Tuning Fork Gyroscope

• US 20070266785A1
• Filed: 05/17/2006
• Published: 11/22/2007
• Est. Priority Date: 05/17/2006
• Status: Active Grant

• Current Assignee: Milli Sensor Systems & Actuators, Inc.
• Original Assignee: Milli Sensor Systems & Actuators, Inc.
• Inventors: Cadarelli, Donato
• Granted Patent: US 7,617,728 B2
• Time in Patent Office: Days
• US Class Current: 73/504.160
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A gyroscope for detecting rotation about a gyro input axis, having a support structure, at least one mass flexibly coupled to the support structure such that it is capable of motion in two directions along a drive axis, the mass offset from the gyro output axis, one or more drives for oscillating the flexibly-coupled masses along the drive axis, one or more mass motion sensors that sense motion of the flexibly-coupled masses along their drive axes, and one or more gyro output sensors that detect rotation of the support structure about the output axis.

Claims

1. A gyroscope for detecting rotation about a gyro input axis, comprising:

a support structure;

at least one mass flexibly coupled to the support structure such that it is capable of motion in two directions along a drive axis, the mass offset from the gyro output axis;

one or more drives for oscillating the flexibly-coupled masses along the drive axis;

one or more mass motion sensors that sense motion of the flexibly-coupled masses along their drive axes; and

one or more gyro output sensors that detect rotation of the support structure about the output axis.

2. The gyroscope of claim 1 in which the flexibly-coupled masses lie in the plane of the instrument, and the gyro output axis is orthogonal to the plane.

3. The gyroscope of claim 1 in which the flexibly-coupled masses are located along a common drive axis and lie in the plane of the instrument, and the gyro output axis is parallel to the plane and orthogonal to the drive axis.

4. The gyroscope of claim 1 in which the drives comprise capacitive drives.

5. The gyroscope of claim 4 in which the drives are comb drives.

6. The gyroscope of claim 1 in which there is one drive on each side of each flexibly-coupled mass.

7. The gyroscope of claim 1 in which the gyro output sensors comprise capacitive sensors.

8. The gyroscope of claim 7 in which the gyro output sensors are comb sensors.

9. The gyroscope of claim 8 in which the comb sensors are radially arranged around the output axis.

10. The gyroscope of claim 7 in which each gyro output sensor comprises a plate located below the mass.

11. The gyroscope of claim 1 in which the drives for oscillating the flexibly-coupled masses comprise actuators.

12. The gyroscope of claim 1 in which the drives for oscillating the masses each comprise two drive members, located on opposite sides of a mass.

13. The gyroscope of claim 12 in which the drive members comprise capacitive comb drives.

14. The gyroscope of claim 1 further comprising a controller, responsive to the mass motion sensors, for controlling the drives such that the masses oscillate at resonance.

15. The gyroscope of claim 1 further comprising a controller, responsive to the mass motion sensors, for maintaining the oscillation amplitude of the masses constant.

16. The gyroscope of claim 1 in which there is at least one pair of flexibly-coupled masses, the masses in each pair moving in opposition along a common drive axis for the pair.

17. The gyroscope of claim 16 in which the drives for oscillating the masses of a pair oscillate those masses at the same frequency in anti-phase.

18. The gyroscope of claim 16 in which there are at least two pairs of flexibly-coupled masses, the masses of each such pair moving in opposition along a common drive axis, in which the drive axes are radial about a center of rotation.

19. The gyroscope of claim 1 in which the gyro output sensors operate differentially to cancel rotary content of the gyroscope output that is due to motion of the masses along their drive axis.

20. The gyroscope of claim 1 further comprising a substrate that supports the support structure.

21. The gyroscope of claim 20 in which the support structure comprises a frame that is movably coupled to the substrate for rotation about the output axis.

22. The gyroscope of claim 21 further comprising flexures between the substrate and the frame to provide for the rotation of the frame about the output axis.

23. The gyroscope of claim 22 in which the flexures are radial relative to the output axis.

24. The gyroscope of claim 22 in which the flexures are aligned with the output axis.

25. The gyroscope of claim 1 in which the support structure encompasses the masses.

26. The gyroscope of claim 25 further comprising flexures that couple the masses to the support structure.

27. The gyroscope of claim 26 in which the flexures that couple the masses to the support structure are located on both ends of each mass.

28. The gyroscope of claim 1 in which the masses are balanced with respect to the gyro output axis.

29. The gyroscope of claim 1 with at least two flexibly-coupled masses, in which all of the flexibly-coupled masses move together towards and away from their center.

30. The gyroscope of claim 1 in which the support structure couples the masses such that they are caused to oscillate at the same frequency.

31. An integrated inertial measurement unit (IMU) comprising at least one gyroscope of claim 1.

32. An inertial measurement unit (IMU) comprising a regular tetrahedron base member, with a gyroscope of claim 1 located on each of three faces of the base member.

33. A gyroscope, comprising:

a substrate;

a frame movably coupled to and supported by the substrate for rotation about an output axis;

at least a pair of masses flexibly coupled to the frame such that they are capable of motion in two directions along a drive axis;

capacitive drives for oscillating the masses at the same frequency in anti-phase along the drive axis;

capacitive mass motion sensors that sense motion of the masses along their drive axes;

a first control loop for holding the oscillation amplitude of the masses constant;

a second control loop for holding the oscillations of the masses at resonance; and

capacitive output sensors for detecting rotation of the frame about an output axis that is orthogonal to the drive axis.