field coupling coefficient, and x and y are the linear displacements of the moving scale base 2 relative to the fixed scale base 1 in the X-axis direction and the Y-axis direction, respectively.

[0049] When the sensing electrode on the moving scale substrate generates an induced signal due to electric field coupling, it indicates that the position of the moving scale substrate has been scanned. At this point, the application of excitation signals to the remaining X or Y excitation pairs is stopped. Next, the above four electrical signals are processed to obtain the X-axis sinusoidal traveling wave signal U. x and the Y-axis sinusoidal traveling wave signal U y The X-axis sinusoidal traveling wave signal U x and the Y-axis sinusoidal traveling wave signal U y After being shaped into a square wave by the shaping circuit, it is simultaneously sent to the FPGA for phase detection processing. It is then compared with a reference square wave of the same frequency. The phase difference is represented by the number of interpolated high-frequency clock pulses. After conversion, the linear displacement x of the moving scale base 2 relative to the fixed scale base 1 in the X-axis direction and the linear displacement y in the Y-axis direction can be obtained. The measurement process of this invention can also be found in [reference needed]. Figure 5 .

[0050] This invention sequentially applies sinusoidal excitation signals of the same frequency and amplitude, with a 90° phase difference, to four excitation units of a given scale substrate along the X and Y directions. When electric field coupling occurs with the induction electrode of the moving scale substrate, the induction electrode outputs an induction signal, thereby locating which pole pair the moving scale substrate is located in on the fixed scale substrate. The host computer then determines the position of the moving scale substrate within that pole pair, ultimately obtaining the absolute displacement value of the two-dimensional time grating. Since an excitation pole pair has a fixed length W, and the excitation electrodes and spacing within the pole pair also have widths Le and Ie, the linear displacement x in the X-axis direction is x = x1W + x2Le + x3Ie, where x1 is the number of complete pole pairs scanned in the X-axis direction, and x2 and x3 are the nth electrode / gap in the next pole pair after the complete pole pair.

[0051] If by Figure 2 As shown, if an excitation signal is applied to the X excitation pair from left to right, then the induction electrode corresponding to the column on the left side of each induction unit (i.e., Figure 4 The induction signal of the induction group consisting of induction electrodes a and b shown is processed; if the excitation signal is applied to the X excitation pair from right to left, then the induction electrode corresponding to the right column of each induction unit (i.e., Figure 4 The induction signal of the induction group composed of induction electrodes c and d (shown as shown) is processed and calculated.

[0052] If by Figure 2 As shown, if an excitation signal is applied to the Y-type excitation pair from top to bottom, then the sensing electrode in the top row of each sensing unit (i.e., Figure 4 The induction signal of the induction group consisting of induction electrodes b and d (shown) is processed; if the excitation signal is applied to the Y excitation pair from bottom to top, then the induction electrode corresponding to the row below each induction unit (i.e., Figure 4 The induction signal of the induction group consisting of induction electrodes a and c shown is processed.

[0053] In actual measurement, excitation signals can be applied simultaneously to k1 X excitation pairs and k2 Y excitation pairs, thus simultaneously achieving displacement measurement in both the X and Y axes. Alternatively, excitation signals can be applied separately to k1 X excitation pairs and k2 Y excitation pairs, thus achieving displacement measurement in the X and Y axes sequentially.

[0054] Figures 6 to 9 The diagrams show the state of the moving scale base on the fixed scale base in four other embodiments of the present invention.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the applicant has described the present invention in detail with reference to preferred embodiments, 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 absolute planar two-dimensional time-grating displacement sensor based on an alternating electric field, comprising a fixed-scale base and a movable-scale base, wherein the lower surface of the movable-scale base and the upper surface of the fixed-scale base are mounted parallel to each other with a gap; 2m rows of excitation electrodes are arranged side-by-side on the upper surface of the fixed-scale base, each row of excitation electrodes consisting of n identical square excitation plates evenly arranged along the X-axis, the distance Ie between two adjacent square excitation plates being greater than the width Le of one square excitation plate, the distance between two adjacent rows of excitation electrodes along the Y-axis being (Ie-Le) / 2, and the starting positions along the X-axis being staggered by (Ie+Le) / 2: the starting positions of the odd-numbered rows of excitation electrodes are the same along the X-axis, and the starting positions of the even-numbered rows of excitation electrodes are the same along the X-axis; wherein, n = 4k1, m = 4k2, where k1 and k2 are both positive integers; A sensing electrode is provided on the lower surface of the moving scale base, and the sensing electrode on the moving scale base is directly opposite the excitation electrode on the fixed scale base; the sensing electrode is composed of r sensing units arranged in a matrix, with a spacing of Ii between two adjacent sensing units; each sensing unit is composed of four identical square sensing electrodes a, b, c, and d arranged in a 2x2 pattern, with a side length of Li for each sensing electrode and a spacing of Ii between two adjacent sensing electrodes, Li + Ii = 2(Le + Ie); the sensing electrodes a in all sensing units are connected to form sensing group a, sensing electrodes b in all sensing units are connected to form sensing group b, sensing electrodes c in all sensing units are connected to form sensing group c, and sensing electrodes d in all sensing units are connected to form sensing group d; characterized in that: In the array of excitation electrodes consisting of all odd-numbered rows of excitation electrodes, all excitation electrodes in each row are connected to form Y excitation units, thus forming m Y excitation units; starting from the first one, every four Y excitation units form a Y excitation pair stage, for a total of k2 Y excitation pair stages; the four Y excitation units in each Y excitation pair stage are called YA excitation unit, YB excitation unit, YC excitation unit and YD excitation unit respectively; In the array of excitation electrodes consisting of all even-numbered rows of excitation electrodes, all excitation electrodes in each column are connected to form X excitation units, thereby forming n X excitation units; starting from the first one, every four X excitation units form an X excitation pair stage, for a total of k1 X excitation pair stages; the four X excitation units in each X excitation pair stage are called XA excitation unit, XB excitation unit, XC excitation unit and XD excitation unit respectively. It also includes a driving circuit, which sequentially drives k1 X-excitation pairs and k2 Y-excitation pairs to generate excitation signals. When driving each X-excitation pair, it applies sinusoidal excitation signals of equal amplitude and frequency with phase differences of π / 2 to the XA, XB, XC, and XD excitation units respectively. When driving each Y-excitation pair, it applies sinusoidal excitation signals of equal amplitude and frequency with phase differences of π / 2 to the YA, YB, YC, and YD excitation units respectively. When the moving scale substrate is electrically coupled to the fixed scale substrate, the a, b, c, and d induction groups generate four induction signals for the X-excitation pairs and Y-excitation pairs respectively. After processing, the linear displacement of the moving scale substrate relative to the fixed scale substrate in the X-axis direction and the linear displacement in the Y-axis direction are obtained.

2. The absolute planar two-dimensional time-grating displacement sensor based on alternating electric field according to claim 1, characterized in that: Let the width of the sensing unit be W, which satisfies W=2(Li+Ii)=4(Le+Ie).

3. A method for measuring absolute planar two-dimensional time-grid displacement based on alternating electric fields, characterized in that: This is achieved using the absolute planar two-dimensional time-grid displacement sensor based on alternating electric field as described in any of claims 1-2; during measurement, Excitation signals are sequentially applied to k1 X excitation pairs. When the induction electrode on the moving scale substrate generates an induction signal due to electric field coupling, the application of excitation signals to the remaining X excitation pairs is stopped. By processing the four electrical signals generated by the induction groups a, b, c, and d, the position of the moving scale substrate within the X excitation pair and its displacement position within the X excitation pair are obtained, thereby obtaining the two-dimensional absolute displacement value of the moving scale substrate relative to the fixed scale substrate in the X direction. Excitation signals are sequentially applied to k2 Y excitation pairs. When the induction electrode on the moving scale substrate generates an induction signal due to electric field coupling, the application of excitation signals to the remaining Y excitation pairs is stopped. By processing the four electrical signals generated by the induction groups a, b, c, and d, the position of the moving scale substrate within the Y excitation pair and its displacement within the Y excitation pair are obtained, thereby obtaining the two-dimensional absolute displacement value of the moving scale substrate relative to the fixed scale substrate in the Y direction. Then, the absolute displacement values ​​of the two-dimensional time grating in the X direction and the absolute displacement values ​​of the two-dimensional time grating in the Y direction are used as the coordinates of the moving scale base in the X and Y directions, thus obtaining the absolute displacement of the moving scale base.

4. The absolute planar two-dimensional time-grid displacement measurement method based on alternating electric field according to claim 3, characterized in that: If an excitation signal is applied to the X excitation pair from left to right, the sensing signal of the sensing group consisting of the sensing electrodes in the column on the left side of each sensing unit is taken for calculation; if an excitation signal is applied to the X excitation pair from right to left, the sensing signal of the sensing group consisting of the sensing electrodes in the column on the right side of each sensing unit is taken for calculation. If the excitation signal is applied to the Y excitation pair stage from top to bottom, the sensing signal of the sensing group composed of the sensing electrodes in the upper row of each sensing unit is taken for calculation and processing; if the excitation signal is applied to the Y excitation pair stage from bottom to top, the sensing signal of the sensing group composed of the sensing electrodes in the lower row of each sensing unit is taken for calculation and processing.

5. The absolute planar two-dimensional time-grid displacement measurement method based on alternating electric field according to claim 3, characterized in that: Excitation signals are applied simultaneously to k1 X excitation pairs and k2 Y excitation pairs.

6. The absolute planar two-dimensional time-grid displacement measurement method based on alternating electric field according to claim 3, characterized in that: Excitation signals are applied to k1 X excitation pairs and k2 Y excitation pairs respectively.

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