Methods and apparatus for a MEMS gyro sensor

• US 20080078246A1
• Filed: 09/29/2006
• Published: 04/03/2008
• Est. Priority Date: 09/29/2006
• Status: Active Grant

• Current Assignee: North Star Innovations Inc. (Wi-LAN Inc.)
• Original Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Inventors: Li, Gary G.
• Granted Patent: US 7,434,464 B2
• Time in Patent Office: Days
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A gyro sensor configured to sense an angular rate about a rotational axis includes a drive mass configured to undergo oscillatory linear motion within a plane, and a sense mass configured to undergo an oscillatory motion out of the plane as a function of the angular rate. A link spring component connects the sense mass to the drive mass such that the sense mass is substantially decoupled from the drive mass with respect to the oscillatory linear motion of the drive mass, but is coupled to the drive mass with respect to the oscillatory motion out of the plane of the sense mass.

Claims

1. A gyro sensor configured to sense an angular rate about a rotational axis, the gyro sensor comprising:

a drive mass configured to undergo oscillatory linear motion within a plane;

a sense mass configured to undergo an oscillatory motion out of the plane as a function of the angular rate; and

a link spring component connecting the sense mass to the drive mass such that the sense mass is substantially decoupled from the drive mass with respect to the oscillatory linear motion of the drive mass, but is substantially coupled to the drive mass with respect to the oscillatory motion out of the plane of the sense mass.

2. The gyro sensor of claim 1, wherein the rotational axis is designated as an x-axis, and the drive mass undergoes the oscillatory linear motion substantially parallel to a y-axis perpendicular to the x-axis.

3. The gyro sensor of claim 2, wherein the oscillatory motion out of the plane occurs along a z-axis orthogonal to the x-axis and the y-axis.

4. The gyro sensor of claim 1, further including a coupling structure connected to the drive mass via a drive spring.

5. The gyro sensor of claim 4, wherein the drive spring is configured such that the drive mass exhibits substantially a single oscillation frequency.

6. The gyro sensor of claim 1, further including a drive electrode structure configured to produce, in response to an electrical signal, the oscillatory linear motion of the drive mass within the plane.

7. The gyro sensor of claim 1, further including a sense electrode structure configured to sense the oscillatory motion out of the plane of the sense mass.

8. The gyro sensor of claim 7, wherein the sense electrode structure includes a plurality of interdigitated capacitive pick-ups.

9. The gyro sensor of claim 8, wherein the interdigitated capacitive pick-ups include a first set elongated pick-ups having a first thickness, and a second set of elongated pick-ups having a second thickness, wherein the first thickness and the second thickness are not equal.

11. The method of claim 1, wherein the rotational axis is designated as an x-axis, and the drive mass undergoes the oscillatory linear motion substantially parallel to a y-axis perpendicular to the x-axis.

12. The method of claim 11, wherein the oscillatory motion out of the plane occurs along a z-axis orthogonal to the x-axis and the y-axis.

10. A method for sensing an angular rate about a rotational axis, the method comprising:

providing a drive mass coupled to a sense mass via a link spring component such that the sense mass is substantially decoupled from the drive mass with respect to an oscillatory linear motion of the drive mass within a plane, but is substantially coupled to the drive mass with respect to an oscillatory motion out of the plane;

actuating the drive mass such that it undergoes the oscillatory linear motion within the plane;

sensing the oscillatory motion out of the plane of the sense mass;

determining the angular rate about the rotational axis based on the sensed oscillatory motion out of the plane of the sense mass.

13. The method of claim 10, further including actuating the drive mass via a drive electrode structure configured to produce, in response to an electrical signal, the oscillatory linear motion.

14. The method of claim 10, further including sensing the oscillatory motion out of the plane of the sense mass via a sense electrode structure.

15. The method of claim 14, wherein the oscillatory motion out of the plane is sensed using interdigitated capacitive pick-ups that include a first set elongated pick-ups having a first thickness, and a second set of elongated pick-ups having a second thickness, where the first thickness and the second thickness are not equal.

16. A micro-electro-mechanical system (MEMS) gyro sensor configured to sense an angular rate about a rotational axis, the gyro sensor comprising:

a substantially planar drive mass configured to undergo oscillatory linear motion within a plane;

a substantially planar sense mass configured to undergo an oscillatory motion out of the plane as a function of the angular rate;

a coupling structure substantially joining the drive mass, wherein the coupling structure is connected to the planar drive mass via a coupling spring structure; and

a link spring component connecting the planar sense mass to the planar drive mass such that the planar sense mass is substantially decoupled from the planar drive mass with respect to the planar oscillatory linear motion of the planar drive mass, but is substantially coupled to the planar drive mass with respect to the oscillatory motion out of the plane of the planar sense mass.

17. The MEMS gyro sensor of claim 16, further including a sense electrode structure configured to sense the oscillatory motion out of the plane of the planar sense mass, wherein the sense electrode structure includes a plurality of interdigitated capacitive pickups.

18. The MEMS gyro sensor of claim 17, wherein the interdigitated capacitive pick-ups include a first set elongated pick-ups having a first thickness, and a second set of elongated pick-ups having a second thickness, wherein the first thickness is not equal to the second thickness.

19. The MEMS gyro sensor of claim 16, wherein the sense mass includes a first pair of MEMS structures exhibiting reflectional symmetrically with respect to the rotational axis, and the drive mass includes a second pair of MEMS structure exhibiting reflectional symmetrically with respect to the rotational axis.

20. The MEMS gyro sensor of claim 16, wherein the link spring component comprises a generally “

u”

-shaped MEMS connector having a major axis substantially perpendicular to the oscillatory motion of the drive mass.