High sensitivity mechanical gyro with reduced quadrature error

• US 8,689,631 B1
• Filed: 06/23/2011
• Issued: 04/08/2014
• Est. Priority Date: 06/23/2011
• Status: Active Grant

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Waters, Richard L., Tally, Charles
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US13/167,539
• Time in Patent Office: 1,020 Days
• Field of Search: 735/041.2, 735/041.4
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5762 the sensing mass being connected to a driving mass, e.g. driving frames

Abstract

A gyroscope comprising: a multi-layer substrate, comprising drive spring and sense spring layers; a rigid support structure formed from the substrate; a plurality of drive springs formed in each drive spring layer wherein each drive spring is operatively coupled to the support structure; a drive mass formed from at least one layer of the substrate, wherein the drive mass is coupled to the support structure via the drive springs; a drive mass driver operatively coupled to the drive mass and configured to cause movement of the drive mass with respect to the support structure; a plurality of sense springs formed in each sense spring layer, wherein each sense spring is operatively coupled to the drive mass; and a sense mass formed from at least one layer, wherein the sense mass is coupled to the drive mass via the sense springs.

Claims

1. A gyroscope comprising:

a substrate comprising at least three layers stacked on top of one another in a y-direction, wherein each layer is either a drive spring layer or a sense spring layer, and wherein the total thickness of the drive spring layers in the y-direction exceeds the total thickness of the sense spring layers in the y-direction, and the drive spring layers and the sense spring layers are alternatingly and symmetrically disposed within the substrate;

a rigid support structure formed from the substrate;

a plurality of drive springs formed in each drive spring layer and designed to deflect only in an xz-plane that is perpendicular to the y-direction, wherein each drive spring is operatively coupled to the support structure;

a drive mass formed from at least one layer of the substrate, wherein the drive mass is coupled to the support structure via the drive springs such that movement of the drive mass with respect to the support structure is substantially restricted to movement in the xz-plane;

a drive mass driver operatively coupled to the drive mass and configured to cause movement of the drive mass in the xz-plane with respect to the support structure;

a plurality of sense springs formed in each sense spring layer and designed to deflect only in the y-direction, wherein each sense spring is operatively coupled to the drive mass; and

a sense mass formed from at least one layer, wherein the sense mass is coupled to the drive mass via the sense springs such that movement of the sense mass with respect to the drive mass is substantially restricted to movement in the y-direction.

2. The gyroscope of claim 1, wherein the drive mass driver comprises a set of electrostatic comb-drives formed in top and bottom layers of the substrate, wherein the electrostatic comb-drives are configured to cause linear oscillation in the xz-plane of the drive mass with respect to the support structure.

3. The gyroscope of claim 2, wherein each sense spring layer further comprises electrical comb-drive tethers configured to electrically couple each half of each comb drive to the rigid structure.

4. The gyroscope of claim 3, wherein at least one of the layers comprises mechanical hard stop features configured to limit motion of the drive mass with respect to the support structure such that teeth of the comb-drives are prevented from making physical contact with each other.

5. The gyroscope of claim 1, further comprising an isolation film disposed between each layer such that the isolation film electrically and thermally isolates each layer from the other layers.

6. The gyroscope of claim 1, wherein the sense spring layers and the drive spring layer are made of silicon.

7. The gyroscope of claim 1, wherein the substrate comprises three layers including a top layer, a bottom layer, and a middle layer, and wherein the top and bottom layers are drive spring layers and the middle layer is a sense spring layer.

8. The gyroscope of claim 1, wherein the substrate comprises five layers including a sense spring layer as a first layer, a drive spring layer as a second layer, a sense spring layer as a third layer, a drive spring layer as a fourth layer, and a sense spring layer as a fifth layer, wherein the second layer is disposed between the first and third layers and wherein the fourth layer is disposed between the third and fifth layers.

9. The gyroscope of claim 1, further comprising a second gyroscope formed out of the same substrate as the gyroscope of claim 1, wherein the second gyroscope is substantially identical to the gyroscope of claim 1 with the exception that the drive mass of the second gyroscope is configured to oscillate 180-degreees out of phase with the drive mass of the gyroscope of claim 1.

10. The gyroscope of claim 1, further comprising an optical interrogation device configured to optically monitor displacement of the sense mass in the y-direction.

11. The gyroscope of claim 1, wherein the thickness and design of the sense and drive springs are configured to reduce quadrature error such that the quadrature error of the gyroscope is controlled mechanically without using electrical quadrature reduction means.

12. A gyroscope comprising:

a three-layer silicon substrate comprising a top layer, a middle layer, and a bottom layer that is substantially identical to the top layer, wherein the three layers are stacked and bonded to each other in a y-direction with a thermal and electrical isolating film between each layer, wherein the thickness of the middle layer in the y-direction exceeds the combined thickness of the top and bottom layers in the y-direction, and wherein the substrate further comprises;

a rigid support structure formed out of all three substrate layers;

a plurality of drive spring members formed out of the middle layer, wherein a first end of each drive spring member is coupled to the rigid support structure;

a drive mass formed out of all three substrate layers, wherein the drive mass is coupled to a second end of each drive spring member such that movement of the drive mass with respect to the support structure is substantially restricted to movement only in an x-direction;

a drive mass driver formed out of the substrate and operatively coupled to the support structure and the drive mass, wherein the drive mass driver is configured to cause sinusoidal oscillation of the drive mass in the x-direction;

a plurality of sense spring members formed out of the top and bottom layers, wherein a first end of each sense spring member is coupled to the drive mass; and

a sense mass formed out of all three substrate layers and coupled to a second end of each sense spring member such that movement of the sense mass is substantially restricted to movement only in a y-direction.

13. The gyroscope of claim 12, wherein each of the three layers comprises an upper and a lower surface, and wherein the lower surface of the top layer is bonded to the upper surface of the middle layer and the lower surface of the bottom layer is bonded to the lower surface of the middle layer.

14. The gyroscope of claim 13, wherein the drive mass driver comprises a set of electrostatic comb-drives formed in the top and bottom layers.

15. The gyroscope of claim 14, wherein the drive spring members are T-shaped and the sense spring members are L-shaped.

16. The gyroscope of claim 15, wherein the top and bottom layers further comprise an electrical tether configured to electrically connect the rigid support structure to the drive mass.

17. The gyroscope of claim 16, wherein at least one of the layers comprises mechanical hard stop features configured to limit motion in the x-direction and in a z-direction such that teeth of the comb-drives are prevented from making physical contact with each other.

18. The gyroscope of claim 17, wherein the top and bottom layers have a thickness of approximately 30 microns and the middle layer has a thickness of approximately 400 microns.

19. The gyroscope of claim 18, further comprising electrical quadrature reduction means operatively coupled to the drive mass.