Feedback mechanism for rate gyroscopes

• US 6,470,748 B1
• Filed: 10/04/2000
• Issued: 10/29/2002
• Est. Priority Date: 10/13/1999
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Geen, John A.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US09/679,462
• Time in Patent Office: 755 Days
• Field of Search: 735/041.2, 735/041.4, 735/041.5, 735/041.6
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A mechanical rate gyroscope including a micro-fabricated mechanical sensor. The mechanical sensor includes a first segmented drive system used to impart vibration to a mass and a transverse segmented drive system used to cancel a Coriolis force applied to the mass when the mechanical sensor undergoes rotation. The mechanical rate gyroscope further includes a force-feedback control mechanism used to provide at least one cycle of drive signals employed by the first drive system to the transverse drive system. The force-feedback control mechanism generates a feedback signal used to control the polarity of the drive signals provided to the transverse drive system. The feedback signal has a pulse repetition frequency proportional to the applied angular rate. The proportionality constant relating the applied angular rate to the pulse repetition frequency includes transduction coefficients that are less sensitive to the mechanical and electrical properties of the gyroscope.

Claims

1. A mechanical rate gyroscope, comprising:

a mechanical sensor including a base, a mass, a first segmented drive system configured to generate a drive force Fd to cause the mass to vibrate relative to the base, a displacement sensor configured to measure deflection of the mass caused by a Coriolis force generated in response to an applied angular rate, and a transverse segmented drive system configured to generate a feedback force Ff to cancel the Coriolis force; and

control circuitry configured to receive the measure of deflection and provide at least one feedback signal based on the measure of deflection to the transverse drive system for generating the feedback force,

wherein the first drive system includes a first number Nd of segments operatively coupled to the mass and the transverse drive system includes a second number Nf of segments operatively coupled to the mass, the segments of the transverse drive system being substantially similar to and transversely oriented relative to the segments of the first drive system, the segments of the first drive system and the segments of the transverse drive system being arranged to cause fringe fields- associated with the respective drive systems to substantially match, and

wherein Fd/Ff is proportional to Nd/Nf.

2. The mechanical rate gyroscope of claim 1 wherein the first drive system and the transverse drive system are electro-static drive systems.

3. The mechanical rate gyroscope of claim 1 wherein the control circuitry is configured to receive at least one sense signal provided by the displacement sensor and having a magnitude proportional to a magnitude of deflection, and to generate an error signal representative of a time average of a difference between the Coriolis force and the feedback force using the sense signal.

4. The mechanical rate gyroscope of claim 3 wherein the error signal comprises a pulse repetition frequency proportional to the applied angular rate.

5. The mechanical rate gyroscope of claim 1 wherein the at least one feedback signal comprises at least one cycle of a drive signal provided to the first drive system for causing the mass to vibrate relative to the base.

6. The mechanical rate gyroscope of claim 1 wherein the segments of the transverse drive system include at least one inactive segment.

7. A mechanical rate gyroscope, comprising:

a mechanical sensor including a base, a mass, a first segmented drive system configured to cause the mass to vibrate relative to the base, a displacement sensor configured to measure deflection of the mass caused by a Coriolis force generated in response to an applied angular rate, and a transverse segmented drive system configured to generate a feedback force to cancel the Coriolis force; and

control circuitry configured to receive the measure of deflection and provide at least one feedback signal based on the measure of deflection to the transverse drive system for generating the feedback force,

wherein the first drive system includes a plurality of segments operatively coupled to the mass and the transverse drive system includes at least one segment operatively coupled to the mass,

wherein the control circuitry is configured to receive at least one sense signal provided by the displacement sensor and having a magnitude proportional to a magnitude of deflection, and to generate an error signal representative of a time average of a difference between the Coriolis force and the feedback force using the sense signal, and

wherein the error signal comprises a pulse repetition frequency proportional to the applied angular rate.

8. A mechanical rate gyroscope, comprising:

a mechanical sensor including a base, a mass, a first segmented drive system configured to cause the mass to vibrate relative to the base, a displacement sensor configured to measure deflection of the mass caused by a Coriolis force generated in response to an applied angular rate, and a transverse segmented drive system configured to generate a feedback force to cancel the Coriolis force; and

control circuitry configured to receive the measure of deflection and provide at least one feedback signal based on the measure of deflection to the transverse drive system for generating the feedback force,

wherein the first drive system includes a plurality of segments operatively coupled to the mass and the transverse drive system includes at least one segment operatively coupled to the mass,

wherein the at least one feedback signal comprises at least one cycle of a drive signal provided to the first drive system for causing the mass to vibrate relative to the base.

9. A mechanical sensor, comprising:

a base;

a mass;

a suspension system configured to couple the mass to the base;

a first segmented drive system including a first number Nd of segments operatively coupled to the mass, the first drive system being configured to generate a drive force Fd to cause the mass to vibrate relative to the base;

a displacement sensor configured to measure a deflection of the mass caused by a Coriolis force; and

a transverse segmented drive system including a second number Nf of segments operatively coupled to the mass, the segments of the transverse drive system being substantially similar to and transversely oriented relative to the segments of the first drive system, the transverse drive system being configured to generate a feedback force Ff to cancel the deflection of the mass,

wherein the segments of the first drive system and the segments of the transverse drive system are arranged to cause fringe fields associated with the respective drive systems to substantially match, and

wherein Fd/Ff is proportional to Nd/Nf.

10. The mechanical sensor of claim 9 wherein the first drive system includes a plurality of segments operatively coupled to the mass and the transverse drive system includes at least one segment operatively coupled to the mass.

11. The mechanical sensor of claim 9 wherein the base is a substrate and at least the mass is micro-machined on the substrate.

12. The mechanical rate gyroscope of claim 9 wherein the segments of the transverse drive system include at least one inactive segment.

13. A method of operating a mechanical rate gyroscope including a mechanical sensor and control circuitry, the mechanical sensor having a base, a mass, a first drive system, a displacement sensor, and a transverse drive system, the method comprising the steps of:

generating a drive force Fd to cause the mass to vibrate relative to the base by the first drive system, the first drive system having a first number Nd of segments operatively coupled to the mass;

measuring a deflection of the mass caused by a Coriolis force generated in response to an applied angular rate by the displacement sensor;

generating a feedback force Ff to cancel the Coriolis force by the transverse drive system, the transverse drive system having a second number Nf of segments operatively coupled to the mass, the segments of the transverse drive system being substantially similar to and transversely oriented relative to the segments of the first drive system, the segments of the first drive system and the segments of the transverse drive system being arranged to cause fringe fields associated with the respective drive systems to substantially match, and Fd/Ff being proportional to Nd/Nf; and

receiving the measure of deflection and providing at least one feedback signal based on the measure of deflection to the transverse drive system for generating the feedback force Ff by the control circuitry.