Spherical motor and method

• US 5,410,232 A
• Filed: 12/18/1992
• Issued: 04/25/1995
• Est. Priority Date: 12/18/1992
• Status: Expired due to Term

• Current Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Original Assignee: Georgia Tech Research Corporation (University System of Georgia)
• Inventors: Lee, Kok-Meng
• Primary Examiner(s): Ip, Paul
• Application Number:
  US07/992,595
• Time in Patent Office: 858 Days
• Field of Search: 318/560-648, 318/687, 318/662, 310/162, 310/156, 310/198, 310/68 R, 310/91, 310/154, 310/8.3, 310/112, 310/12, 310/323, 310/317, 310/328, 901/18, 901/25, 901/29, 901/5, 901/28, 901/47, 74/479, 74/5.6, 74/5.7, 74/5, 74/5.1, 74/5 R, 250/229, 250/221, 250/231.12
• US Class Current: 318/568.11
• CPC Class Codes: H02K 2201/18 Machines moving with multiple degrees of freedom
• CPC Class Codes: H02K 41/03 Synchronous motors; Motors moving step by step; Reluctance motors H02K41/035 takes precedence
• CPC Class Codes: H02K 7/088 radially supporting the rotor directly

Abstract

A spherical motor (10) provides smooth isotropic motion. The spherical motor (10) has a spherical stator (12) surrounding a spherical rotor (18). A motor shaft (24) is mounted to the rotor (18), or alternatively, to the stator (12) for performing work in isotropic motion. A grid pattern is situated to move substantially concentrically with the rotor (18) and in conjunction with the motor shaft (24). A vision system (80) monitors the grid pattern (42) and determines in real time the position of the motor shaft (24). The vision system (80) has at least one image sensor (44) positioned on the stator (12) and a computer system (82) for processing data independent of a remote host computer (122). Further, a motor controller (191) using a motor control algorithm (200) may be interfaced with the vision system (80) to thereby derive a motor control system (190) for controlling the spherical motor (10) based upon the rotor orientation information retrieved by the vision system (80). Finally, a video controller (106) can be interfaced with the vision system (80) for converting digital image data in real time to analog image data conforming to the RS-170 television standard for viewing on a display device (116).

Claims

1. A spherical motor for providing smooth isotropic motion, comprising:

a spherical stator having a plurality of stator poles;

a spherical rotor surrounded by said stator and having a plurality of rotor poles;

a motor shaft mounted to either said rotor or said stator, said motor shaft for moving isotopically;

means for injecting a fluid between said rotor and said stator to allow relative movement between said rotor and said stator;

sensor means for sensing a position of said rotor relative to said stator; and

control means for varying the amount of fluid injected between said rotor and said stator in order to provide a desired gap between said rotor and said stator.

2. The motor of claim 1, further comprising:

a grid pattern substantially concentric with said rotor and movable concentrically about said rotor in conjunction with said motor shaft;

said sensor means comprising an image sensor for viewing said grid pattern; and

processing means associated with said image sensor, said processing means for determining a shaft position of said motor shaft based upon said grid pattern.

3. The motor of claim 1, wherein said rotor poles are positioned on said rotor at geometric vertices of a first regular polyhedron and wherein said stator poles are positioned on said stator at geometric vertices of a second regular polyhedron.

4. The motor of claim 1, comprising more of said stator poles than said rotor poles.

5. The motor of claim 1, wherein said relative movement between said rotor and said stator is accomplished via variable reluctance.

6. The motor of claim 1, wherein said fluid means provides at least three pairs of opposing normal forces acting radially towards the center of said rotor.

7. The motor of claim 1, further comprising:

jet means for projecting air to provide said gap between said rotor and said stator; and

said sensor means comprising an optical sensor for determining a measured gap between said rotor and said stator;

wherein said control means receives said measured gap and controls said jet means to provide said desired gap.

8. The motor of claim 2, further comprising a hemispherical cover shell connected to said rotor shaft and having said grid pattern.

9. The motor of claim 2, wherein said grid pattern resides on said rotor.

10. The motor of claim 1, wherein said fluid comprises air.

11. The motor of claim 1, wherein said sensor means comprises an optical sensor for measuring a distance between said rotor and said stator and a controller for varying said amount of fluid injected into said stator based upon a difference between said desired gap and said measured distance.

12. A spherical motor for providing smooth isotropic motion, comprising:

a spherical stator having a plurality of stator poles;

a spherical rotor surrounded by said stator and having a plurality of rotor poles;

a motor shaft mounted to either said rotor or said stator, said motor shaft for moving isotopically;

means for permitting relative movement between said rotor and said stator;

a grid pattern substantially concentric with said rotor and movable concentrically about said rotor in conjunction with said motor shaft;

an image sensor for viewing said grid pattern;

control means for varying an amount of fluid injected between said rotor and said stator in order to provide a desired gap between said rotor and said stator; and

processing means associated with said image sensor, said processing means for determining a shaft position of said motor shaft based upon said grid pattern.

13. The motor of claim 12, wherein said means for permitting relative movement comprises ball bearings.

14. The motor of claim 12, wherein said means for permitting relative movement comprises fluid means for suspending said rotor within said stator.

15. The motor of claim 12, further comprising a hemispherical cover shell connected to said rotor shaft and having said grid pattern.

16. The motor of claim 12, wherein said grid pattern resides on said rotor.

17. The motor of claim 12, wherein said rotor poles are positioned on said rotor at geometric vertices of a first regular polyhedron and wherein said stator poles are positioned on said stator at geometric vertices of a second regular polyhedron.

18. The motor of claim 12, comprising more of said stator poles than said rotor poles.

19. The motor of claim 12, wherein said relative movement between said rotor and said stator is accomplished via variable reluctance.

20. A method for providing frictionless isotropic motion in a spherical motor comprising a spherical stator having a plurality of stator poles, a spherical rotor surrounded by said stator and having a plurality of rotor poles, and a motor shaft for moving isotopically, the method comprising the steps of:

injecting a fluid into said stator;

measuring a gap between said rotor and said stator;

controlling an amount of fluid injected into said stator so that said gap between said rotor and said stator is uniform; and

suspending said rotor within said stator to allow relative movement between said rotor and said stator.

21. The method of claim 20, further comprising the step of sensing the rate of said relative movement by monitoring current magnetically induced in a stator pole.

22. The method of claim 20, further comprising the step of providing said relative movement by creating variable reluctance between said stator poles and said rotor poles.

23. The method of claim 20, further comprising the steps of:

moving a grid pattern with said motor shaft, said grid pattern being substantially concentric with said rotor;

viewing said grid pattern; and

determining a rotor orientation based upon said viewing of said grid pattern.

24. The method of claim 20, further comprising the steps of:

determining torques to be applied by said stator upon said rotor to achieve a desired rotor trajectory; and

controlling said stator coils to achieve said torques.

25. The method of claim 24, further comprising the steps of:

determining stator current values for said plurality of stator poles in order to achieve said torques;

comparing said stator current values with respective maximum current values corresponding with said stator poles;

replacing each stator current value with a corresponding maximum current value when said stator current value exceeds said maximum current value; and

forwarding said stator current values to said plurality of said stator poles.

26. The method of claim 25, further comprising the step of minimizing total energy input to said stator poles in order to achieve said desired rotor trajectory.

27. The method of claim 25, further comprising the step of controlling said stator poles by computing a control vector from said torques, said control vector having three orthogonal vector components, each of said vector components having a weighting factor coefficient.

28. The method of claim 20, wherein said step of injecting said fluid into said stator comprises the step of injecting air.

29. The method of claim 20, wherein said step of injecting said fluid occurs at least at three opposing locations within said stator to thereby produce at least three pairs of normal forces acting radially towards a center of said rotor.