Positioning device for planar positioning

• US 5,334,892 A
• Filed: 12/22/1992
• Issued: 08/02/1994
• Est. Priority Date: 12/22/1992
• Status: Expired due to Term

• Current Assignee: Anorad Corporation (Rockwell Automation, Inc.)
• Original Assignee: Anorad Corporation (Rockwell Automation, Inc.)
• Inventors: Chitayat, Anwar
• Primary Examiner(s): Voeltz, Emanuel T.
• Assistant Examiner(s): JONES, JUDSON
• Application Number:
  US07/995,589
• Time in Patent Office: 588 Days
• Field of Search: 74/24, 74/25, 74/26, 74/27, 74/88, 74/89, 310/12
• US Class Current: 310/12.06
• CPC Class Codes: B23Q 1/623 followed perpendicularly by a single rotating pair
• CPC Class Codes: H02K 2201/18 Machines moving with multiple degrees of freedom
• CPC Class Codes: H02K 41/031 of the permanent magnet type
• CPC Class Codes: Y10T 74/18568 Reciprocating or oscillating to or from alternating rotary

Abstract

A positioning device has a shuttle slidably and rotatably supported above a base assembly. A first linear motor moves the shuttle linearly in a first direction while the second and third linear motors move the shuttle linearly in a second direction, normal to the first direction. The second and third linear motors are separated along an axis in the first direction. The linear motors have magnetic arrays including rows of magnets or a checkerboard array of magnets and provide continuously variable positioning. Rotary movement of the shuttle is achieved by operating the second and third linear motors in opposing directions or at differing rates. The positions of three points on the shuttle are determined by three optical encoders, or three interferometers, whose signals provide feedback to a controller which actuates the linear motors accordingly. The controller employs an algorithm for the translation of the three point positions into shuttle position and orientation information and for implementing a closed loop control system whereby the shuttle may be positioned with respect to a reference point, torque thereupon may be compensated for, and the shuttle may be rotated.

Claims

1. A positioning device comprising:

a shuttle;

a base assembly having a planar surface;

means for slidably supporting said shuttle in a plane above said planar surface of said base assembly;

said means for slidably supporting including means for permitting said shuttle to slide in any direction in said plane;

a plurality of linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said plurality of linear motors including a plurality of magnets;

said linear motors passing a current through a magnetic field produced by said plurality of magnets thereby producing a force;

said first axis defining a first direction; and

said second axis defining a second direction.

2. A positioning device of claim 1 wherein:

said means for slidably supporting said shuttle includes at least one of air bearings and magnetic bearings; and

said means for slidably supporting includes means for permitting rotation of said shuttle.

10. A positioning device of claim 1 wherein the magnets of said linear motors include:

a checkerboard magnet array having magnets distributed in a checkerboard pattern having rows and columns;

said magnets alternating with non-magnetic spaces along both said rows and said columns of said checker board pattern;

said rows and said columns having said magnets in uniform pole orientations within each thereof;

said rows and columns alternating orientations of said uniform pole orientations thereof; and

said rows and columns being oriented in said first and said second directions, respectively.

11. A positioning device of claim 10 comprising:

an optical grating having lines engraved thereon;

first, second and third optical encoders having means for detecting travel with respect to said optical grating in a direction normal to said lines;

said optical gratings being mounted fixed with respect to one of said shuttle and said base assembly and said optical encoders being mounted fixed with respect to another one of said shuttle and said base assembly;

said first optical encoder detecting displacement in said first direction;

said second and third optical encoders detecting displacement in said second direction; and

said second and third encoders being spaced a distance apart from one and other in said first direction so that rotating motion of said shuttle is detected.

12. A positioning device of claim 11 wherein said optical grating is mounted upon said shuttle and said first second and third optical encoders are mounted upon a bridge over the shuttle and supported by the base assembly.

13. A positioning device of claim 10 comprising:

a controller;

first, second, and third interferometers;

first and second mirrors;

said first interferometer and said first mirror being mounted such that displacement in said first direction is detected and a signal sent to said controller;

said second and third interferometers and said second mirror being mounted such that displacement of said shuttle in said second direction is detected; and

said second and third interferometers being spaced apart in the said first direction so that rotating motion of said shuttle is detected.

14. A positioning device of claim 10 wherein said checkerboard magnet array is affixed to said base assembly and said first, second, and third coil assemblies are affixed to said shuttle.

15. A positioning device of claim 10 wherein said checkerboard magnet array is affixed to said shuttle and said first, second, and third coil assemblies are affixed to said base assembly.

16. A positioning device of claim 10 wherein said means for slidably supporting comprise:

air bearings;

said surface of said base assembly including one of a hard flat sheet of material, a ceramic coating, and a flat surface of a base; and

said surface being suitable for operation of said air bearing thereon.

3. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle is slidable in a plane;

linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said linear motors including magnets generating forces by acting upon a current traveling through a magnetic field of said magnets;

said first axis defining a first direction;

said second axis defining a second direction;

said linear motors including at least first, second and third linear motors;

said first, second and third linear motors including first, second and third coil assemblies, respectively;

said first linear motor including means for producing a first force on said shuttle along said first axis;

said second and third linear motors including means for producing second and third forces at spaced-apart locations on said shuttle along said second axis whereby differential actuation thereof is effective to produce a torque on said shuttle.

4. A positioning device of claim 3 wherein:

said first linear motor includes said magnets comprising a first magnetic array having magnets in a row with pole orientations alternating in a direction of said first axis; and

said second and third linear motors includes said magnets comprising second and third magnetic arrays, respectively, each having magnets in a row with pole orientations alternating in a direction of said second axis.

5. A positioning device of claim 4 wherein said first, second, and third magnetic arrays are affixed to said base assembly and said first, second, and third coil assemblies, respectively interacting therewith, are affixed to said shuttle.

6. A positioning device of claim 4 wherein said first, second, and third magnetic arrays are affixed to said shuttle and said first, second, and third coil assemblies, respectively interacting therewith, are affixed to said base assembly.

7. A positioning device of claim 4 wherein said means for slidably supporting includes:

first, second and third air bearings;

each of said first, second and third air bearings being associated with one of said first, second and third linear motors, respectively;

said surface of said base assembly including one of a hard flat sheet of material, a ceramic coating, and a flat surface of a base; and

said surface being of suitable flatness for operation of said air bearing thereon.

8. A positioning device of claim 4 comprising:

first, second and third optical gratings parallel to said surface and having lines engraved thereon;

first, second and third optical encoders having means for detecting travel over said first, second and third optical gratings, respectively, in directions normal to said lines;

said first, second and third optical gratings being fixed to one of said shuttle and said base assembly and said first, second and third optical encoders being fixed to the other of said shuttle and said base assembly;

said first optical encoder detecting displacement along said first axis;

said second and a third encoders detecting displacement along said second axis; and

said second and third encoders being spaced apart a distance in a direction of said first axis so that rotating motion of said shuttle is detected.

9. A positioning device of claim 4 comprising:

a first, a second, and a third interferometer;

a first and a second mirror;

said first interferometer and said first mirror being mounted such that displacement in said first direction is detected and a first signal sent to said controller;

said second and third interferometers and said second mirror being mounted such that displacement of said shuttle in said second direction is detected, and second and third signals are sent to said controller; and

said second and third interferometers being spaced apart from each other in a direction of said first axis so that rotating motion of said shuttle is detected.

17. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle is slidable in any direction in said plane;

linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said linear motors including means for producing magnetic fields;

said linear motor including means for carrying currents in said magnetic fields, thereby producing forces;

said first axis defining a first direction;

said second axis defining a second direction;

means for determining a position of said shuttle in said first and second directions;

said means for carrying current including coil assemblies;

said linear motors including means for producing magnetic fields;

said means for producing magnetic fields including a coil array having coils in a rows along said first axis and said second axis; and

said coil array being positioned to interact with said coil assemblies by inducing the production of magnetic fields by said coil array by induction due to the generation of magnetic fields by said coil assemblies, whereby the coil arrays move relative to the coil assemblies.

18. A positioning device of claim 17 wherein said coil array is affixed to one of said base assembly and said shuttle, and said coil assemblies are affixed to another one of said shuttle and said base assembly.

20. A positioning device of claim 17 wherein said means for slidably supporting include:

air bearings;

said surface of said base assembly being planar and including one of a hard flat sheet of material, a ceramic coating, and a flat surface of a base;

said surface being suitably flat for operation of said air bearing thereon; and

said air bearings interfacing with said surface such that said shuttle is rotatable.

19. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle is slidable in all dimensions of said plane;

linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said linear motors including means for producing magnetic fields;

said linear motor including means for carrying currents in said magnetic fields, thereby producing forces;

said first axis defining a first direction;

said second axis defining a second direction;

means for determining a position of said shuttle in said first and second directions;

said means for carrying current including coil assemblies;

said means for producing magnetic fields including a coil array having coils in a rows along said first axis and said second axis;

said coil array being positioned so as to function with said coil assemblies such that magnetic fields are produced by said coil array by means of induction due to the generation of magnetic fields by said coil assemblies, whereby the coil arrays move relative to the coil assemblies;

said linear motors including at least first, second and third linear motors;

said first, second and third linear motors including first, second and third coil assemblies, respectively, of said coil assemblies;

said first linear motor including means for producing a first force on said shuttle along said first axis; and

said second and third linear motors including means for producing second and third forces at spaced-apart locations on said shuttle along said second axis whereby differential actuation thereof is effective to produce a torque on said shuttle and rotation thereof.

21. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle may slide in a plane;

linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said linear motors generating forces by means of a magnetic field, acting upon a current traveling through the magnetic field;

said first axis defining a first direction;

said second axis defining a second direction;

means for determining a position of said shuttle in said first and second directions;

said linear motors including coil assemblies;

said linear motors including means for producing magnetic fields;

said means for producing magnetic fields including a coil array having coils in a rows along said first axis and said second axis;

said coil array being positioned so as to function with said coil assemblies such that magnetic fields are produced by said coil array by means of induction due to the generation of magnetic fields by said coil assemblies, whereby the coil arrays move relative to the coil assemblies;

said means for producing magnetic fields having a checkerboard coil array having coils distributed in a checkerboard pattern having rows and columns;

said rows and columns being oriented in said first and said second directions, respectively; and

said checkerboard coil array being positioned so as to function with said first, second, and third coil assemblies such that magnetic fields are produced by said checkerboard coil array by means of induction due to the generation of magnetic fields by said first, second, and third coil assemblies, respectively, so that said coil arrays move relative to said coil assemblies.

22. A positioning device of claim 21 wherein said checkerboard coil array is affixed to one of said base assembly and said shuttle, and said first, second, and third coil assemblies are affixed to another one of said base assembly and said shuttle.

23. A positioning device of claim 21 wherein:

said linear motors include at least first, second and third linear motors;

said first, second and third linear motors include first, second and third coil assemblies, respectively, of said coil assemblies;

said first linear motor includes means for producing a first force on said shuttle along said first axis;

said second and third linear motors include means for producing second and third forces at spaced-apart locations on said shuttle along said second axis whereby differential actuation thereof is effective to produce a torque on said shuttle and rotation thereof.

24. A positioning device of claim 21 wherein said means for slidably supporting comprise:

air bearings;

said surface of said base assembly including one of a hard flat sheet of material, a ceramic coating, and a flat surface of a base; and

said surface being suitable for operation of said air bearing thereon.

25. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle may slide in a plane and may rotate;

linear motors for linearly moving and rotating said shuttle above said surface of said base assembly along orthogonal first and second axes;

said first axis defining a first direction;

said second axis defining a second direction;

means for determining a position of said shuttle in said first and second directions;

said means for determining a position being located at a position apart from a position of said linear motors;

a controller for driving said linear motors utilizing said means for determining a position as a source of feedback signals; and

said controller transforming coordinates of the position of the means for determining a position to transformed coordinates of a position of said linear motors and using said transformed coordinates to effect positioning of said linear motors.

26. A positioning device of claim 25 wherein said controller comprises:

means for translating said feedback signals from said means for determining a position into displacement information;

means for adjusting said displacement information to compensate for positions of said means for determining on said shuttle;

means for computing positions and orientations of said shuttle with respect to an initial reference point from said displacement information;

means for determining rates of movement and acceleration from said positions and orientations of said shuttle; and

means for selectively driving said linear motors independently so as to maintain said positions, orientations, and movement and acceleration rates at predetermined values thus moving said shuttle in a planar both linearly and rotatably.

27. A positioning device of claim 26 wherein:

said linear motors include at least first, second and third linear motors;

said first, second and third linear motors including first, second and third coil assemblies, respectively;

said first linear motor producing a first force on said shuttle along said first axis;

said second and third linear motors producing second and third forces at spaced-apart locations on said shuttle along said second axis whereby differential actuation thereof is effective to produce a torque on said shuttle.

said means for selectively driving includes means for proportionally driving said second and third linear motors so as to both rotate said shuttle and compensate for torque upon said shuttle.

28. A positioning device driven by a controller comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle above a surface of said base assembly including one of air beatings and magnetic beatings;

at least first, second and third linear motors for linearly urging said shuttle above said surface along orthogonal first and second axes;

first, second and third coil assemblies associated with said first, second and third linear motors;

said at least three linear motors including means for producing magnetic fields normal to said surface of said base assembly and with alternating polarity along said orthogonal first and second axes;

said means for producing magnetic fields including first, second and third magnetic arrays;

said first magnetic array having magnets in a row with pole orientations alternating along said first axis;

said second and third magnetic arrays having magnets in parallel rows with pole orientations alternating along said second axis;

said first, second, and third magnetic arrays being positioned so as to function with said first, second, and third coil assemblies;

said coil assemblies and said means for producing magnetic fields being mounted such that said shuttle is moved relative to said base assembly;

said first linear motor urging said shuttle in direction of said first axis;

said second and third linear motors being separated in a direction of said first axis;

said second and third linear motors each independently urging said shuttle in a direction of said second axis that at least one of linear and rotary motion is produced;

first means for determining a position of said shuttle along said first axis; and

second and third means spaced apart along a direction of said first axis for detecting positions of two positions on said shuttle along said second axis.

29. A positioning device driven by a controller comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle above a surface of said base assembly including one of air bearings and magnetic bearings;

at least first, second and third linear motors for linearly moving and rotating said shuttle above said surface of said base assembly along orthogonal first and second axes comprising in a continuously variable manner;

at least first, second and third coil assemblies;

said first linear motor including first means for producing a first magnetic field normal to said surface of said base assembly and with alternating polarity along said first axis;

said second and third linear motors including second and third means for producing second and third magnetic fields normal to said surface with alternating polarities along said second axis;

said first, second and third means for producing magnetic fields including a checkerboard magnet array having magnets distributed in a checkerboard pattern having rows and columns;

said magnets alternating with non-magnetic spaces along both said rows and said columns of said checker board pattern;

said rows and said columns having said magnets in uniform pole orientations within each of said rows and columns;

said rows and columns alternating orientations of said uniform pole orientations thereof;

said rows and columns being oriented in directions of said first and said second axes, respectively;

said coil assemblies and said means for producing magnetic fields being mounted such that said shuttle is moved relative to said base assembly;

said first linear motor urging said shuttle in said first direction;

said second and third linear motors being separated along a direction of said first axis; and

each of said second and third linear motors independently urging said shuttle in a direction of said second axis such that at least one of linear and rotary motion is produced.

30. An omni-directional linear motor comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle above a surface of said base assembly;

linear motors for linearly moving and rotating said shuttle above said surface of said base assembly along orthogonal axis comprising;

first, second and third coil assemblies;

means for producing magnetic fields normal to said surface of said base assembly and with alternating polarity along a first and a second direction; and

said first and second directions being normal to each other in a plane of the surface of said base assembly;

said means for producing magnetic fields comprising;

a checkerboard magnet array having magnets distributed in a checkerboard pattern having rows and columns;

said magnets alternating with non-magnetic spaces along both said rows and said columns of said checker board pattern;

said rows and said columns having said magnets in uniform pole orientations within each of said rows and columns;

said rows and columns alternating orientations of said uniform pole orientations thereof;

said rows and columns being oriented in said first and said second directions, respectively;

said coil assemblies and said means for producing magnetic fields being mounted such that said shuttle is movable relative to said base assembly;

said first coil assembly urging said shuttle in said first direction;

said second and a third coil assemblies being separated along an axis in the first direction; and

said second and third coil assemblies each independently urging said shuttle in said second direction such that at least one of linear and rotary motion is produced.

31. A positioning device comprising:

a shuttle;

a base assembly;

means for slidably supporting said shuttle in a plane above a surface of said base assembly such that said shuttle may slide in a plane;

linear motors for linearly moving said shuttle above said surface of said base assembly along orthogonal first and second axes in a continuously variable manner;

said linear motors generating forces by means of a magnetic field, produced by magnets, acting upon a current traveling through the magnetic field;

said first axis defining a first direction;

said second axis defining a second direction;

said linear motors including a first magnetic array having magnets in a row with pole orientations alternating in a direction of said first axis; and

said linear motors including second and third magnetic arrays, respectively, each having magnets in a row with pole orientations alternating in a direction of said second axis.