Micromachined gyroscope

• US 6,877,374 B2
• Filed: 02/06/2003
• Issued: 04/12/2005
• Est. Priority Date: 02/06/2002
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Geen, John A.
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US10/360,987
• Publication Number:
  US 20030172753A1
• Time in Patent Office: 796 Days
• Field of Search: 735/040.1, 735/040.2, 735/040.4, 735/041.2, 735/041.4, 735/041.6, 735/143.2, 735/141.6, 735/142.9, 735/143.6
• US Class Current: 73/504.14
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: Y10T 74/12 Gyroscopes

Abstract

A micromachined gyroscope makes use of Coriolis acceleration to detect and measure rotation rate about a plane normal to the surface of a substrate. Specifically, various resonating structures are suspended within a frame. The resonating structures include phase and anti-phase masses that are mechanically coupled in order to produce a single resonance frequency for the entire resonating system. Rotation of the micromachined gyroscope about the plane produces a rotational force on the frame. The frame is suspended in such a way that its motion is severely restricted in all but the rotational direction. Sensors on all sides of the frame detect the rotational deflection of the frame for measuring the change in direction.

Claims

1. Apparatus for detecting rotation about an axis, the apparatus comprising:

a substrate;

a frame suspended above and substantially parallel to the substrate by a first plurality of suspension flexures disposed along an outer perimeter of the frame, the first plurality of suspension flexures affixed to the substrate and formed so as to substantially prevent translational movement of the frame relative to the substrate within a plane of the frame and to permit rotational movement of the frame about an axis perpendicular to the frame and the substrate; and

a plurality of resonator structures disposed within an inner perimeter of the frame, the resonator structures operating substantially within the plane of the frame.

2. Apparatus according to claim 1, wherein the plurality of resonator structures is suspended solely from the inner perimeter of the frame.

3. Apparatus according to claim 1, wherein the resonator structures include a plurality of vibratory masses mechanically coupled through a plurality of levers, pivots, and flexures so as to produce substantially a single resonance frequency for the plurality of vibratory masses.

4. Apparatus according to claim 3, wherein the plurality of vibratory masses includes:

a first pair of masses mechanically coupled through a flexure; and

a second pair of masses mechanically coupled through a flexure, wherein the first pair of masses and the second pair of masses resonate in anti-phase to one another.

5. Apparatus according to claim 3, wherein each of the levers includes a plurality of lever fingers interdigitated with corresponding fingers affixed to the substrate for at least one of driving the lever and sensing position of the lever.

6. Apparatus according to claim 5, wherein each of the levers moves with an arcuate motion, and wherein the lever fingers are disposed at varying angles so as to maintain substantially equal distances from said corresponding fixed fingers during movement of the levers.

7. Apparatus according to claim 1, further comprising:

a plurality of frame fingers disposed along the outer perimeter of the frame, the frame fingers interdigitated with corresponding sensing fingers affixed to the substrate for sensing said rotational movement of the frame.

8. Apparatus according to claim 7, wherein the frame fingers are disposed at varying angles so as to maintain substantially equal distances from said corresponding sensing fingers during rotational movement of the frame.

9. Apparatus according to claim 4, wherein each mass includes a plurality of drive fingers interdigitated with a corresponding array of fixed drive fingers affixed to the substrate.

10. Apparatus according to claim 9, wherein each array of fixed drive fingers is affixed to the substrate using a plurality of anchors, and wherein the anchors for pairs of anti-phase arrays of fixed drive fingers are arranged to be co-linear in a lateral direction relative to the motion of the mass.

11. Apparatus according to claim 1, wherein the outer perimeter of the frame is substantially square.

12. Apparatus according to claim 11, wherein each of the first plurality of suspension flexures is positioned diagonally at a corner of the frame.

13. Apparatus according to claim 11, wherein each of the first plurality of suspension flexures is positioned substantially at a center point of a side of the frame.

14. Apparatus according to claim 11, further comprising:

a plurality of frame fingers disposed along each side of the frame, the frame fingers interdigitated with corresponding sensing fingers affixed to the substrate for sensing said rotational movement of the frame.

15. Apparatus according to claim 1, wherein the rotational movement of the frame is induced by Coriolis acceleration when the resonator structures are resonating and the apparatus is rotated about the axis.

16. Apparatus according to claim 1, further comprising:

means for causing the resonator structures to resonate.

17. Apparatus according to claim 1, further comprising:

means for substantially inhibiting net rotational motion of the plurality of resonator structures.

18. Apparatus according to claim 4, further comprising:

means for selectively applying lateral forces to the masses for quadrature suppression.

19. Apparatus according to claim 1, wherein the frame, suspension flexures, resonator structures, and frame fingers are micromachined from a single wafer.

20. Apparatus according to claim 1, further comprising:

means for sensing rotation of the frame about the axis.