Positioning device for planar positioning

Claims

What is claimed is:

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.

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.

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.

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.

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.

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.

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.

BACKGROUND OF THE INVENTION

The present invention relates to positioning devices and, more particularly, to a positioning device having a floating shuttle propelled by independently controlled linear motors, capable of linear motion along two axes and rotary motion, and employing a closed loop control system.

Conventional positioning systems employ electric motors which drive lead screws oriented about orthogonal axes. A table is supported upon a set of rails, or their equivalent, and incorporates a recirculating ball nut which engages the lead screw and thereby propels the table upon rotation of the lead screw. Motion is thus provided along a single linear axis. To facilitate motion along two orthogonal axes, the aforementioned apparatus may be mounted normal to and upon a second set of rails further incorporating a lead screw to drive a recirculating ball nut propelling the first set of rails. The mass of the entire first apparatus must therefore be propelled by the second apparatus, limiting the speed of operation. The use of lead screws and ball nuts requires expensive components and time consuming alignment. Additionally, the mass of the components results in substantial inertia being developed and thus restricts the rapid acceleration and de-acceleration of the table. Furthermore, wear upon the lead screw, the recirculating balls, and the rails results in decreased accuracy, down-time, and maintenance costs.

Other conventional positioning systems employ linear motors which drive a table along orthogonal X-Y coordinate axes, thereby eliminating the use of a lead screw with recirculating balls. In such systems the table once again rides upon a first set of rails in the X-direction, for example, and a second set of rails in the Y-direction. While the first set of rails supports the table and a first linear motor, the second set of rails supports the first set of rafts, the table, the first linear motor, and a second linear motor. The rails slidably support their respective loads upon roller or ball beatings.

In these prior art systems, the second linear motor must drive the weight of the first set of rails and the entire first linear motor along with the table. Once again, rates of acceleration are compromised. The mass necessitates the use of high power linear motors to acceptably accelerate the table to required speeds. Furthermore, the mass limits the rate at which changes in direction may be implemented.

The conventional linear motors employed in positioning devices of the prior art comprise coil assemblies mounted upon a first member, magnet assemblies mounted upon a second member, and the first and second members engaging each other so as to allow linear movement in a single axis. Generally, one member takes the form of a pair of rafts or a channel while the other member slides upon the rails or in the channel by means of ball or roller bearings. In such systems the motion generated is restricted to a single axis. While the table may move linearly in the single axis its orientation remains constant; the table cannot rotate. Furthermore, the rails or the channels must be precisely machined and are subject to wear, thus increasing production and maintenance costs. Finally, if motion is required in a plane rather than in a single axis, an entire second linear motor assembly is employed to move the first linear motor assembly in a direction normal to its axis of motion. This further exacerbates the costs involved.

In the prior art, such as that disclosed in U.S. Pat. No. 3,376,578, positioning devices employ shuttles which float over a surface and are driven by linear stepper motors. Such devices do not provide for rotational motion of the shuttle. Also, the motion such devices are capable of is limited to movement in discrete increments defined the stepper motor controller, the configuration of the stepper motor poles, and the surface configuration of a platen upon which the shuttle rests. Thus, continuously variable positioning cannot be achieved. Another difficulty encountered in such devices is the discontinuous torque applied by the stepping action, which translates into pulsing acceleration and movement; Smooth uniform motion cannot be achieved. Additionally, although pairs of linear stepper motors are employed in such devices, further compensation for offset center of gravities upon the shuttles is not provided nor are means for detecting the torque effects of such offset centers of gravities. Furthermore, such devices are prone to mispositioning of the shuttle due to lost step counts and the inability to independently locate the position of the shuttle.

OBJECTS AND SUMMARY OF THE INVENTION

Accordingly, it is an object of the invention to provide a positioning device which overcomes the drawbacks of the prior art.

It is a further object of the invention to provide a positioning device employing a floating shuttle slidably and rotatably supported by air bearings above a base assembly, capable of motion in a plane, eliminating the need for dual rail or channel structures employed in the prior art.

It is a still further object of the invention to provide a positioning device employing linear motors to linearly and rotatably drive a floating shuttle in a plane without the use of mechanical engagements.

It is yet another object of the invention to provide a positioning device using a floating shuttle wherein offset centers of gravity applied upon the shuttle are compensated for during motion by the use of three linear motors, one operating along a first axis, and two operating along a second axis normal to the first axis. The two linear motors may be operated at dissimilar force levels and directions in order to compensate for the effect of the offset center of gravity.

An object of the present invention is to provide a positioning device having a floating shuttle, driven by linear motors, having optical encoders and gratings for determining the position of the shuttle.

Another object of the present invention is to provide a positioning device having a floating shuttle, driven by linear motors, having laser interferometers and mirror for determining the position of the shuttle.

Additionally, an object of the present invention is to provide a positioning device having reduced travel restrictions employing a checkerboard pattern magnetic array above which a shuttle having linear motor coil assemblies may move in a plane. The checkerboard pattern magnet array provides alternating magnetic field orientations along orthogonal axes with which the coil assemblies functionally interact.

Yet another object of the present invention is to provide a positioning device having a floating shuttle and employing optical encoders and bi-directional optical gratings as position sensing devices. The bi-directional optical gratings reduce travel restriction in conjunction with the checkerboard pattern magnet array above which the shuttle is supported.

Furthermore, the present invention provides a positioning device employing a floating shuttle having three position sensing devices, one of which operates in a first axis, and two of which operate in parallel second and third axis normal to the first axis. The two position sensors detect rotating movements due to offset centers of gravity and send signals to the controller so that linear motors on the shuttle may control the offset.

Still another object of the present invention is to provide a positioning device employing a floating shuttle incorporating linear motor coils assemblies and having internal fin structures for use with either forced-air, fluid, or convection cooling of the coil assemblies.

Still further, the present invention provides a positioning device employing a floating shuttle with linear servo motors wherein the device is capable of continuously variable orthogonal and rotational motion in a plane and continuously sensing a position of the shuttle.

Finally, it is an object of the present invention to provide an omnidirectional linear motor having a shuttle slidably and rotatably supported by air bearings in a plane, employing coil assemblies and a magnet array of a checkerboard configuration in order to provide smooth continuous motion in the plane.

Briefly stated, the present invention provides a positioning device having a shuttle slidably and rotatably supported above a base assembly. A first linear motor urges the shuttle linearly in a first direction while the second and third linear motors urge the shuttle 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. 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.

In accordance with these and other objects of the invention, there is provided a positioning device driven by a controller comprising: a shuttle, a base assembly, means for slidably supporting the shuttle above a surface of the base assembly, linear motors for linearly moving, along orthogonal axes, and rotating the shuttle above the surface of the base assembly, and means for determining a position of the shuttle.

The present invention also provides a positioning device comprising: a shuttle, a base assembly, means for slidably supporting the shuttle in a plane above a surface of the base assembly such that the shuttle may slide in all directions in a plane and may rotate, linear motors for linearly moving and rotating the shuttle above the surface of the base assembly along orthogonal first and second axes, the first axis defining a first direction, the second axis defining a second direction, means for determining a position of the shuttle in the first and second directions, and a controller for driving the linear motor utilizing the means for determining a positions as a source of feedback.

According to a feature of the invention, there is further provided a positioning device driven by a controller comprising: a shuttle, a base assembly, means for slidably supporting the shuttle above a surface of the base assembly including one of air bearings and magnetic beatings, means for linearly moving and rotating the shuttle above the surface of the base assembly without physical contact therebetween comprising: at least three linear motors having coil assemblies, the at least three linear motors including means for producing magnetic fields normal to the surface of the base assembly and with alternating polarity along a first and a second direction, and, the first and second directions being normal to each other in a plane of the surface of the base assembly; the means for producing magnetic fields comprising: a first magnetic array having magnets in a row with pole orientations alternating along an axis in the first direction, second and third magnetic arrays having magnets in a row with pole orientations alternating along an axis in the second direction, and the first, second, and third magnetic arrays being positioned so as to function with the first, second, and third coil assemblies; the coil assemblies and the means for producing magnetic fields being mounted such that the shuttle is moved relative to the base assembly, a first linear motor, of the at least three linear motors, moving the shuttle in the first direction, and a second and a third, of the at least three linear motors, being separated along an axis in the first direction, and each independently moving the shuttle in the second direction such that one of linear and rotary motion is produced, and means for determining a position of the shuttle.

The present invention further includes a positioning device driven by a controller comprising: a shuttle, a base assembly, means for slidably supporting the shuttle above a surface of the base assembly including one of air bearings and magnetic bearings, means for linearly moving and rotating the shuttle above the surface of the base assembly without physical contact therebetween comprising: at least three linear motors having coil assemblies, the at least three linear motors including means for producing magnetic fields normal to the surface of the base assembly and with alternating polarity along a first and a second direction, and the first and second directions being normal to each other in a plane of the surface of the base assembly; the means for producing magnetic fields comprising: a checkerboard magnet array having magnets distributed in a checkerboard pattern having rows and columns, the magnets alternating with nonmagnetic spaces along both the rows and the columns of the checker board pattern, the rows and the columns having the magnets in uniform pole orientations within each of the rows and columns, the rows and columns having alternating orientations of the uniform pole orientations thereof, and the rows and columns being oriented in the first and the second directions, respectively; the coil assemblies and the means for producing magnetic fields being mounted such that the shuttle is moved relative to the base assembly, a first linear motor, of the at least three linear motors, moving the shuttle in the first direction, a second and a third, of the at least three linear motors, being separated along an axis in the first direction, and each independently moving the shuttle in the second direction such that one of linear and rotary motion is produced, and means for determining a position of the shuttle.

According to a still further feature of the invention, there is further provided an omni-directional linear motor comprising: a shuttle, a base assembly, means for slidably supporting the shuttle above a surface of the base assembly, means for linearly moving and rotating the shuttle above the surface of the base assembly without physical contact therebetween comprising: coil assemblies, means for producing magnetic fields normal to the surface of the base assembly with alternating polarity along a first and a second direction, and the first and second directions being normal to each other in a plane of the surface of the base assembly; the means for producing magnetic fields comprising: a checkerboard magnet array having magnets distributed in a checkerboard pattern having rows and columns, the magnets alternating with non-magnetic spaces along both the rows and the columns of the checker board pattern, the rows and the columns having the magnets in uniform pole orientations within each of the rows and columns, the rows and columns alternating orientations of the uniform pole orientations thereof, and the rows and columns being oriented in the first and the second directions, respectively; the coil assemblies and the means for producing magnetic fields being mounted such that the shuttle is moved relative to the base assembly, a first coil assembly of the coil assemblies moving the shuttle in the first direction, a second and a third coil assembly, of the coil assemblies, being separated along an axis in the first direction, and each independently moving the shuttle in the second direction such that one of linear and rotary motion is produced, and, means for driving the coil assemblies.

The present invention also includes the above embodiments wherein, in the alternative, the means for producing magnetic fields comprises: a first coil array having coils in a row along an axis in the first direction, second and third coil arrays having coils in a row along an axis in the second direction, and the first, second, and third magnetic arrays being positioned so as to function with the first, second, and third coil assemblies such that magnetic fields are produced by the first second and third coil arrays by means of induction due to the generation of magnetic fields by the first, second, and third coil assemblies, respectively, such that the coil arrays move relative to the coil assemblies.

The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified front view of a small travel range positioner in accordance with the present invention.

FIG. 2 is a simplified top view of the small travel range positioner of FIG. 1.

FIG. 3 is a diagram showing the relationship of a center of gravity to the positions of linear motors in the present invention.

FIG. 4 is a top view of the base assembly 15 with motor magnet arrays of the small travel range positioner.

FIG. 5 is a simplified top view of a small travel range positioner with a shuttle having an X-direction optical encoder and two Y-direction optical encoders.

FIG. 6 is a front view of a base assembly of the small travel range positioner of FIG. 5 showing the optical encoders positioned above optical encoder gratings.

FIG. 7a is a top view of a base assembly of a large travel range positioner having a checker board magnet array with motor coils superposed thereupon.

FIG. 7b is a front view of the base assembly of FIG. 7b.

FIG. 8 is a simplified top view of a positioner of the present invention having laser interferometers.

FIG. 9 is a side view of the positioner of FIG. 8.

FIG. 10 is a detailed top view of an embodiment of a shuttle frame showing rib and fin structures.

FIG. 11 is a detailed side view of the shuttle frame of FIG. 10 showing a middle plate between the rib and fin structure.

FIG. 12 is a detailed top view of a positioner having the shuttle frame of FIGS. 10 and 11.

FIG. 13 is a detailed side view of the positioner of FIG. 12.

FIG. 14 is a detailed front view of the positioner of FIGS. 12 and 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a simplified top view of a small travel range positioner 10 in accordance with the present invention. Positioner has a shuttle 12 upon which are mounted linear motors M1, M2, and M3, wherein the term "linear motor" refers specifically to the coil assemblies thereof. The shuttle 12 is supported above a base assembly 15 by air bearings A1, A2, and A3.

The air bearings A1, A2, and A3, support the shuttle 12 over the base assembly 15 eliminating the need for mechanical beatings, used in the prior art, which would require physical contact with the base assembly 15. Mechanical bearings experience wear which results in loss of positioning accuracy due to inconsistent travel. Additionally, the need to replace worn bearings, in order to maintain accuracy, results in labor and downtime expenses. Thus, the use of a shuttle 12 supported by air bearings A1, A2, and A3, results in a more reliable positioner which is less expensive to maintain. In the alternative, magnetic bearings may also be used to support the shuttle 12 above the surface of the base assembly 15. Furthermore, either magnetic bearings or air bearings A1, A2, and A3, may incorporate a pivotal means of attachment to the shuttle thereby allowing the bearings to pivot and adapt to surface irregularities.

Motor magnet arrays 16, 17, and 18, are imbedded in the base assembly 15 and interact with linear motors M1, M2, and M3, respectively, to move the shuttle 12 in both the X and the Y directions, as depicted in FIG. 1, and in a rotational direction about a Z-axis. The range of motion of the shuttle 12 is limited to ranges wherein the linear motors M1, M2, and M3 remain above their respective motor magnet arrays 16, 17 and 18, respectively.

Referring to FIG. 2, motor magnet array 16 is shown mounted in a recess in a base 19. A surface sheet 20 covers motor magnet array 16 and motor magnet arrays 17, and 18 (not shown). The surface sheet 20 may be composed of a hard non-magnetic material such as glass or a ceramic. The surface sheet 20 provides a hard flat surface above which the air bearings A1, A2, and A3, float upon a cushion of air. The distance between the surface and the air bearings may be on the order of 0.0002 inches.

Alternatively, a ceramic coating may be applied to the base instead of a sheet of ceramic. Yet another alternative includes machining and/or grinding the surface of the base 19 along with motor magnet arrays 16, 17, and 18, to provide an adequately smooth surface over which the air bearings A1, A2, and A3 may float.

Alternative embodiments of the present invention include a configuration wherein linear motors are mounted in a base and magnet arrays are mounted in a shuttle. This arrangement calls for distributing motor coils of the linear motors over areas of a base over which a shuttle is intended to travel.

FIG. 3 depicts the relationship of a center of gravity 29 to the positions of linear motors M1, M2, and M3. Linear motor M1 produces movement in the X-direction while linear motors M2 and M3 produce movement in the Y-direction. Distances a, b, and c represent the distances from the center of gravity to the centers of the various linear motors M1, M2, and M3 along the x-y axes. The linear motors M1, M2, and M3, may be of varying construction, however, in the present embodiment three phase linear servo motors are employed having either magnetic or nonmagnetic armatures. Electromagnetic couplings of the polyphase motors provide for smooth and continuous motion and torque.

When the center of gravity 29 is in line with linear motor M1 in the X-direction, movement in the X-direction may be produced by linear mot