CN111564953A - Planar motor displacement device - Google Patents

Abstract

The invention discloses a plane motor displacement device, comprising a mover and a stator, wherein a magnet array is arranged on the stator to form a working area, and at least one first-direction plane scale and at least one non-overlapping plane scale are laid in the working area. a second direction flat scale, the traces of at least one first direction flat scale are parallel to each other and spaced apart along the first direction, the traces of at least one second direction flat scale are parallel to each other and spaced apart along the second direction, The first direction and the second direction intersect with each other; the mover is provided with a three-phase coil array in the first direction and a three-phase coil array in the second direction, and is arranged to be able to move above the working area, and is provided with at least one reading in the first direction Head and at least one second direction reading head, at least one first direction reading head and at least one second direction reading head with the movement of the mover, respectively in at least one first direction plane scale and at least one second direction plane scale move within the tile range.

Description

Planar motor displacement device

technical field

The invention relates to the field of precision motion, in particular to a plane motor displacement device.

Background technique

The magnetic levitation plane motor motion table is mainly used in semiconductor equipment, such as scanning projection lithography machine, wafer cutting machine, flip-chip bonding machine, etc. Its function is to carry the wafer for precise movement of micro-nano precision, so as to realize the precision movement of the wafer. precise machining. The maglev plane motor motion table generally includes a set of plane motors, a set of six-degree-of-freedom displacement measurement systems, a set of power amplifiers, and a set of motion controllers. For example, the documents of patent numbers US6496093 and EP3320400B1 make innovations in the topology structure of the planar motor, and the six-degree-of-freedom displacement measurement system still uses the traditional solution.

The traditional six-degree-of-freedom displacement measurement system integrates a set of three-axis laser interferometer and a set of eddy-current displacement sensors. Among them, the three-axis laser interferometer is used to measure the X-direction translation, Y-direction translation and Z-direction rotation of the moving table in real time; at least three eddy current displacement sensors are used to measure the X-direction rotation, Y-direction rotation and Z-direction rotation of the moving table in real time. Translation in the Z direction. However, laser interferometers are expensive and their accuracy is very sensitive to the measurement environment: changes in temperature, humidity, and air movement can cause disturbances that reduce their accuracy. Eddy current displacement sensors are also very expensive. Another solution is to use a flat scale system to replace the laser interferometer, but the cost of the flat scale is an order of magnitude with the laser interferometer. Both solutions are very susceptible to environmental disturbances, such as airflow, particle contamination, stains, etc., resulting in reduced sensor accuracy or even complete failure, resulting in motion table failure.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a displacement device to solve the problems in the prior art that the magnetic levitation plane motor moving table is too expensive and susceptible to environmental interference.

To this end, the present invention provides a planar motor displacement device, including a mover and a stator, wherein

The stator is provided with a magnet array extending on a plane, the magnet array forms a working area, and at least one first-direction plane scale and at least one second-direction plane scale are also tiled on the stator, so The traces of the at least one first direction plane scale are parallel to each other and spaced apart along a first direction, the traces of the at least one second direction plane scale are parallel to each other and spaced apart in a second direction, the first direction and the second direction intersect each other;

The mover is provided with a first-direction three-phase coil array and a second-direction three-phase coil array, and is arranged to be able to move above the working area, and is provided with at least one first-direction reading head and at least one second-direction reading head. A direction reading head, the at least one first direction reading head and the at least one second direction reading head are respectively on the at least one first direction plane scale and the at least one second direction plane with the movement of the mover Move within the tile range of the scale.

In an embodiment, the traces of the at least one first direction plane scale and/or the at least one second direction plane scale are made of a conductive material.

In one embodiment, the first direction and the second direction are orthogonal to each other, and the magnet array is a two-dimensional Halbach array.

In one embodiment, the at least one reading head in the first direction is at least two reading heads in the first direction, or the at least one reading head in the second direction is at least two reading heads in the second direction.

In one embodiment, the at least one first-direction reading head is two first-direction reading heads located at a pair of diagonal corners of the workbench, and the at least one second-direction reading head is located at the Two second-direction readheads at the other pair of diagonal corners of the table.

In one embodiment, the at least one first-direction plane scale is two first-direction plane scales covering a corresponding pair of diagonal regions of the working area, and/or the at least one second-direction plane scale. The scales are two second-direction plane scales covering the corresponding other pair of diagonal regions of the working area, the trace of the at least one first-direction plane scale and the trace of the at least one second-direction plane scale Lines are equally spaced.

In one embodiment, the at least one first-direction readhead is two first-direction readheads located at spaced apart positions on one edge of the workbench, and the at least one second-direction readhead is located on the workbench. A second orientation readhead on the edge of the stage opposite the one edge.

In one embodiment, the at least one first-direction plane scale is at least one first-direction plane scale that covers an area near a corresponding edge of the working area, and the at least one second-direction plane scale is a plane scale that covers all areas. The working area corresponds to a second-direction plane scale in an area near an edge.

In one embodiment, at least three Hall sensor arrays that are not on the same straight line are provided on the worktable.

In one embodiment, the Hall sensor array includes three Hall sensors that are not on the same line.

In one embodiment, the three Hall sensors are located at the vertices of an isosceles right triangle.

In one embodiment, the hypotenuse of the isosceles right triangle extends along the first direction or the second direction.

In one embodiment, the distance between the centers of adjacent N magnets and S magnets in the magnet array is τ, and the length of the right-angled side of the isosceles right triangle is a, then a=τ/2+nτ, where n is not. Integer less than zero.

In one embodiment, the displacement device includes four Hall sensor arrays, and the four Hall sensor arrays are evenly spaced on the outer periphery of the mover.

The displacement device proposed by the invention integrates a plane motor and a one-way plane scale, uses a one-way plane scale and a one-way reading head to replace the laser interferometer and the plane scale, reduces the cost of the displacement sensor by two orders of magnitude, and greatly reduces the cost of the displacement sensor. The overall cost of the planar motor motion table enhances its market competitiveness while improving its measurement accuracy. Among them, the precision of the one-way plane scale based on the eddy current effect can reach ten nanometers, and it is not easily affected by the environment; the precision of the optical one-way plane scale can reach the nanometer or sub-nanometer level, and its precision is higher. By integrating the Hall sensor array, the entire device can achieve six-degree-of-freedom magnetic levitation motion, that is, long-stroke motion in the X and Y directions, as well as fine-tuning of the other four degrees of freedom.

Description of drawings

1 is a schematic diagram of a displacement device according to an embodiment of the present invention;

2 is a schematic diagram of a displacement device according to still another embodiment of the present invention

3 is a schematic diagram of a magnet array according to another embodiment of the present invention;

4 is a schematic diagram of a magnet array according to yet another embodiment of the present invention;

5 is a schematic diagram of a magnet array according to yet another embodiment of the present invention.

List of reference numbers:

500-displacement device; 100-stator; 200-mover; 10-magnet array; 10X-first magnet group; 10Y-second magnet group; 101-first magnet block; 102-second magnet block; 103-th Three-magnet block; 104-fourth magnet block; 20-coil array; 201-first X-direction three-phase coil set; 202-first Y-direction three-phase coil set; 203-second X-direction three-phase coil set; 204 - Second Y three-phase coil set; 30X-X plane scale; 30Y-Y plane scale; 301 - First X plane scale; 302 - First Y plane scale; 303 - Second plane scale X plane scale; 304-second Y plane scale; 40X-X readhead; 30Y-Y readhead; 401-first X readhead; 402-first Y readhead; 403- Second X readhead; 404 - Second Y readhead; 50 - Hall sensor array.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so as to more clearly understand the objects, features and advantages of the present invention. It should be understood that the embodiments shown in the accompanying drawings are not intended to limit the scope of the present invention, but are only intended to illustrate the essential spirit of the technical solutions of the present invention.

In the following description, for the purpose of illustrating various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of these specific details. In other instances, well-known devices, structures and techniques associated with this application may not be shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

Unless the context requires otherwise, throughout the specification and claims, the word "comprising" and variations thereof, such as "comprising" and "having", should be construed in an open, inclusive sense, i.e., should be interpreted as "including, but not limited to".

In the following description, in order to clearly show the structure and working mode of the present invention, many directional words will be used for description, but "left", "right", "outer", "inner", "upper", "lower" ” and other words are to be understood as words that are convenient to describe the relative positional relationship, and should not be understood as limiting words.

Referring to FIG. 1 , there is shown a top view of a planar motor displacement device 500 according to an embodiment of the present invention. The planar motor displacement device 500 includes a stator 100 and a mover 200 . As shown in the figure, the drawing plane of the drawing is the XY plane, in which the horizontal and rightward direction in the drawing plane is the X direction, the upward direction in the drawing plane is the Y direction, and the direction perpendicular to the drawing plane is the Z direction. In this embodiment, the X direction, the Y direction and the Z direction are orthogonal to each other. However, it should be understood that the X, Y and Z directions are not necessarily orthogonal to each other, as long as they intersect each other. The following embodiments of the present invention will be described by taking the case where the X direction, the Y direction and the Z direction are orthogonal to each other as an example.

The stator 100 is provided with a magnet array 10 extending substantially in a plane, the magnet array 10 forming a working area. Preferably, the magnet array 10 extends in an XY plane. The mover 200 is provided with the coil array 20 so that the mover 200 can be suspended above the working area through the interaction with the magnet array 10 . In the illustrated embodiment, the mover 200 is a substantially square plate, but it should be understood that the mover 200 can also be provided in other shapes, such as a rectangular plate, a circular plate, and the like, as required. In the illustrated embodiment, the coil array 20 is provided on the upper surface of the mover 200 . However, it should be understood that the coil array 20 may also be disposed on the lower surface of the mover 200 . In the illustrated embodiment, the coil array 20 includes a first X-direction three-phase coil set 201 , a first Y-direction three-phase coil set 202 , a second X-direction three-phase coil set 203 , and a second Y-direction three-phase coil set 204 . The first X-direction three-phase coil group 201 and the second X-direction three-phase coil group 203 are arranged in a pair of diagonal regions of the three-phase coil array 20, while the first Y-direction three-phase coil group 202 and the second Y-direction three-phase coil group 202 are arranged in a pair of diagonal regions of the three-phase coil array 20. The phase coil sets 204 are arranged in another pair of diagonal regions of the coil array 20 . Wherein each three-phase coil group is preferably arranged on the same plane, the first and second X-direction three-phase coil groups 201 and 203 can interact with the magnet array 10 to generate X-direction and Z-direction thrust, while the first and second X-direction three-phase coil groups 201 and 203 The two Y-direction three-phase coil sets 202 and 204 can interact with the magnet array 10 to generate Y-direction and Z-direction thrust, thereby driving the mover 200 to perform six degrees of freedom movement within the working area, namely X, Y , translation in Z direction and rotation around X, Y and Z directions. It should also be understood that the three-phase coil groups may also be arranged on the mover 200 in other manners. A X-direction three-phase coil group and a Y-direction three-phase coil group are arranged on the mover 200 to realize the translational movement of the mover 200 along the X, Y, and Z directions and the rotation of the X and Y directions, and then increase the One X-direction or Y-direction three-phase coil group can realize Z-direction rotation of the mover 200 . Therefore, in order to realize motion with six degrees of freedom, at least three three-phase coil groups need to be provided, including at least one X-direction coil group and at least one Y-direction coil group.

As shown in FIG. 1 , there are four reading heads on the mover 200: a first X-direction reading head 401, a first Y-direction reading head 402, a second X-direction reading head 403, and a second Y-direction reading head 404 , which are respectively arranged near the four vertices of the mover 200 . However, it should be understood that the positions of the above four read heads are not limited to this, as long as a quadrilateral can be formed. Four plane scales are correspondingly laid on the mover 200 : a first X-direction plane scale 301 , a first Y-direction plane scale 302 , a second X-direction plane scale 303 and a second Y-direction plane scale 304 . Each flat scale can be a grating, or a magnetic scale, a capacitive scale, or a scale based on the eddy current principle. Correspondingly, the traces of the scale may be made of light conducting material (ie transparent material), magnetic conducting material or conducting material. Preferably, the traces are made of conductive material. Preferably, the plane scales do not overlap in the working area, so as to prevent the coordinate values read by the reading head through the grating traces from being confused. In the illustrated embodiment, the first X-direction plane scale 301 and the second X-direction plane scale 303 are respectively located in a pair of diagonal areas of the working area, in the illustrated figures, the lower left corner area and the upper right corner area; On the other hand, the first Y-plane scale 302 and the second Y-plane scale 304 are located in another pair of diagonal regions of the working area, which are the upper left corner region and the lower right corner region in the shown figure. Correspondingly, during the movement of the mover 200, the above-mentioned four reading heads are respectively on the first X-direction plane scale 301, the first Y-direction plane scale 302, the second X-direction plane scale 303, and the second Y-direction plane scale. The scale 304 is moved within the tiled range to read the X coordinates of the first and second X readheads and the Y coordinates of the first and second Y readheads through the traces of the flat scale. The displacement signals are read by the four read heads, and the displacement signals are fed back to the controller. The controller provides control signals to control the translation of the mover 200 in the X and Y directions and the rotation around the Z direction.

Although in the illustrated embodiment, there are a total of four flat scales and four reading heads, it should be understood that the number of X-direction reading heads and Y-direction reading heads is not limited to this, and at least one X-direction reading head may be provided and at least one Y-direction readhead and corresponding at least one X-direction plane scale and at least one Y-direction plane scale. When only one X-direction reading head and one Y-direction reading head are provided, the translation in the X and Y directions of the mover 200 can be calculated and controlled according to the coordinate values read from the two reading heads. When another X-direction reading head or another Y-direction reading head is set, the displacement signal can be read from the three reading heads and the displacement signal is fed back to the controller, and the controller provides a control signal to control the movement. Translation of the sub-200 in the X and Y directions and rotation around the Z direction. It should also be understood that, in order to expand the movement stroke of the mover 200 along the X and Y directions in the working area, the X-direction reading head and the Y-direction reading head should be spaced as far as possible, so as to avoid the X-direction plane scale and the Y-direction to the greatest extent possible. Plane scales overlap. It should also be understood that the arrangement of the reading heads on the mover 200 and the plane scale in the working area is not limited to the above-mentioned embodiment, as long as the reading heads are properly spaced, and the laying range of the plane scale corresponding to each reading head is not smaller than that of the moving head. The movement range of each reading head on the sub 200 is sufficient.

FIG. 2 shows an embodiment in which three reading heads and two flat scales 30X and 30Y are arranged on the mover 200, wherein an X-direction reading head 40X and a first Y-direction reading head 302 and a second Y-direction reading head are arranged 304. The first Y-direction reading head 302 and the second Y-direction reading head 304 are arranged at two adjacent corner positions of the mover 200, which are the upper left corner and the upper right corner in the drawing, and the X-direction reading head 40X is arranged at the same At the midpoint of the edges opposite the edges of the two Y-directed readheads. Correspondingly, the X-direction plane scale 30X is disposed below the work area, and the Y-direction plane scale 30Y is disposed above the work area. It should be understood, however, that the positions of the three readheads are not limited to this. As long as the reading heads are properly spaced, so that the corresponding plane scales do not overlap, and the tiling range of the corresponding plane scales is not less than the movement range of each reading head on the mover 200 . In this embodiment, the two Y-direction reading heads correspond to one Y-direction plane scale, but it should be understood that two Y-direction plane scales spaced apart from each other may also be provided. With this configuration, the three read heads can be used to measure and control the movement of the mover 200 in three degrees of freedom, ie, X-direction displacement, Y-direction displacement, and Z-direction rotation.

The magnet array 10 shown in FIG. 1 is a two-dimensional Halbach array in which a plurality of N magnets, S magnets and H magnets are periodically arranged in a two-dimensional Halbach manner along an XY plane. That is, the H magnet is provided between the adjacent N magnet and the S magnet, and the magnetization direction of the H magnet points to the N magnet. The distance between the centers of the adjacent N magnets and the S magnets is τ, and the angle between the arrangement direction of the magnets N-H-S-H-N-H-S-H and the X direction is α=π/4.

A top view of another embodiment of the magnet array 10 is shown in FIG. 3 , compared to the embodiment of the magnet array 10 shown in FIG. 1 only in that the magnet array in FIG. 2 has the magnet array shown in FIG. 1 removed The H magnet in the examples. Similarly, the N magnets and the S magnets are periodically arranged in rows and columns along an XY plane, the N magnets and the adjacent S magnets are spaced apart, and the center distance between the adjacent N magnets and the S magnets is τ, the rows of the magnets S-N-S-N The angle between the cloth direction and the X direction is α=π/4.

A top view of yet another embodiment of the magnet array 10 is shown in FIG. 4 . The magnet array 10 includes a first magnet group 10X and a second magnet group 10Y, and the first magnet group 10X and the second magnet group 10Y are alternately arranged in rows and columns along the X and Y directions. The first magnet group 10X includes four magnets sequentially arranged in a one-dimensional Halbach array along the Y direction: S magnets, H magnets, N magnets and H magnets, in an S-H-N-H arrangement, wherein the magnetization direction of the H magnets points to the N magnets, adjacent to the N magnets. The center-to-center distance between the N magnet and the S magnet is τ. The second magnet group 10Y includes four magnets sequentially arranged in a one-dimensional Halbach array along the X direction: S magnets, H magnets, N magnets, and H magnets in an S-H-N-H arrangement, wherein the magnetization direction of the H magnets points to the N magnets, adjacent to the N magnets. The center-to-center distance between the N magnet and the S magnet is τ. That is, the second magnet group 10Y is formed by rotating the first magnet group 10X counterclockwise along the XY plane by 90° in plan view.

A top view of yet another embodiment of the magnet array 10 is shown in FIG. 5 . The magnet array 10 includes a plurality of square sub-arrays periodically arranged in rows and columns along the X and Y directions, and the sub-array consists of a first magnet block 101 , a second magnet block 102 , a third magnet block 103 and a fourth magnet block 104 composition. In the illustrated embodiment, the first magnet block 101 is arranged in the upper left area of the sub-array, the second magnet block 102 is arranged in the lower left area of the sub-array, the third magnet block 103 is arranged in the lower right area of the sub-array, and the fourth magnet Blocks 104 are arranged in the upper right area of the sub-array. The first magnet block 101 includes S magnets and H magnets arranged in sequence along the Y direction, wherein the magnetization direction of the H magnets is away from the S magnets. The second magnet block 102 includes S magnets and H magnets arranged in sequence along the X direction, wherein the magnetization direction of the H magnets is away from the S magnets. The third magnet block 103 includes N magnets and H magnets arranged in sequence along the Y direction, and the magnetization direction of the H magnets points to the N magnets. The fourth magnet block 104 includes N magnets and H magnets arranged in sequence along the X direction, and the magnetization direction of the H magnets points to the N magnets. The second magnet block 102 is formed by rotating the first magnet block 101 counterclockwise by 90° along the XY plane in a plan view. The fourth magnet block 104 is formed by rotating the third magnet block 103 counterclockwise by 90° along the XY plane in a plan view. The distance between the Y-direction centers of the S magnets in the first magnet block 101 and the N magnets in the third magnet block 103 is τ, and the X-direction centers of the S magnets in the second magnet block 102 and the N magnets in the fourth magnet block 104 The spacing is τ.

Although only the above-described four embodiments of the magnet array 10 are described in this specification, it should be understood that the magnet array 10 of the present invention may employ any planar motor stator, existing or to-be-developed magnet array.

In order to realize the movement of six degrees of freedom, a Hall sensor array 50 is also arranged on the mover 200 . Each Hall sensor array 50 can obtain its displacement in the Z direction by measuring the magnetic field strength generated by the magnet array 10. The Hall sensor can be configured to measure the magnetic field strength in the X direction, the Y direction or the Z direction, and is preferably configured to measure the Z direction Directional magnetic field strength. By arranging at least three Hall sensor arrays 50 that are not on the same straight line to measure the Z-direction displacements of the three positions of the mover, and synthesizing the output signals of the three Hall sensor arrays, the displacements of the three degrees of freedom of the mover 200 can be calculated. , that is, the translation of the mover 200 along the Z direction, the rotation in the X direction, and the rotation in the Y direction. The Hall sensor arrays 50 are preferably arranged on the same plane, and more preferably, the plane where the Hall sensors are located is farther away from the magnet array than the plane where the three-phase coil group is located.

In the embodiment shown in FIG. 1 , the mover 200 includes four Hall sensor arrays 50 , and the four Hall sensor arrays 50 are arranged on the outer periphery of the mover 200 and are evenly spaced from each other. Each Hall sensor array 50 includes 3 Hall sensors distributed in a triangle, in the embodiment shown, the 3 Hall sensors are located at the vertices of an isosceles right triangle. The hypotenuse of the isosceles right triangle extends along the X direction or the Y direction. In this embodiment, the distance between the centers of the adjacent N magnets and the S magnets in the magnet array 10 is τ, then the length of the right angle side of the isosceles right triangle is a, then

a=τ/2+nτ, n is an integer not less than zero.

The Hall sensor array 50 of this arrangement can be applied to the case where the magnets in the magnet array 10 are arranged in rows and columns along the angle α=π/4 with the X direction. For example, when the embodiment of the magnet array 10 shown in FIG. 2 is used, the Hall sensor array 50 arranged in the above-mentioned isosceles right triangle can also be applied.

Although only one embodiment of Hall sensor array 50 is described above, it should be understood that the number and arrangement of sensors in Hall sensor array 50 may vary as desired without departing from the scope of the present invention.

Multiple Hall sensor array signals and reading head signals are fed back to the controller. The controller calculates the control signal according to the preset control algorithm, and controls the coil current through the driver, thereby generating the displacement of the motion table with 6 degrees of freedom.

According to the planar motor displacement device of the present invention, by using the Hall sensor array to replace the eddy current displacement sensor and using the planar scale and the reading head to replace the laser interferometer, the cost of the planar motor displacement device is significantly reduced, and the motion control is improved. precision.

The preferred embodiments of the present invention have been described in detail above, but it is to be understood that aspects of the embodiments can be modified, if desired, to employ aspects, features and concepts of various patents, applications and publications to provide additional embodiments.

These and other changes can be made to the embodiments in light of the above detailed description. In general, in the claims, the terms used should not be construed as limiting to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments, along with all equivalents to which these claims are entitled scope.

Claims (14)

1. A planar motor displacement device is characterized in that,

comprising a mover and a stator, wherein

The stator is provided with a magnet array extending on a plane, the magnet array forms a working area, the stator is also tiled with at least one first-direction planar grid ruler and at least one second-direction planar grid ruler, the traces of the at least one first-direction planar grid ruler are parallel to each other and are arranged at intervals along the first direction, the traces of the at least one second-direction planar grid ruler are parallel to each other and are arranged at intervals along the second direction, and the first direction and the second direction are intersected with each other;

the rotor is provided with a first direction three-phase coil array and a second direction three-phase coil array, the first direction three-phase coil array and the second direction three-phase coil array are arranged to be capable of moving above the working area, at least one first direction reading head and at least one second direction reading head are arranged, and the at least one first direction reading head and the at least one second direction reading head move along with the movement of the rotor in the tiling range of the at least one first direction plane grid ruler and the at least one second direction plane grid ruler respectively.

2. The planar motor displacement device of claim 1 wherein the traces of the at least one first direction planar ruler and/or the at least one second direction planar ruler are made of a conductive material.

3. The planar motor displacement apparatus of claim 1 wherein the first and second directions are orthogonal to each other and the magnet array is a two-dimensional Halbach array.

4. The planar motor displacement apparatus of claim 1, wherein the at least one first direction readhead is at least two first direction readheads, or the at least one second direction readhead is at least two second direction readheads.

5. The planar motor displacement apparatus as claimed in any one of claims 1 and 4, wherein the at least one first direction reading head is two first direction reading heads located at one pair of diagonal corner positions of the table, and the at least one second direction reading head is two second direction reading heads located at the other pair of diagonal corner positions of the table.

6. The planar motor displacement device of claim 1, wherein the at least one first direction grid ruler is two first direction grid rulers covering a corresponding pair of diagonal regions of the working area, and/or the at least one second direction grid ruler is two second direction grid rulers covering a corresponding other pair of diagonal regions of the working area, and traces of the at least one first direction grid ruler and traces of the at least one second direction grid ruler are arranged at equal intervals.

7. A planar motor displacement apparatus according to any one of claims 1 to 4 wherein the at least one first direction reading head is two first direction reading heads located at spaced apart positions on one edge of the table and the at least one second direction reading head is one second direction reading head located on an opposite edge of the table to the one edge.

8. The planar motor displacement apparatus as claimed in claim 7, wherein the at least one first direction flat gauge is at least one first direction flat gauge covering a region near a corresponding one of the edges of the working area, and the at least one second direction flat gauge is at least one second direction flat gauge covering a region near a corresponding one of the edges of the working area.

9. The planar motor displacement device of claim 1, wherein the workbench is provided with at least three hall sensor arrays which are not in the same line.

10. The planar motor displacement device of claim 9, wherein the hall sensor array comprises three hall sensors that are not collinear.

11. The planar motor displacement device of claim 10, wherein the three hall sensors are located at the vertices of an isosceles right triangle.

12. The planar motor displacement apparatus of claim 11, wherein the hypotenuse of the isosceles right triangle extends in the first direction or the second direction.

13. The planar motor displacement device of claim 11, wherein the distance between the centers of the N magnet and the S magnet adjacent to each other in the magnet array is τ, the length of the right angle of the isosceles right triangle is a, and a ═ τ/2+ N τ is obtained, and N is an integer not less than zero.

14. The planar motor displacement device of claim 9, wherein the displacement device comprises 4 hall sensor arrays, and the 4 hall sensor arrays are uniformly arranged on the periphery of the rotor at intervals.

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