Torsional rate sensor with momentum balance and mode decoupling

• US 7,222,533 B2
• Filed: 06/06/2005
• Issued: 05/29/2007
• Est. Priority Date: 06/06/2005
• Status: Active Grant

• Current Assignee: Emcore Corporation
• Original Assignee: BEI Technologies, Incorporated
• Inventors: Acar, Cenk, Mao, Minyao, Costlow, Lynn Edward
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US11/146,401
• Publication Number:
  US 20060272410A1
• Time in Patent Office: 722 Days
• Field of Search: 735/040.2, 735/040.4, 735/041.2, 735/041.4, 735/041.6
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

Rate sensor having a plurality of generally planar masses, a drive axis in the planes of the masses, an input axis perpendicular to the drive axis, and sense axes perpendicular to the drive axis and the input axis. The masses are driven to oscillate about the drive axes and are mounted for torsional movement about the sense axes in response to Coriolis forces produced by rotation of the masses about the input axis, with sensors responsive to the torsional movement about the sense axis for monitoring rate of rotation.

Claims

1. A rate sensor comprising a plurality of generally planar masses, means for driving the masses to oscillate about a drive axis in the plane of the masses, an input axis perpendicular to the drive axis, sense axes perpendicular to the drive axis and the input axis, means mounting the masses for torsional movement about the sense axes in response to Coriolis forces produced by rotation of the masses about the input axis, and means responsive to the torsional movement about the sense axis for monitoring rate of rotation about the input axis.

2. The rate sensor of claim 1 wherein a first one of the masses is positioned within a second, and the sense axes of the first and second masses are coincident.

3. The rate sensor of claim 1 including means coupling adjacent ones of the masses together in a manner which constrains the adjacent masses for movement in phase opposition about the sense axes while permitting those masses to oscillate about the drive axis either in phase or out of phase with each other.

4. The rate sensor of claim 1 wherein the masses are mounted on frames by flexures which bend in the plane of the masses to permit the masses to rotate about the sense axes, and the frames are mounted on torsion springs which extend along the drive axis and permit the frames and the masses to oscillate in see-saw fashion about the drive axis.

5. The rate sensor of claim 4 wherein drive mode frequency is determined primarily by stiffness of the torsion springs, and sense mode frequency is determined primarily by stiffness of the flexures.

6. The rate sensor of claim 1 wherein the means for monitoring rate of rotation about the input axis includes sensing frames which are constrained for rotation about the sensing axes.

7. The rate sensor of claim 6 wherein the sensing frames are coupled to the masses by springs which are highly compliant to rotation of the masses about the drive axes so that the sensing frames are decoupled from drive mode movement of the masses.

8. The rate sensor of claim 6 including coupling springs connected between the sensing frames, the coupling springs being relatively flexible in a direction parallel to the drive axis and relatively stiff in a direction parallel to the input axis.

9. The rate sensor of claim 1 including a mechanical link coupling the masses together for rotation in concert about the sense axes while permitting both in-phase and anti-phase oscillation of the masses about the drive axis.

10. The rate sensor of claim 1 wherein the masses are mounted on frames by torsion springs which extend along the drive axis and permit the masses to oscillate in see-saw fashion about the drive axis, and the frames are mounted on flexures which bend in the plane of the masses to permit the masses to rotate about the sense axes.

11. The rate sensor of claim 10 wherein drive mode frequency is determined primarily by stiffness of the torsion springs, and sense mode frequency is determined primarily by stiffness of the flexures.

12. The rate sensor of claim 10 including means connecting adjacent ones of the masses together in a manner which permits both in-phase and anti-phase oscillation of the masses in a drive mode and constrains the adjacent masses for rotation in opposite directions about the sense axes in a sense mode.

13. The rate sensor of claim 12 wherein adjacent edge portions of the masses are coupled together by a coupling spring in the form of a small rectangular frame with relatively long, flexible arms extending in a direction parallel to the input axis and relatively short, stiff arms extending in the direction of the drive axis.

14. The rate sensor of claim 1 wherein the masses are mounted on frames by torsion springs for oscillation about the drive axis, the frames are mounted on flexures for rotation in accordance with the torsional movement of the masses about the sense axes, and the means for monitoring the rate of rotation about the input axis comprises plates which are mounted on the frames and interleaved with other plates to form capacitors which vary in value in accordance with the positions of the frames.

15. The rate sensor of claim 14 wherein the frames and the capacitors are located within the lateral confines of the masses.

16. The rate sensor of claim 14 wherein the sensing frames and the masses are symmetrical about the input and drive axes and have the same centers of rotation about the sense axes.

17. The rate sensor of claim 14 including means connecting adjacent ones of the masses together in a manner which permits both in-phase and anti-phase oscillation of the masses in a drive mode and constrains the adjacent masses for rotation in opposite directions about the sense axes in a sense mode.

18. The rate sensor of claim 17 wherein adjacent edge portions of the masses are coupled together by a coupling spring in the form of a small rectangular frame with relatively long, flexible arms extending in a direction parallel to the input axis and relatively short, stiff arms extending in the direction of the drive axis.

19. The rate sensor of claim 18 wherein the torsion springs are substantially stiffer than the coupling spring with regard to rotation about the drive axis.

20. The rate sensor of claim 1 wherein the masses are suspended by generally U-shaped drive springs having torsion springs extending in the direction of the drive axis with rigid connecting bars extending between the torsion springs, and the means for monitoring the rate of rotation about the input axis comprises sensing frames mounted on flexures for rotation about the sense axes in accordance with the torsional movement of the masses about the sense axes and plates which are mounted on the sensing frames and ;

interleaved with other plates to form capacitors which vary in value in accordance with the positions of the sensing frames.

21. The rate sensor of claim 20 wherein the sensing frames and the capacitors are located within the lateral confines of the masses.

26. The rate sensor of claim 1 wherein the means for monitoring rate of rotation about the input axis includes sensing frames which are constrained for rotation about axes which are parallel to the sensing axes.

22. A rate sensor comprising first and second generally coplanar masses mounted one within the other for rotational movement about a common drive axis in the plane of the masses, an input axis perpendicular to the drive axis, a sense axis perpendicular to the drive axis and the input axis, means mounting the masses for torsional movement about the sense axis in response to Coriolis forces produced by rotation of the masses about the in put axis, mechanical links constraining the two masses for anti-phase movement about both the drive axis and the sense axis, at least one sensing frame coupled to the masses for movement in response to the torsional movement of the masses about the sense axis, and a capacitor having plates which move relative to other plates in response to the movement of the sensing frame.

23. The rate sensor of claim 22 wherein two sensing frames are coupled to the masses such that the two sensing frames rotate in phase with each other.

24. A rate sensor comprising three generally planar proof masses mounted side-by-side for rotation about three parallel drive axes in the plane of the masses, means constraining adjacent ones of the masses to oscillate in phase opposition about the drive axes with the momentum of the two outer masses balancing the momentum of the inner mass, an input axis perpendicular to the drive axes, a sense axis perpendicular to the drive axes and the input axis, means mounting the masses for torsional movement about the sense axis in response to Coriolis forces produced by rotation of the masses about the input axis, with adjacent ones of the masses rotating in opposite directions so that the angular momentum of the two outer masses balances the angular momentum of the inner mass, sensing frames coupled to the two outer masses for rotation in response to the torsional movement of the masses about the sense axis, and means responsive to rotation of the sensing frames for monitoring rate of rotation about the input axis.

25. The rate sensor of claim 24 wherein the means for monitoring the rate of rotation comprises capacitors having plates which move relative to other plates in response to rotation of the sensing frames.

27. The rate sensor of claim 24 wherein the sensing frames are U-shaped and extend along three sides of the outer masses.

28. A rate sensor comprising first and second generally planar masses disposed side-by-side in a plane, a drive axis and an input axis in the plane, support frames disposed in openings in the masses and mounted on torsion springs which extend along the drive axis and constrain the frames for oscillation in see-saw fashion about the drive axis, flexures mounting the masses on the frames for rotation about sense axes perpendicular to the plane in response to Coriolis forces produced by rotation of the masses about the input axis, sensing frames rotatable about axes parallel to the sense axes, and means coupling the sensing frames to the masses for movement corresponding to rotation of the masses about the sense axes.

29. The rate sensor of claim 28 wherein the drive axis and the sense axes pass through the centers of the masses.

30. The rate sensor of claim 28 wherein adjacent edge portions of the masses are coupled together by a torsional coupling spring which extends along the drive axis and permits the masses to be driven either in phase or out of phase about the drive axis while constraining the masses for rotation in opposite directions about the sense axes.

31. The rate sensor of claim 30 wherein the sensing frames are coupled to opposite sides of the masses for rotation in opposite directions relative to each other and to the masses to which the sensing frames are coupled.

32. The rate sensor of claim 28 wherein the sensing frames are connected together by coupling springs which are relatively flexible in the direction of the drive axis and relatively stiff in the direction of the input axis.

33. A rate sensor comprising first and second generally planar masses disposed side-by-side in a plane, a drive axis and an input axis in the plane, support frames mounted in openings in the masses for rotation about sense axes perpendicular to the plane, torsion springs extending along the drive axis between the frames and the masses constraining the masses for oscillation in see-saw fashion about the drive axis and for rotation in concert with the support frames about the sense axes in response to Coriolis forces produced by rotation of the masses about the input axis, sensing frames rotatable about axes parallel to the sense axes, and means coupling the sensing frames to the masses for movement corresponding to rotation of the masses about the sense axes.

34. The rate sensor of claim 33 wherein the drive axis and the sense axes pass through the centers of the masses.

35. The rate sensor of claim 33 wherein adjacent edge portions of the masses are coupled together by a coupling spring which permits the masses to be driven either in phase or out of phase about the drive axis while constraining the masses for rotation in opposite directions about the sense axes.

36. The rate sensor of claim 35 wherein the coupling spring is in the form of a small rectangular frame, with relatively long, flexible arms extending in the direction of the input axis and relatively short, stiff arms extending in the direction of the drive axis.

37. The rate sensor of claim 33 wherein the sensing frames are coupled to opposite sides of the masses for rotation in opposite directions relative to each other and to the masses to which the sensing frames are coupled.

38. The rate sensor of claim 33 wherein the sensing frames are connected together by coupling springs which are relatively flexible in the direction of the drive axis and relatively stiff in the direction of the input axis.

39. A rate sensor comprising first and second generally planar masses disposed side-by-side in a plane, a drive axis and an input axis in the plane, sensing frames mounted in openings in the masses for rotation about sense axes perpendicular to the plane, and torsion springs which extend along the drive axis between the sensing frames and the masses and constrain the masses for oscillation in see-saw fashion about the drive axis and for rotation in concert with the sensing frames about the sense axes in response to Coriolis forces produced by rotation of the masses about the input axis.

40. The rate sensor of claim 39 including means mounted in the openings responsive to rotation of the sensing frames for monitoring the rate of rotation about the input axis.

41. The rate sensor of claim 40 wherein the means for monitoring the rate of rotation comprises capacitors having plates which move relative to other plates in response to rotation of the sensing frames.

42. The rate sensor of claim 39 wherein the drive axis and the sense axes pass through the centers of the masses.

43. The rate sensor of claim 39 wherein the masses and the sensing frames are symmetrical about the drive axis and the input axis and have the same centers of rotation about the sense axis.

44. The rate sensor of claim 39 wherein adjacent edge portions of the masses are coupled together by a coupling spring which permits the masses to be driven either in phase or out of phase about the drive axis while constraining the masses for rotation in opposite directions about the sense axes.

45. The rate sensor of claim 44 wherein the coupling spring is in the form of a small rectangular frame, with relatively long, flexible arms extending in the direction of the input axis and relatively short, stiff arms extending in the direction of the drive axis.

46. A rate sensor comprising first and second generally planar masses disposed in a plane with the second mass in an opening in the first mass, a drive axis and an input axis in the plane of the masses, means mounting the masses for oscillation about the drive axis and for rotation about a sense axis perpendicular to the plane of the masses, coupling frames disposed in the opening on opposite sides of the second mass constraining the masses for rotation in opposite directions about the drive axis, detection frames disposed in openings in the coupling frames and constrained for rotation about axes parallel to the sense axis, and means connecting the coupling frames to the detection frames for transferring rotation of the masses about the sense axis to the detection frames.

47. The rate sensor of claim 46 wherein the masses are symmetrical about the input axis and the drive axis and have the same center of rotation about the sense axis.

48. The rate sensor of claim 46 wherein the masses, the coupling frames and the detection frames are symmetrical about the drive axis, the input axis, and the sense axis.

49. The rate sensor of claim 46 wherein the means mounting the masses for oscillation about the drive axis and for rotation about the sense axis comprises torsion springs which extend along the drive axis.

50. The rate sensor of claim 46 wherein opposite sides of the coupling frames are connected to the first and second masses, and the coupling frames are connected to the detection frames in a manner which constrains the detection frames for rotation of equal amplitude and similar direction about the axes parallel to the sense axis.

51. The rate sensor of claim 46 wherein the masses are mounted to fixed anchors by torsional mounting springs which extend along the drive axis, and the masses are coupled to the detection frames through torsional coupling springs which are connected between the coupling frames and the detection frames and extend along axes parallel to the drive axis.

52. The rate sensor of claim 51 wherein the coupling springs are torsionally weaker than the mounting springs.

53. The rate sensor of claim 46 including capacitor plates connected to the detection frames within the openings in the coupling frames for monitoring rotation of the masses about the sense axis.

54. The rate sensor of claim 46 wherein the means connecting the coupling frames to the detection frames includes torsion springs which extend along and permit the coupling frames to rotate about axes which are parallel to the drive axis.

55. A rate sensor comprising first and second generally planar masses disposed side-by-side in a plane, a drive axis and an input axis in the plane, sensing frames mounted in openings in the masses for rotation about sense axes perpendicular to the plane, drive springs interconnecting the masses and the sensing frames on opposite sides of the drive axis and constraining the masses for oscillation in see-saw fashion about the drive axis, and means coupling the masses and the sensing frames together for rotation in concert about the sense axes in response to Coriolis forces produced by rotation of the masses about the input axis.

56. The rate sensor of claim 55 wherein each of the drive springs includes a pair of spaced apart torsion springs which extend in a direction parallel to the drive axis and are connected together at one end by a rigid bar, with the other ends of the torsion springs being connected respectively to one of the sensing frames and to one of the masses.

57. The rate sensor of claim 55 wherein the drive springs are disposed symmetrically of the drive axis and the centers of the masses.

58. The rate sensor of claim 55 wherein four of the drive springs are disposed symmetrically of the drive axis and the center of each of the masses.

59. The rate sensor of claim 55 wherein the masses and the sensing frames are symmetrical about the input axis and the drive axis and have the same centers of rotation about the sense axes.

60. A rate sensor comprising a central proof mass and two outer proof masses mounted side-by-side for rotation about three parallel drive axes in the plane of the masses, means mounting the masses for rotation about sense axes perpendicular to the plane of the masses in response to Coriolis forces produced by rotation of the masses about an input axis in the plane of the masses, means constraining the outer masses for out-of-phase movement relative to the central mass and in-phase movement relative to each other about both the drive axes and the sense axes, detection frames mounted for rotation about detection axes perpendicular to the plane of the masses, and means coupling the detection frames to the outer masses for transferring rotation of the outer masses about the sense axes to the detection frames.

61. The rate sensor of claim 60 wherein the outer proof masses are rotatively mounted on the detection frames by torsion springs which extend along the drive axes, and the detection frames are mounted for rotation about the detection axes by flexures which extend along the drive axes and are aligned axially with the torsion springs.

62. The rate sensor of claim 60 wherein the detection frames are generally U-shaped and extend along three sides of the outer proof masses.

63. The rate sensor of claim 60 including capacitor plates connected to the detection frames for monitoring rotation of the masses about the sense axes.

64. The rate sensor of claim 63 wherein some of the capacitor plates extend in a direction parallel to the drive axes, and some of the plates extend in a direction parallel to the input axis.