XY-Axis Shell-Type Gyroscopes with Reduced Cross-Talk Sensitivity and/or Mode Matching

• US 20130319116A1
• Filed: 05/29/2012
• Published: 12/05/2013
• Est. Priority Date: 11/05/2010
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Johari-Galle, Houri
• Granted Patent: US 9,091,544 B2
• Time in Patent Office: Days
• US Class Current: 73/504.13
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5698 using acoustic waves, e.g. surface acoustic wave gyros

Abstract

Cross-talk sensitivity in an xy-axis shell-type gyroscope can be rejected or reduced by operating the gyroscope with a single in-plane flexural or bulk resonance mode and sensing two out-of-plane degenerate or non-degenerate resonance modes resulting from rotations about two axes in the plane of the resonator. Mode matching in an xy-axis shell-type gyroscope can be achieved by configuring the resonator (e.g., size, shape, thickness) to match the in-plane and out-of-plane resonance frequencies for the drive and sense modes of interest.

Claims

1. A shell-type gyroscope with improved cross-talk sensitivity, the shell-type gyroscope comprising:

a resonator substantially disposed in a resonator plane;

a plurality of drive electrodes disposed substantially in the resonator plane; and

a plurality of sense electrodes disposed parallel to the resonator plane, wherein the resonator is driven via the drive electrodes in an in-plane flexural or bulk resonance mode substantially in the resonator plane, and wherein rotations about two orthogonal axes in the resonator plane are sensed via the sense electrodes using two out-of-plane flexural or bulk modes of the resonator caused by rotation about the axes, the in-plane drive mode substantially rejecting cross-talk between the two orthogonal sense axes.

2. A shell-type gyroscope according to claim 1, wherein the out-of-plane modes are degenerate modes.

3. A shell-type gyroscope according to claim 1, wherein the two out-of-plane modes are non-degenerate modes.

4. A shell-type gyroscope according to claim 1, wherein the two axes include orthogonal x and y axes, the drive and sense electrodes are aligned with the x and y axes, and the in-plane mode is an elliptical mode having anti-nodes substantially along the x and y axes, and wherein the sense electrodes that are parallel to the resonator plane and aligned with the x axis are configured for sensing rotation rate about the y axis and the sense electrodes that are parallel to the resonator plane and aligned with the y axis are configured for sensing rotation rate about the x axis.

5. A shell-type gyroscope according to claim 1, wherein the resonator is configured such that the frequency of the in-plane mode substantially matches the frequency of the out-of-plane mode.

6. A shell-type gyroscope according to claim 5, wherein at least one of the size, shape, or thickness of the resonator is specially configured to substantially match the frequencies.

7. A shell-type gyroscope according to claim 1, further comprising:

a second plurality of sense electrodes disposed substantially in the resonator plane, wherein rotations about a z-axis normal to the resonator plane are sensed via the second plurality of sense electrodes.

8. A shell-type gyroscope according to claim 7, wherein the in-plane mode is an elliptical mode having anti-nodes substantially along x and y axes, and wherein the second plurality of sense electrodes are located substantially at the anti-nodes of an elliptical mode having anti-nodes along axes offset substantially 45 degrees from the x and y axes.

9. A method for operating a shell-type gyroscope having a resonator substantially disposed in a resonator plane, a plurality of drive electrodes disposed substantially in the resonator plane, and a plurality of sense electrodes disposed parallel to the resonator plane, the method comprising:

driving, via the drive electrodes, resonance of the resonator in an in-plane flexural or bulk resonance mode substantially in the resonator plane; and

sensing, via the sense electrodes, rotations about two orthogonal axes in the resonator plane using two out-of-plane flexural or bulk modes of the resonator caused by rotation about the axes, the in-plane drive mode substantially rejecting cross-talk between the two orthogonal sense axes.

10. A method according to claim 9, wherein the out-of-plane modes are degenerate modes.

11. A method according to claim 9, wherein the two out-of-plane modes are non-degenerate modes.

12. A method according to claim 9, wherein the two axes include orthogonal x and y axes, the drive and sense electrodes are aligned with the x and y axes, and the in-plane mode is an elliptical mode having anti-nodes substantially along the x and y axes, and wherein the sense electrodes that are parallel to the resonator plane and aligned with the x axis are configured for sensing rotation rate about the y axis and the sense electrodes that are parallel to the resonator plane and aligned with the y axis are configured for sensing rotation rate about the x axis.

13. A method according to claim 9, further comprising:

sensing rotations about a z-axis normal to the resonator plane via a second plurality of sense electrodes disposed substantially in the resonator plane.

14. A method according to claim 13, wherein the in-plane mode is an elliptical mode having anti-nodes substantially along x and y axes, and wherein the second plurality of sense electrodes are located substantially at the anti-nodes of an elliptical mode having anti-nodes along axes offset substantially 45 degrees from the x and y axes.

15. Apparatus for operating a shell-type gyroscope having a resonator substantially disposed in a resonator plane, a plurality of drive electrodes disposed substantially in the resonator plane, and a plurality of sense electrodes disposed parallel to the resonator plane, the apparatus comprising:

a drive circuit configured to drive, via the drive electrodes, resonance of the resonator in an in-plane flexural or bulk resonance mode substantially in the resonator plane; and

a sense circuit configured to sense, via the sense electrodes, rotations about two orthogonal axes in the resonator plane using two out-of-plane flexural or bulk modes of the resonator caused by rotation about the axes, the in-plane drive mode substantially rejecting cross-talk between the two orthogonal sense axes.

16. Apparatus according to claim 15, wherein the out-of-plane modes are degenerate modes.

17. Apparatus according to claim 15, wherein the two out-of-plane modes are non-degenerate modes.

18. Apparatus according to claim 15, wherein the two axes include orthogonal x and y axes, the drive and sense electrodes are aligned with the x and y axes, and the in-plane mode is an elliptical mode having anti-nodes substantially along the x and y axes, and wherein the sense circuit is configured to sense rotation rate about the y axis using the sense electrodes aligned with the x axis and to sense rotation rate about the x axis using the electrodes aligned with the y axis.

19. Apparatus according to claim 18, where in the sense circuit includes:

a first circuit configured to receive signals from the sense electrodes aligned with the y-axis indicative of a first resonant sense mode in the z-direction caused by rotation rate about the x-axis and output a signal indicative of rotation rate about the x-axis based on the signals from the sense electrodes in the z-direction and aligned with the y-axis and a velocity signal indicative of velocity of the resonator along the y-axis; and

a second circuit configured to receive signals from the sense electrodes aligned with the x-axis indicative of a second resonant sense mode in the z-direction caused by rotation rate about the y-axis and output a signal indicative of rotation rate about the y-axis based on the signals from the sense electrodes in the z-direction and aligned with the x-axis and a velocity signal indicative of velocity of the resonator along the x-axis.

20. Apparatus according to claim 15, wherein the gyroscope further comprises a second plurality of sense electrodes disposed substantially in the resonator plane, and wherein the sense circuit is configured to receive signals from the second plurality of sense electrodes indicative of a resonant sense mode in the resonator plane caused by rotation rate about a z-axis normal to the resonator plane and output a signal indicative of rotation rate about the z-axis based on the signals from the second plurality of sense electrodes.

21. Apparatus according to claim 20, wherein the in-plane mode is an elliptical mode having anti-nodes substantially along x and y axes, and wherein the second plurality of sense electrodes are located substantially at the anti-nodes of an elliptical mode having anti-nodes along axes offset substantially 45 degrees from the x and y axes.

22. A method for reducing cross-talk sensitivity in an xy-axis shell-type gyroscope, the method comprising:

operating the gyroscope with a single in-plane flexural or bulk resonance mode; and

sensing two out-of-plane degenerate or non-degenerate resonance modes resulting respectively from rotations about two axes in the plane of the resonator.

23. An xy-axis shell-type gyroscope comprising:

a resonator substantially disposed in a resonator plane;

at least one drive electrode for driving a resonator drive mode; and

at least one sense electrode for sensing a resonator sense mode, wherein one of modes is an in-plane mode and the other is an out-of-plane mode, and wherein the resonator is specially configured to substantially match the resonance frequencies of the modes.