Magnetic actuator with long travel in one direction

• US 6,066,998 A
• Filed: 09/12/1996
• Issued: 05/23/2000
• Est. Priority Date: 09/12/1996
• Status: Expired due to Fees

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Schwartz, Lawrence S., Trumper, David L.
• Primary Examiner(s): Gellner, Michael L.
• Assistant Examiner(s): BARRERA, RAMON M
• Application Number:
  US08/712,852
• Time in Patent Office: 1,349 Days
• Field of Search: 310/90.5, 310/12, 310/13, 310/14, 310/15, 310/20, 310/22, 310/23, 310/24, 335/229-234, 335/222, 335/223
• US Class Current: 335/229
• CPC Class Codes: H01F 2029/143 with control winding for generating magnetic bias
• CPC Class Codes: H01F 7/066 Electromagnets with movable winding
• CPC Class Codes: H02K 16/00 Machines with more than one rotor or stator machines for transmitting mechanical power from a driving shaft to a driven shaft and comprising structurally interrelated motor and generator parts H02K51/00; permanent magnet machines with multiple rotors or stators relatively rotated for vectorially combining the excitation fields or the armature voltages H02K21/029
• CPC Class Codes: H02K 2201/18 Machines moving with multiple degrees of freedom
• CPC Class Codes: H02K 41/0356 moving along a straight path

Abstract

An actuator made up of a plurality of actuator elements is provided which actuator provides long travel in one dimension and short travel in five additional dimensions, with each actuator element providing long travel in the one dimension and short travel in at least two additional dimensions. For preferred embodiments, each actuator element includes a suspension core, the long travel being in one linear dimension and each actuator element providing short travel in two additional linear dimensions and at least one rotary dimension. More particularly, each actuator element includes an electrodynamic drive for providing controlled movement in the first dimension, which drive includes a voice coil mounted in a voice coil gap and at least one elongated high permeability core which is movable in the first dimension with respect to the voice coil; an electromagnetic drive for providing controlled movement in the at least one additional dimension (and in the two additional linear dimensions and at least one rotary dimension for preferred embodiments), which drive includes at least one high permeability suspension core spaced from the at least one elongated core by small gaps and windings for selectively inducing fluxes in the small gaps; and a magnetic source for providing bias flux to both the voice coil gap and the small gaps.

Claims

1. An actuator element for providing long travel in a first dimension and short travel in at least one additional dimension comprising:

an electrodynamic drive for providing controlled movement in said first dimension, said drive including a single phase, noncommutated voice coil mounted in a voice coil gap and at least one elongated high permeability core which is movable in the first dimension with respect to the voice coil;

an electromagnetic drive for providing controlled movement in said at least one additional dimension, said drive including at least one high permeability suspension core spaced from said at least one elongated core by small gaps, and windings for selectively inducing fluxes in said small gaps; and

a magnetic source for providing a bias flux to both said voice coil gap and said small gaps.

2. An actuator element as claimed in claim 1 wherein said magnetic source includes at least one permanent magnet mounted to a said elongated core on at least one side of said voice coil gap.

3. An actuator element as claimed in claim 1 including means for reducing the magnet flux in said at least one suspension core to prevent saturation of said electromagnetic drive.

4. An actuator element as claimed in claim 3 wherein said means for reducing includes shims for diverting magnetic flux away from said suspension cores by providing a parallel bypass path for said suspension cores for some of said flux.

5. An actuator element as claimed in claim 4 wherein said shims provide at least one high magnetic permeability bypass path.

6. An actuator element as claimed in claim 4 wherein said shims provide at least one bypass gap which bypass gap is much shorter and much narrower than said voice coil gap.

7. An actuator element as claimed in claim 4 wherein said shims provide at least one narrow high magnetic permeability bypass path for said suspension cores.

8. An actuator element as claimed in claim 4 wherein said shims are permanent magnet shims.

9. An actuator element as claimed in claim 1 wherein said voice coil and said at least one suspension core are stationary and wherein said at least one elongated core and said source are connected to form part of a moving platen.

10. An actuator element as claimed in claim 1 wherein said at least one elongated core includes a center core around which said voice coil is wound and a pair of outer return cores, voice coil gaps being formed between the center core and each return core;

and

wherein each said at least one suspension core includes a pair of high permeability E-cores spaced from the center core and the return cores by small gaps.

11. An actuator element as claimed in claim 10 wherein said source includes a permanent magnet mounted to each return core between the return core and the center core.

12. An actuator element as claimed in claim 1 wherein at least one of said elongated core and said suspension core are laminated to provide superior high frequency response.

13. An actuator element as claimed in claim 1 wherein said electrodynamic drive provides controlled movement in one linear dimension, wherein said electromagnetic drive provides controlled movement in two additional linear dimensions and in at least one rotary dimension, and wherein said at least one suspension core has poles angled to provide force components in both of said two additional linear dimensions.

14. An actuator element as claimed in claim 13 wherein there are windings either on or between sufficient ones of said pole pieces to provide controlled forces in at least said two additional linear dimensions and said at least one rotary dimension.

15. An actuator element as claimed in claim 13 wherein there are at least two of said elongated cores, at least one of which passes through a said voice coil, and wherein said at least one suspension core has at least two pole pieces adjacent each elongated core, the pole pieces being shaped and angled relative to the corresponding elongated core to apply forces thereto having components in said two additional linear dimensions when currents are applied to windings corresponding to said pole pieces.

16. An actuator element as claimed in claim 15 wherein the magnetic source includes a permanent magnet affixed to each elongated core on the side thereof adjacent the other elongated core.

17. An actuator element as claimed in claim 13 wherein there is a single elongated core having magnets mounted to opposite sides thereof, the elongated core and magnets passing through a said voice coil;

and

wherein the elongated core passes between pole pieces of said at least one suspension core which pole pieces are shaped and angled to apply forces to said elongated core having components in said two additional linear dimensions.

18. An actuator element as claimed in claim 17 wherein said at least one suspension core has a substantially circular internal opening through which at least said elongated core passes, which opening is slotted to form said pole pieces, and wherein said elongated core has substantially circular sides adjacent said pole pieces.

19. An actuator element as claimed in claim 17 wherein said elongated core has sides which angle outward from the top and bottom to a point, and wherein said at least one suspension core has a pole piece forming a small gap with each angled side.

20. An actuator element as claimed in claim 17 including a pair of return cores substantially parallel to the elongated core and spaced therefrom, said return cores terminating at said at least one suspension core.

21. An actuator providing long travel in a first dimension and short travel in five additional dimensions comprising:

at least three actuator elements of the type claimed in claim 1 interconnected so that they all have their long travel in said first dimension.

22. An actuator providing long travel in a first dimension and short travel in five additional dimensions comprising:

at least one electrodynamic drive for providing controlled movement in said first dimension, said drive including a single phase, noncommutated voice coil mounted in a voice coil gap and at least one elongated high permeability core, the core and voice coil being movable in the first dimension with respect to each other;

at least two electromagnetic drives each providing controlled movement in at least one additional dimension, each said drive including at least one high permeability suspension core spaced from the at least one elongated core by small gaps, said drives being spaced from each other along the at least one elongated core, and windings for selectively inducing fluxes in said small gaps;

and a magnetic source for providing a bias flux to both said voice coil gap and said small gaps for both electromagnetic drives.

23. An actuator as claimed in claim 22 wherein said electrodynamic drive provides controlled movement in one linear dimension, wherein said electromagnetic drives each provide controlled movement in two additional linear dimensions and in at least one rotary dimension, and wherein said at least one suspension core for each electromagnetic drive has pole pieces angled to provide force components in both of said two additional linear dimensions.

24. An actuator as claimed in claim 23 wherein there are windings either on or between sufficient ones of said pole pieces to provide controlled forces in at least said two additional linear dimensions and said at least one rotary dimension.

25. An actuator as claimed in claim 22 wherein there are at least two of said elongated cores, at least one of which passes through a said voice coil, and wherein each said suspension core has at least two pole pieces adjacent each elongated core, the pole pieces being shaped and angled relative to the corresponding elongated core to apply forces thereto having components in said two additional linear dimensions when currents are applied to windings corresponding to said pole pieces.

26. An actuator as claimed in claim 22 wherein there is a single elongated core having magnets mounted to opposite sides thereof, the elongated core and magnet passing through a said voice coil;

and

wherein the elongated core passes between pole pieces of each said suspension core which pole pieces are shaped and angled to apply forces to said elongated core having components in said two additional linear dimensions.

27. An actuator as claimed in claim 26 wherein each said suspension core has a substantially circular internal opening through which at least said elongated core passes, which opening is slotted to form said pole pieces, and wherein said elongated core has substantially circular sides adjacent said pole pieces.

28. An actuator as claimed in claim 26 wherein said elongated core has sides which angle outward from the top and bottom to a point, and wherein each said suspension core has a pole piece forming a small gap with each angled side.

29. An actuator as claimed in claim 26 including a pair of return cores substantially parallel to the elongated core and spaced therefrom, each said return core terminating at and being in contact with a pair of spaced suspension cores.

30. An actuator as claimed in claim 22 including means for reducing the magnetic flux in said suspension cores to prevent saturation of said electromagnetic drive.

31. An actuator element for providing long travel in a first linear dimension and short travel in two additional linear dimensions and in at least one rotary dimension comprising:

an electrodynamic drive for providing controlled movement in said first linear dimension, said drive including a single phase, noncommulated voice coil mounted in a voice coil gap and at least one elongated high permeability core which is movable in the first dimension with respect to the voice coil;

an electromagnetic drive for providing controlled movement in said two additional linear dimensions and at least one rotary dimension, said drive including at least one high permeability suspension core spaced from said at least one elongated core by small gaps, and windings for selectively inducing fluxes in said small gaps, said at least one suspension core having poles angled to provide force components in both of said two additional linear dimensions; and

a magnetic source for providing a bias flux to both said voice coil gap and said small gaps.

32. An actuator element as claimed in claim 31 wherein said magnetic source includes at least one permanent magnet mounted to a said elongated core on at least one side of said voice coil gap, said magnet being elongated in said first direction.

33. An actuator element as claimed in claim 31 including means for reducing the magnet flux in said small gaps to prevent saturation of said electromagnetic drive.

34. An actuator as claimed in claim 33 wherein said means for reducing includes shims for diverting magnetic flux away from said suspension cores by providing a parallel bypass path for said suspension cores for some of said flux.

35. An actuator as claimed in claim 31 wherein at least one of said elongated core and said suspension core is laminated to provide superior high frequency response in at least said two additional linear dimensions.

36. An actuator as claimed in claim 31 wherein there are windings either on or between sufficient ones of said pole pieces to provide controlled forces in at least said two additional linear dimensions and said at least one rotary dimension.

37. An actuator as claimed in claim 31 wherein there are at least two of said elongated cores, at least one of which passes through a said voice coil, and wherein said at least one suspension core has at least two pole pieces adjacent each elongated core, the pole pieces being shaped and angled relative to the corresponding elongated core to apply forces thereto having components in said two additional linear dimensions when currents are applied to windings corresponding to said pole pieces.

38. An actuator as claimed in claim 37 wherein the magnetic source includes a permanent magnet affixed to each elongated core on the side thereof adjacent the other elongated core.

39. An actuator as claimed in claim 31 wherein there is a single elongated core having magnets mounted to opposite sides thereof, the elongated core and magnets passing through a said voice coil;

and

wherein the elongated core passes between pole pieces of said at least one suspension core which pole pieces are shaped and angled to apply forces to said elongated core having components in said two additional linear dimensions.

40. An actuator as claimed in claim 39 wherein said at least one suspension core has a substantially circular internal opening through which at least said elongated core passes which opening is slotted to form said pole pieces, and wherein said elongated core has substantially circular sides adjacent said pole pieces.

41. An actuator as claimed in claim 39 wherein said elongated core has sides which angle outward from the top and bottom to a point, and wherein said at least one suspension core has a pole piece forming a small gap with each angled side.

42. An actuator as claimed in claim 39 including a pair of return cores substantially parallel to the elongated core and spaced therefrom, said return cores terminating at and being in contact with said at least one suspension core.