Micromachined vibratory gyroscope with electrostatic coupling

• US 6,966,224 B2
• Filed: 03/02/2004
• Issued: 11/22/2005
• Est. Priority Date: 03/06/2003
• Status: Active Grant

• Current Assignee: Continental Teves AG & Co. OHG (Continental AG), Conti Temic Microelectronic GmbH (Continental AG), Emcore Corporation
• Original Assignee: BEI Technologies, Incorporated, Continental Teves AG & Co. OHG (Continental AG), Conti Temic Microelectronic GmbH (Continental AG)
• Inventors: Kapser, Konrad, Hartmann, Bernhard, Rose, Matthias, Burghardt, Roland, Yan, Hai
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US10/792,043
• Publication Number:
  US 20040173023A1
• Time in Patent Office: 630 Days
• Field of Search: 735/040.4, 735/041.2, 735/040.2, 735/041.4, 735/041.5
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: Y10T 74/1275 Electrical

Abstract

Micromachined vibratory gyroscope having two or more coplanar movable masses suspended over a planar substrate. Two perpendicular axes (x and y) are defined within the substrate plane, while a third, the z-axis or input axis, is defined to be perpendicular to the substrate plane. The movements of the two masses along the x-axis are coupled through an electrostatic coupling means so that the natural resonant frequency of the in-phase mode and that of the anti-phase mode are separated from each other for the resonances along the x-axis. When the two masses are driven to vibrate along the x-axis in the anti-phase mode and the device experiences rotation about the z-axis, Coriolis forces act differentially on the masses in the Y-direction, causing the two masses to dither in an anti-phase motion along the y-axis. The anti-phase dithering along the y-axis can be sensed directly by a rate sensor to measure the rate of rotation about the z-axis. Alternatively, the anti-phase dithering of the first and second bodies along the y-axis can be transferred to other movable bodies (i.e., rate-sensing masses) whose movement is then sensed to measure the rate of rotation about the z-axis. The sensing bodies are preferably suspended in such manner that, in the absence of Coriolis forces, the x-axis motion of the vibrating masses does not affect the sensing bodies. That inhibits motion of the sensing bodies in response to linear acceleration within the plane of the substrate, but permits those bodies to respond readily to the Coriolis-induced motion about an axis perpendicular to the substrate plane.

Claims

1. A micromachined vibratory gyroscope, comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and differential motion along a second axis in response to a Coriolis force produced by rotation about a third axis, and means for coupling the masses together through electrostatic forces which are a function of the relative positions of the masses.

2. The micromachined vibratory gyroscope of claim 1 wherein the electrostatic coupling forces are directed along the first axis so that the masses have different resonant frequencies for anti-phase and in-phase motion along the first axis.

3. The micromachined vibratory gyroscope of claim 1 wherein the masses are coupled electrostatically along both the first axis and the second axis so that the masses have different resonant frequencies for anti-phase and in-phase motion along each of the first and second axes.

4. The micromachined vibratory gyroscope of claim 1 wherein the means for coupling the masses together includes a plurality of parallel plates connected to the masses for movement in concert with the masses.

5. The micromachined vibratory gyroscope of claim 4 wherein the plates connected to the first mass are spaced equally between the plates connected the second mass so that motion of the masses toward each other and away from each other results in substantially equal electrostatic forces.

6. The micromachined vibratory gyroscope of claim 1 wherein the means for coupling the masses together includes a third mass which is coupled electrostatically between the first and second masses.

7. The micromachined vibratory gyroscope of claim 1 further including a plurality of sensors capacitively coupled to the first and second masses for monitoring movement of the masses along the second axis.

8. The micromachined vibratory gyroscope of claim 1 further including a sensing element coupled to the first and second masses, and a plurality of sensors capacitively coupled to the sensing element for monitoring movement of the masses along the second axis.

9. The micromachined vibratory gyroscope of claim 8 wherein the sensing element is coupled to the masses electrostatically.

10. The micromachined vibratory gyroscope of claim 1 wherein the masses are spaced above a planar substrate, the first and second axes lie in a plane parallel to the substrate, and the third axis is perpendicular to the substrate.

11. The micromachined vibratory gyroscope of claim 1 wherein the masses are spaced above a planar substrate, the first and third axes lie in a plane parallel to the substrate, and the second axis is perpendicular to the substrate.

12. A micromachined rate sensor, comprising first and second masses which are coupled together electrostatically and mounted in a manner permitting anti-phase dithering motion along a first axis and differential motion along a second axis in response to a Coriolis force produced by rotation about a third axis.

13. The micromachined rate sensor of claim 12 wherein the first and second masses are coupled together through electrostatic forces which are a function of the relative positions of the masses.

14. The micromachined rate sensor of claim 12 wherein the electrostatic coupling forces are directed along the first axis so that the masses have different resonant frequencies for anti-phase and in-phase motion along the first axis.

15. The micromachined rate sensor of claim 12 wherein the messes are coupled electrostatically along both the first axis and the second axis so that the masses have different resonant frequencies for anti-phase and in-phase motion along each of the first and second axes.

16. The micromachined rate sensor of claim 12 further including a plurality of sensors capacitively coupled to the first and second masses for monitoring movement of the masses along the second axis.

17. The micromachined rate sensor of claim 12 further including a sensing element coupled to the first and second masses, and a plurality of sensors capacitively coupled to the sensing element for monitoring movement of the masses along the second axis.

18. The micromachined rate sensor of claim 17 wherein the sensing element is electrostatically coupled to the masses.

20. The micromachined rate sensor of claim 12 wherein the first and second axes are perpendicular to each other and to the third axis.

19. A micromachined rate sensor, comprising first and second masses which are coupled together electrostatically and mounted in a manner permitting anti-phase dithering along a first axis and differential motion along a second axis in response to a Coriolis force produced by rotation about a third axis, a sensing element comprising a rectangular frame which surrounds, is coplanar with, and is coupled to the first and second masses, and a plurality of sensors capacitively coupled to the sensing element for monitoring movement of the masses along the second axis.

21. A micromachined rate sensor, comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and movement in opposite directions along a second axis in response to a Coriolis force produced by rotation about a third axis, and a plurality of capacitive coupling plates attached to the masses and interleaved along the first axis to provide electrostatic coupling between the masses when a voltage is applied to the plates.

22. The micromachined rate sensor of claim 21 including additional coupling plates which are attached to the masses and interleaved along the second axis to provide electrostatic coupling between the masses along the second axis when a voltage is applied thereto.

23. A micromachined rate sensor, comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and movement in opposite directions along a second axis in response to a Coriolis force produced by rotation about a third axis, and capacitive coupling plates attached to the masses and disposed in facing relation to each other along the first axis to provide electrostatic coupling between the masses when a voltage is applied to the plates.

24. A micromachined rate sensor, comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and movement in opposite directions along a second axis in response to a Coriolis force produced by rotation about a third axis, a third mass mounted between the first and second masses in a manner permitting movement along the first axis, and capacitive coupling plates attached to the masses and disposed in facing relation to each other along the first axis to provide electrostatic coupling between the first and third masses and between the second and third masses when a voltage is applied to the plates.

25. A micromachined rate sensor comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and movement in opposite directions along a second axis in response to a Coriolis force produced by rotation about a third axis, a third mass mounted between the first and second masses in a manner permitting movement along the first axis, capacitive coupling plates attached to the masses and disposed in facing relation to each other along the first axis to provide electrostatic coupling between the first and third masses and between the second and third masses when a voltage is applied to the plates, and a sensing mass connected to the first and second masses for movement along the second axis with the first and second masses without impairing the motion of the first and second masses along the first axis.

26. The micromachined rate sensor of claim 25 wherein the sensing mass comprises a rectangular frame which surrounds and is coplanar with the first and second masses.

27. A micromachined rate sensor, comprising:

first and second masses mounted in a manner permitting anti-phase dithering motion along a first axis and movement in opposite directions along a second axis in response to a Coriolis force produced by rotation about a third axis, capacitive coupling plates attached to the masses and disposed in facing relation to each other along the first axis to provide electrostatic coupling between the masses when a voltage is applied thereto, a sensing mass in the form of a rectangular frame which surrounds and is coplanar with the masses and is mounted in a manner preventing motion along the first and second axes while permitting rotation about the third axis, and capacitive coupling plates attached to the first and second masses and to the sensing mass disposed in facing relation to each other along the second axis to provide electrostatic coupling between the first and second masses and the sensing mass when a voltage is applied thereto.