System and method to control planar motors
First Claim
1. A method for controlling a planar electric motor comprising a magnet array having magnets with magnetic fields and a coil array comprising coils generally disposed in a plane, comprising:
- determining currents to be applied to coils to generate forces between the magnet array and the coil array in first and second directions;
determining a resultant torque between the magnet array and the coil array generated by the forces generated by the determined currents;
determining current adjustments to compensate for the resultant torque such that a total torque between the magnet array and the coil array becomes a desired value; and
applying a sum of the determined currents and determined current adjustments to the coils to interact with the magnetic fields of the magnet array to control the planar electric motor.
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Accused Products
Abstract
A method for controlling and positioning a two-dimensional electric motor is disclosed. The electric motor has a coil array and a magnet array. The method controls the motor in two directions in the plane of the magnet array and about a third direction generally orthogonal to the plane. The method includes: determining currents for generating the desired forces, determining a resultant torque that would be generated from applying the determined currents, determining current adjustments to compensate for the resultant torque, and applying a current equal to the sum of the determined currents and the current adjustments to the coils to interact with the magnetic fields of the magnet array. The currents are applied to the portion of the coil array within the magnetic field of the magnet array, including those coils which are only partially within the magnetic field of the magnet array. Alternatively, the currents could be applied to all of the coils. Applying the current to all of the coils requires more electrical power, but uses for amplifiers so the electronics are simpler and less expensive. The method of the present invention may be used in applications such as positioning wafers in semiconductor fabrication.
65 Citations
37 Claims
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1. A method for controlling a planar electric motor comprising a magnet array having magnets with magnetic fields and a coil array comprising coils generally disposed in a plane, comprising:
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determining currents to be applied to coils to generate forces between the magnet array and the coil array in first and second directions;
determining a resultant torque between the magnet array and the coil array generated by the forces generated by the determined currents;
determining current adjustments to compensate for the resultant torque such that a total torque between the magnet array and the coil array becomes a desired value; and
applying a sum of the determined currents and determined current adjustments to the coils to interact with the magnetic fields of the magnet array to control the planar electric motor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for determining current to be applied to control a planar electric motor, the motor having a magnet array and a coil array having coils generally disposed in a plane, comprising:
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determining currents to be applied to coils for generating forces between the magnet array and the coil array in first and second directions defined by the plane, the currents being dependent upon the position of the magnet array and desired forces in the first and second directions or torque about a third direction generally perpendicular to the first and second directions;
determining a resultant torque that would be generated by the currents; and
determining current adjustments to be added to the currents to compensate for the resultant toque such that a total torque between the magnet array and the coil array becomes a desired value. - View Dependent Claims (13, 14, 15, 16)
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17. A method for positioning a wafer in a lithography system, comprising:
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providing a frame;
providing a stage for supporting the wafer and movable to position the wafer relative to the frame;
providing a coil array attached to the frame, the coil array having coils;
providing a magnet array adjacent a portion of the coil array, the magnet array being attached to the stage and having magnets generally disposed in a plane, the plane defining first and second directions;
determining current to be applied to coils in the portion of coil array to generate forces between the magnet array and the coil array in the first and second directions;
determining a resultant toque between the magnet array and the coil array generated by the forces;
determining current adjustments to compensate for the resultant torque such that a total torque between the magnet array and the coil array becomes a desired value; and
applying a sum of the determined currents and determined current adjustments to the coils to interact with magnetic fields of the magnet array. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. A planar motor comprising:
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a first member;
a second member interacting with the first member to generate driving force, the second member being movable relative to the first member in at least two directions by the driving force; and
a controller connected to at least one of the first and second members, the controller determining information related to a resultant torque between the first and second members generated by the driving force, the controller determining adjustment information to compensate for the resultant torque such that a total torque between the first and second members becomes a desired value. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36, 37)
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Specification