Micromachined vibratory gyroscope and method with electronic coupling

• US 20050166675A1
• Filed: 01/30/2004
• Published: 08/04/2005
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: BEI Technologies, Incorporated
• Original Assignee: BEI Technologies, Incorporated
• Inventors: Wang, Feiyue, Hobbs, Larry P.
• Granted Patent: US 6,964,195 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

Micromachined vibratory gyroscope and method in which the vibrating masses are coupled electronically, e.g. by electronically adjusting the resonance frequency of one or more of the masses so that all of the masses have the same resonance frequency.

Claims

1. A micromachined vibratory gyroscope having drive and sense modes of operation, comprising:

a plurality of physically uncoupled masses mounted on a substrate for movement independently of each other along drive and sense axes, and means coupling the masses together electronically in at least one of the modes by the applying electrical signals to adjust the resonance frequency of at least of the masses.

2. The gyroscope of claim 1 wherein the means coupling the masses together electronically includes means for making the resonance frequencies of the masses the same.

3. The gyroscope of claim 1 wherein the means coupling the masses together electronically includes means responsive to motion of the masses along one of the axes for providing a correction signal corresponding to any frequency or phase difference in the motion of the masses, and means for applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same.

4. The gyroscope of claim 3 wherein the means for applying the correction signal includes means for applying correction signals of opposite polarity to the masses.

5. The gyroscope of claim 1 including a plurality of comb fingers affixed to each of the masses and extending in a direction parallel to the sense axis, additional comb fingers interleaved between the fingers affixed to the masses, and means mounting the additional comb fingers to the substrate in a manner permitting the additional fingers to move in concert with the fingers affixed to the masses along the drive axis but not the sense axis.

6. The gyroscope of claim 5 wherein the means mounting the additional comb fingers to the substrate includes a flexible beam extending along the sense axis.

7. A method of operating a micromachined vibratory gyroscope with drive and sense modes, comprising the steps of:

allowing a plurality of physically uncoupled masses to move independently of each other along drive and sense axes, and coupling the masses together electronically in at least one of the modes by using electrical signals to adjust the resonance frequency of at least one of the masses.

8. The method of claim 7 wherein the resonance frequencies of the masses are adjusted to be the same.

9. The method of claim 7 wherein the masses are coupled together electronically by monitoring motion of the masses along one of the axes, providing a correction signal corresponding to any frequency or phase difference in the monitored motion, and applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same.

10. The method of claim 9 wherein correction signals of opposite polarity are applied to the masses.

11. A micromachined vibratory gyroscope having drive and sense modes of operation, comprising:

a plurality of drive masses and sensing masses, means coupling the drive masses and sensing masses together in such manner that the drive masses move independently of the sensing masses along a drive axis and the sensing masses move in concert with the drive masses along a sense axis, and means coupling the masses together electronically in the sense mode by application of electrical signals to adjust the resonance frequencies of at least one of the masses in the sense mode.

12. The gyroscope of claim 11 wherein the means coupling the drive and sensing masses together electronically in the sense mode includes means for making the resonance frequencies of the masses be the same in the sense mode.

13. The gyroscope of claim 11 wherein the means coupling the masses together electronically Includes means responsive to motion of the drive and sensing masses along the sense axis for providing a correction signal corresponding to any frequency or phase difference in the motion of the masses, and means for applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same in the sense mode.

14. The gyroscope of claim 13 wherein the means for applying the correction signal includes means for applying correction signals of opposite polarity to the masses.

15. The gyroscope of claim 11 wherein the means coupling the drive masses and sensing masses together comprises a first set of beams which are relatively rigid along the drive axis and relatively flexible along the sense axis connected between the sensing masses and fixed anchors to prevent the sensing masses from moving along the drive axis and allowing the sensing masses to move along the sense axis, and a second set of beams which are relatively flexible along the drive axis and relatively rigid along the sense axis interconnecting the drive masses and the sense sensing masses.

16. The gyroscope of claim 15 wherein the beams in the first set have middle portions connected to the anchors and end portions connected to the sensing masses, and the beams in the second set have middle portions connected to the drive masses and end portions connected to the sensing masses.

17. The gyroscope of claim 11 including a pair of sensing capacitors associated with each of the sensing masses for detecting movement of the sensing masses along the sense axis, means for subtracting a signal from one of the capacitors associated with each sensing mass from a signal from the other capacitor in the pair to obtain an output signal for the mass, and means for subtracting the output signal for one sensing mass from the output signal for another.

18. A method of operating a micromachined vibratory gyroscope having a plurality of drive masses and sensing masses, with drive and sense modes of operation, comprising the steps of:

allowing the drive masses to move independently of the sensing masses along a drive axis, constraining the sensing masses to move in concert with the drive masses along a sense axis, and coupling the masses together electronically in the sense mode by using electrical signals to adjust the resonance frequencies of at least one of the masses in the sense mode.

19. The method of claim 18 wherein the resonance frequencies of the masses are adjusted to be the same in the drive mode.

20. The method of claim 18 wherein the masses are coupled together electronically by monitoring motion of the masses along the sense axis, providing a correction signal corresponding to any frequency or phase difference in the monitored motion, and applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same in the sense mode.

21. The method of claim 20 wherein correction signals of opposite polarity are applied to the masses.

22. The method of claim 18 including the steps of detecting movement of the sensing masses along the sense axis with a pair of sensing capacitors associated with each of the sensing masses, subtracting a signal from one of the capacitors associated with each sensing mass from a signal from the other capacitor in the pair to obtain an output signal for the mass, and subtracting the output signal for one sensing mass from the output signal for another.

23. A micromachined vibratory gyroscope having drive and sense modes, comprising:

a plurality of masses which are uncoupled and free to move independently of each other along a drive axis, a pickoff beam coupling the masses together for movement in opposite directions along a sense axis, means responsive to movement of the pickoff beam for sensing movement of the masses along the sense axis, and means coupling the masses together electronically in the drive mode by application of electrical signals to adjust the resonance frequencies of the masses in the drive mode.

24. The gyroscope of claim 23 wherein the means coupling the masses together electronically includes means for making the resonance frequencies of the masses the same in the drive mode.

25. The gyroscope of claim 23 wherein the means coupling the masses together electronically includes means responsive to motion of the masses along the drive axis for providing a correction signal corresponding to any frequency or phase difference in the motion of the masses, and means for applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same in the drive mode.

26. The gyroscope of claim 23 wherein the means for applying the correction signal includes means for applying correction signals of opposite polarity to the masses.

27. The gyroscope of claim 23 wherein the pickoff beam is free to rotate about an input axis perpendicular to the drive and sense axes and constrained against translation along the drive and sense axes.

28. The gyroscope of claim 27 wherein the pickoff beam is mounted on a first beam which is flexible along the drive axis and rigid along the sense axis and a second beam which is rigid along the drive axis and flexible along the sense axis.

29. The gyroscope of claim 28 wherein the first beam extends in a direction parallel to the sense axis between a fixed anchor and the pickoff beam, and the second beam extends in a direction parallel to the drive axis between a fixed anchor and the pickoff beam.

30. A method of operating a micromachined vibratory gyroscope having a plurality of masses which are uncoupled and free to move independently of each other along a drive axis and a pickoff beam coupling the masses together for movement in opposite directions along a sense axis, comprising the steps of:

monitoring movement of the pickoff beam to sense movement of the masses along the sense axis, and coupling the masses together electronically in a drive mode by applying electrical signals to adjust the resonance frequency of at least one of the masses in the drive mode.

31. The method of claim 30 wherein the resonance frequencies of the masses are adjusted to be the same in the drive mode.

32. The method of claim 30 wherein the masses are coupled together electronically by monitoring motion of the masses along the drive axis, providing a correction signal corresponding to any frequency or phase difference in the monitored motion, and applying the correction signal to at least one of the masses to make the resonance frequencies of the masses the same in the drive mode.

33. The method of claim 32 wherein correction signals of opposite polarity are applied to the masses.