MEMS DEVICE WITH IMPROVED SPRING SYSTEM

• US 20120125101A1
• Filed: 01/30/2012
• Published: 05/24/2012
• Est. Priority Date: 09/11/2009
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: SEEGER, Joseph, ANAC, Ozan
• Granted Patent: US 9,097,524 B2
• Time in Patent Office: Days
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5733 Structural details or topology
• CPC Class Codes: G01C 19/5755 the devices having a single sensing mass

Abstract

A system and method in accordance with an embodiment reduces the cross-axis sensitivity of a gyroscope. This is achieved by building a gyroscope using a mechanical transducer that comprises a spring system that is less sensitive to fabrication imperfection and optimized to minimize the response to the rotations other than the intended input rotation axis. The longitudinal axes of the first and second flexible elements are parallel to each other and parallel to the first direction

Claims

1. A MEMS device comprising:

a proof mass; and

a spring system compliant in a first direction of motion, coupled to the proof mass, the spring system comprising a first flexible element;

a rigid element coupled to the first flexible element; and

a second flexible element coupled to the rigid element, wherein the first flexible element and the second flexible element each have a longitudinal axis parallel to the first direction of motion;

the proof-mass and spring system are disposed in a plane;

wherein the proof-mass moves in the first direction of motion in the plane in response to a force.

2. The MEMS device of claim 1 further comprising a transducer capable of detecting motion of the proof mass in response to the force.

3. The MEMS device of claim 2 wherein the transducer comprises capacitive sensors.

4. The MEMS device of claim 1 wherein the first flexible element and the second flexible element each has a midpoint aligned along an axis perpendicular to the first direction of motion.

5. The MEMS device of claim 1 wherein the first flexible element and the second flexible element are both coupled to the rigid element on a first side of the rigid element.

6. The MEMS device of claim 1 wherein the first flexible element is coupled to the rigid element on a first side of the rigid element and the second flexible element is coupled to the rigid element on an opposite side of the rigid element.

7. The MEMS device of claim 1 wherein the force is in response to gravity

8. The MEMS device of claim 1 wherein the force is in response to acceleration of the MEMS device.

9. The MEMS device of claim 1 wherein the force is in response to a magnetic field.

10. The MEMS device of claim 1 wherein the force is a Coriolis force in response to angular velocity.

11. The MEMS device of claim 1 wherein the force is an electrostatic force.

12. A gyroscope that detects angular velocity comprising:

a structure including a proof mass wherein the proof-mass oscillates in a driving direction, wherein a Coriolis force acts on the proof-mass in a sensing direction that is orthogonal to the driving direction when the gyroscope is rotated with an angular velocity about an input axis orthogonal to the driving and sensing directions;

a spring system compliant in a first direction of motion, coupled to the structure, the spring system comprising a first flexible element;

a rigid element coupled to the first flexible element; and

a second flexible element coupled to the rigid element, wherein the first flexible element and the second flexible element, each has a longitudinal axis parallel to the first direction of motion, wherein the structure and spring system are disposed substantially in a plane; and

a transducer responsive to the Coriolis force acting on the proof mass.

13. The gyroscope of claim 12 wherein the transducer comprises capacitive sensors.

14. The gyroscope of claim 12 wherein the spring system deflects when the proof mass oscillates.

15. The gyroscope of claim 12 wherein the first flexible element and the second flexible element each has a midpoint aligned along an axis perpendicular to the first direction of motion.

16. The gyroscope of claim 12 wherein the first flexible element and the second flexible element are both coupled to the rigid element on a first side of the rigid element.

17. The gyroscope of claim 12 wherein the first flexible element is coupled to the rigid element on a first side of the rigid element and the second flexible element is coupled to the rigid element on an opposite side of the rigid element.

18. The gyroscope of claim 12 wherein the second flexible element is anchored.

19. The gyroscope of claim 12 further comprising a third flexible element, wherein the first flexible element, the second flexible element, and the third flexible element are coupled to the rigid element.

20. The gyroscope of claim 19 further comprising a second structure including a second proof mass;

the first flexible element is coupled to the first structure and the third flexible element is coupled to the second structure, wherein the first and second proof masses move in opposite directions, wherein the spring systems deflects when the first and second proof masses oscillate.

21. The gyroscope of claim 14 wherein the driving direction is parallel to the first direction of motion.

22. The gyroscope of claim 12 wherein the spring system is coupled to the proof-mass;

wherein the Coriolis force acts on the proof-mass in the sensing direction parallel to the first direction of motion; and

the proof-mass moves and the spring system deflects in response to angular velocity about the input axis.

23. The gyroscope of claim 12 wherein the oscillating proof mass responds to an angular velocity about the input axis normal to the plane of the gyroscope.

24. The gyroscope of the claim 12 wherein the oscillating proof mass responds to an angular velocity about the input axis in the plane of the gyroscope.

25. The gyroscope of claim 12 wherein the oscillating proof mass oscillates at a frequency greater than 20 kHz.