Magnetic levitation gravity compensation device and moving stage including said device

Abstract

This invention discloses a magnetic levitation gravity compensation device that includes an inner bottom magnetic steel member extending along the axial direction; first and second end magnetic steel members located at the two axial ends of the inner bottom magnetic steel member, each extending along the axial direction and with their outer diameters gradually increasing in the direction away from the two axial ends of the inner bottom magnetic steel member; and an outer magnetic steel member having a cylindrical shape, located coaxially with the inner bottom magnetic steel member and outside the inner bottom magnetic steel member, and spaced radially from the inner bottom magnetic steel member. This invention realizes the characteristic that the magnetic levitation output is linear along the stroke, and the output at the zero point can offset the gravity of a vertical structure. This invention compensates for the gravity of a vertical movement mechanism and achieves constant stiffness compensation based on the linearization of the magnetic field, balancing the elastic deformation reaction force of the flexible mechanism within the stroke range, reducing the load on the vertical actuator, and significantly improving the vertical performance of the fine movement stage.

Description

[Technical field]

[0001] The present invention relates to the field of integrated circuit device manufacturing, and more specifically to a constant stiffness magnetically levitated gravity compensation device and a motion stage including the same. This patent application claims priority to a Chinese patent application filed on December 1, 2020, bearing application number 202011379009.X and entitled "Magnetic levitation gravity compensation device and moving stage including the same," the entire text of which is incorporated herein by reference. [Background technology]

[0002] In the field of semiconductor silicon wafer manufacturing or inspection, the worktable is required to be able to use the silicon wafer transmission system to complete the transfer of the silicon wafer, and at the same time, it must be able to transport the silicon wafer to complete the accurate positioning of the silicon wafer, and finally complete the manufacturing or inspection of the silicon wafer. Therefore, in the worktable device applied to manufacturing or inspection, the fine movement stage is its core component, which can complete the accurate positioning of the silicon wafer in the three vertical axes of Z / Rx / Ry. In the conventional vertical three-axis fine movement stage, three actuators are usually used to perform three-point positioning, and then a flexible mechanism is used to perform vertical guide and movement decoupling to ensure vertical performance. However, with the continuous improvement of the yield requirements of wafer manufacturing or wafer inspection, and the high precision of manufacturing or inspection, the working speed, acceleration and performance of the worktable are also improved, and the requirements for the movement accuracy, acceleration and speed of the fine movement stage parts are becoming higher and higher. Therefore, the gravity compensation technology is proposed in the industry to improve the performance of the fine movement stage. However, in a fine-motion stage with a flexible mechanism, the spring stiffness of the flexible mechanism is constant within a small stroke range, and the reaction force acting on the vertical actuator increases or decreases linearly with respect to the vertical displacement, making it difficult for a conventional constant-force gravity compensator to meet the high performance requirements of the vertical stage.

[0003] Therefore, US Patent US9172291B2 proposes using a magnetic levitation device and a mechanical spring to compensate for the gravity in the vertical direction, and using a voice coil motor to compensate for the reaction force of the flexible mechanism, and since the acting force of the flexible mechanism changes according to the displacement, the number of turns of the coil of the device also changes according to the vertical displacement to compensate for the acting force of the flexible mechanism. However, the structure of the device is complicated, the processing and manufacturing of the coil is somewhat difficult, and the coupling force between the mechanical spring and the magnetic levitation device also has a certain nonlinearity, which is disadvantageous for realizing high control precision.

[0004] The magnetic levitation voice coil motor device proposed in US Patent US2009066168A1 uses the magnetic resistance of the magnetic levitation gravity compensation device to compensate for the gravity of the vertical moving module, and adjusts the amplitude and direction of the coil input current to compensate for the acting force of the flexible mechanism. However, the magnetic levitation voice coil motor not only has a complicated magnetic circuit structure, but also has a near-zero rigidity of the output magnetic levitation, so it must be controlled with a control algorithm to achieve control accuracy.

[0005] Therefore, at present, a gravity compensation device with a simple structure, constant stiffness within a small stroke range, and opposite stiffness to the flexible mechanism is required, that is, the compensator at the zero point can output an action force with the same amplitude and opposite direction as the gravity of the vertical moving module, and the output stiffness of the compensator can be guaranteed to be constant. The air-floating gravity compensation device commonly used in the industry can achieve constant stiffness gravity compensation by adjusting the pressure of compressed gas in real time with a proportional valve, but the structure of the air-floating gravity compensation device is very complicated, and the air pressure control has hysteresis, which affects the improvement of vertical performance. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a constant stiffness magnetic levitation gravity compensation device which is simple in structure and control and free of hysteresis in control, thereby solving the problems existing in the prior art. [Means for solving the problem]

[0007] Specifically, the present invention provides a magnetic levitation gravity compensation device, An inner bottom magnetic steel extending along the axial direction; a first end magnetic steel and a second end magnetic steel, each located at two axial ends of the inner bottom magnetic steel, extending along the axial direction, and each having an outer diameter gradually increasing along a direction away from the two axial ends of the inner bottom magnetic steel; The outer magnetic ring magnetic steel has a cylindrical shape, is positioned outside the inner bottom magnetic steel coaxially with the inner bottom magnetic steel, and is spaced apart from the inner bottom magnetic steel in the radial direction.

[0008] In one embodiment, the magnetization direction of the first end magnetic steel and the second end magnetic steel is axially outward from the inner bottom magnetic steel, and the magnetization direction of the outer magnetic ring magnetic steel is radially outward.

[0009] In one embodiment, the first end magnetic steel and the second end magnetic steel are mirror images of each other with respect to an axial dividing plane of the inner bottom magnetic steel.

[0010] In one embodiment, the inner bottom magnetic steel, the first end magnetic steel and the second end magnetic steel have central axes that overlap each other and are rotationally symmetrical about the central axis.

[0011] In one embodiment, the inner bottom magnetic steel has an axial through hole, and the first end magnetic steel and the second end magnetic steel have axial through holes.

[0012] In one embodiment, the inner bottom magnetic steel has a cylindrical shape, the first end magnetic steel is made of multi-stage cylindrical magnetic steel adjacent to each other along the axial direction, and the second end magnetic steel is made of multi-stage cylindrical magnetic steel adjacent to each other along the axial direction, the inner diameters of the multi-stage cylindrical magnetic steel are the same, and the outer diameters of each gradually decrease from the cylindrical magnetic steel away from the inner bottom magnetic steel to the cylindrical magnetic steel close to the inner bottom magnetic steel.

[0013] In one embodiment, in the multi-stage cylindrical magnetic steel of the first end magnetic steel, the difference in outer diameter of each adjacent cylindrical magnetic steel is equal, and the axial length is equal, In the multi-stage cylindrical magnetic steel of the second end magnetic steel, the difference in outer diameter between adjacent cylindrical magnetic steel pieces is equal, and the axial length is equal.

[0014] In one embodiment, the first end magnetic steel comprises three sections of cylindrical magnetic steel adjacent to each other along the axial direction, and the second end magnetic steel comprises three sections of cylindrical magnetic steel adjacent to each other along the axial direction.

[0015] In one embodiment, the cylindrical magnetic steel of the first end magnetic steel and the second end magnetic steel that is farthest from the inner bottom magnetic steel has an outer diameter R5 and an axial length L5, the outer diameter of the inner bottom magnetic steel is R2, and the axial length of the outer magnetic steel is L1, where R2 / 2≦R5≦R2 and L1 / 4≦L5≦L1 / 2.

[0016] In one embodiment, the radial dimension of the axial through hole of the inner bottom magnetic steel is the same as the radial dimension of the axial through hole of the first end magnetic steel and the second end magnetic steel.

[0017] In one embodiment, a radial dimension of the axial through hole of the first end magnetic steel and the second end magnetic steel decreases from the end away from the inner bottom magnetic steel to the inner bottom magnetic steel.

[0018] In one embodiment, the relationship between the radial angle β between the first end magnetic steel and the second end magnetic steel and the inner surface of the axial through hole and the radial angle α between the outer circumferential surfaces of the first end magnetic steel and the second end magnetic steel is α≦β≦135°.

[0019] In one embodiment, the outer magnetic ring magnetic steel is made of a plurality of arc plates adjacent to each other along the circumferential direction.

[0020] In one embodiment, the inner bottom magnetic steel includes a reduced diameter portion, the reduced diameter portion being located in the axial middle of the inner bottom magnetic steel and having an outer diameter smaller than that of the remaining portion.

[0021] In one embodiment, the axial length of the outer magnetic ring magnetic steel is L1, the axial length of the end magnetic steel is L2, and the axial length of the inner bottom magnetic steel is L3, the stroke of the end magnetic steel and the inner bottom magnetic steel moving along the axial direction relative to the outer magnetic ring magnetic steel is S, the difference between the mechanical stroke and the effective stroke is ΔS, where L3+2L2-L1=S+ΔS, where the range of possible values ​​of ΔS / S is [0.1,3.0].

[0022] In one embodiment, the base angle α of the end magnetic steel is 60° to 88°.

[0023] In one embodiment, the base angle α of the end magnetic steel is 75°. Effect of the Invention

[0024] The present invention further provides a moving stage including a worktable and a base, the worktable being configured to rotate and move vertically relative to the base, and the magnetic levitation gravity compensation device being provided below the worktable. The magnetic levitation gravity compensation device of the present invention solves the problems of the air constant stiffness gravity compensation device in the prior art, such as complex structure, complex control, and control hysteresis, and solves the problem of the stiffness of the conventional gravity compensation device being zero or nonlinear. The present invention realizes the characteristic that the output of the magnetic levitation is linear along the stroke, and the output at the zero point can offset the gravity of the vertical structure. The invention compensates for the gravity of the vertical moving mechanism, and realizes constant stiffness compensation based on the linearization of the magnetic field, balances the elastic deformation reaction force of the flexible mechanism within the stroke range, reduces the load of the vertical actuator, and greatly improves the vertical performance of the fine movement stage. [Brief description of the drawings]

[0025] [Figure 1] 1 is a structural schematic diagram of a magnetic levitation type gravity compensation device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic vertical cross-sectional view of the embodiment shown in FIG. [Diagram 3]FIG. 2 is a schematic diagram of the magnetization direction of the magnetic steel of the embodiment shown in FIG. 1. [Figure 4] FIG. 2 is a dimensional schematic diagram of the magnetic steel of the embodiment shown in FIG. [Diagram 5] 2 is a power curve within the stroke range of the embodiment shown in FIG. 1. [Figure 6] FIG. 5 is a structural schematic diagram of a magnetic levitation type gravity compensation device according to a second embodiment of the present invention. [Figure 7] 13 is a dimensional schematic diagram (D2>D3) of magnetic steel of a magnetic levitation type gravity compensation device according to a third embodiment of the present invention. FIG. [Figure 8] A schematic diagram of the dimensions of the magnetic steel of the magnetic levitation gravity compensation device according to the third embodiment of the present invention (D2 <D3)である。 [Figure 9] FIG. 11 is a schematic diagram showing dimensions (R3=R2) of magnetic steel of a magnetic levitation type gravity compensation device according to a third embodiment of the present invention. [Figure 10] 13 is a schematic diagram showing dimensions of magnetic steel of a magnetic levitation type gravity compensation device according to a third embodiment of the present invention (R3>R3). [Figure 11] FIG. 11 is a schematic diagram showing the magnetization direction of magnetic steel of a magnetic levitation type gravity compensation device according to a fourth embodiment of the present invention. [Figure 12] 13 is an output curve of a magnetic levitation type gravity compensation device according to a fourth embodiment of the present invention. [Figure 13] FIG. 11 is a schematic diagram showing the structure of a magnetic levitation type gravity compensation device and the magnetization direction of magnetic steel according to a fourth embodiment of the present invention. [Figure 14] FIG. 13 is a structural schematic diagram of a wedge-shaped hole of a magnetic levitation type gravity compensation device according to a fifth embodiment of the present invention. [Figure 15] FIG. 13 is a structural schematic diagram of a magnetic levitation type gravity compensation device according to a sixth embodiment of the present invention. [Figure 16] FIG. 13 is a structural schematic diagram of a stepped magnetic steel group according to a seventh embodiment of the present invention. [Figure 17] FIG. 13 is a schematic diagram of the magnetization direction of a stepped magnetic steel sheet according to a seventh embodiment of the present invention. [Figure 18] FIG. 13 is a dimensional schematic diagram of a stepped magnetic steel group according to a seventh embodiment of the present invention. [Figure 19]FIG. 13 is a structural schematic diagram of a truncated cone magnetic steel and a ring magnetic steel solution according to the eighth embodiment of the present invention; [Figure 20] FIG. 13 is a schematic diagram showing dimensions of a truncated cone magnetic steel and an annular magnetic steel according to the eighth embodiment of the present invention. [Figure 21] 3 shows an arrangement of a magnetic levitation type gravity compensation device according to the present invention on a moving stage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In order to make the objects, features and advantages of the present invention more clearly understood, the preferred embodiments of the present invention will be described in detail below with reference to the drawings, which are not intended to limit the scope of the present invention, but are merely intended to describe the substantial spirit of the technical solution of the present invention.

[0027] In the following description, for the purpose of explaining various disclosed embodiments, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the art will recognize that the embodiments may be practiced without one or more of these specific details. In other instances, well-known devices, structures and techniques related to the present application may not be shown or described in detail so as not to unnecessarily obscure the description of the embodiments.

[0028] References throughout this specification to "one embodiment" or "one embodiment" indicate that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of "one embodiment" or "one embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment. Moreover, the particular features, structures, or characteristics may be combined in any manner in one or more embodiments.

[0029] In the following description, many directional terms are used to clearly show the structure and operation method of the present invention, but terms such as "front", "rear", "left", "right", "outside", "inside", "outward", "inward", "upper", and "lower" should be understood as terms of convenience rather than limiting terms. In this specification, "X direction", "X direction" and "Y direction" refer to directions intersecting each other along the horizontal direction, and "Z direction" refers to the vertical direction.

[0030] In the field of semiconductor silicon wafer manufacturing or inspection, a worktable is required to realize the rotation around the Z direction and vertical lifting and lowering of a silicon wafer carried thereon. The worktable can be driven by a voice coil motor to realize its lifting and lowering, and a gravity compensation device such as a magnetic levitation gravity compensation device is usually provided to reduce the load of the voice coil motor and improve the accuracy of vertical movement. In order to realize the tilt of the worktable relative to the base, an elastic connecting member can be installed between the worktable and the base, and when the worktable rises and falls along the vertical direction, an elastic force is generated in the elastic connecting member, and the elastic force changes linearly according to the stroke of the worktable. The present invention provides a magnetic levitation gravity compensation device that changes linearly according to the stroke of the worktable to realize compensation for the gravity of the worktable and the elastic force of the elastic connecting member.

[0031] Hereinafter, various embodiments of the present invention will be described with reference to the drawings.

[0032] As shown in Figures 1 and 2, a magnetic levitation gravity compensation device 100 according to an embodiment of the present invention includes an inner bottom magnetic steel 103, a first end magnetic steel 102a, a second end magnetic steel 102b, and an outer magnetic wheel magnetic steel 101. Here, the inner bottom magnetic steel 103 has a cylindrical shape, and the first end magnetic steel 102a and the second end magnetic steel 102b are located at two axial ends of the inner bottom magnetic steel 103 and extend downward and upward along the axial direction, respectively. In the embodiment shown, the first end magnetic steel 102a is located axially below the inner bottom magnetic steel 103, and the second end magnetic steel 102b is located axially above the inner bottom magnetic steel 103.

[0033] In the illustrated embodiment, the first end magnetic steel 102a and the second end magnetic steel 102b are frustum-shaped, and the outer diameters gradually increase downward and upward from the two axial ends adjacent to the inner bottom magnetic steel 103, respectively. The first end magnetic steel 102a and the second end magnetic steel 102b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 103 have the same diameter and communicate with each other. The first end magnetic steel 102a and the second end magnetic steel 102b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 103. The outer magnetic wheel magnetic steel 101 is cylindrical, and is located outside the inner bottom magnetic steel 103 coaxially with the inner bottom magnetic steel 103, and is radially spaced from the inner bottom magnetic steel 103. In the embodiment shown, the first end magnetic steel 102a and the second end magnetic steel 102b are adjacent to the inner bottom magnetic steel 103, but it should be understood that there may be a certain gap therebetween, which is typically 1 mm or less.

[0034] In this embodiment, the outer magnetic ring magnetic steel 101 is the stator magnetic steel of the gravity compensation device, and the inner bottom magnetic steel 103 and the first end magnetic steel 102a and the second end magnetic steel 102b are the mover magnetic steel of the gravity compensation device. Alternatively, the outer magnetic ring magnetic steel 101 may be the mover magnetic steel of the gravity compensation device, and the inner bottom magnetic steel 103 and the first end magnetic steel 102a and the second end magnetic steel 102b may be the stator magnetic steel of the gravity compensation device.

[0035] As shown in the cross-sectional view of FIG. 2, there is no mechanical connection between the stator magnetic steel and the movable magnetic steel of the magnetic levitation gravity compensation device 100, and within the stroke range, the stator magnetic steel and the movable magnetic steel can generate a certain rigidity vertical acting force by interacting with each other, and in the present invention, the vertical acting force can be understood as the magnetic buoyancy of the device, where when the outer magnetic wheel magnetic steel 101 and the inner bottom magnetic steel 103 are axially centered relative to each other, that is, the zero point of the device, and since the gravity of the worktable needs to be compensated when the device is at the zero point, the amplitude of the magnetic buoyancy output must be equal to the gravity of the worktable, and the elastic force of the elastic connecting member is zero, and in this case, the direction of the magnetic levitation output by the magnetic levitation gravity compensation device is vertically upward. Since the output of the elastic connecting member installed between the worktable and the base changes linearly with the vertical movement of the worktable, the magnetic levitation output by the device also changes linearly with the vertical movement of the worktable, and only when the slopes of the changes of the two are equal can the magnetic levitation gravity compensation device fully realize the compensation effect of the gravity of the worktable and the elastic force of the elastic connecting member. Based on this, the outer dimensions of the first end magnetic steel 102a and the second end magnetic steel 102b of the device must gradually increase downward and upward respectively from both ends adjacent to the inner bottom magnetic steel 103, and further, when the gradient of change in the outer dimensions of the first end magnetic steel 102a and the second end magnetic steel 102b matches the gradient of change in the elastic force output by the elastic connecting member, at any position in the vertical direction, the amplitude of the magnetic buoyancy force output by the device and the amplitude of the elastic force output by the elastic connecting member are both equal.

[0036] 3 shows the magnetization direction of each magnetic steel in the magnetic levitation gravity compensation device 100. Here, the magnetization direction of the inner bottom magnetic steel 103 and the second end magnetic steel 102b is the same and both are axially upward, the magnetization direction of the first end magnetic steel 102a is axially downward, and the magnetization direction of the outer magnetic ring magnetic steel 101 is radially outward. Similarly, the magnetization direction of the outer magnetic ring magnetic steel 101 may be radially inward, the magnetization direction of the first end magnetic steel 102a is axially upward, and the magnetization directions of the second end magnetic steel 102b and the inner bottom magnetic steel 103 are the same and both are axially downward.

[0037] Furthermore, as shown in FIG. 1, the outer magnetic ring magnetic steel 101 is joined by eight divided magnetic steel pieces. Here, the eight divided magnetic steel pieces are circular arc plate magnetic steel pieces obtained by dividing a cylinder along the radial direction at equal angular intervals of 45°. The outer magnetic ring magnetic steel 101 may be joined by other numbers of divided magnetic steel pieces, and the number of divisions N is set to an even number such as two, four, or six pieces in order to remove the radial unbalance force generated in the outer magnetic ring magnetic steel 101. By joining the outer magnetic ring magnetic steel 101 by divided magnetic steel pieces, it becomes easier to magnetize and process the magnetic steel. When the outer magnetic ring magnetic steel 101 is joined by multiple magnetic steel pieces, the value of the pole arc coefficient a of the magnetic steel has a positive relationship with the output stiffness of the magnetic levitation gravity compensation device, and the pole arc coefficient a of the magnetic steel is the ratio of the pole arc length of the magnetic steel to the pole distance, and the value of the pole arc coefficient a is preferably [0.7, 0.95].

[0038] 2, the outer diameter of one end of the first end magnetic steel 102a and the second end magnetic steel 102b adjacent to the inner bottom magnetic steel 103 is larger than the outer diameter of the inner bottom magnetic steel 103. Note that the outer diameter of one end of the first end magnetic steel 102a and the second end magnetic steel 102b adjacent to the inner bottom magnetic steel 103 may be equal to or smaller than the outer diameter of the inner bottom magnetic steel 103, and the size of the outer diameter dimensions of the first end magnetic steel 102a and the second end magnetic steel 102b affects the gradient of the magnetic buoyancy force output within the stroke range of the magnetic levitation type gravity compensation device.

[0039] Fig. 4 is a schematic diagram showing dimensions of the magnetic levitation gravity compensation device 100. As shown in Fig. 4, the axial lengths of the outer magnetic wheel magnetic steel 101, the first end magnetic steel 102a and the second end magnetic steel 102b, and the inner bottom magnetic steel 103 are L1, L2, and L3, respectively, the radii of one end of the first end magnetic steel 102a and the second end magnetic steel 102b adjacent to the inner bottom magnetic steel 103 and the radius of the inner bottom magnetic steel 103 are indicated by R2 and R3, respectively, and the radius of one end of the first end magnetic steel 102a and the second end magnetic steel 102b away from the inner bottom magnetic steel 103 is indicated by R4. 21The diameter of the axial through hole of the first end magnetic steel 102a, the second end magnetic steel 102b and the inner bottom magnetic steel 103 is indicated by D0, and the base angle of the first end magnetic steel 102a and the second end magnetic steel 102b is indicated by α. If the total stroke of the magnetic levitation gravity compensator is S and the difference between the mechanical stroke and the effective stroke is ΔS, the relationship between the axial length of the outer magnetic wheel magnetic steel 101, the first end magnetic steel 102a, the second end magnetic steel 102b and the inner bottom magnetic steel 103 is L3+2L2-L1=S+ΔS, where the value of ΔS is mainly related to the total stroke S of the compensator, and the value of ΔS / S is usually in the range of [0.1, 3.0]. The relationship between the radius of one end of the first end magnetic steel 102a and the second end magnetic steel 102b adjacent to the inner bottom magnetic steel 103 and the radius of the inner bottom magnetic steel 103 depends on the magnitude of the weight that the magnetic levitation gravity compensation device should compensate at the zero point, that is, the gravity of the worktable. In this embodiment, preferably R2>R3. When the outer diameters of the first end magnetic steel 102a, the second end magnetic steel 102b and the inner bottom magnetic steel 103 are determined, the size of the diameter D0 of the axial through hole is related to the rigidity of the magnetic levitation gravity compensation device. In this embodiment, considering the difficulty of the integration and assembly process of the magnetic levitation gravity compensation device, the dimensions of the axial through holes of the first end magnetic steel 102a, the second end magnetic steel 102b and the inner bottom magnetic steel 103 are the same. The base angle α of the first end magnetic steel 102a and the second end magnetic steel 102b determines the linearity of the magnetic field, and also affects the rigidity of the magnetic levitation gravity compensation device. When the diameter of the axial through hole and the length of the effective gap are determined, the larger the base angle α of the first end magnetic steel 102a and the second end magnetic steel 102b, the greater the rigidity of the magnetic levitation gravity compensation device. The value range of the base angle α is [60°, 88°]. Usually, the base angle α is expressed as tan α=L2 / (R 21 -R2), and in this embodiment, the base angle α between the first end magnetic steel 102a and the second end magnetic steel 102b is preferably selected as 75°.

[0040] FIG. 5 shows the output simulation curve of the magnetic levitation gravity compensation device 100. In the figure, the horizontal axis indicates the stroke of the magnetic levitation gravity compensation device, and the vertical axis indicates the amplitude of the output. In the figure, two stroke end points, a zero point, and their corresponding outputs are indicated. In the figure, x is the limit displacement in one direction, G is the gravity of the work platform to be compensated by the individual magnetic levitation gravity compensation device, and the design stiffness of the magnetic levitation gravity compensation device is k. As can be seen from this, the output range of the magnetic levitation gravity compensation device is [-F+G, F+G]. As can be seen from the figure, the output of the magnetic levitation gravity compensation device changes linearly with the stroke, thereby compensating for the gravity of the work platform and the linearly changing elastic force generated by the elastic connecting member.

[0041] FIG. 6 shows a magnetic levitation gravity compensation device 200 according to another embodiment of the present invention. This embodiment is basically the same as the magnetic levitation gravity compensation device 100, that is, the magnetic levitation gravity compensation device 200 includes an inner bottom magnetic steel 203, a first end magnetic steel 202a and a second end magnetic steel 202b, and an outer magnetic wheel magnetic steel 201. Here, the inner bottom magnetic steel 203 has a cylindrical shape, and the first end magnetic steel 202a and the second end magnetic steel 202b are respectively located at two axial ends of the inner bottom magnetic steel 203 and extend downward and upward along the axial direction from the inner bottom magnetic steel 203. In the embodiment shown, the first end magnetic steel 202a is located axially below the inner bottom magnetic steel 203, and the second end magnetic steel 202b is located axially above the inner bottom magnetic steel 203. The first end magnetic steel 202a and the second end magnetic steel 202b are frustum-shaped, and the outer diameter gradually increases from the two axial ends close to the inner bottom magnetic steel 203 toward the direction away from the inner bottom magnetic steel 203. The first end magnetic steel 202a and the second end magnetic steel 202b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 203 have the same diameter and communicate with each other. The first end magnetic steel 202a and the second end magnetic steel 202b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 203 in the axial direction. The outer magnetic wheel magnetic steel 201 is cylindrical, and is located outside the inner bottom magnetic steel 203 coaxially with the inner bottom magnetic steel 203, and is spaced apart from the inner bottom magnetic steel 203 in the radial direction. The magnetic levitation type gravity compensation device 200 is distinguished from the magnetic levitation type gravity compensation device 100 in that the outer magnetic wheel magnetic steel 201 is made of a single sheet of magnetic steel that is magnetized in the radial direction.

[0042] 7 and 8 show a magnetic levitation type gravity compensation device 300 according to a third embodiment of the present invention. This embodiment is basically the same as the magnetic levitation type gravity compensation device 100, that is, the magnetic levitation type gravity compensation device 300 includes an inner bottom magnetic steel 303, a first end magnetic steel 302a and a second end magnetic steel 302b, and an outer magnetic wheel magnetic steel 301. Here, the inner bottom magnetic steel 303 has a cylindrical shape, and the first end magnetic steel 302a and the second end magnetic steel 302b are respectively located at two axial ends of the inner bottom magnetic steel 303 and extend downward and upward along the axial direction from the inner bottom magnetic steel 303. In the embodiment shown, the first end magnetic steel 302a is located axially below the inner bottom magnetic steel 303, and the second end magnetic steel 302b is located axially above the inner bottom magnetic steel 303. The first end magnetic steel 302a and the second end magnetic steel 302b are frustum-shaped, and the outer diameter gradually increases from the two axial ends close to the inner bottom magnetic steel 303 in the direction away from the inner bottom magnetic steel 303. The first end magnetic steel 302a and the second end magnetic steel 302b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 303 communicate with each other. The first end magnetic steel 302a and the second end magnetic steel 302b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 303 in the axial direction. The outer magnetic wheel magnetic steel 301 is cylindrical, and is located outside the inner bottom magnetic steel 303 coaxially with the inner bottom magnetic steel 303, and is arranged with a radial gap from the inner bottom magnetic steel 303.

[0043] The magnetic levitation gravity compensator 300 is distinguished from the magnetic levitation gravity compensator 100 in that the diameters of the axial through holes of the first end magnetic steel 302a and the second end magnetic steel 302b are different from the diameter of the axial through hole of the inner bottom magnetic steel 303. The diameters of the axial through holes of the first end magnetic steel 302a and the second end magnetic steel 302b may be smaller (FIG. 7) or larger (FIG. 8) than the diameter of the axial through hole of the inner bottom magnetic steel 303. Note that the relationship between the axial through holes of the first end magnetic steel 302a and the second end magnetic steel 302b and the axial through hole of the inner bottom magnetic steel 303 is related to the mounting method of the magnetic steels and is unrelated to the output stiffness of the magnetic levitation gravity compensator and the value of the compensated gravity at the zero point. The value of the compensating gravity at the zero point of the magnetic levitation gravity compensation device is related to the magnetic field strength provided by the inner bottom magnetic steel 303, and when the outer magnetic wheel magnetic steel 301 is the same, the greater the magnetic field strength of the inner bottom magnetic steel 303, the greater the value of the compensating gravity at the zero point.

[0044] 9 and 10 show a magnetic levitation type gravity compensation device 400 according to a fourth embodiment of the present invention. This embodiment is basically the same as the magnetic levitation type gravity compensation device 100, that is, the magnetic levitation type gravity compensation device 400 includes an inner bottom magnetic steel 403, a first end magnetic steel 402a and a second end magnetic steel 402b, and an outer magnetic wheel magnetic steel 401. Here, the inner bottom magnetic steel 403 has a cylindrical shape, and the first end magnetic steel 402a and the second end magnetic steel 402b are respectively located at two axial ends of the inner bottom magnetic steel 403 and extend downward and upward along the axial direction from the inner bottom magnetic steel 403. In the embodiment shown, the first end magnetic steel 402a is located axially below the inner bottom magnetic steel 403, and the second end magnetic steel 402b is located axially above the inner bottom magnetic steel 403. The first end magnetic steel 402a and the second end magnetic steel 402b are frustum-shaped, and the outer diameter gradually increases from the two axial ends of the inner bottom magnetic steel 403 in the direction away from the inner bottom magnetic steel 403. The first end magnetic steel 402a and the second end magnetic steel 402b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 403 communicate with each other. The first end magnetic steel 402a and the second end magnetic steel 402b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 403 in the axial direction. The outer magnetic wheel magnetic steel 401 is cylindrical, and is located outside the inner bottom magnetic steel 403 coaxially with the inner bottom magnetic steel 403, and is arranged with a radial gap from the inner bottom magnetic steel 403.

[0045] The difference is that in the magnetic levitation type gravity compensation device 100, the outer diameter of one end of the first end magnetic steel 102a and the second end magnetic steel 102b adjacent to the inner bottom magnetic steel 103 is smaller than the outer diameter of the inner bottom magnetic steel 103, whereas in the magnetic levitation type gravity compensation device 400, the outer diameter of one end of the first end magnetic steel 402a and the second end magnetic steel 402b adjacent to the inner bottom magnetic steel 403 is smaller than the outer diameter of the inner bottom magnetic steel 403.

[0046] FIG. 11 shows a magnetic levitation gravity compensation device 500 according to a fourth embodiment of the present invention. This embodiment is basically the same as the magnetic levitation gravity compensation device 100, that is, the magnetic levitation gravity compensation device 500 includes an inner bottom magnetic steel 503, a first end magnetic steel 502a and a second end magnetic steel 502b, and an outer magnetic wheel magnetic steel 501. Here, the inner bottom magnetic steel 503 has a cylindrical shape, and the first end magnetic steel 502a and the second end magnetic steel 502b are respectively located at two axial ends of the inner bottom magnetic steel 503 and extend downward and upward along the axial direction from the inner bottom magnetic steel 503. In the embodiment shown, the first end magnetic steel 502a is located axially below the inner bottom magnetic steel 503, and the second end magnetic steel 502b is located axially above the inner bottom magnetic steel 503. The first end magnetic steel 502a and the second end magnetic steel 502b are frustum-shaped, and the outer diameter gradually increases from the two axial ends close to the inner bottom magnetic steel 503 in the direction away from the inner bottom magnetic steel 503. The first end magnetic steel 502a and the second end magnetic steel 502b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 503 communicate with each other. The first end magnetic steel 502a and the second end magnetic steel 502b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 503 in the axial direction. The outer magnetic wheel magnetic steel 501 is cylindrical, and is located outside the inner bottom magnetic steel 503 coaxially with the inner bottom magnetic steel 503, and is arranged at a radial distance from the inner bottom magnetic steel 503.

[0047] The difference is that in the magnetic levitation gravity compensation device 100, the magnetization direction of the inner bottom magnetic steel 103 is in the axial direction, whereas in the magnetic levitation gravity compensation device 500, the magnetization direction of the inner bottom magnetic steel 503 and the magnetization direction of the outer magnetic wheel magnetic steel 501 are the same and both are radially outward. In addition, in the magnetic levitation gravity compensation device 500, the magnetization direction of the first end magnetic steel 502a and the second end magnetic steel 502b is from one end away from the inner bottom magnetic steel 503 toward the inner bottom magnetic steel 503, and the magnetization directions of the inner bottom magnetic steel 503 and the outer magnetic wheel magnetic steel 501 may be the same and both are radially inward. In some application environments, the gravity compensation device does not need to compensate for the gravity of the work platform at the zero point, so the magnetic levitation gravity compensation device 500 can use the above magnetization direction. In this case, the inner bottom magnetic steel 504 may be alternatively configured to be joined together with a plurality of divided magnetic steel pieces magnetized in the radial direction (see the magnetic levitation type gravity compensation device 800 of the seventh embodiment).

[0048] In addition, the inner-bottom magnetic steel 504 can be further replaced with a cylinder 505 made of a non-magnetized high-permeability material, as shown in FIG. 13, if the inner-bottom magnetic steel is not magnetized, the output rigidity of the magnetic levitation gravity compensation device will decrease, and the high-permeability material described in this embodiment is preferably Permalloy.

[0049] FIG. 12 shows the output curve of the magnetic levitation gravity compensator 500. In the figure, the horizontal axis is the stroke of the magnetic levitation gravity compensator, the vertical axis is the output amplitude, and the two stroke end points, the zero point, and their corresponding outputs are shown in the figure. As can be seen from the figure, the output amplitude of the magnetic levitation gravity compensator at the zero point is zero. If the design stiffness of the magnetic levitation gravity compensator is k, then the output amplitude of the magnetic levitation gravity compensator at the forward stroke end point is F=kx, which shows that the output range of the magnetic levitation gravity compensator is [-F, F].

[0050] FIG. 14 shows a magnetic levitation gravity compensation device 600 according to a fifth embodiment of the present invention. This embodiment is basically the same as the magnetic levitation gravity compensation device 100, that is, the magnetic levitation gravity compensation device 600 includes an inner bottom magnetic steel 603, a first end magnetic steel 602a and a second end magnetic steel 602b, and an outer magnetic wheel magnetic steel 601. Here, the inner bottom magnetic steel 603 has a cylindrical shape, and the first end magnetic steel 602a and the second end magnetic steel 602b are respectively located at two axial ends of the inner bottom magnetic steel 603 and extend downward and upward along the axial direction from the inner bottom magnetic steel 603. In the embodiment shown, the first end magnetic steel 602a is located axially below the inner bottom magnetic steel 603, and the second end magnetic steel 602b is located axially above the inner bottom magnetic steel 603. The first end magnetic steel 602a and the second end magnetic steel 602b are frustum-shaped, and the outer diameter gradually increases from the two axial ends of the inner bottom magnetic steel 603 in the direction away from the inner bottom magnetic steel 603. The first end magnetic steel 602a and the second end magnetic steel 602b are each provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 603 communicate with each other. The first end magnetic steel 602a and the second end magnetic steel 602b have the same shape and size, and are mirror images symmetrical about a radial plane dividing the inner bottom magnetic steel 603. The outer magnetic wheel magnetic steel 601 is cylindrical, and is located outside the inner bottom magnetic steel 603 coaxially with the inner bottom magnetic steel 603, and is arranged with a radial gap from the inner bottom magnetic steel 603.

[0051] The difference is that in the magnetic levitation type gravity compensation device 100, the diameter of the axial through hole of the first end magnetic steel 602a and the second end magnetic steel 602b is maintained constant along the axial direction, whereas in the magnetic levitation type gravity compensation device 600, the diameter of the axial through hole of the first end magnetic steel 602a and the second end magnetic steel 602b gradually increases in the direction from the inner bottom magnetic steel 403 to away from the inner bottom magnetic steel 403, that is, the axial through hole has a truncated cone shape. Although machining of the truncated cone-shaped through hole is more difficult than maintaining the diameter of the axial through hole constant, the output stiffness k of the magnetic levitation gravity compensation device can be fine-tuned to some extent by adjusting the relationship between the base angle β of the truncated cone-shaped through hole of the first end magnetic steel 602a and the second end magnetic steel 602b and the base angle α of the first and second end magnetic steels, where the relationship between the base angle β of the truncated cone-shaped through hole and the base angle α of the first and second end magnetic steels can be expressed as (1) 60°≦α≦88°, (2) α≦β≦135°. In this embodiment, the values ​​of α and β are preferably α=75° and β=82°.

[0052] FIG. 15 shows a magnetic levitation gravity compensation device 700 according to a sixth embodiment of the present invention. This embodiment is basically the same as the magnetic levitation gravity compensation device 100, that is, the magnetic levitation gravity compensation device 700 includes an inner bottom magnetic steel 703, a first end magnetic steel 702a and a second end magnetic steel 702b, and an outer magnetic wheel magnetic steel 701. The first end magnetic steel 702a and the second end magnetic steel 702b are respectively located at two axial ends of the inner bottom magnetic steel 703 and extend downward and upward along the axial direction from the inner bottom magnetic steel 703. In the embodiment shown, the first end magnetic steel 702a is located axially below the inner bottom magnetic steel 703, and the second end magnetic steel 702b is located axially above the inner bottom magnetic steel 703. The first end magnetic steel 702a and the second end magnetic steel 702b are frustum-shaped, and the outer diameter gradually increases from the two axial ends of the inner bottom magnetic steel 703 in the direction away from the inner bottom magnetic steel. The first end magnetic steel 702a and the second end magnetic steel 702b are identical in shape and size, and are mirror images of each other about a radial plane dividing the inner bottom magnetic steel 703. The outer magnetic wheel magnetic steel 701 is cylindrical, and is located outside the inner bottom magnetic steel 703 coaxially with the inner bottom magnetic steel 703, and is spaced apart from the inner bottom magnetic steel 703 in the radial direction.

[0053] The difference is that in this embodiment, the inner bottom magnetic steel 703 is cylindrical, the first end magnetic steel 702a and the second end magnetic steel 702b are truncated cones, and the inner bottom magnetic steel 703, the first end magnetic steel 702a and the second end magnetic steel 702b do not have an axial through hole. This configuration increases the difficulty of assembling the magnetic steel to a certain extent, but the outer diameters of the first end magnetic steel 702a, the second end magnetic steel 702b and the inner bottom magnetic steel 703 are correspondingly reduced, and the volume of the magnetic levitation gravity compensation device can be reduced to a certain extent while keeping the design output stiffness k of the magnetic levitation gravity compensation device constant, or the design output stiffness k of the magnetic levitation gravity compensation device can be increased while keeping the volume of the magnetic levitation gravity compensation device constant.

[0054] In order to facilitate the processing of the first end magnetic steel 702a and the second end magnetic steel 702b, the first end magnetic steel 702a and the second end magnetic steel 702b may be formed of a plurality of stepped magnetic steel groups that are cylindrical and stacked up and down in the axial direction, where the number of axial divisions of the stepped magnetic steel group is N t The difference between the radial dimension and the axial dimension of the adjacent magnetic steel pieces in the axial direction should be obtained by repeating the simulation according to the design requirements. Usually, the number of divisions of the axial magnetic steel pieces in the stepped magnetic steel group, N t The value range is N t ≧2, Nt∈Z, the difference in the radial dimension of the magnetic steel pieces adjacent in the axial direction determines the output stiffness of the magnetic levitation gravity compensation device, and the value of the axial dimension of the magnetic steel pieces adjacent in the axial direction and the difference therebetween determine the magnitude of the output displacement of the compensation device. t is 3, and the difference in radial dimension of each of the magnetic steel pieces adjacent in the axial direction is 2.0 mm.

[0055] 16 shows a magnetic levitation type gravity compensation device 800 according to a seventh embodiment of the present invention. The magnetic levitation type gravity compensation device 800 includes an inner bottom magnetic steel 805, first end magnetic steels 804a, 803a, 802a, second end magnetic steels 804b, 803b, 802b, and an outer magnetic wheel magnetic steel 801. Here, the inner bottom magnetic steel 805 has a cylindrical shape, and the first end magnetic steels 804a, 803a, 802a and second end magnetic steels 804b, 803b, 802b are located at two axial ends of the inner bottom magnetic steel 805, respectively, and extend downward and upward from the inner bottom magnetic steel 805 in the axial direction in order. In the embodiment shown, the first end magnetic steel 804a, 803a, 802a is located axially below the inner bottom magnetic steel 805, and the second end magnetic steel 804b, 803b, 802b is located axially above the inner bottom magnetic steel 805. Each of the first end magnetic steel 804a, 803a, 802a and each of the second end magnetic steel 804b, 803b, 802b has a cylindrical shape, and the outer diameter increases sequentially from both ends of the inner bottom magnetic steel 805 in the direction away from the inner bottom magnetic steel 805. Each of the first end magnetic steel 804a, 803a, 802a and each of the second end magnetic steel 804b, 803b, 802b is provided with an axial through hole, and the axial through hole and the axial through hole of the inner bottom magnetic steel 805 have the same diameter and communicate with each other. The first end magnetic steel pieces 804a, 803a, 802a and the second end magnetic steel pieces 804b, 803b, 802b have the same shape and dimensions, and are mirror images of each other about a radial plane obtained by dividing the inner bottom magnetic steel piece 805 in the axial direction. The outer magnetic wheel magnetic steel piece 801 is cylindrical, and is located outside the inner bottom magnetic steel piece 805 coaxially with the inner bottom magnetic steel piece 805, and is spaced apart from the inner bottom magnetic steel piece 805 in the radial direction.

[0056] 17 is a schematic diagram showing the magnetization direction of the magnetic steel of the magnetic levitation gravity compensation device 800. Here, the magnetization direction of the outer magnetic ring magnetic steel 801 is radial magnetization, and the magnetization direction of the inner bottom magnetic steel 805 and each of the first and second end magnetic steels is axial magnetization, where the magnetization direction of each of the first end magnetic steels 804a, 803a, 802a is axially upward, the magnetization direction of each of the second end magnetic steels 804b, 803b, 802b is axially downward, the magnetization direction of the inner bottom magnetic steel 805 is axially upward, and the magnetization direction of the outer magnetic ring magnetic steel 801 is radially outward. Alternatively, the magnetization direction of the outer magnetic ring magnetic steel 801 may be radially inward, the magnetization direction of each of the first end magnetic steels 804a, 803a, 802a may be axially downward, the magnetization direction of each of the second end magnetic steels 804b, 803b, 802b may be axially upward, and the magnetization direction of the inner bottom magnetic steel 805 may be axially downward. Alternatively, the magnetization direction of the outer magnetic ring magnetic steel 801 may be axially magnetized, and the magnetization direction of the inner bottom magnetic steel 805 and each of the first and second end magnetic steels may be radially magnetized.

[0057] FIG. 18 is a dimensional schematic diagram of a magnetic levitation type gravity compensation device 800 according to a seventh embodiment of the present invention. In the figure, the number of divisions N of the axial magnetic steel of the magnetic steel group is t Here, the axial lengths of the outer magnetic ring magnetic steel 801, the inner bottom magnetic steel 805, the first end magnetic steels 804a, 803a, 802a, and the second end magnetic steels 804b, 803b, 802b are represented by L1, L5, L4, L3, and L2, respectively, the axial through holes of the inner bottom magnetic steel 805 and the first and second end magnetic steels are the same and represented by D0, and the inner bottom magnetic steel 805 and the annular magnetic steel 80 4 ~80 2 The radii of the magnetic steel are represented by R5, R4, R3, and R2, respectively. In order to facilitate the assembly of the magnetic steel, in this embodiment, the diameter of the axial through hole and the dimensional relationship of each magnetic steel are L2+L4=2L3, R2+R4=2R3, and L2+L3+L4≧L1. In the above preferred embodiment, the number of divisions N of the axial magnetic steel of the stepped magnetic steel group is t The number of divisions N of the axial magnetic steel pieces of the stepped magnetic steel pieces in the embodiment is 3, and the difference in the radial dimension of each of the magnetic steel pieces adjacent in the axial direction is 2.0 mm. tThe design criteria for the dimensional relationship of each end magnetic steel can be derived from the above. Referring to the value of the base angle α of the end magnetic steel in Example 1, TIFF0007636540000001.tif14160 is established, where L i is the axial length of each end magnetic steel, where the axial length of the end magnetic steel farthest from the inner bottom magnetic steel is L2, and the axial length of the end magnetic steel closest to the inner bottom magnetic steel is L Nt-1 It is said that. t When the value of becomes infinite and each L i When these are equal, the value of the base angle of the end magnetic steel coincides with that of Example 1.

[0058] In order to ensure the consistency of the output stiffness of the compensation device, preferably, the difference in the radial dimension and the difference in the axial dimension of the magnetic steels adjacent in the axial direction are all equal, that is, R5-R4=R4-R3=R3-R2, L2-L3=L3-L4=L4-L5. The difference in the radial dimension and the difference in the axial dimension may be different from each other. Furthermore, the diameter D0 of the axial through hole of the inner bottom magnetic steel 805 and each of the first and second end magnetic steels may be different from each other, or one or more of them may be configured to have no axial through hole.

[0059] The diameter R5 and axial length L5 of the inner bottom magnetic steel are closely related to the weight of the vertical moving mechanism of the worktable, and the value range of R5 is usually R2 / 2≦R5≦R2, and the value range of L5 is L1 / 4≦L5≦L1 / 2. When the weight to be compensated by the magnetic levitation gravity compensator increases or decreases, only R5 and L5 need to be adjusted to ensure the output rigidity of the compensator remains constant.

[0060] FIG. 19 shows a magnetic levitation gravity compensation device 900 according to an eighth embodiment of the present invention. The magnetic levitation gravity compensation device 900 includes an inner bottom magnetic steel 903, a first end magnetic steel 902a, a second end magnetic steel 902b, and an outer magnetic wheel magnetic steel 901. The first end magnetic steel 902a and the second end magnetic steel 902b are located at the two axial ends of the inner bottom magnetic steel 903, respectively, and extend downward and upward along the axial direction from the inner bottom magnetic steel 903. In the embodiment shown, the first end magnetic steel 902a is located axially below the inner bottom magnetic steel 903, and the second end magnetic steel 902b is located axially above the inner bottom magnetic steel 903. The first end magnetic steel 902a and the second end magnetic steel 902b are frustum-shaped, and the outer diameter gradually increases from the two axial ends of the inner bottom magnetic steel 903 in the direction away from the inner bottom magnetic steel 903. The first end magnetic steel 902a and the second end magnetic steel 902b have the same shape and dimensions, and are mirror images of each other about a radial plane obtained by dividing the inner bottom magnetic steel 903 in the axial direction. The outer magnetic wheel magnetic steel 901 is cylindrical, and is located outside the inner bottom magnetic steel 903 coaxially with the inner bottom magnetic steel 903, and is spaced apart from the inner bottom magnetic steel 903 in the radial direction. The first end magnetic steel 902a and the second end magnetic steel 902b may be configured as a pair of cylindrical magnetic steel pieces adjacent to each other in the axial direction.

[0061] The difference is that in this embodiment, the axial middle portion of the inner bottom magnetic steel 903 of the magnetic levitation type gravity compensation device 900 has a reduced diameter portion 904, and both axial ends of the reduced diameter portion 904 are the first axial portion 903a and the second axial portion 903b. The diameter of the reduced diameter portion 904 is smaller than the diameter of the first axial portion 903a and the second axial portion 903b. Here, the magnetization directions of the first end magnetic steel 902a and the first axial portion 903a are all axially downward, and the magnetization directions of the reduced diameter portion 904, the second end magnetic steel 902b and the second axial portion 903b are all axially upward. The magnetic levitation type gravity compensation device 900 is applicable to operating conditions in which the rigidity near the zero point is somewhat large, the rigidity of both end points remains the same, and the damping force near the zero point is relatively large.

[0062] FIG. 20 shows a schematic diagram of the dimensions of the magnetic levitation gravity compensation device 900. Here, the diameters of the axial through holes of the first end magnetic steel 902a, the second end magnetic steel 902b, and the inner bottom magnetic steel 903 are equal, and are all D0. The outer diameters of one end of the first end magnetic steel 902a and the second end magnetic steel 902b adjacent to the inner bottom magnetic steel 903, and the outer diameters of the first axial portion 903a and the second axial portion 903b of the inner bottom magnetic steel 903 are respectively represented by R2 and R3, and preferably R2=R3, in which case the linearity of the magnetic levitation gravity compensation device 900 can reach the optimum. The diameter of the reduced diameter portion 904 is represented by R4, and R4 <R3である。

[0063] In each of the embodiments described above, preferably, the inner bottom magnetic steel, the first end magnetic steel and the second end magnetic steel have a common central axis and are rotationally symmetrical about the central axis, thereby ensuring that the generated magnetic force is uniformly distributed along the circumferential direction.

[0064] The present invention further provides a motion stage including a worktable and a base, the worktable being configured to rotate and move vertically relative to the base, where the worktable is used to transport a workpiece to be processed.

[0065] FIG. 21 shows a bottom view of a worktable using the magnetic levitation gravity compensator according to the present invention. A concave cavity for accommodating the magnetic levitation gravity compensator according to the present invention is provided below the worktable. Here, the concave cavity below the worktable may be one, two, three or four. The figure shows schematic diagrams of a central point arrangement of one magnetic levitation gravity compensator, a parallel arrangement of two magnetic levitation gravity compensators, an equilateral triangle arrangement of three magnetic levitation gravity compensators, and a square arrangement of four magnetic levitation gravity compensators, but it should be understood that other numbers and arrangements of magnetic levitation gravity compensators can also be installed. The shape of the worktable using the magnetic levitation gravity compensator is not limited to the square shown in the figure, and can be set to any shape as necessary. Note that the vertical line on which the equivalent center of gravity of the magnetic levitation gravity compensator is located must be on the same line as the vertical line on which the center of gravity of the vertical movement mechanism is located.

[0066] The magnetic levitation gravity compensation device of the present invention can provide a magnetic levitation force that changes linearly with the stroke, i.e., can compensate for the gravity of the worktable and compensate for the elastic force generated by the constant stiffness elastic connection device, and can meet the needs for gravity compensation of the moving stage in some situations.

[0067] Although the preferred embodiment of the present invention has been described in detail above, it will be understood that those skilled in the art, upon reading the above teachings of the present invention, may make various changes or modifications to the present invention, the equivalents of which are also included within the scope defined by the appended claims of this application.

Claims

1. An inner bottom magnetic steel extending along the axial direction; a first end magnetic steel and a second end magnetic steel, each located at two axial ends of the inner bottom magnetic steel, extending along the axial direction, and each having an outer diameter gradually increasing along a direction away from the two axial ends of the inner bottom magnetic steel; An outer magnetic ring magnetic steel having a cylindrical shape, positioned outside the inner bottom magnetic steel coaxially with the inner bottom magnetic steel, and spaced apart from the inner bottom magnetic steel in the radial direction; A magnetic levitation type gravity compensation device characterized in that the magnetization direction of the first end magnetic steel and the second end magnetic steel is outward in the axial direction from the inner bottom magnetic steel, and the magnetization direction of the outer magnetic wheel magnetic steel is outward in the radial direction.

2. 2. The magnetic levitation gravity compensation device according to claim 1, wherein the first end magnetic steel and the second end magnetic steel are mirror images of each other with respect to an axial dividing plane of the inner bottom magnetic steel.

3. The magnetic levitation gravity compensation device according to claim 1, characterized in that the inner bottom magnetic steel, the first end magnetic steel and the second end magnetic steel have central axes that overlap each other and are rotationally symmetrical with respect to the central axis.

4. 2. The magnetic levitation gravity compensation device according to claim 1, wherein the inner bottom magnetic steel has an axial through hole, and the first end magnetic steel and the second end magnetic steel have axial through holes.

5. The magnetic levitation type gravity compensation device of claim 1, characterized in that the inner bottom magnetic steel is cylindrical, the first end magnetic steel is made of multi-stage cylindrical magnetic steel adjacent to each other along the axial direction, and the second end magnetic steel is made of multi-stage cylindrical magnetic steel adjacent to each other along the axial direction, the inner diameters of the multi-stage cylindrical magnetic steel are the same, and the outer diameters of each gradually decrease from the cylindrical magnetic steel away from the inner bottom magnetic steel to the cylindrical magnetic steel close to the inner bottom magnetic steel.

6. In the multi-stage cylindrical magnetic steel of the first end magnetic steel, the difference in outer diameter of each adjacent cylindrical magnetic steel is equal, and the axial length is equal, A magnetic levitation type gravity compensation device as described in claim 1 or 5, characterized in that in the multi-stage cylindrical magnetic steel of the second end magnetic steel, the difference in outer diameter of each adjacent cylindrical magnetic steel is equal and the axial length is equal.

7. The magnetic levitation type gravity compensation device according to claim 5, characterized in that the first end magnetic steel is made up of three stages of cylindrical magnetic steel adjacent to each other along the axial direction, and the second end magnetic steel is made up of three stages of cylindrical magnetic steel adjacent to each other along the axial direction.

8. The cylindrical magnetic steel of the first end magnetic steel and the second end magnetic steel that is farthest from the inner bottom magnetic steel has an outer diameter of R2 and an axial length of L2, the outer diameter of the inner bottom magnetic steel is R5, and the axial length of the outer magnetic ring magnetic steel is L １ where R ２ / 2≦R ５ ≦R ２ , L １ / 4≦L2≦L １ 6. The magnetic levitation gravity compensation device according to claim 1, wherein the magnetic levitation gravity compensation device is a magnetic levitation gravity compensation device.

9. The magnetic levitation type gravity compensation device according to claim 5, characterized in that the radial dimension of the axial through hole of the inner bottom magnetic steel is the same as the radial dimension of the axial through hole of the first end magnetic steel and the second end magnetic steel.

10. The magnetic levitation gravity compensation device according to claim 5, characterized in that the radial dimension of the axial through hole of the first end magnetic steel and the second end magnetic steel decreases from the end away from the inner bottom magnetic steel to the inner bottom magnetic steel.

11. The magnetic levitation type gravity compensation device as described in claim 10, characterized in that the relationship between the angle β between the inner surface of the axial through hole of the first end magnetic steel and the second end magnetic steel and the radial direction and the angle α between the outer surface of the first end magnetic steel and the second end magnetic steel and the radial direction is α≦β≦135°.

12. 2. The magnetic levitation gravity compensation device according to claim 1, wherein the outer magnetic ring magnetic steel is made up of a plurality of arc plates adjacent to each other along the circumferential direction.

13. 2. The magnetic levitation gravity compensation device according to claim 1, wherein the inner bottom magnetic steel includes a tapered portion, the tapered portion being located in the axial middle of the inner bottom magnetic steel and having an outer diameter smaller than that of the remaining portion.

14. The axial length of the outer magnetic wheel magnetic steel is L １ and the axial length of the end magnetic steel is L ２ The axial length of the inner bottom magnetic steel is L ３ The stroke of the end magnetic steel and the inner bottom magnetic steel moving in the axial direction relative to the outer magnetic wheel magnetic steel is S, and L ３ +2L ２ -L １ 2. The magnetic levitation gravity compensation device according to claim 1, wherein ΔS / S has a value in the range of [0.1, 3.0].

15. 2. The magnetic levitation gravity compensation device according to claim 1, wherein the base angle α of the first end magnetic steel and the second end magnetic steel is 60° to 88°.

16. 16. The magnetic levitation gravity compensation device according to claim 15, wherein a base angle α between the first end magnetic steel and the second end magnetic steel is 75°.

17. A moving stage comprising a worktable and a base, the worktable being configured to be capable of rotating and moving vertically relative to the base, and a magnetic levitation type gravity compensation device according to any one of claims 1 to 15 being provided below the worktable.

Images