Actuator with opposing repulsive magnetic forces

• US 6,002,184 A
• Filed: 09/17/1997
• Issued: 12/14/1999
• Est. Priority Date: 09/17/1997
• Status: Expired due to Fees

• Current Assignee: Coactive Drive Corporation
• Original Assignee: Coactive Drive Corporation
• Inventors: Delson, Nathan J., Houston, John S
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Jones, Judson H.
• Application Number:
  US08/932,741
• Time in Patent Office: 818 Days
• Field of Search: 310/12, 310/13, 310/14, 310/17, 310/23, 310/28, 310/75 R, 310/112, 273/148 R, 341/20, 901/2, 901/15, 74/471 R
• US Class Current: 310/14
• CPC Class Codes: H02K 2201/18 Machines moving with multiple degrees of freedom
• CPC Class Codes: H02K 23/00 DC commutator motors or generators having mechanical commutator; Universal AC/DC commutator motors
• CPC Class Codes: H02K 26/00 Machines adapted to function as torque motors, i.e. to exert a torque when stalled
• CPC Class Codes: H02K 41/0352 Unipolar motors

Abstract

A new class of actuators and mechanisms use opposing repulsive magnetic forces. The repulsive forces are typically generated between a stationary magnet and a moving magnet, where the moving magnet is coupled to the mechanism output member. The mechanisms are generally configured such that the repulsive force from one electromagnet is opposed by a repulsive force from another electromagnet, where the opposing forces are simultaneously applied to the mechanism'"'"'s output member. This configuration is similar in certain aspects to the way biological flexor and extensor muscles are configured in a musculoskeletal system. The opposing configuration allows for open loop control of position and stiffness. The actuator mechanism may have both rotary and linear motion output, and may have either a single degree of freedom or multiple degrees of freedom. Permanent magnets can be used to create a baseline repulsive force without electric power, and electromagnets can modulate the repulsive force magnitude. The actuator can provide high fidelity motion and force output, and is well suited for human interface devices, such as force feedback joysticks. Other applications include adjustable stiffness devices, and high bandwidth mechanisms.

Claims

1. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion, said work performed by said first actuator on said interface member arising from the application of a torque; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition.

2. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition, said work performed by said force generator also arising from magnetic repulsion.

4. The actuator unit of claim 2, said force generator comprising a second actuator, each of said first and second actuators comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, where said movable magnet of said first actuator and said movable magnet of said second actuator is the same magnet, which is shared by both actuators.

5. The actuator unit of claim 4, said shared movable magnet comprising said electromagnet.

6. The actuator unit of claim 4, said shared movable magnet comprising a permanent magnet.

3. An actuator unit comprising:

a. an interface member;

b. a first actuator, comprising two magnets arranged movably relative to each other, each along a travel path to provide a tangential gap closure, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition.

7. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, comprising a second actuator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition; and

d. a second force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of work on said interface member by said first and second actuators, said second force generator being arranged in opposition.

8. The actuator unit of claim 7, said work performed by said second actuator and second force generator arising from magnetic repulsion.

9. The actuator unit of claim 7, said work performed by said second force generator arising from a mechanical spring.

10. The actuator unit of claim 7, said first and second actuators arranged such that any work performed by said first and second actuators causes motion of said interface member with respect to a first DOF, said second force generator being arranged such that any work performed by said second force generator causes motion of said interface member with respect to a second DOF.

11. The actuator unit of claim 10, said second force generator comprising a third actuator, said actuator unit further comprising a third force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performace of work on said interface member by said first, second and third actuators, said third force generator being arranged in opposition.

12. The actuator unit of claim 11, said third force generator arranged such that any work performed by said third force generator causes motion of said interface member with respect to a third DOF.

13. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition, such that any work performed by said first actuator and said force generator causes motion of said interface member with respect to a first DOF;

d. a second actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

e. a second force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of work on said interface member by said second actuator, said second actuator and said second force generator being in opposition such that work done by said second actuator and said second force generator causes motion of said interface member with respect to a second DOF.

14. The actuator unit of claim 13, said actuator unit further comprising:

a. a third actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from a magnetic repulsion; and

b. a third force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with application of work performed on said interface member by said third actuator, said third actuator and said third force generator being in opposition, said work performed by said third actuator and said third force generator causing motion of said interface member with respect to a third DOF.

15. An actuator unit comprising:

a. an interface member sized and shaped to engage with a human scale body member selected from the group consisting of finger, hand, arm, head, tongue, mouth, foot, leg, buttocks and torso;

b. a first actuator, coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition.

16. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is an electromagnet and that is fixed relative to a reference, a second magnet that is a permanent magnet and that is movable relative to said reference, and a third magnet, which is fixed relative to said reference, and which is arranged to establish magnetic repulsion with said movable second magnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition.

17. The actuator unit of claim 16, said electromagnet being arranged to generate a magnetic field that:

a. counters said magnetic repulsion that arises between said second and third magnets if current is applied to said electromagnet in a first direction; and

b. enhances said magnetic repulsion that arises between said second and third magnets if current is applied to said electromagnet in a second, opposite direction.

18. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition; and

d. a travel guide that permits motion of said second magnet relative to said travel guide so that said magnetic repulsion is maintained non-zero.

19. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, comprising a second actuator comprising an electromagnet, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition, work performed by said second actuator arising from magnetic repulsion; and

d. circuitry for delivering a different current signal to each of said electromagnets.

20. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, and an additional movable magnet, movable relative to said reference, said additional movable magnet being spaced from said movable second magnet, and said additional movable magnet being arranged such that magnetic repulsion arises between said movable second magnet and said additional movable magnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition.

21. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition;

said work performed by said first actuator and said force generator arising from a force applied by said actuator and said force generator to said interface member, said forces applied by each of said actuators having a component that is not colinear with any component of force applied by the other of said actuator and said force generator.

22. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition; and

d. a current supply for delivering to said electromagnet current at a level that corresponds to a preselected position of said interface member with respect to said reference, said current supply comprising;

i. a signal generator that specifies said preselected position;

ii. a position lookup table that correlates said preselected position to a current level for said electromagnet, coupled to said signal generator; and

iii. a current amplifier that generates current supplied to said electromagnet at a level based on a correlation from said lookup table to a corresponding preselected position from said signal generator.

23. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition; and

d. a current supply for delivering to said electromagnet current at a level that corresponds to a preselected stiffness of said interface member with respect to a DOF of motion and said reference.

24. The actuator unit of claim 23, said current supply comprising:

a. a signal generator that specifies said preselected stiffness;

b. a stiffness lookup table that correlates said preselected stiffness to a current level for said electromagnet, coupled to said signal generator; and

c. a current amplifier that generates current at a level based on a correlation from said lookup table to a corresponding preselected stiffness from said signal generator.

25. An actuator unit comprising:

a. an interface member;

b. a first actuator comprising a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets comprising an electromagnet, said first actuator coupled to said interface member, arranged to perform work on said interface member, said work arising from magnetic repulsion;

c. a force generator, comprising a second actuator, which also comprises a first magnet that is fixed relative to a reference, and a second magnet that is movable relative to said reference, one of said fixed and movable magnets of said second actuator comprising an electromagnet, said second actuator also coupled to said interface member, arranged to perform work on said interface member simultaneously with performance of said work on said interface member by said first actuator, said first actuator and said force generator arranged in opposition, said force applied by said second actuator arising from magnetic repulsion; and

d. for each of said first and second actuators, a current supply for delivering to said respective electromagnet of each actuator, current at levels that correspond to a preselected combination of stiffness with respect to a DOF of motion and position of said interface member with respect to said DOF.

26. The actuator unit of claim 25, said current supply comprising:

a. a signal generator that specifies said preselected combination of stiffness and position;

b. a stiffness and position lookup table that correlates said preselected combination of stiffness and position to a current level for each of said electromagnets, coupled to said signal generator; and

c. for each actuator, a current amplifier that generates current at a level based on a correlation from said lookup table to a corresponding preselected combination of stiffness and position from said signal generator.

27. An actuator assembly comprising:

a. an interface member;

b. a first actuator unit comprising two force generators, each coupled to said interface member such that each force generator performs work on said interface member, each of said force generators being in opposition, any work performed by said force generators causing motion of said interface member with respect to a first DOF, one of said force generators comprising an actuator, said work performed by said actuator arising from magnetic repulsion;

c. a second actuator unit comprising two force generators, each coupled to said interface member such that each force generator of said second actuator unit performs work on said interface member, each of said force generators of said second actuator unit being in opposition, said work performed by said force generators of said second unit causing motion of said interface member with respect to a second DOF, one of said force generators of said second actuator unit comprising an actuator, said work performed by said actuator of said second actuator unit arising from magnetic repulsion.

28. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to apply torque to said interface member, said torque arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to apply torque to said interface member simultaneously with application of torque to said interface member by said first actuator, said force generator torque having a component opposing said torque applied by said first actuator.

29. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to apply force and torque to said interface member, said force and torque arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to apply force and torque to said interface member simultaneously with application of force and torque to said interface member by said first actuator, said force generator force and torque having a component opposing said force and torque applied by said first actuator.

30. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to apply force to said interface member that urges said interface member to move in a first direction, said force arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to apply force to said interface member simultaneously with application of force to said interface member by said first actuator, said force generator force urging said interface member to move in a second direction, having a component opposite to said first direction.

31. The actuator unit of claim 30, said first direction comprising a rotation around a reference point.

32. The actuator unit of claim 30, said first direction comprising a translation relative to a reference point.

33. An actuator unit comprising:

a. an interface member;

b. a first actuator, coupled to said interface member, arranged to apply torque to said interface member that urges said interface member to move in a first direction, said torque arising from magnetic repulsion; and

c. a force generator, also coupled to said interface member, arranged to apply torque to said interface member simultaneously with application of force to said interface member by said first actuator, said force generator torque urging said interface member to move in a second direction, having a component opposite to said first direction.

34. The actuator unit of claim 33, said first direction comprising a rotation around a reference point.

35. The actuator unit of claim 33, said first direction comprising a translation relative to a reference point.