Rotation sensor

• US 5,284,059 A
• Filed: 06/02/1993
• Issued: 02/08/1994
• Est. Priority Date: 08/29/1991
• Status: Expired due to Fees

• Current Assignee: BEI Mems, Inc.
• Original Assignee: BEI Medical Systems Co., Inc. (Boston Scientific Corporation)
• Inventors: Wan, Lawrence A.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/071,866
• Time in Patent Office: 251 Days
• Field of Search: 73/505, 73/510, 73/DIG. 1
• US Class Current: 73/504.15
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure

Abstract

A silicon chip is micromachined so that a plurality of tines extend radially and coplanarly from an outer peripheral surface of a circular base. First and second mounting members extend from the base for mounting the base to a support. The first mounting member is disposed generally perpendicularly to the second mounting member. A pulse generator applies electrostatic or electromagnetic pulses to successive free ends of the plurality of tines so that each tine momentarily vibrates in the plane in rotational sequence along the circumference of the base. The successive vibrations establish a net angular momentum approximating a spinning wheel so that rotation of the sensor about the axis of one of the first or second mounting members causes the other mounting member to experience a deformation due to coriolus force. A plurality of strain gages interconnected to form wheatstone bridges are disposed on the first and second mounting members for respectively sensing deformation of the first and second mounting members in a push-pull manner. The output signals from the strain gages provide an indication of the amount of angular motion. A linear accelerometer may be combined on the same silicon chip, and three such chips may be combined to create an inertial measurement unit that senses rotation and linear acceleration relative to three axes.

Claims

1. A tine structure for a rotation sensor comprising:

a base having an outer peripheral surface;

a plurality of tines extending radially outwardly from the peripheral surface of the base so that free ends of the plurality of tines define a circle; and

mounting means for mounting the base to the support so that the plurality of tines are disposed between the base and the support, the mounting means comprising;

a first mounting member extending radially from the base, the first mounting member having a first end mounted to the base and a second end mounted to the support;

a second mounting member extending radially from the base, the second mounting member having a first end mounted to the base and a second end mounted to the support;

wherein the first mounting member and the second mounting member extend from opposite sides of the base along a first axis;

a third mounting member extending radially from the base, the third mounting member having a first end mounted to the base and a second end mounted to the support;

a fourth mounting member extending radially from the base, the fourth mounting member having a first end mounted to the base and a second end mounted to the support;

wherein the third mounting member and the fourth mounting member extend from opposite sides of the base along a second axis;

wherein the first axis is orthogonal to the second axis.

2. A tine structure for a rotation sensor comprising:

a base;

a plurality of tines extending radially from the base; and

drive means for causing each tine to vibrate in rotational sequence about the base so that the plurality of tines establish a net angular momentum which approximates a spinning wheel.

3. The tine structure according to claim 2 wherein the base and the plurality of tines are formed from a silicon wafer.

4. The tine structure according to claim 2 wherein free ends of the plurality of tines define a circle.

5. A rotation sensor comprising:

a plurality of radially extending tines;

drive means for causing each tine to vibrate in rotational sequence so that the plurality of tines establish a net angular momentum which approximates a spinning wheel;

mounting means for mounting the plurality of tines to a support, so that rotation of the structure about a selected axis causes the mounting means to deform; and

deformation sensing means, disposed on the mounting means, for sensing deformation of the mounting means.

6. The rotation sensor according to claim 5 wherein the plurality of tines are generally coplanar.

7. The rotation sensor according to claim 6 wherein the drive means comprises pulse means for providing pulses to free ends of the plurality of tines so that each tine vibrates momentarily in sequence in the plane.

8. The rotation sensor according to claim 6 wherein free ends of the plurality of tines define a circle.

9. The rotation sensor according to claim 8 further comprising a base, and wherein the plurality of tines extend from the base.

10. The rotation sensor according to claim 9 wherein the base has a generally circular outer peripheral surface, and wherein the plurality of tines extend from the outer peripheral surface.

11. The rotation sensor according to claim 10 wherein the plurality of tines are disposed evenly about the base.

12. The rotation sensor according to claim 5 further comprising a base, and wherein the plurality of tines originate from the base.

13. The rotation sensor according to claim 12 wherein the mounting means extends from the base to the support.

14. The rotation sensor according to claim 13 wherein the deformation sensing means comprises a plurality of strain gages disposed on the mounting means and interconnected to form a wheatstone bridge.

15. The rotation sensor according to claim 12 wherein the mounting means comprises:

a first mounting member extending from the base to the support;

a second mounting member extending from the base to the support; and

wherein the second mounting member is disposed generally perpendicularly to the first mounting member.

16. The rotation sensor according to claim 15 wherein the deformation sensing means comprises:

a first plurality of strain gages disposed on the first mounting member and interconnected to form a first wheatstone bridge for sensing deformation of the first mounting member; and

a second plurality of strain gages disposed on the second mounting member and interconnected to form a second wheatstone bridge for sensing deformation of the second mounting member.

17. The rotation sensor according to claim 5 further comprising an ASIC disposed on the support.

18. The rotation sensor according to claim 5 further comprising:

a first silicon cover;

a second silicon cover;

wherein the plurality of tines, the mounting means, and the support are disposed between the first and second silicon covers; and

wherein the first and second silicon covers are bonded together.

19. The rotation sensor according to claim 18 wherein the first and second silicon covers are bonded together through ion infusion for forming a unitary housing for the plurality of tines, the mounting means, and the support.

20. The rotation sensor according to claim 18 further comprising an ASIC disposed on the first silicon cover.

21. A rotation sensor comprising:

a base having an outer peripheral surface;

a plurality of tines extending radially and coplanarly from the outer peripheral surface of the base;

a first mounting member extending from the base for mounting the base to a support;

a second mounting member extending from the base for mounting the base to the support;

wherein the second mounting member is disposed generally perpendicularly to the first mounting member;

pulse means for providing pules to free ends of the plurality of tines so that each tine vibrates momentarily in rotational sequence in the plane for establishing a net angular momentum which approximates a spinning wheel;

wherein rotation of the sensor about one of the first mounting member or second mounting member causes the other mounting member to deform;

a first plurality of strain gages disposed on the first mounting member and interconnected to form a first Wheatstone bridge for sensing deformation of the first mounting member; and

a second plurality of strain gages disposed on the second mounting member and interconnected to form a second Wheatstone bridge for sensing deformation of the second mounting member.

22. The rotation sensor according to claim 21 wherein the plurality of tines are disposed evenly about the base.

23. The rotation sensor according to claim 22 wherein free ends of the plurality of tines define a circle.

24. The rotation sensor according to claim 23 wherein the base, the plurality of tines, the first mounting member, and the second mounting member are each formed of silicon.

25. An inertial measurement unit formed from a silicon wafer comprising:

a plurality of radially extending tines;

drive means for causing each tine to vibrate in rotational sequence so that the plurality of tines establish a net angular momentum which approximates a spinning wheel;

mounting means for mounting the plurality of tines to a support, so that rotation of the structure about a selected axis causes the mounting means to deform;

deformation sensing means, disposed on the mounting means, for sensing deformation of the mounting means; and

a linear accelerometer disposed on the support.

26. The inertial measurement unit according to claim 25 wherein the linear accelerometer comprises a plurality of interconnected strain gages.

27. The inertial measurement unit according to claim 26 wherein the plurality of strain gages are diffused into the support.

28. The inertial measurement unit according to claim 25 further comprising an ASIC disposed on the support.

29. An inertial measurement unit comprising:

first, second and third inertial measurement chips, each chip being formed from a silicon wafer and including;

a plurality of radially extending tines;

drive means for causing each tine to vibrate in rotational sequence so that the plurality of tines establish a net angular momentum which approximates a spinning wheel;

mounting means for mounting the plurality of tines to a support, so that rotation of the structure about a selected axis causes the mounting means to deform;

deformation sensing means, disposed on the mounting means, for sensing deformation of the mounting means; and

a plurality of strain gages disposed on the support and interconnected to from a linear accelerometer;

wherein the first, second, and third inertial measurement chips are mounted generally perpendicularly to each other.