An absolute planar two-dimensional time grating displacement sensor

Abstract

The application discloses an absolute plane two-dimensional time grating displacement sensor, which comprises a first excitation coil line array with X-direction coarse measurement excitation groups I and II, a second excitation coil line array with Y-direction coarse measurement excitation groups I and II, a third excitation coil line array with X-direction fine measurement excitation groups I and II and a fourth excitation coil line array with Y-direction fine measurement excitation groups I and II; and the sensor further comprises a first induction coil which forms an X-direction coarse measurement channel with the first excitation coil line array, a second induction coil which forms a Y-direction coarse measurement channel with the second excitation coil line array, a third induction coil which forms an X-direction fine measurement channel with the third excitation coil line array and a fourth induction coil which forms a Y-direction fine measurement channel with the fourth excitation coil line array. The coarse measurement and fine measurement are excited at different times, the induction signals are calculated, and the absolute linear displacement values in the X-direction and the Y-direction are obtained. The application can realize integrated plane two-dimensional absolute linear displacement measurement and ensure measurement accuracy.

Description

Technical Field

[0001] This invention belongs to the technical field of planar two-dimensional displacement precision measurement sensor, specifically relating to an absolute planar two-dimensional time-grating displacement sensor. 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 mainly include planar two-dimensional grating displacement sensors, capacitance-based two-dimensional displacement sensors, and electromagnetic induction-based two-dimensional displacement sensors. Among these, the planar two-dimensional grating displacement sensor is the most widely used, possessing advantages such as high accuracy, large measurement range, high resolution, and good dynamic performance. However, it relies heavily on ultra-precise grating spacing, and current manufacturing processes are nearing their limits, making further breakthroughs in accuracy difficult. Furthermore, it has high cost and weak resistance to oil contamination. Capacitance-based two-dimensional displacement sensors employ non-contact measurement, featuring frictionless, wear-free, and inertial characteristics. They offer a high signal-to-noise ratio, high sensitivity, high resolution, and good accuracy stability. However, their measurement range is generally small, their anti-interference capability is weak, and displacement measurement in two directions requires complex decoupling calculations.

[0003] In recent years, a planar two-dimensional time-grating displacement sensor based on the principle of electromagnetic induction and using clock pulses as the displacement measurement reference has been developed in China. It can achieve high-resolution and high-precision displacement measurement without relying on precise spatial markings. 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-off. Furthermore, the displacement calculation in the X and Y directions is relatively complex. Previous research on absolute one-dimensional linear time-grating displacement sensors employed two schemes to achieve absolute position measurement: "single-pole coarse measurement + multi-pole fine measurement" and differential pole positioning. These two schemes represent special cases where the number of poles is coprime. "Single-pole + multi-pole" involves a combination of sensors with one pole and N poles, while differential pole positioning involves a combination of sensors with N-1 poles and N poles. However, the "single-pole + multi-pole" combination requires high measurement accuracy for the single pole and is not easy to achieve absolute positioning; the differential pole combination has high measurement accuracy in the coarse measurement part but a small error limit, also making absolute positioning difficult. Summary of the Invention

[0004] The purpose of this invention is to provide an absolute planar two-dimensional time-grid displacement sensor to reduce cumulative and random errors and improve measurement accuracy.

[0005] The absolute planar two-dimensional time-grid displacement sensor of the present invention includes a fixed scale and a movable scale parallel to and opposite the fixed scale with an installation gap. The fixed scale includes a fixed scale base and an excitation unit disposed on the fixed scale base. The movable scale includes a movable scale base and a sensing unit disposed on the movable scale base.

[0006] The excitation unit includes a first excitation coil array, a second excitation coil array, a third excitation coil array, and a fourth excitation coil array located on different layers and insulated from each other. The first excitation coil array has an X-direction coarse excitation group I and an X-direction coarse excitation group II, with a pole pitch of W1 and a number of pole pairs of M. The second excitation coil array has a Y-direction coarse excitation group I and a Y-direction coarse excitation group II, with a pole pitch of W1 and a number of pole pairs of M. The third excitation coil array has an X-direction fine excitation group I and an X-direction fine excitation group II, with a pole pitch of W2 and a number of pole pairs of N. The fourth excitation coil array has a Y-direction fine excitation group I and a Y-direction fine excitation group II, with a pole pitch of W2 and a number of pole pairs of N. Wherein, M and N are coprime numbers, 1 < M < N-1, and M*W1 = N*W2.

[0007] The sensing unit includes a first induction coil, a second induction coil, a third induction coil, and a fourth induction coil. The first induction coil and the first excitation coil array are parallel and directly opposite each other in the Z-direction, forming a coarse measurement channel in the X-direction. The second induction coil and the second excitation coil array are parallel and directly opposite each other in the Z-direction, forming a coarse measurement channel in the Y-direction. The third induction coil and the third excitation coil array are parallel and directly opposite each other in the Z-direction, forming a fine measurement channel in the X-direction. The fourth induction coil and the fourth excitation coil array are parallel and directly opposite each other in the Z-direction, forming a fine measurement channel in the Y-direction.

[0008] During operation, the moving scale moves parallel to the fixed scale. First, excitation electrical signals U with frequency f1, amplitude A, and phase difference of 90° are applied to the X-axis coarse measurement excitation group I and X-axis coarse measurement excitation group II, respectively. sx with U cx Excitation electrical signals U with frequency f2, amplitude A, and phase difference of 90° are respectively applied to Y-direction coarse measurement excitation group I and Y-direction coarse measurement excitation group II. sy with U cy At this time, the third and fourth excitation coil arrays are grounded (i.e., the third and fourth excitation coil arrays are not working). The first induction coil outputs a first traveling wave signal (an induction signal carrying displacement information), and the second induction coil outputs a second traveling wave signal (an induction signal carrying displacement information). Both the first and second traveling wave signals are converted into square wave signals and stored. Then, the excitation electrical signal U is quickly... sx with U cx Switch to X-axis precision measurement excitation group I and X-axis precision measurement excitation group II, and transmit the excitation electrical signal U. sy with U cySwitching to Y-axis fine measurement excitation group I and Y-axis fine measurement excitation group II, the first and second excitation coil arrays are grounded (i.e., the first and second excitation coil arrays are not working). The third induction coil outputs a third traveling wave signal (an induction signal carrying displacement information), and the fourth induction coil outputs a fourth traveling wave signal (an induction signal carrying displacement information). The third traveling wave signal is then processed to obtain the X-axis fine measurement displacement value x2. The fourth traveling wave signal is processed to obtain the Y-axis fine measurement displacement value y2. The stored square wave signal converted from the first traveling wave signal is processed to obtain the X-axis coarse measurement displacement value x1. The stored square wave signal converted from the second traveling wave signal is processed to obtain the Y-axis coarse measurement displacement value y1. Finally, using x1, x2, y1, and y2, a two-dimensional absolute displacement calculation is performed to obtain the X-axis absolute linear displacement value x. abs and the absolute linear displacement value y in the Y direction abs .

[0009] The first excitation coil array consists of coils of the same size and width. M first-winding rectangular coils, M second-winding rectangular coils, M first-winding rectangular coils, and M second-winding rectangular coils, each with a length greater than N*W2, are arranged alternately at equal intervals (d) along the X-axis. The M first-winding rectangular coils and M first-winding rectangular coils are connected in series to form the X-axis coarse excitation group I. The M second-winding rectangular coils and M second-winding rectangular coils are connected in series to form the X-axis coarse excitation group II.

[0010] The second excitation coil array consists of coils of the same size and width. M first-winding rectangular coils, M second-winding rectangular coils, M first-winding rectangular coils, and M second-winding rectangular coils, each with a length greater than N*W2, are arranged alternately at equal intervals (d) along the Y-axis. The M first-winding rectangular coils and M first-winding rectangular coils are connected in series to form the Y-axis coarse excitation group I. The M second-winding rectangular coils and M second-winding rectangular coils are connected in series to form the Y-axis coarse excitation group II.

[0011] The third excitation coil array consists of coils of the same size and width. N third forward-wound rectangular coils, N fourth forward-wound rectangular coils, N third reverse-wound rectangular coils, and N fourth reverse-wound rectangular coils, each with a length greater than M*W1, are arranged alternately at equal intervals (d) along the X-axis. These N third forward-wound rectangular coils and N third reverse-wound rectangular coils are connected in series to form the X-axis precision measurement excitation group I. These N fourth forward-wound rectangular coils and N fourth reverse-wound rectangular coils are connected in series to form the X-axis precision measurement excitation group II.

[0012] The fourth excitation coil array consists of coils of the same size and width. N third forward-wound rectangular coils, N fourth forward-wound rectangular coils, N third reverse-wound rectangular coils, and N fourth reverse-wound rectangular coils, each with a length greater than M*W1, are arranged alternately at equal intervals (d) along the Y-axis. The N third forward-wound rectangular coils and N third reverse-wound rectangular coils are connected in series to form the Y-axis precision measurement excitation group I. The N fourth forward-wound rectangular coils and N fourth reverse-wound rectangular coils are connected in series to form the Y-axis precision measurement excitation group II.

[0013] The first induction coil consists of two sinusoidal conductor segments I and II, wound along the X-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. Sinusoidal conductor segments I and II are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the first traveling wave signal output terminals. In other words, the first induction coil is formed by connecting two sinusoidal conductor segments I and II, wound along the X-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180° in series (equivalent to two sinusoidal coils wound in reverse series).

[0014] The third induction coil consists of two sinusoidal conductor segments III and IV, wound along the X-direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the third traveling wave signal output terminals. In other words, the third induction coil is formed by connecting two sinusoidal conductor segments III and IV in series along the X-direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180° (equivalent to two sinusoidal coils wound in reverse series).

[0015] The second induction coil consists of two sinusoidal conductor segments I and II, wound along the Y-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. Sinusoidal conductor segments I and II are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the second traveling wave signal output terminals. In other words, the second induction coil is formed by connecting two sinusoidal conductor segments I and II, wound along the Y-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180° in series (equivalent to two sinusoidal coils wound in reverse series).

[0016] The fourth induction coil consists of two sinusoidal conductor segments III and IV, wound along the Y-direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the fourth traveling wave signal output terminals. In other words, the fourth induction coil is formed by connecting two sinusoidal conductor segments III and IV, wound along the Y-direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°, in series (equivalent to two sinusoidal coils wound in reverse series).

[0017] The sinusoidal conductor segment I of the first induction coil and the sinusoidal conductor segment III of the third induction coil are distributed on the same layer, and the sinusoidal conductor segment II of the first induction coil and the sinusoidal conductor segment IV of the third induction coil are distributed on the same layer. The starting ends of the first induction coil and the starting ends of the third induction coil are aligned in the X direction and spaced h1 apart in the Y direction; where h1 = B1 + B2 + k1, and k1 represents the minimum distance between the first and third induction coils in the Y direction.

[0018] The sinusoidal conductor segment I of the second induction coil and the sinusoidal conductor segment III of the fourth induction coil are distributed on the same layer, and the sinusoidal conductor segment II of the second induction coil and the sinusoidal conductor segment IV of the fourth induction coil are distributed on the same layer. The starting ends of the second induction coil and the fourth induction coil are aligned in the Y direction and spaced h apart in the X direction; where h2 = B1 + B2 + k2, and k2 represents the minimum distance between the second and fourth induction coils in the X direction.

[0019] The n=2. The first, second, third, and fourth induction coils are formed by winding two sinusoidal coils of the same size with a bipole pitch (corresponding to n=2) in reverse series, forming a differential structure. This structure can eliminate the fourth displacement harmonic error of the sensor, enhance the strength of the induced signal and the signal-to-noise ratio, and improve the measurement accuracy of the sensor.

[0020] The The amplitudes of sinusoidal conductor segment I and sinusoidal conductor segment II are designed as follows: The height of the first and second induction coils is W1-d, which is exactly equal to the total width occupied by a first forward-wound rectangular coil, a second forward-wound rectangular coil, a first reverse-wound rectangular coil, and a second reverse-wound rectangular coil arranged along the X / Y direction. This can better avoid introducing unnecessary high-order harmonic errors into the coarsely measured induction signal and make it easier to decouple the coarsely measured X and Y direction induction signals.

[0021] The The amplitudes of sinusoidal conductor segments III and IV are designed as follows: The height of the third and fourth induction coils is W2-d, which is exactly equal to the total width occupied by a third forward-wound rectangular coil, a fourth forward-wound rectangular coil, a third reverse-wound rectangular coil, and a fourth reverse-wound rectangular coil arranged along the X / Y direction. This can better avoid introducing unnecessary high-order harmonic errors into the precisely measured induction signal and make it easier to decouple the precisely measured X and Y direction induction signals.

[0022] f1≠f2. Different frequencies of excitation electrical signals are used in the X and Y directions, which makes it simpler and more convenient to decouple the induction signals in the X and Y directions and to calculate the two-dimensional absolute displacement.

[0023] Two-dimensional absolute displacement calculations are performed using x1, x2, y1, and y2 to obtain the absolute linear displacement value x in the X direction. abs and the absolute linear displacement value y in the Y direction abs The method is as follows: First, use x1 and x2 to perform X-axis pole alignment, and determine the number of X-axis pole alignments Q that the moving ruler passes through. x ; then use the formula: x abs =Q x *W2+x2, calculate the absolute linear displacement value x in the X direction. abs First, use y1 and y2 to perform Y-axis pole alignment to determine the number of Y-axis pole alignments Q that the moving ruler passes through. y ; then use the formula: y abs =Q y *W2+y2, calculate the absolute linear displacement value y in the Y direction. abs Where 0≤Q x ≤N-1, 0≤Q y ≤N-1.

[0024] Using x1 and x2 for X-axis pole alignment, determine the number of X-axis pole alignments Q traversed by the moving scale. x There are two methods: one is suitable for theoretical situations, and the other is suitable for practical situations.

[0025] In theory, using x1 and x2 for X-axis pole alignment, the number of X-axis pole alignments Q traversed by the moving ruler can be determined. x The methods include:

[0026] Step S11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then execute step S12.

[0027] Step S12: Increase the number of pole numbers Q in the X direction traversed by the moving ruler. x =0 (i.e., give Q) x Assign an initial value of 0), and then execute step S13.

[0028] Step S13: Determine if Δx = 0 (i.e., determine if Δx equals 0). If yes, end the process; otherwise, proceed to step S14.

[0029] Step S14: Decrease Δx by W2, so that Q x Increment by 1, then proceed to step S15.

[0030] Step S15: Determine whether Δx < 0. If yes, proceed to step S16; otherwise, return to step S13.

[0031] Step S16: Increase Δx by W1, then return to step S13.

[0032] In practice, x1 and x2 are used for X-axis pole alignment to determine the number of X-axis pole alignments Q traversed by the moving ruler. x The methods include:

[0033] Step P11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then proceed to step P12.

[0034] Step P12: Determine whether -σ < Δx < σ. If yes, proceed to step P13; otherwise, proceed to step P14. Here, σ represents a preset small error.

[0035] Step P13: Increase the number of pole numbers Q in the X direction traversed by the moving ruler. x =0, then end.

[0036] Step P14: Determine if Δx > 0. If yes, proceed to step P16; otherwise, proceed to step P15.

[0037] Step P15: Increase Δx by W1, then return to step P14.

[0038] Step P16: Determine whether Δx is within a certain position interval of the preset X-direction pole number table. If it is, proceed to step P18; otherwise, proceed to step P17. The preset X-direction pole number table is a table showing the correspondence between the X-direction coarse measurement pole number position interval and the X-direction pole number when the X-direction fine measurement pole number position is 0.

[0039] Step P17: Report an error, then end.

[0040] Step P18: Query the preset X-axis pole number table according to Δx, and use the X-axis pole number obtained from the table as Q. x Then it ends.

[0041] The pole number Q in the X direction traversed by the moving ruler is obtained by looking up a table. xThe proposed solution avoids the impact of random errors in actual conditions on the solution results, and can easily achieve absolute position positioning in the X direction while ensuring high accuracy.

[0042] Using y1 and y2 for Y-axis pole alignment, determine the number of Y-axis poles Q traversed by the moving ruler. y There are two methods: one is suitable for theoretical situations, and the other is suitable for practical situations.

[0043] In theory, using y1 and y2 for Y-axis pole finding, the number of Y-axis poles Q traversed by the moving ruler can be determined. y The methods include:

[0044] Step S21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then execute step S22.

[0045] Step S22: Increase the number of pole numbers Q in the Y direction traversed by the moving ruler. y =0 (i.e., give Q) y Assign an initial value of 0), and then execute step S23.

[0046] Step S23: Determine whether Δy = 0 (i.e., determine whether Δy equals 0). If yes, end the process; otherwise, proceed to step S24.

[0047] Step S24: Decrease Δy by W2, so that Q y Increment by 1, then proceed to step S25.

[0048] Step S25: Determine whether Δy < 0. If yes, proceed to step S26; otherwise, return to step S23.

[0049] Step S26: Increase Δy by W1, then return to step S23.

[0050] In practice, Y-axis pole alignment is performed using y1 and y2 to determine the number of Y-axis pole alignments Q traversed by the moving ruler. y The methods include:

[0051] Step P21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then proceed to step P22.

[0052] Step P22: Determine whether -σ < Δy < σ. If yes, proceed to step P23; otherwise, proceed to step P24. Here, σ represents the preset small error.

[0053] Step P23: Increase the number of pole numbers Q in the Y direction traversed by the moving ruler. y =0, then end.

[0054] Step P24: Determine if Δy > 0. If yes, proceed to step P26; otherwise, proceed to step P25.

[0055] Step P25: Increase Δy by W1, then return to step P24.

[0056] Step P26: Determine whether Δy is within a certain position interval of the preset Y-direction pole number table. If yes, proceed to step P28; otherwise, proceed to step P27. The preset Y-direction pole number table is a table showing the correspondence between the position interval of the Y-direction coarse measurement pole and the Y-direction pole number when the position of the Y-direction fine measurement pole is 0.

[0057] Step P27: Report an error, then end.

[0058] Step P28: Query the preset Y-axis pole number table according to Δy, and use the Y-axis pole number obtained from the table as Q. y Then it ends.

[0059] The number of pole numbers Q in the Y direction traversed by the moving ruler is obtained by looking up a table. y The proposed solution avoids the impact of random errors in actual conditions on the solution results, and can easily achieve absolute Y-axis positioning while ensuring high accuracy.

[0060] The preset X-axis pole number table is obtained in the following way:

[0061] First, the sensor X-axis vector path L1 is divided into N regions, and the maximum value of the precise position within the pole in the X-axis of each region is... The minimum value is 0, with displacement a in the X direction. x Plot the X-axis fine measurement pair's position curve as the x-axis and the X-axis fine measurement pair's position within the polar region as the y-axis. Obtain the X-direction displacement value when the X-direction precise measurement pole position is 0. Where i takes all integers from 0 to N-1, and L1 = N*W2.

[0062] Secondly, the sensor X-vector path L1 is divided into M regions, and the maximum value of the coarse X-axis position within the pole in each region is... The minimum value is 0, with displacement a in the X direction. x Plot the X-axis coarse measurement pair's position curve as the x-axis and the X-axis coarse measurement pair's position within the polar region as the y-axis. Here, j takes all integers from 0 to M-1.

[0063] Then, the X-direction displacement value Substitute into the X-axis coarse measurement of the pole position curve F2(a) x In the process, the X-axis coarse measurement pole position point is obtained when the X-axis fine measurement pole position is 0.

[0064] Finally, taking i as the x-axis parallel extremum, As the interval of the X-axis coarse measurement pair's inner pole position when the X-axis fine measurement pair's inner pole position is 0, Each i corresponds one-to-one with i, forming the preset X-axis pole number table.

[0065] The preset Y-axis pole number table is obtained in the following way:

[0066] First, the sensor's Y-vector path L2 is divided into N regions, and the maximum value of the precise Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Plot the Y-axis precision measurement pair's intrapolar position curve using the x-axis as the x-axis and the Y-axis precision measurement pair's intrapolar position as the y-axis. Obtain the Y-direction displacement value when the Y-direction precise measurement pole position is 0. Where i takes all integers from 0 to N-1, and L2 = N*W2.

[0067] Secondly, the sensor's Y-vector path L2 is divided into M regions, and the maximum value of the coarse Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Plot the Y-axis coarse measurement pair's inner position curve as the x-axis and the Y-axis coarse measurement pair's inner position as the y-axis. Here, j takes all integers from 0 to M-1.

[0068] Then, the Y-axis displacement value Substitute into the Y-axis coarse measurement of the inner position curve F2(a) y In the process, the Y-direction coarse measurement inner pole position point is obtained when the Y-direction fine measurement inner pole position is 0.

[0069] Finally, taking i as the Y-axis epipolar number, As the interval of the inner pole position of the coarse Y-axis measurement pair when the inner pole position of the fine Y-axis measurement pair is 0, Each i corresponds one-to-one with the preset Y-axis pole number table.

[0070] Compared with the prior art, the present invention has the following advantages:

[0071] (1) Under the premise of ensuring sensor stability, real-time performance and high resolution, an integrated planar two-dimensional absolute linear displacement measurement is realized, which has the advantages of eliminating sensor cumulative error, no need to manually find zero when powered on, and no data loss when powered off.

[0072] (2) The excitation coil array in the excitation unit adopts a structure with coprime pole numbers, and 1 < M < N-1. Compared with the differential pole absolute positioning method of "N pole pairs and N-1 pole pairs", the error limit is larger. Compared with the combination absolute positioning scheme of "single pole pair + multiple pole pairs", the coarse measurement positioning accuracy is higher. It can achieve absolute positioning more easily and ensure high accuracy.

[0073] (3) Coarse and fine measurement are time-division excitation. Different frequency excitation electrical signals are used in the X and Y directions. While reducing the power consumption of the sensor circuit, the signal decoupling in the X and Y directions and the two-dimensional absolute displacement calculation are simpler and more convenient.

[0074] (4) The excitation unit and the sensing unit adopt PCB processing technology, which ensures high precision and strong anti-interference ability of the sensor, while making the processing convenient and quick, the manufacturing cost low, and suitable for mass production. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of the absolute planar two-dimensional time-grid displacement sensor of the present invention.

[0076] Figure 2 This diagram shows the positional relationship between the first and second induction coils and the first and second excitation coil linear arrays in the X-axis coarse measurement channel and the Y-axis coarse measurement channel of the present invention.

[0077] Figure 3 This is a diagram showing the positional relationship between the third and fourth induction coils and the third and fourth excitation coil linear arrays in the X-axis and Y-axis precision measurement channels of the present invention.

[0078] Figure 4 This is a schematic diagram of the arrangement of the first excitation coil array in this invention.

[0079] Figure 5 This is a schematic diagram of the arrangement of the fourth excitation coil array in this invention.

[0080] Figure 6 This is a diagram showing the positional relationship between the first and third induction coils in this invention.

[0081] Figure 7 This is a diagram showing the positional relationship between the second and fourth induction coils in this invention.

[0082] Figure 8 This is a block diagram illustrating the signal processing principle of the present invention.

[0083] Figure 9 In Embodiment 1 of the present invention, the number of pole pairs Q in the X direction traversed by the moving ruler is determined. x The method flowchart.

[0084] Figure 10 In Embodiment 1 of the present invention, the number of Y-axis poles Q traversed by the moving ruler is determined.y The method flowchart.

[0085] Figure 11 In Embodiment 2 of the present invention, the number of pole pairs Q in the X direction traversed by the moving ruler is determined. x The method flowchart.

[0086] Figure 12 In Embodiment 2 of the present invention, the number of Y-axis poles Q traversed by the moving ruler is determined. y The method flowchart.

[0087] Figure 13 The X-axis fine and coarse measurement of the inner pole position curve F1(a) in Embodiment 2 of the present invention x ), F2(a x A schematic diagram of ).

[0088] Figure 14 The Y-axis fine and coarse measurement of the inner pole position curve F1(a) in Embodiment 2 of the present invention y ), F2(a y A schematic diagram of ). Detailed Implementation

[0089] Example 1: As Figures 1 to 7 As shown, the absolute planar two-dimensional time-grid displacement sensor in this embodiment includes a fixed scale 1 and a movable scale 2 installed parallel to the fixed scale 1 with a gap of 0.8 mm. The fixed scale 1 includes a fixed scale base 10 and an excitation unit arranged on the upper surface of the fixed scale base 10. The movable scale 2 includes a movable scale base 20 and a sensing unit arranged on the lower surface of the movable scale base 20.

[0090] like Figures 2 to 5 As shown, the excitation unit includes a first excitation coil array 11, a second excitation coil array 12, a third excitation coil array 13, and a fourth excitation coil array 14, which are located on different layers and are insulated from each other.

[0091] The first excitation coil array 11 has an X-direction coarse measurement excitation group I and an X-direction coarse measurement excitation group II. The pole pitch of the first excitation coil array 11 is W1, and the number of pole pairs is M. Preferably, the first excitation coil array 11 consists of coils of the same size and width. A series of M first-winding rectangular coils, M second-winding rectangular coils, M first-winding rectangular coils, and M second-winding rectangular coils, each with a length greater than N*W2, are arranged alternately at equal intervals (distance d) along the X-axis. Each of these coils forms a pole pair. The M first-winding rectangular coils and M first-winding rectangular coils are connected in series to form X-axis coarse excitation group I. The M second-winding rectangular coils and M second-winding rectangular coils are connected in series to form X-axis coarse excitation group II.

[0092] The second excitation coil array 12 has a Y-direction coarse measurement excitation group I and a Y-direction coarse measurement excitation group II. The pole pitch of the second excitation coil array 12 is W1, and the number of pole pairs is M. Preferably, the second excitation coil array 12 consists of coils of the same size and width. A series of M first-winding rectangular coils, M second-winding rectangular coils, M first-winding rectangular coils, and M second-winding rectangular coils, each with a length greater than N*W2, are arranged alternately at equal intervals (distance d) along the Y-axis. Each of these coils forms a pole pair. The M first-winding rectangular coils and M first-winding rectangular coils are connected in series to form Y-axis coarse excitation group I. The M second-winding rectangular coils and M second-winding rectangular coils are connected in series to form Y-axis coarse excitation group II.

[0093] The third excitation coil array 13 has an X-direction precision excitation group I and an X-direction precision excitation group II. The pole pitch of the third excitation coil array 13 is W2, and the number of pole pairs is N. Preferably, the third excitation coil array 13 consists of coils of the same size and width. A series of N third-direct-wound rectangular coils, N fourth-direct-wound rectangular coils, N third-reverse-wound rectangular coils, and N fourth-reverse-wound rectangular coils, each with a length greater than M*W1, are arranged alternately at equal intervals (distance d) along the X-axis. Each of these coils forms a pole pair. The N third-direct-wound and N third-reverse-wound rectangular coils are connected in series to form X-axis precision excitation group I. The N fourth-direct-wound and N fourth-reverse-wound rectangular coils are connected in series to form X-axis precision excitation group II.

[0094] The fourth excitation coil array 14 has a Y-direction precision excitation group I and a Y-direction precision excitation group II. The pole pitch of the fourth excitation coil array 14 is W2, and the number of pole pairs is N. Preferably, the fourth excitation coil array 14 consists of coils of the same size and width. A series of N third-direct-wound rectangular coils, N fourth-direct-wound rectangular coils, N third-reverse-wound rectangular coils, and N fourth-reverse-wound rectangular coils, each with a length greater than M*W1, are arranged alternately at equal intervals along the Y-axis. Each of these coils forms a pole pair. The N third-direct-wound rectangular coils and N third-reverse-wound rectangular coils are connected in series to form Y-axis precision excitation group I. The N fourth-direct-wound rectangular coils and N fourth-reverse-wound rectangular coils are connected in series to form Y-axis precision excitation group II.

[0095] In this embodiment, M and N are coprime numbers, 1 < M < N-1, M = 5, W1 = 10.5 mm, d = 0.15 mm, N = 7, W2 = 7.5 mm, sensor X vector range L1 = M * W1 = N * W2 = 52.5 mm, sensor Y vector range L2 = M * W1 = N * W2 = 52.5 mm, and the total sensor range is 52.5 mm × 52.5 mm. The lengths of the first and second forward-wound rectangular coils and the first and second reverse-wound rectangular coils in the first excitation coil array 11 along the Y direction are 55 mm, which covers the sensor Y vector range while avoiding end effects. The lengths of the first and second forward-wound rectangular coils and the first and second reverse-wound rectangular coils in the second excitation coil array 12 along the X direction are 55 mm, which covers the sensor X vector range while avoiding end effects. The third and fourth forward-wound rectangular coils and the third and fourth reverse-wound rectangular coils in the third excitation coil array 13 have a length of 55 mm along the Y direction, which covers the sensor's Y-vector range while avoiding end effects. Similarly, the third and fourth forward-wound rectangular coils and the third and fourth reverse-wound rectangular coils in the fourth excitation coil array 14 have a length of 55 mm along the X direction, which covers the sensor's X-vector range while avoiding end effects. In other embodiments, the total sensor range can be extended to a larger range, provided that its coprime pole numbers M and N satisfy 1 < M < N-1.

[0096] like Figure 6 , Figure 7 As shown, the sensing unit includes a first sensing coil 21, a second sensing coil 22, a third sensing coil 23, and a fourth sensing coil 24.

[0097] The first induction coil 21 is composed of two sinusoidal conductor segments I and II, wound along the X-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the first traveling wave signal output terminals. In other words, the first induction coil 21 is formed by connecting two sinusoidal conductor segments I and II, wound along the X-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. The first induction coil 21 and the first excitation coil array 11 are parallel and directly opposite each other in the Z-direction, forming a coarse measurement channel in the X-direction. In this embodiment, n = 2.

[0098] The second induction coil 22 consists of two sinusoidal conductor segments I and II, wound along the Y-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the second traveling wave signal output terminals. In other words, the second induction coil 22 is formed by connecting two sinusoidal conductor segments I and II, wound along the Y-direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. The second induction coil 22 and the second excitation coil array 12 are parallel and directly opposite each other in the Z-direction, forming a coarse measurement channel in the Y-direction.

[0099] The third induction coil 23 is composed of two sinusoidal conductor segments III and IV, wound along the X-direction with the same starting position, amplitude B, period W2, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the third traveling wave signal output terminals. In other words, the third induction coil 23 is formed by connecting two sinusoidal conductor segments III and IV in series along the X-direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°. The third induction coil 23 and the third excitation coil array 13 are parallel and directly opposite each other in the Z-direction, forming an X-direction precision measurement channel. In this embodiment,

[0100] The fourth induction coil 24 is composed of two sinusoidal conductor segments III and IV, wound along the Y direction with the same starting position, amplitude B, period W2, number of periods n, and phase difference of 180°. These two segments are arranged in two layers, with their starting ends connected via vias and their ending ends serving as the fourth traveling wave signal output terminals. In other words, the fourth induction coil 24 is formed by connecting two sinusoidal conductor segments III and IV, wound along the Y direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180° in series. The fourth induction coil 24 and the fourth excitation coil array 14 are parallel and directly opposite each other in the Z direction, forming a Y-direction precision measurement channel.

[0101] Preferably, the sinusoidal conductor segment I of the first induction coil 21 and the sinusoidal conductor segment III of the third induction coil 23 are distributed in the same layer, and the sinusoidal conductor segment II of the first induction coil 21 and the sinusoidal conductor segment IV of the third induction coil 23 are distributed in the same layer. The starting ends of the first induction coil 21 and the starting ends of the third induction coil 23 are aligned in the X-direction and spaced h1 apart in the Y-direction. Wherein, h1 = B1 + B2 + k1, and k1 represents the minimum distance between the first induction coil 21 and the third induction coil 23 in the Y-direction (i.e., the distance between the trough of the sinusoidal conductor segment II of the first induction coil 21 and the crest of the sinusoidal conductor segment III of the third induction coil 23 in the Y-direction). In this embodiment, k1 = 3.15 mm, h1 = 12 mm.

[0102] Preferably, the sinusoidal conductor segment I of the second induction coil 22 and the sinusoidal conductor segment III of the fourth induction coil 24 are distributed in the same layer, and the sinusoidal conductor segment II of the second induction coil 22 and the sinusoidal conductor segment IV of the fourth induction coil 24 are distributed in the same layer. The starting ends of the second induction coil 22 and the fourth induction coil 24 are aligned in the Y direction and spaced h2 apart in the X direction. Wherein, h2 = B1 + B2 + k2, and k2 represents the minimum distance between the second induction coil 22 and the fourth induction coil 24 in the X direction (i.e., the distance between the trough of the sinusoidal conductor segment II of the second induction coil 22 and the crest of the sinusoidal conductor segment III of the fourth induction coil 24 in the X direction). In this embodiment, k2 = 3.15 mm, and h2 = 12 mm.

[0103] like Figures 8 to 14 As shown, during operation, the moving scale 2 moves parallel to the fixed scale 1. First, excitation electrical signals U with frequency f1, amplitude A, and a 90° phase difference are applied to the X-axis coarse measurement excitation group I and X-axis coarse measurement excitation group II, respectively. sx =Asin(ω1t) and U cx =Acos(ω1t), and excitation electrical signals U with frequency f2, amplitude A, and phase difference of 90° are respectively applied to Y-direction coarse measurement excitation group I and Y-direction coarse measurement excitation group II. sy =Asin(ω2t) and U cy=Acos(ω2t), where the angular frequencies of the excitation signals are ω1 = 2πf1 and ω2 = 2πf2, f1 ≠ f2. At this time, the third excitation coil array 13 and the fourth excitation coil array 14 are grounded (i.e., the third excitation coil array 13 and the fourth excitation coil array 14 are not working). The first induction coil 21 outputs the first traveling wave signal U1, and the second induction coil 22 outputs the second traveling wave signal U2. The first traveling wave signal U1 is amplified, filtered, and shaped by the pre-amplifier signal processing circuit into a first square wave signal, and the second traveling wave signal U2 is amplified, filtered, and shaped by the pre-amplifier signal processing circuit into a second square wave signal. The first and second square wave signals are stored in the memory of the FPGA signal processing module. K1 and K2 are constants. y1 represents the initial phase of the fundamental component, x1 represents the coarse displacement value in the X direction, and y1 represents the coarse displacement value in the Y direction.

[0104] Then, the excitation electrical signal U is quickly (i.e., within 1 ms) transmitted. sx with U cx Switch to X-axis precision measurement excitation group I and X-axis precision measurement excitation group II, and apply the excitation electrical signal U. sy with U cy Switching to Y-direction precision measurement excitation group I and Y-direction precision measurement excitation group II, the first excitation coil array 11 and the second excitation coil array 12 are grounded (i.e., the first excitation coil array 11 and the second excitation coil array 12 are not working), the third induction coil 23 outputs the third traveling wave signal U3, and the fourth induction coil 24 outputs the fourth traveling wave signal U4. Among these, K3 and K4 are constants. y2 represents the initial phase of the fundamental component, x2 represents the precise displacement value in the X direction, and y2 represents the precise displacement value in the Y direction.

[0105] The third traveling wave signal U3, after being amplified, filtered, and shaped by the pre-amplifier signal processing circuit, is sent to the FPGA signal processing module for phase comparison with a reference signal of the same frequency that has been converted to a square wave. The phase difference is interpolated using a high-frequency clock pulse to obtain the X-axis precision measurement phase P3 within the pole pair. The fourth traveling wave signal U4, after being amplified, filtered, and shaped by the pre-amplifier signal processing circuit, is sent to the FPGA signal processing module for phase comparison with a reference signal of the same frequency that has been converted to a square wave. The phase difference is interpolated using a high-frequency clock pulse to obtain the Y-axis precision measurement phase P4 within the pole pair. Among these,

[0106] The stored first square wave signal is compared with a reference signal of the same frequency that has been converted to a square wave. The phase difference is interpolated using a high-frequency clock pulse to obtain the coarsely measured intra-pole phase P1 in the X direction. The stored second square wave signal is compared with a reference signal of the same frequency that has been converted to a square wave. The phase difference is interpolated using a high-frequency clock pulse to obtain the coarsely measured intra-pole phase P2 in the Y direction.

[0107] P1, P2, P3, and P4 are sent to the host computer. After receiving P1, P2, P3, and P4, the host computer performs conversion to obtain the X-direction coarse displacement value x1, the Y-direction coarse displacement value y1, the X-direction fine displacement value x2, and the Y-direction fine displacement value y2.

[0108] The host computer then uses x1, x2, y1, and y2 to perform two-dimensional absolute displacement calculations, obtaining the absolute linear displacement value x in the X direction. abs and the absolute linear displacement value y in the Y direction abs .

[0109] like Figure 9 , Figure 10 As shown, the absolute displacement in the X direction is calculated using x1 and x2, yielding the absolute linear displacement value x in the X direction. abs The method is the theoretical method, which is as follows:

[0110] First, use x1 and x2 to perform X-axis pole alignment, and determine the number of X-axis pole alignments Q that the moving ruler passes through. x Then use the formula: x abs =Q x *W2+x2, calculate the absolute linear displacement in the X direction. Where, 0≤Q x ≤6.

[0111] As a preferred option, determine the number of pole pairs Q in the X direction traversed by the moving ruler. x The method (see) Figure 9 ),include:

[0112] Step S11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then execute step S12.

[0113] Step S12, make Q x =0 (i.e., give Q) x Assign an initial value of 0), and then execute step S13.

[0114] Step S13: Determine if Δx = 0. If yes, end the process; otherwise, proceed to step S14.

[0115] Step S14: Decrease Δx by W2 (i.e., Δx = Δx - W2), so that Q x Increment by 1 (i.e., Q)x =Q x +1), then proceed to step S15.

[0116] Step S15: Determine whether Δx < 0. If yes, proceed to step S16; otherwise, return to step S13.

[0117] Step S16: Increase Δx by W1 (i.e., Δx = Δx + W1), then return to step S13.

[0118] First, use y1 and y2 to perform Y-axis pole alignment, and determine the number Q of Y-axis pole alignments traversed by the moving ruler. y Then use the formula: y abs =Q y *W2+y2, calculate the absolute linear displacement in the Y direction. Where, 0≤Q y ≤6.

[0119] As a preferred option, determine the number of pole pairs Q in the Y direction traversed by the moving ruler. y The method (see) Figure 10 ),include:

[0120] Step S21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then execute step S22.

[0121] Step S22, make Q y =0 (i.e., give Q) y Assign an initial value of 0), and then execute step S23.

[0122] Step S23: Determine if Δy = 0. If yes, end the process; otherwise, proceed to step S24.

[0123] Step S24: Decrease Δy by W2 (i.e., Δy = Δy - W2), so that Q y Increment by 1 (i.e., Q) y =Q y +1), then proceed to step S25.

[0124] Step S25: Determine whether Δy < 0. If yes, proceed to step S26; otherwise, return to step S23.

[0125] Step S26: Increase Δy by W1 (i.e., Δy = Δy + W1), then return to step S23.

[0126] The above method, based on the principle of synchronous movement of the coarse and fine measurement channels, calculates the X-direction coarse measurement pole position Δx when the fine measurement pole position in the X direction is 0 using Δx = x1 - x2, and calculates the Y-direction coarse measurement pole position Δy when the fine measurement pole position in the Y direction is 0 using Δy = y1 - y2. This process is repeated cyclically until Δx = 0 and Δy = 0, at which point the number of X-direction poles traversed by the moving scale, Q, is obtained. x And the Y-axis pole number Q y This enables coarse polarity positioning.

[0127] In reality, sensors exhibit random errors during measurement, leading to slight deviations in the pole position calculated by the host computer. Using the cyclic decrementing method described in Example 1 for pole number calculation would result in an infinite loop, preventing accurate calculation. Therefore, the method for determining the X-axis and Y-axis pole numbers traversed by the moving scale in Example 1 is only suitable for simulation testing and not for actual situations.

[0128] Example 2: The structure of the absolute planar two-dimensional time-grating displacement sensor in this example is the same as that in Example 1, except that the host computer uses x1, x2, y1, and y2 to perform two-dimensional absolute displacement calculation to obtain the absolute linear displacement value x in the X direction. abs and the absolute linear displacement value y in the Y direction abs The method.

[0129] like Figure 11 , Figure 12 As shown, in this embodiment, x1 and x2 are used to calculate the absolute displacement in the X direction, and the absolute linear displacement value x in the X direction is obtained. abs The method described is based on real-world conditions and can eliminate the influence of random errors on the solution results. Specifically, the method is as follows:

[0130] First, use x1 and x2 to perform X-axis pole alignment, and determine the number of X-axis pole alignments Q that the moving ruler passes through. x Then use the formula: x abs =Q x *W2+x2, calculate the absolute linear displacement in the X direction. Where, 0≤Q x ≤6.

[0131] As a preferred option, determine the number of pole pairs Q in the X direction traversed by the moving ruler. x The method (see) Figure 11 ),include:

[0132] Step P11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then proceed to step P12.

[0133] Step P12: Determine if -σ < Δx < σ. If yes, proceed to step P13; otherwise, proceed to step P14. Here, σ represents a preset small error. σ is determined by the actual error within the sensor's X and Y axes.

[0134] Step P13, make Q x =0, then end.

[0135] Step P14: Determine if Δx > 0. If yes, proceed to step P16; otherwise, proceed to step P15.

[0136] Step P15: Increase Δx by W1 (i.e., Δx = Δx + W1), then return to step P14.

[0137] Step P16: Determine whether Δx is within a certain position interval of the preset X-direction pole number table. If yes, proceed to step P18; otherwise, proceed to step P17. The preset X-direction pole number table is a table showing the correspondence between the X-direction coarse measurement pole number position interval and the X-direction pole number when the X-direction fine measurement pole number position is 0.

[0138] Step P17: Report an error and then end. After reporting the error, the absolute linear displacement values ​​in the X and Y directions will no longer be calculated, and the measurement needs to be reinstalled.

[0139] Step P18: Query the preset X-axis pole number table according to Δx, and use the X-axis pole number obtained from the table as Q. x Then it ends.

[0140] Preferably, the preset X-axis pole number table (see Table 1) is obtained as follows:

[0141] First, the sensor's X-axis vector range L1 = 52.5 mm is divided into N = 7 regions. The maximum value of the precise X-axis position within the pole in each region is... The minimum value is 0, with displacement a in the X direction. x Using the x-axis as the horizontal axis and the X-axis precise measurement pair's intrapolar position as the vertical axis, plot the X-axis precise measurement pair's intrapolar position curve F1(a). x (See also) Figure 13 (the jagged, thick dashed line in the middle) Obtain the X-direction displacement value when the X-direction precise measurement pole position is 0. Where i takes any integer from 0 to 6.

[0142] Secondly, the sensor X-vector path L1 is divided into M = 5 regions, and the maximum value of the coarse X-axis position within the pole in each region is... The minimum value is 0, with displacement a in the X direction. x Using the x-axis as the x-axis and the X-axis coarse measurement position within the pole as the y-axis, plot the X-axis coarse measurement position within the pole curve F2(a).x (See also) Figure 13 (the thick solid serrated lines in the middle) Here, j takes all integers from 0 to 4.

[0143] Then, the X-direction displacement value Substitute into the X-axis coarse measurement of the pole position curve F2(a) x In the process, the X-axis coarse measurement pole position point is obtained when the X-axis fine measurement pole position is 0.

[0144] Finally, taking i as the x-axis parallel extremum, As the interval of the X-axis coarse measurement pair's inner pole position when the X-axis fine measurement pair's inner pole position is 0, Each i corresponds one-to-one with the preset X-axis pole number table (see Table 1), where Δx is in mm.

[0145] Table 1

[0146] [0-σ, 0+σ] 0 [7.5-σ, 7.5+σ] 1 [4.5-σ, 4.5+σ] 2 [1.5-σ, 1.5+σ] 3 [9-σ, 9+σ] 4 [6-σ, 6+σ] 5 [3-σ, 3+σ] 6

[0147] First, use y1 and y2 to perform Y-axis pole alignment, and determine the number Q of Y-axis pole alignments traversed by the moving ruler. y Then use the formula: y abs =Q y *W2+y2, calculate the absolute linear displacement in the Y direction. Where, 0≤Q y ≤6.

[0148] As a preferred option, determine the number of pole pairs Q in the Y direction traversed by the moving ruler. y The method (see) Figure 12 ),include:

[0149] Step P21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then proceed to step P22.

[0150] Step P22: Determine whether -σ < Δy < σ. If yes, proceed to step P23; otherwise, proceed to step P24. Here, σ represents the preset small error.

[0151] Step P23, make Q y =0, then end.

[0152] Step P24: Determine if Δy > 0. If yes, proceed to step P26; otherwise, proceed to step P25.

[0153] Step P25: Increase Δy by W1 (i.e., Δy = Δy + W1), then return to step P24.

[0154] Step P26: Determine whether Δy is within a certain position interval of the preset Y-direction pole number table. If yes, proceed to step P28; otherwise, proceed to step P27. The preset Y-direction pole number table is a table showing the correspondence between the Y-direction coarse measurement pole number position interval and the Y-direction pole number when the Y-direction fine measurement pole number position is 0.

[0155] Step P27: Report an error and then end. After reporting the error, the absolute linear displacement values ​​in the X and Y directions will no longer be calculated, and the measurement needs to be reinstalled.

[0156] Step P28: Query the preset Y-axis pole number table according to Δy, and use the Y-axis pole number obtained from the table as Q. y Then it ends.

[0157] As a preferred embodiment, the preset Y-axis pole number table (see Table 2) is obtained as follows:

[0158] First, the sensor's Y-vector range L2 = 52.5 mm is divided into N = 7 regions. The maximum value of the precise Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Using the x-axis as the abscissa and the Y-axis precise measurement pair's intrapolar position as the y-axis, plot the Y-axis precise measurement pair's intrapolar position curve F1(a). y (See also) Figure 14 (the jagged, thick dashed line in the middle) Obtain the Y-direction displacement value when the Y-direction precise measurement pole position is 0. Where i takes any integer from 0 to 6.

[0159] Secondly, the sensor's Y-vector path L2 is divided into M regions, and the maximum value of the coarse Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Using the x-axis as the horizontal axis and the Y-axis coarse measurement position within the polar region as the y-axis, plot the curve F2(a) of the Y-axis coarse measurement position within the polar region. y (See also) Figure 14 (the thick solid serrated lines in the middle) Here, j takes all integers from 0 to 4.

[0160] Then, the Y-axis displacement value Substitute into the Y-axis coarse measurement of the inner position curve F2(a) y In the process, the Y-direction coarse measurement inner pole position point is obtained when the Y-direction fine measurement inner pole position is 0.

[0161] Finally, taking i as the Y-axis epipolar number, As the interval of the inner pole position of the coarse Y-axis measurement pair when the inner pole position of the fine Y-axis measurement pair is 0, A pre-defined table of Y-axis pole numbers is formed, corresponding one-to-one with i (see Table 2), where Δy is in mm.

[0162] Table 2

[0163] [0-σ, 0+σ] 0 [7.5-σ, 7.5+σ] 1 [4.5-σ, 4.5+σ] 2 [1.5-σ, 1.5+σ] 3 [9-σ, 9+σ] 4 [6-σ, 6+σ] 5 [3-σ, 3+σ] 6

Claims

1. An absolute planar two-dimensional time-grid displacement sensor, comprising a fixed scale (1) and a movable scale (2) parallel to and facing the fixed scale with an installation gap, wherein the fixed scale (1) comprises a fixed scale base (10) and an excitation unit disposed on the fixed scale base (10), and the movable scale (2) comprises a movable scale base (20) and a sensing unit disposed on the movable scale base (20); characterized in that: The excitation unit includes a first excitation coil array (11), a second excitation coil array (12), a third excitation coil array (13), and a fourth excitation coil array (14) located on different layers and insulated from each other; the first excitation coil array (11) has an X-direction coarse measurement excitation group I and an X-direction coarse measurement excitation group II, with a pole pitch of W1 and a pole number of M; the second excitation coil array (12) has a Y-direction coarse measurement excitation group I and a Y-direction coarse measurement excitation group II, with a pole pitch of W1 and a pole number of M; the third excitation coil array (13) has an X-direction fine measurement excitation group I and an X-direction fine measurement excitation group II, with a pole pitch of W2 and a pole number of N; the fourth excitation coil array (14) has a Y-direction fine measurement excitation group I and a Y-direction fine measurement excitation group II, with a pole pitch of W2 and a pole number of N; wherein, M and N are coprime numbers, 1 <M<N-1,M*W1=N*W2; The sensing unit includes a first sensing coil (21), a second sensing coil (22), a third sensing coil (23), and a fourth sensing coil (24); the first sensing coil (21) is directly opposite to the first excitation coil array (11) in the Z direction, the second sensing coil (22) is directly opposite to the second excitation coil array (12) in the Z direction, the third sensing coil (23) is directly opposite to the third excitation coil array (13) in the Z direction, and the fourth sensing coil (24) is directly opposite to the fourth excitation coil array (14) in the Z direction. During operation, the moving scale moves parallel to the fixed scale. First, excitation electrical signals U with frequency f1, amplitude A, and phase difference of 90° are applied to the X-axis coarse measurement excitation group I and X-axis coarse measurement excitation group II, respectively. sx with U cx Excitation electrical signals U with frequency f2, amplitude A, and phase difference of 90° are respectively applied to Y-direction coarse measurement excitation group I and Y-direction coarse measurement excitation group II. sy with U cy At this time, the third and fourth excitation coil arrays (13, 14) are grounded, the first induction coil (21) outputs the first traveling wave signal, and the second induction coil (22) outputs the second traveling wave signal. The first and second traveling wave signals are converted into square wave signals and stored. Then, the excitation electrical signal U is quickly converted into a square wave signal. sx with U cx Switch to X-axis precision measurement excitation group I and X-axis precision measurement excitation group II, and transmit the excitation electrical signal U. sy with U cy Switch to Y-direction precision excitation group I and Y-direction precision excitation group II. At this time, the first and second excitation coil arrays (11, 12) are grounded, the third induction coil (23) outputs the third traveling wave signal, and the fourth induction coil (24) outputs the fourth traveling wave signal. Then process the third and fourth traveling wave signals to obtain the X-direction precision displacement value x2 and the Y-direction precision displacement value y2. Process the stored square wave signal to obtain the X-direction coarse displacement value x1 and the Y-direction coarse displacement value y1. Finally, use x1, x2, y1, and y2 to perform two-dimensional absolute displacement calculation to obtain the X-direction absolute linear displacement value x. abs and the absolute linear displacement value y in the Y direction abs .

2. The absolute planar two-dimensional time-grid displacement sensor according to claim 1, characterized in that: The first excitation coil array (11) consists of coils of the same size and width. M first forward-wound rectangular coils, M second forward-wound rectangular coils, M first reverse-wound rectangular coils, and M second reverse-wound rectangular coils with a length greater than N*W2 are arranged alternately at equal intervals along the X-direction; the M first forward-wound rectangular coils and the M first reverse-wound rectangular coils are connected in series to form the X-direction coarse excitation group I; the M second forward-wound rectangular coils and the M second reverse-wound rectangular coils are connected in series to form the X-direction coarse excitation group II. The second excitation coil array (12) consists of coils of the same size and width. M first forward-wound rectangular coils, M second forward-wound rectangular coils, M first reverse-wound rectangular coils, and M second reverse-wound rectangular coils with a length greater than N*W2 are arranged alternately at equal intervals along the Y direction; the M first forward-wound rectangular coils and the M first reverse-wound rectangular coils are connected in series to form the Y-direction coarse excitation group I; the M second forward-wound rectangular coils and the M second reverse-wound rectangular coils are connected in series to form the Y-direction coarse excitation group II. The third excitation coil array (13) consists of coils of the same size and width. N third forward-wound rectangular coils, N fourth forward-wound rectangular coils, N third reverse-wound rectangular coils, and N fourth reverse-wound rectangular coils with a length greater than M*W1 are arranged alternately at equal intervals along the X-direction; N third forward-wound rectangular coils and N third reverse-wound rectangular coils are connected in series to form the X-direction precision measurement excitation group I; N fourth forward-wound rectangular coils and N fourth reverse-wound rectangular coils are connected in series to form the X-direction precision measurement excitation group II; The fourth excitation coil array (14) consists of coils of the same size and width. N third forward-wound rectangular coils, N fourth forward-wound rectangular coils, N third reverse-wound rectangular coils, and N fourth reverse-wound rectangular coils with a length greater than M*W1 are arranged alternately at equal intervals along the Y direction; N third forward-wound rectangular coils and N third reverse-wound rectangular coils are connected in series to form the Y-direction precision measurement excitation group I; N fourth forward-wound rectangular coils and N fourth reverse-wound rectangular coils are connected in series to form the Y-direction precision measurement excitation group II. Where d represents the spacing.

3. The absolute planar two-dimensional time-grid displacement sensor according to claim 2, characterized in that: The first induction coil (21) is composed of a sinusoidal conductor segment I and a sinusoidal conductor segment II wound along the X direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. The sinusoidal conductor segment I and the sinusoidal conductor segment II are respectively arranged in two layers, and their starting ends are connected through vias and their ending ends are used as the first traveling wave signal output ends. The third induction coil (23) is composed of sinusoidal conductor segments III and IV wound along the X direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°. The sinusoidal conductor segments III and IV are respectively arranged in two layers, and their starting ends are connected through vias, and their ending ends serve as the third traveling wave signal output ends. The second induction coil (22) is composed of a sinusoidal conductor segment I and a sinusoidal conductor segment II wound along the Y direction with the same starting position, amplitude B1, period W1, number of periods n, and phase difference of 180°. The sinusoidal conductor segment I and the sinusoidal conductor segment II are respectively arranged in two layers, and their starting ends are connected through vias, and their ending ends serve as the second traveling wave signal output ends. The fourth induction coil (24) is composed of sinusoidal conductor segments III and IV wound along the Y direction with the same starting position, amplitude B2, period W2, number of periods n, and phase difference of 180°. The sinusoidal conductor segments III and IV are respectively arranged in two layers, and their starting ends are connected through vias, and their ending ends serve as the fourth traveling wave signal output ends.

4. The absolute planar two-dimensional time-grid displacement sensor according to claim 3, characterized in that: The sinusoidal conductor segment I of the first induction coil (21) and the sinusoidal conductor segment III of the third induction coil (23) are distributed on the same layer, and the sinusoidal conductor segment II of the first induction coil (21) and the sinusoidal conductor segment IV of the third induction coil (23) are distributed on the same layer; the starting end of the first induction coil (21) and the starting end of the third induction coil (23) are aligned in the X direction and spaced h1 in the Y direction; where h1 = B1 + B2 + k1, and k1 represents the minimum distance between the first induction coil (21) and the third induction coil (23) in the Y direction; The sinusoidal conductor segment I of the second induction coil (22) and the sinusoidal conductor segment III of the fourth induction coil (24) are distributed on the same layer, and the sinusoidal conductor segment II of the second induction coil (22) and the sinusoidal conductor segment IV of the fourth induction coil (24) are distributed on the same layer; the starting end of the second induction coil (22) and the starting end of the fourth induction coil (24) are aligned in the Y direction and spaced h2 apart in the X direction; where h2 = B1 + B2 + k2, and k2 represents the minimum distance between the second induction coil (22) and the fourth induction coil (24) in the X direction.

5. The absolute planar two-dimensional time-grid displacement sensor according to claim 3, characterized in that: The n=2, the The 6. The absolute planar two-dimensional time-grating displacement sensor according to any one of claims 1 to 5, characterized in that: f1≠f2.

7. The absolute planar two-dimensional time-grid displacement sensor according to any one of claims 1 to 5, characterized in that: Two-dimensional absolute displacement calculations are performed using x1, x2, y1, and y2 to obtain the absolute linear displacement value x in the X direction. abs and the absolute linear displacement value y in the Y direction abs The method is as follows: First, use x1 and x2 to perform X-axis pole alignment, and determine the number of X-axis pole alignments Q that the moving ruler passes through. x ; then use the formula: x abs =Q x *W2+x2, calculate the absolute linear displacement value x in the X direction. abs ; First, use y1 and y2 to perform Y-axis pole alignment, and determine the number Q of Y-axis pole alignments traversed by the moving ruler. y ; then use the formula: y abs =Q y *W2+y2, calculate the absolute linear displacement value y in the Y direction. abs ; Where 0≤Q x ≤N-1, 0≤Q y ≤N-1.

8. The absolute planar two-dimensional time-grating displacement sensor according to claim 7, characterized in that: Using x1 and x2 for X-axis pole alignment, determine the number of X-axis pole alignments Q traversed by the moving scale. x The methods include: Step S11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then execute step S12; Step S12, make Q x =0, then proceed to step S13; Step S13: Determine if Δx = 0. If yes, end; otherwise, proceed to step S14. Step S14: Decrease Δx by W2, so that Q x Increment by 1, then proceed to step S15; Step S15: Determine if Δx < 0. If yes, proceed to step S16; otherwise, return to step S13. Step S16: Increase Δx by W1, then return to step S13. Using y1 and y2 for Y-axis pole alignment, determine the number of Y-axis poles Q traversed by the moving ruler. y The methods include: Step S21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then execute step S22; Step S22, make Q y =0, then proceed to step S23; Step S23: Determine if Δy = 0. If yes, end; otherwise, proceed to step S24. Step S24: Decrease Δy by W2, so that Q y Increment by 1, then proceed to step S25; Step S25: Determine if Δy < 0. If yes, proceed to step S26; otherwise, return to step S23. Step S26: Increase Δy by W1, then return to step S23.

9. The absolute planar two-dimensional time-grating displacement sensor according to claim 7, characterized in that: Using x1 and x2 for X-axis pole alignment, determine the number of X-axis pole alignments Q traversed by the moving scale. x The methods include: Step P11: Using the formula: Δx=x1-x2, calculate the X-direction coarse measurement position Δx when the X-direction fine measurement position is 0, and then proceed to step P12; Step P12: Determine whether -σ < Δx < σ. If yes, proceed to step P13; otherwise, proceed to step P14. Here, σ represents a preset small error. Step P13, make Q x =0, then end; Step P14: Determine if Δx > 0. If yes, proceed to step P16; otherwise, proceed to step P15. Step P15: Increase Δx by W1, then return to step P14. Step P16: Determine whether Δx is within a certain position range of the preset X-direction pole number table. If it is, proceed to step P18; otherwise, proceed to step P17. The preset X-direction pole number table is a table showing the correspondence between the X-direction coarse measurement pole position range and the X-direction pole number when the X-direction fine measurement pole position is 0. Step P17: Report an error and then end; Step P18: Query the preset X-direction pole number table according to Δx, and use the X-direction pole number obtained from the table as Q. x Then it ends; Using y1 and y2 for Y-axis pole alignment, determine the number of Y-axis poles Q traversed by the moving ruler. y The methods include: Step P21: Using the formula: Δy=y1-y2, calculate the Y-direction coarse measurement position Δy when the Y-direction fine measurement position is 0, and then proceed to step P22; Step P22: Determine whether -σ < Δy < σ. If yes, proceed to step P23; otherwise, proceed to step P24. Wherein, σ represents a preset small error. Step P23, make Q y =0, then end; Step P24: Determine if Δy > 0. If yes, proceed to step P26; otherwise, proceed to step P25. Step P25: Increase Δy by W1, then return to step P24. Step P26: Determine whether Δy is within a certain position range of the preset Y-direction pole number table. If yes, proceed to step P28; otherwise, proceed to step P27. The preset Y-direction pole number table is a table showing the correspondence between the Y-direction coarse measurement pole number position range and the Y-direction pole number when the Y-direction fine measurement pole number position is 0. Step P27: Report an error and then end; Step P28: Query the preset Y-axis pole number table according to Δy, and use the Y-axis pole number obtained from the table as Q. y Then it ends.

10. The absolute planar two-dimensional time-grating displacement sensor according to claim 9, characterized in that: The preset X-axis pole number table is obtained in the following way: First, the sensor X-axis vector path L1 is divided into N regions, and the maximum value of the precise position within the pole in the X-axis of each region is... The minimum value is 0, with displacement a in the X direction. x Plot the X-axis fine measurement pair's position curve as the x-axis and the X-axis fine measurement pair's position within the polar region as the y-axis. Obtain the X-direction displacement value when the X-direction precise measurement pole position is 0. Where i takes all integers from 0 to N-1, and L1 = N*W2; Secondly, the sensor X-vector path L1 is divided into M regions, and the maximum value of the coarse X-axis position within the pole in each region is... The minimum value is 0, with displacement a in the X direction. x Plot the X-axis coarse measurement pair's position curve as the x-axis and the X-axis coarse measurement pair's position within the polar region as the y-axis. Where j takes all integers from 0 to M-1; Then, the X-direction displacement value Substitute into the X-axis coarse measurement of the pole position curve F2(a) x In the process, the X-axis coarse measurement pole position point is obtained when the X-axis fine measurement pole position is 0. Finally, taking i as the x-axis parallel extremum, As the interval of the X-axis coarse measurement pair's inner pole position when the X-axis fine measurement pair's inner pole position is 0, Each i corresponds one-to-one with i, forming the preset X-axis pole number table; The preset Y-axis pole number table is obtained in the following way: First, the sensor's Y-vector path L2 is divided into N regions, and the maximum value of the precise Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Plot the Y-axis precision measurement pair's intrapolar position curve using the x-axis as the x-axis and the Y-axis precision measurement pair's intrapolar position as the y-axis. Obtain the Y-direction displacement value when the Y-direction precise measurement pole position is 0. Where i takes all integers from 0 to N-1, and L2 = N*W2; Secondly, the sensor's Y-vector path L2 is divided into M regions, and the maximum value of the coarse Y-axis position within the pole in each region is... The minimum value is 0, with a displacement a in the Y direction. y Plot the Y-axis coarse measurement pair's inner position curve as the x-axis and the Y-axis coarse measurement pair's inner position as the y-axis. Where j takes all integers from 0 to M-1; Then, the Y-axis displacement value Substitute into the Y-axis coarse measurement of the inner position curve F2(a) y In the process, the Y-direction coarse measurement inner pole position point is obtained when the Y-direction fine measurement inner pole position is 0. Finally, taking i as the Y-axis epipolar number, As the interval of the inner pole position of the coarse Y-axis measurement pair when the inner pole position of the fine Y-axis measurement pair is 0, Each i corresponds one-to-one with the preset Y-axis pole number table.

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