Micromachined silicon tuned counterbalanced accelerometer-gyro with quadrature nulling

• US 6,651,500 B2
• Filed: 10/03/2001
• Issued: 11/25/2003
• Est. Priority Date: 10/03/2001
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: Litton Systems Incorporated (Northrop Grumman Corporation)
• Inventors: Stewart, Robert E., Wyse, Stanley F.
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US09/971,345
• Publication Number:
  US 20030061877A1
• Time in Patent Office: 783 Days
• Field of Search: 735/10, 735/11, 735/040.3, 735/040.4, 735/140.1, 735/140.2, 735/141.5, 735/142.9, 735/041.2, 735/040.2
• US Class Current: 73/511
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

An integrated rate and accelerometer sensor includes two counter vibrating tuned accelerometers formed in a single substantially planar silicon body to form the sensing element. The two vibrating accelerometers are interleaved in a manner that places their respective centers of mass in the same line parallel to the direction of the vibration and has the centers of percussion of the two (pendulum) proof masses coincident. A phase insensitive quadrature nulling method is utilized for each of the two vibrating accelerometers. The sensor structure utilizes Pyrex for the top and bottom covers. Metalized electrodes, feedthrus and contact pads are also utilized for the sensing element, instead of interlayer wire bonds.

Claims

1. A combined angular rate and acceleration sensor formed from a substantially planar monolithic body of electrically conductive material having first and second major surfaces, said sensor comprising:

a frame structure having a length and width formed in said body between said first and second major surfaces;

a first dither mass suspended from the frame structure for vibrating motion within the frame structure in a first direction parallel to the first and second major surfaces;

a first proof mass connected to the first dither mass by a flexure joint for motion in a direction perpendicular to the vibrating motion of the first dither mass about an axis parallel to the motion of the first dither mass;

a second dither mass suspended from the frame structure for vibrating motion with the frame structure in a second direction, parallel to the first and second major surfaces, opposed to the first direction of the first dither mass; and

a second proof mass connected to the second dither mass by a flexure joint for motion in a direction perpendicular to the vibrating motion of the second dither mass about an axis parallel to the motion of the second dither mass;

the first and second proof masses being interleaved in a manner that locates the center of percussion of both proof masses at the same point, and the first and second dither masses are shaped and located within the frame structure to place the center of mass for the dither masses on a line parallel to the vibrating motion of both dither masses.

2. The combined sensor of claim 1 wherein said first dither mass comprises an L-shaped member with one leg of the L-shaped member disposed along the length of the frame structure and the other leg of the L-shaped member disposed along the width of the frame structure.

3. The combined sensor of claim 2 wherein said second dither mass comprises an L-shaped member with one leg of the L-shaped member disposed along the length of the frame structure and the other leg of the L-shaped member disposed along the width of the frame structure.

4. The combined sensor of claim 2 further comprising:

a dither coupling spring attached to the frame structure; and

a dither suspension attached to the dither coupling spring and the first dither mass.

5. The combined sensor of claim 4 wherein said dither suspension comprises two spring elements, each spring element connected to the dither coupling spring.

6. The combined sensor of claim 3 further comprising:

a first dither coupling spring attached to the frame structure;

a first dither suspension attached to the first dither coupling spring and the first dither mass;

a second dither coupling spring attached to the frame structure; and

a second dither suspension attached to the second dither coupling spring and the second dither mass.

7. The combined sensor of claim 6 wherein said first dither suspension comprises two spring elements, a first spring element connected to the first dither coupling spring, a second spring element connected to the second dither coupling spring, and both spring elements connected to a leg of the first dither mass.

8. The combined sensor of claim 7 wherein said second dither suspension comprises two spring elements, a first spring element connected to the second dither coupling spring, a second spring element connected to the first dither coupling spring, and both spring elements connected to a leg of the second dither mass.

9. The combined sensor of claim 8 wherein the first spring element of the first dither suspension is connected to the leg of the first dither mass and the second spring element of the first dither suspension is connected to the leg of the second dither mass.

10. The combined sensor of claim 9 wherein the first spring element of the second dither suspension is connected to the leg of the second dither mass, and the second spring element of the second dither suspension is connected to the leg of the first dither mass.

11. The combined sensor of claim 3 wherein the first proof mass is U-shaped and is attached to the first dither mass by a flexure joint.

12. The combined sensor of claim 11 wherein said second proof mass is U-shaped and is attached to the second dither mass by a flexure joint.

13. The combined sensor of claim 12 further comprising:

a dither coupling spring attached to the frame structure; and

a dither suspension attached to the dither coupling spring and the first dither mass.

14. The combined sensor of claim 13 wherein said dither suspension comprises spring elements, each spring element connected to the dither coupling spring.

15. The combined sensor of claim 12 further comprising:

a first dither coupling spring attached to the frame structure;

a first dither suspension attached to the first dither coupling spring and the first dither mass;

a second dither coupling attached to the frame structure; and

a second dither suspension attached to the second dither coupling spring and the second dither mass.

16. The combined sensor of claim 15 wherein said first dither suspension comprises two spring elements, a first spring element connected to the first dither coupling spring, a second spring element connected to the second dither coupling spring, and both spring elements connected to a leg of the first dither mass.

17. The combined sensor of claim 16 wherein said second dither suspension comprises two spring elements, a first spring element connected to the second dither coupling spring, a second spring element connected to the first dither coupling spring, and both spring elements connected to a leg of the second dither mass.

18. The combined sensor of claim 17 wherein the first spring element of the first dither suspension is connected to the leg of the first dither mass and the second spring element of the first dither suspension is connected to the leg of the second dither mass.

19. The combined sensor of claim 18 wherein the first spring element of the second dither suspension is connected to the leg of the second dither mass, and the second spring element of the second dither suspension is connected to the leg of the first dither mass.

20. The combined sensor of claim 19 wherein the first proof mass is attached to the leg of the first dither mass, and the second proof mass is attached to the leg of the second proof mass.

21. The combined sensor of claim 1 further comprising:

a top cover for said sensor, having a top and bottom side, the top cover having electrodes on the bottom side to drive the first and second dither mass, and tuning electrodes to bias the first and second proof mass; and

a bottom cover for said sensor having a top and bottom side, the bottom cover having electrodes on the bottom side to drive the first and second dither mass, and tuning electrodes to bias the first and second proof mass.

22. The combined sensor of claim 21 wherein said top cover further comprises a quadrature error nulling electrode, and said bottom cover further comprises a quadrature error nulling electrode.

23. The combined sensor of claim 21 wherein said top cover further comprises a coriolis forcing electrode, and said bottom cover further comprises a coriolis forcing electrode.

24. The combined sensor of claim 21 wherein the top cover further comprises a plurality of contact pads and feedthru vias on the top side, and the bottom cover further comprises a plurality of contact pads and feedthru vias on the top side.

25. The combined sensor of claim 24 further comprising a first top cover plate overlaying the feedthru vias on the top cover and being sealed thereto, and a second top cover plate overlaying the feedthru vias on the bottom cover and being sealed thereto.

26. The combined sensor of claim 24 further comprising a housing for the sensor, said housing suspending the sensor in a sealed environment by a plurality of compliant mounting pads.

27. The combined sensor of claim 26 wherein the housing further comprises a plurality of feedthru electrical conductors passing through hermetically sealed apertures in walls of the housing.

28. The combined sensor of claim 27 wherein said plurality of feedthru conductors are electrically connected to the plurality of contact pads on the top cover and the bottom cover.

29. The combined sensor of claim 28 wherein the housing further comprises a flange for mounting the housing to a platform.