Planar two-dimensional micro-displacement sensor based on four-quadrant eddy current effect

Abstract

The invention discloses a planar two-dimensional micro-displacement sensor based on a four-quadrant eddy current effect, which comprises a detection coil array plate and a target conductor array plate which are parallel up and down, and is characterized in that the detection coil array plate is provided with four planar coils arranged in a shape like a Chinese character'tian 'on an insulating substrate; the target conductor array plate is provided with four metal panels which are arranged in a shape like a Chinese character'tian 'on an insulating substrate. According to the invention, identical excitation signals are introduced into four planar coils on a detection coil array plate, two-dimensional micro-displacement of the detection coil array plate relative to a target conductor array plate is converted into voltage signals of the four planar coils by using an inductance measurement circuit, and the four voltage signals are processed by using a microprocessor system; therefore, the two-dimensional plane relative displacement of the detection coil array plate and the target conductor array plate is obtained. The device is simple in structure, high in measurement precision and suitable for scenes requiring precise measurement of planar two-dimensional micro-displacement in severe environments such as dust and greasy dirt.

Description

Technical Field

[0001] The present invention belongs to the field of planar micro-displacement measurement, and particularly relates to a planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect. Background Art

[0002] Planar two-dimensional micro-displacement sensors have extensive application requirements in fields such as semiconductor manufacturing and optical measurement systems. Currently, there are mainly the following two methods to achieve planar two-dimensional micro-displacement measurement, namely one-dimensional displacement measurement separately and two-dimensional displacement measurement simultaneously. The first method is to use two sets of independent micro-displacement sensors to obtain displacements in the X and Y directions respectively, and achieve two-dimensional micro-displacement measurement through combined measurement. For example, the two-dimensional nano-optical measurement system proposed in Patent CN105674883B achieves a measurement accuracy of micrometers within a millimeter-level measurement range. However, using two sets of single-degree-of-freedom sensors will cause uneliminable Abbe errors and multi-axis cumulative errors due to installation problems, affecting the measurement accuracy. The second method is to directly measure two-dimensional displacements with a single sensor, mainly including planar two-dimensional micro-displacement sensors based on the capacitance principle. For example, CN119437015A proposes a two-dimensional capacitance micro-displacement sensor, which realizes linear measurement in two planar directions. Additionally, there are two-dimensional displacement measurement sensors based on the electromagnetic induction principle. For example, the differential inductance type two-dimensional displacement measurement sensor proposed in CN1904561A places a U-shaped iron core and a coil in the X and Y directions respectively, and measures the displacement by measuring the inductance change of the coil. However, the above-mentioned capacitive sensors are easily affected by environmental factors such as dust and oil, and their applicability is limited in complex working conditions such as metallurgy and petroleum; the above-mentioned inductive sensors have the advantage of being less affected by environmental factors, but there is a large non-linearity in the planar motion characteristics, and the actual application performance indicators are greatly limited. Summary of the Invention

[0003] The purpose of the present invention is to provide a planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect, which has a large linearity within the measurement range and can simultaneously meet the measurement requirements of complex working conditions.

[0004] To achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions:

[0005] A planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect includes a detection coil array board and a target conductor array board.

[0006] The detection coil array board is in the XY plane and includes four planar coils and an insulating matrix inlaid with the planar coils. The four planar coils are arranged in a "field" shape;

[0007] The target conductor array board is in the XY plane and includes four metal panels and an insulating matrix for fixing the metal panels. The four metal panels are arranged in a "field" shape;

[0008] The detection coil array board and the target conductor array board are arranged parallel to each other up and down. The symmetry centers of the detection coil array board and the target conductor array board coincide vertically at the initial position. The detection coil array board and the target conductor array board translate relative to each other in the XY plane, and the vertical distance remains unchanged.

[0009] The four planar coils of the detection coil array board are respectively fed with the same sinusoidal excitation signal. The four inductance measurement circuits respectively measure the inductance values L1, L2, L3, and L4 of the four planar coils, and output four voltage signals U1, U2, U3, and U4. The four voltage signals are connected to the microprocessor system for data processing, and two position signals U x 、U y :

[0010] By calibrating the relationship between U x 、U y and the relative displacements in the X and Y directions, the relative displacements of the detection coil array board and the target conductor array board in the X and Y directions are obtained.

[0011] Further technology of the present invention:

[0012] Preferably, the shape of the planar coil is square or circular.

[0013] Preferably, the outer diameter or side length of the planar coil is D, and the center distance between adjacent planar coils in the X and Y directions is 1.5D.

[0014] Preferably, the shape of the metal panel is square or circular.

[0015] Preferably, the outer diameter or side length of the metal panel is D, and the center distance between adjacent metal panels in the X and Y directions is 2D.

[0016] Preferably, the vertical distance range between the detection coil array board and the target conductor array board is (0, 0.1D).

[0017] Preferably, the displacement range of the detection coil array board relative to the target conductor array board in the X and Y directions is (-0.25D, 0.25D).

[0018] Preferably, the inductance measurement circuit measures and outputs four voltage signals U1, U2, U3, and U4 that are linearly related to the inductance values L1, L2, L3, and L4 of the four planar coils by using the resonance method.

[0019] Preferably, the four voltage signals are connected to the microprocessor system for data processing, and two position signals U x 、U y are output, specifically:

[0020]

[0021] U1 is the voltage signal output by the inductance measurement circuit corresponding to the first planar coil, reflecting the change in the inductance of the first planar coil.

[0022] U2 is the voltage signal output by the inductance measurement circuit corresponding to the second planar coil, reflecting the change in the inductance of the second planar coil.

[0023] U3 is the voltage signal output by the inductance measurement circuit corresponding to the third planar coil, reflecting the change in the inductance of the third planar coil.

[0024] U4 is the voltage signal output by the inductance measurement circuit corresponding to the fourth planar coil, reflecting the change in the inductance of the fourth planar coil.

[0025] The calculated U x is a function of the displacement of the detection coil array board relative to the target conductor array board in the X-axis direction, and U y is a function of the displacement of the detection coil array board relative to the target conductor array board in the Y-axis direction. By inverse solution, the displacements of the detection coil array board relative to the target conductor array board in the X-axis and Y-axis directions can be obtained.

[0026] Preferably, the material of the planar coil is enameled wire; the material of the metal panel is aluminum.

[0027] The beneficial effects of the present invention are:

[0028] Compared with traditional capacitive and optoelectronic planar two-dimensional micro displacement sensors, the planar coil and metal panel structure based on the eddy current measurement principle is simple. The planar coil serves as both the excitation coil and the induction coil, and is not affected by environmental factors such as dust and oil. It can maintain high reliability under complex working conditions.

[0029] Compared with traditional inductive two-dimensional displacement sensors, a four-quadrant "field" layout is adopted. The same coil winding direction and excitation signal are used to avoid mutual interference between planar coils. The planar coil and the metal panel have a specific spacing and positional relationship. Voltage signals U1, U2, U3, and U4 are output through the inductance measurement circuits of the four planar coils, and differential operations in the X and Y directions are formed by adding and subtracting them in pairs, and two position signals U x 、U y have good linearity within the measurement range of the XY plane. By calibrating the relationship between U x 、U y and the relative displacement in the X and Y directions, high measurement accuracy can be obtained.

[0030] In summary, the planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect provided by the present invention has the advantages of simple structure and high measurement accuracy, and is not affected by environmental factors such as dust and oil. It has more competitive advantages in complex working condition application scenarios such as chemical industry, metallurgy, and mechanical manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 It is a schematic diagram of the sensor measurement principle;

[0033] Figure 2 It is a schematic diagram of the structure of the sensor detection coil array board;

[0034] Figure 3 It is a schematic diagram of the structure of the sensor target conductor array board;

[0035] Figure 4 It is a schematic diagram of the initial positions of the detection coil array board and the target conductor array board;

[0036] Figure 5 It is a graph of the relationship between the inductance value of the first detection coil and displacement;

[0037] Figure 6 It is a graph of the relationship between the inductance value of the second detection coil and displacement;

[0038] Figure 7 It is a graph of the relationship between the inductance value of the third detection coil and displacement;

[0039] Figure 8 It is a graph of the relationship between the inductance value of the fourth detection coil and displacement;

[0040] Figure 9 It is a graph of the relationship between the displacement signal output by the microprocessor system and the displacement in the X direction;

[0041] Figure 10 It is a graph of the relationship between the displacement signal output by the microprocessor system and the displacement in the Y direction;

[0042] Detection coil array board 1, detection coil 11, target conductor array board 2, target conductor 21, inductance measurement circuit 3, displacement operation circuit 4. DETAILED DESCRIPTION OF THE INVENTION

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Embodiment 1: As Figures 1 to 4 shown, a planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect includes a detection coil array board 1 and a target conductor array board 2. The detection coil array board 1 and the target conductor array board 2 are placed in parallel with a small gap therebetween, and the size of the gap is 0.05D.

[0045] As Figure 2 shown, the detection coil array board 1 includes four planar coils 11, and their shapes are circular. The outer diameter of the planar coil 11 is D, and the material is enameled wire. The number of turns of the four planar coils 11 is equal and they are arranged in a "field" shape on the insulating substrate. The center distances between adjacent planar coils 11 in the X direction and the Y direction are both 1.5D.

[0046] As Figure 3 shown, the target conductor array board 2 includes four metal panels 21, and their shapes are square. The side length of the metal panel 21 is D, and the material is aluminum. The four metal panels 21 are arranged in a "field" shape on the insulating substrate. The center distances between adjacent metal panels 21 in the X direction and the Y direction are both 2D.

[0047] In this embodiment, the outer diameter of the planar coil 11 is 20 mm. The side length of the metal panel 21 is 20 mm, and the distance between the planar coil 11 and the metal panel 21 is 1 mm. The maximum distance that the detection coil array board 1 can move in a single direction in the XY plane is 5 mm, and the total range is 10×10 mm 2 。

[0048] The four planar coils 11 are respectively fed with completely identical AC excitation signals, and the AC frequency is 1 MHz. The excitation signals cause the four coils to generate alternating magnetic fields. When the four planar coils 11 are in the initial position, the alternating magnetic fields generated by the four planar coils 11 will form eddy currents on the surfaces of the four metal panels 21. The alternating magnetic fields generated by the eddy currents will in turn affect the coil impedance of the planar coils 11, causing the inductance values of the planar coils 11 to change.

[0049] When the detection coil array board 1 and the target conductor array board 2 are vertically coincident at the symmetry center and in the initial position, the coincident center point is taken as the coordinate origin. At this time, the four planar coils 11 are respectively in the four quadrants. In the initial position, the overlapping areas of the four planar coils 11 with the metal panels 21 are equal. Therefore, the influence of the four metal panels 21 on the four planar coils 11 is the same, that is, the inductance values of the four planar coils 11 are exactly the same at this time. According to the four-quadrant detection method, it can be determined that the detection coil array is at the origin position at this time.

[0050] When the detection coil array board 1 starts to move in the XY plane, the positions of the four metal panels 21 relative to the respective facing planar coils 11 change differently. For example, when the detection coil array board 1 moves along the X-axis direction from the initial position, the overlapping areas of the planar coils 11 in the first and fourth quadrants with the lower target conductor become larger (smaller), resulting in a decrease (increase) in the inductance values of these two planar coils 11; the overlapping areas of the planar coils 11 in the second and third quadrants with the lower target conductor become smaller (larger), resulting in an increase (decrease) in the inductance values of these two planar coils 11. When the detection coil array board 1 moves along the Y-axis direction from the initial position, the overlapping areas of the planar coils 11 in the first and second quadrants with the lower target conductor become larger (smaller), resulting in a decrease (increase) in the inductance values of these two planar coils 11; the overlapping areas of the planar coils 11 in the third and fourth quadrants with the lower target conductor become smaller (larger), resulting in an increase (decrease) in the inductance values of these two planar coils 11. The inductance changes of the planar coils 11 are detected by the inductance measurement circuit 3 and processed by the subsequent microprocessor system 4 to obtain the displacements of the detection coil array board 1 in the X and Y directions.

[0051] When the planar coil 11 moves in the XY plane, the relationship between the inductance value of the coil in the first quadrant and the displacement is as Figure 5 shown; the relationship between the inductance value of the coil in the second quadrant and the displacement is as Figure 6 shown; the relationship between the inductance value of the coil in the third quadrant and the displacement is as Figure 7 shown; the relationship between the inductance value of the coil in the fourth quadrant and the displacement is as Figure 8 shown.

[0052] This embodiment provides an inductance measurement circuit with the design idea of resonance method. Its effect is that four planar coils 11 respectively correspond to four output voltages U1, U2, U3, and U4, and their values are proportional to the inductance values L1, L2, L3, and L4 of the four coils. Assume that U1 and U2 are the output voltages of the two planar coils 11 on the positive half-axis of the Y-axis, U3 and U4 are the output voltages of the two planar coils 11 on the negative half-axis of the Y-axis, U1 and U4 are the output voltages of the two planar coils 11 on the positive half-axis of the X-axis, and U2 and U3 are the output voltages of the two planar coils 11 on the negative half-axis of the X-axis. Subtract U2 + U3 from U1 + U4 to obtain the difference U x , subtract U3 + U4 from U1 + U2 to obtain U y , from the value of U x , the displacement of the detection coil array board 1 in the X-axis direction can be obtained, and from the value of U y , the displacement of the detection coil array board 1 in the Y-axis direction can be obtained. By combining U x and U y , the displacement of the detection coil array board 1 in the XY plane can be obtained.

[0053] Specifically:

[0054] The four planar coils are respectively fed with exactly the same AC excitation signal U. When the detection coil array board 1 moves in the XY plane. By connecting the planar coil in parallel with a capacitor to construct an L-C resonant circuit, the resonant frequency can be obtained:

[0055]

[0056] where the capacitor C is a fixed constant, and through hardware operation, the acquisition circuit outputs a voltage U proportional to 1 / f LC 2 .

[0057] The circuit output corresponding to the first planar coil outputs an electrical signal U1 reflecting the inductance of the first planar coil:

[0058]

[0059] The circuit output corresponding to the second planar coil outputs an electrical signal U2 reflecting the inductance of the second planar coil.

[0060]

[0061] The circuit output corresponding to the third planar coil outputs an electrical signal U3 reflecting the inductance of the third planar coil.

[0062]

[0063] The circuit output corresponding to the fourth planar coil outputs an electrical signal U4 reflecting the inductance of the fourth planar coil.

[0064]

[0065] Input the four-channel voltage signals U1, U2, U3, and U4 into the microprocessor system 4, perform pairwise addition and pairwise subtraction on U1, U2, U3, and U4 to obtain U x and U y , under the probe layout of the present invention, this differential voltage value has a linear relationship with the X and Y displacement amounts:

[0066] U x = U1 + U4 - (U2 + U3) ∝ L1 + L4 - (L2 + L3) ∝ x

[0067] U y = U1 + U2 - (U3 + U4) = L1 + L2 - (L3 + L4) ∝ y

[0068] Through calibration, the mathematical relationships between U x , U y and X, Y can be obtained.

[0069] It is worth mentioning that during the measurement process of the detection coil, its impedance change is not limited to the inductance only. Its resistance will also change simultaneously, and the change of the resistance R shows relatively poor regularity compared with the inductance L, making it difficult to calculate and calibrate. Therefore, compared with traditional signal detection circuits such as AC bridges, the above scheme or similar resonance methods have the advantage of ignoring the influence brought by the resistance change and improving the system accuracy. When those skilled in the art apply the present invention, detection methods such as AC bridges and impedance analysis can also be adopted.

[0070] The above content is only an example and explanation of the structure of the present invention. Those skilled in the art of this technology make various modifications or supplements to the described specific embodiments or use similar ways to replace them. As long as they do not deviate from the structure of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect, comprising a detection coil array board (1) and a target conductor array board (2), characterized in that: The detection coil array board (1) is in the XY plane, including four planar coils (11) and an insulating matrix inlaid with the planar coils (11), and the four planar coils (11) are arranged in a "field" shape; The target conductor array board (2) is in the XY plane, including four metal panels (21) and an insulating matrix for fixing the metal panels (21), and the four metal panels (21) are arranged in a "field" shape; The detection coil array board (1) and the target conductor array board (2) are arranged parallel to each other up and down. The symmetry centers of the detection coil array board (1) and the target conductor array board (2) coincide vertically in the initial position. The detection coil array board (1) and the target conductor array board (2) translate relative to each other in the XY plane, and the vertical distance remains unchanged; The four planar coils (11) of the detection coil array board (1) are respectively fed with the same sinusoidal excitation signal. The four-way inductance measurement circuits (3) respectively measure the inductance values L1, L2, L3, and L4 of the four planar coils (11), and output four-way voltage signals U1, U2, U3, and U4. The four-way voltage signals are connected to the microprocessor system (4) for data processing, and two-way position signals U x , U y : By calibrating U x and U y and the relative displacement relationship in the X and Y directions, the relative displacement of the detection coil array board (1) and the target conductor array board (2) in the X and Y directions is obtained.

2. The planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 1, characterized in that: The shape of the planar coil (11) is square or circular.

3. A planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 2, characterized in that: The outer diameter or side length of the planar coil (11) is D, and the center distance between adjacent planar coils (11) in the X and Y directions is 1.5D.

4. A planar two-dimensional micro displacement sensor based on the four-quadrant eddy current effect according to claim 3, characterized in that: The shape of the metal panel (21) is square or circular.

5. The planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 4, characterized in that: The outer diameter or side length of the metal panel (21) is D, and the center distance between adjacent metal panels (21) in the X and Y directions is 2D.

6. The planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 5, wherein: The vertical distance range between the detection coil array board (1) and the target conductor array board (2) is (0, 0.1D).

7. The planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 6, wherein: The displacement range of the detection coil array board (1) relative to the target conductor array board (2) in the X and Y directions is (-0.25D, 0.25D).

8. A planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 1, characterized in that: The inductance measurement circuit (3) measures four voltage signals U1, U2, U3, U4 that are linearly related to the inductance values L1, L2, L3, L4 of the four planar coils (11) by using the resonance method.

9. A planar two-dimensional micro-displacement sensor based on the four-quadrant eddy current effect according to claim 1, characterized in that: The four-way voltage signals are connected to a microprocessor system (4) for data processing and two position signals U x and U y are output, specifically: U1 is the voltage signal output by the inductance measurement circuit corresponding to the first planar coil, reflecting the inductance change of the first planar coil; U2 is the voltage signal output by the inductance measurement circuit corresponding to the second planar coil, reflecting the inductance change of the second planar coil; U3 is the voltage signal output by the inductance measurement circuit corresponding to the third planar coil, reflecting the inductance change of the third planar coil; U4 is the voltage signal output by the inductance measurement circuit corresponding to the fourth planar coil, reflecting the inductance change of the fourth planar coil.

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