Time domain switched gyroscope

• US 8,650,955 B2
• Filed: 01/18/2012
• Issued: 02/18/2014
• Est. Priority Date: 01/18/2012
• 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 the navy
• Inventors: Swanson, Paul D., Waters, Richard L.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US13/353,205
• Publication Number:
  US 20130180333A1
• Time in Patent Office: 762 Days
• Field of Search: 735/041.2, 735/040.2
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5762 the sensing mass being connected to a driving mass, e.g. driving frames

Abstract

A gyroscope comprising: a support structure; a drive mass springedly coupled to the support structure such that movement of the drive mass with respect to the support structure is substantially restricted to movement in a first direction; a driver configured to cause the drive mass to oscillate with respect to the support structure in the first direction; a sense mass springedly coupled to the drive mass such that movement of the sense mass with respect to the drive mass is substantially restricted to movement in a second direction, which is orthogonal to the first direction; and a digital trigger comprising a proximity switch coupled between the drive mass and the sense mass, wherein the switch is configured to switch from an open state to a closed state each time the sense mass is in a reference position with respect to the drive mass.

Claims

1. A gyroscope comprising:

a rigid support structure;

a drive mass springedly coupled to the support structure such that movement of the drive mass with respect to the support structure is substantially restricted to movement in a first direction;

a drive mass driver configured to cause the drive mass to oscillate with respect to the support structure in the first direction;

a first sense mass springedly coupled to the drive mass such that movement of the first sense mass with respect to the drive mass is substantially restricted to movement in a second direction, wherein the second direction is orthogonal to the first direction; and

a first digital trigger comprising a first proximity switch coupled between the drive mass and the first sense mass, wherein the first switch is configured to switch from an open state to a closed state each time the first sense mass is in a first reference position with respect to the drive mass.

2. The gyroscope of claim 1, wherein the first switch is further configured to switch from an open state to a closed state each time the first sense mass is in a second reference position with respect to the drive mass.

3. The gyroscope of claim 1 further comprising:

a second sense mass springedly coupled to the drive mass such that movement of the second sense mass with respect to the drive mass is substantially restricted to movement in a third direction, wherein the third direction is orthogonal to the first and second directions; and

a second digital trigger comprising a second proximity switch coupled between the drive mass and the second sense mass, wherein the second switch is configured to switch from an open state to a closed state each time the second sense mass is in a third reference position with respect to the drive mass.

4. The gyroscope of claim 3, further comprising a third digital trigger comprising a third proximity switch coupled between the drive mass and the support structure, wherein the third switch is configured to switch from an open state to a closed state each time the drive mass is in a fourth reference position with respect to the support structure.

5. The gyroscope of claim 4, wherein for each respective oscillation period, each of the first, second, and third proximity switches is configured to switch from an open state to a closed state at least twice corresponding to at least two relative positions between the two elements to which each respective switch is attached.

6. The gyroscope of claim 5, wherein the first switch comprises:

first and second electron tunneling tips mounted on the drive mass, wherein the first and second tips are aligned with each other in the second direction and separated from each other in the second direction by a distance d₁;

third and forth electron tunneling tips mounted to the first sense mass, wherein the third and fourth tips are aligned with each other in the second direction and separated from each other in the second direction by the distance d₁; and

wherein the first, second, third, and fourth tips are positioned with respect to each other such that when the first sense mass is in the first reference position, a current pulse passes from the first and second tips over a gap to the third and fourth tips respectively, and such that when the first sense mass is displaced from the first reference position in the second direction by the distance +d₁ a current pulse passes from the second tip to the third tip, and such that when the first sense mass is displaced from the first reference position in the second direction by the distance −

d₁ a current pulse passes from the first tip to the fourth tip.

7. The gyroscope of claim 6, wherein the second switch comprises:

fifth and sixth electron tunneling tips mounted on the drive mass, wherein the fifth and sixth tips are aligned with each other in the third direction and separated from each other in the third direction by a distance d₂;

seventh and eighth electron tunneling tips mounted to the second sense mass, wherein the seventh and eighth tips are aligned with each other in the third direction and separated from each other in the third direction by the distance d₂; and

wherein the fifth, sixth, seventh, and eighth tips are positioned with respect to each other such that when the second sense mass is in the third reference position, a current pulse passes from the fifth and sixth tips over a gap to the seventh and eighth tips respectively, and such that when the second sense mass is displaced from the third reference position in the third direction by the distance +d₂ a current pulse passes from the sixth tip to the seventh tip, and such that when the second sense mass is displaced from the third reference position in the third direction by the distance −

d₂ a current pulse passes from the fifth tip to the eighth tip.

8. The gyroscope of claim 7, wherein the third switch comprises:

ninth and tenth electron tunneling tips mounted on the support structure, wherein the ninth and tenth tips are aligned with each other in the first direction and separated from each other in the first direction by a distance d₃;

eleventh and twelfth electron tunneling tips mounted to the drive mass, wherein the eleventh and twelfth tips are aligned with each other in the first direction and separated from each other in the first direction by the distance d₃; and

wherein the ninth, tenth, eleventh, and twelfth tips are positioned with respect to each other such that when the drive mass is in the fourth reference position with respect to the support structure, a current pulse passes from the ninth and tenth tips over a gap to the eleventh and twelfth tips respectively, and such that when the drive mass is displaced from the fourth reference position in the first direction by the distance +d₃ a current pulse passes from the tenth tip to the eleventh tip, and such that when the drive mass is displaced from the fourth reference position in the first direction by the distance −

d₃ a current pulse passes from the ninth tip to the twelfth tip.

9. The gyroscope of claim 8 wherein the gyroscope is monolithically integrated.

10. The gyroscope of claim 9, wherein the support structure, the drive mass, the first sense mass, and the second sense mass are vacuum-sealed between top and bottom cap wafers.

11. The gyroscope of claim 10, wherein the drive mass driver comprises capacitive comb drives.

12. The gyroscope of claim 1, further comprising a first sense mass driver configured to drive the first sense mass to oscillate in the second direction at the resonant frequency of the first sense mass, and wherein the resonant frequency of the first sense mass is substantially larger than a drive frequency of the drive mass.

13. The gyroscope of claim 1, wherein the resonant frequency of the first sense mass is approximately equal to a drive frequency of the drive mass.

14. A monolithic gyroscope comprising:

a rigid support structure;

a drive mass springedly coupled to the support structure;

a drive mass driver configured to drive the drive mass to oscillate with respect to the support structure in approximately only an x-direction;

a first sense mass springedly coupled to the drive mass, wherein the first sense mass is configured to move with respect to the drive mass in approximately only a z-direction, which is orthogonal to the x-direction, in response to Coriolis forces from rotation of the support structure about a y-axis, which is orthogonal to both the z- and x-directions; and

a first digital trigger comprising a first proximity switch coupled between the drive mass and the first sense mass configured to pass from an open state to a closed state when the first sense mass passes through a first reference position such that rotation of the support structure about the y-axis may be determined by monitoring the state of the first proximity switch with respect to time.

15. The gyroscope of claim 14, further comprising:

a second sense mass springedly coupled to the drive mass, wherein the second sense mass is configured to move with respect to the drive mass in approximately only the y-direction in response to Coriolis forces from rotation of the support structure about the z-axis; and

a second digital trigger comprising a second proximity switch coupled between the drive mass and the second sense mass and configured to pass from an open state to a closed state when the second sense mass passes through a reference position with respect to the drive mass such that rotation of the support structure about the z-axis may be determined by monitoring the state of the second proximity switch.

16. The gyroscope of claim 15, further comprising a third digital trigger comprising a third proximity switch coupled between the drive mass and the support structure and configured to pass from an open state to a closed state when the drive mass passes through a third reference position such that acceleration of the support structure in the x-direction may be determined by monitoring the state of the third proximity switch.

17. The gyroscope of claim 16, wherein each of the first, second, and third switches comprises four electron tunneling electrode tips configured with respect to each other such that the first, second, and third switches pass through closed states when the drive mass, the first sense mass, and the second sense mass respectively are displaced from their respective reference positions by a distance of ±

d₁, ±

d₂, and ±

d₃ respectively in their respective directions of oscillation.

18. The gyroscope of claim 17, further comprising a first sense mass driver configured to drive the first sense mass to oscillate in the z-direction at the resonant frequency of the first sense mass, wherein the resonant frequency of the first sense mass is substantially larger than a drive frequency of the drive mass.

19. The gyroscope of claim 17, wherein the resonant frequency of the first sense mass is approximately equal to a drive frequency of the drive mass.

20. The gyroscope of claim 17, wherein the support structure, the drive mass, the drive mass driver, the first sense mass, and the second sense mass are vacuum-sealed between top and bottom cap wafers.