System, apparatus, and method for resonator and coriolis axis control in vibratory gyroscopes

• US 9,709,400 B2
• Filed: 04/07/2015
• Issued: 07/18/2017
• Est. Priority Date: 04/07/2015
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Kapusta, Ronald Alan
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US14/680,776
• Publication Number:
  US 20160298965A1
• Time in Patent Office: 833 Days
• Field of Search: 7350412, 7350414, 7350402, 7350404
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

A gyroscope control circuit for a vibratory gyroscope system includes an open-loop RSP control circuit and a closed-loop CSP control circuit. The gyroscope control circuit optionally may include a Q compensation circuit to compensate for variations in gyroscope sensitivity due to variations in resonator signal path Q. The resonator signal path and the Coriolis signal path may have transduction factors that are proportional to each other such that sensitivity of the gyroscope varies directly with resonator signal path quality factor (Q).

Claims

1. Apparatus comprising a gyroscope control circuit for a vibratory gyroscope having a resonator mass and an accelerometer for generating a Coriolis output rate signal, the gyroscope control circuit comprising:

a resonator signal path including an open-loop resonator signal path control circuit configured to drive movement of the resonator mass based on a resonator sense signal without use of amplitude information contained in the resonator sense signal; and

a Coriolis signal path including a closed-loop Coriolis signal path control circuit configured to produce the Coriolis output rate signal based on a Coriolis sense signal and to provide a feedback signal to the accelerometer based on the Coriolis sense signal; and

a quality factor compensation circuit configured to compensate for variations in gyroscope sensitivity based on variations in a resonator signal path quality factor while the gyroscope is operating.

2. The apparatus according to claim 1, wherein the quality factor compensation circuit comprises:

a quality factor measurement circuit configured to measure the resonator signal path quality factor.

3. The apparatus according to claim 2, wherein the quality factor compensation circuit further comprises:

a multiplier that combines the measured resonator signal path quality factor and the Coriolis output rate signal generated by the closed-loop Coriolis signal path control circuit to produce a compensated Coriolis output rate signal.

4. The apparatus according to claim 2, wherein the quality factor compensation circuit further comprises a feedback loop from the quality factor measurement circuit to the open-loop resonator signal path control circuit, wherein the open-loop resonator signal path control circuit is further configured to adjust a resonator drive signal based on the measured resonator signal path quality factor to reduce variations in the resonator signal path quality factor.

5. The apparatus according to claim 2, wherein the quality factor measurement circuit is configured to evaluate performance parameters of the resonator mass in response to different drive forces while the gyroscope is operational.

6. The apparatus according to claim 1, wherein the gyroscope is mode-matched.

7. The apparatus according to claim 1, wherein the resonator signal path and the Coriolis signal path have transduction factors that are proportional to each other such that sensitivity of the gyroscope varies directly with resonator signal path quality factor (Q).

8. The apparatus according to claim 1, further comprising an ASIC wafer, wherein the open-loop resonator signal path control circuit is formed on the ASIC wafer.

9. A gyroscope system comprising:

a gyroscope including a resonator mass and an accelerometer for generating a Coriolis output rate signal; and

a gyroscope control circuit including (a) a resonator signal path including an open-loop resonator signal path control circuit configured to drive movement of the resonator mass based on a resonator sense signal without use of amplitude information contained in the resonator sense signal and (b) a Coriolis signal path including a closed-loop Coriolis signal path control circuit configured to produce the Coriolis output rate signal based on a Coriolis sense signal and to provide a feedback signal to the accelerometer based on the Coriolis sense signal and (c) a quality factor compensation circuit configured to compensate for variations in gyroscope sensitivity based on variations in a resonator signal path quality factor while the gyroscope is operating.

10. The gyroscope system according to claim 9, wherein the quality factor compensation circuit comprises:

a quality factor measurement circuit configured to measure the resonator signal path quality factor.

11. The gyroscope system according to claim 10, wherein the quality factor compensation circuit further comprises:

a multiplier that combines the measured resonator signal path quality factor and the Coriolis output rate signal generated by the closed-loop Coriolis signal path control circuit to produce a compensated Coriolis output rate signal.

12. The gyroscope system according to claim 10, wherein the quality factor compensation circuit further comprises a feedback loop from the quality factor measurement circuit to the open-loop resonator signal path control circuit, wherein the open-loop resonator signal path control circuit is further configured to adjust a resonator drive signal based on the measured resonator signal path quality factor to reduce variations in the resonator signal path quality factor.

13. The gyroscope system according to claim 10, wherein the quality factor measurement circuit is configured to evaluate performance parameters of the resonator mass in response to different drive forces while the gyroscope is operational.

14. The gyroscope system according to claim 9, wherein the gyroscope is mode-matched.

15. The gyroscope system according to claim 9, wherein the resonator signal path and the Coriolis signal path have transduction factors that are proportional to each other such that sensitivity of the gyroscope varies directly with a resonator signal path quality factor (Q).

16. The gyroscope system according to claim 9, wherein the open-loop resonator signal path control circuit is implemented on an ASIC wafer, and wherein the gyroscope is implemented on a separate MEMS wafer bonded to the ASIC wafer.

17. The gyroscope system according to claim 9, wherein the open-loop resonator signal path control circuit and the gyroscope are implemented on a common wafer.

18. A method of operating a vibratory gyroscope having a resonator signal path including a resonator mass and having a Coriolis signal path including an accelerometer for generating a Coriolis output rate signal, the method comprising:

operating the resonator signal path using open-loop control in which movement of the resonator mass is driven based on a resonator sense signal without use of amplitude information contained in the resonator sense signal;

operating the Coriolis signal path using closed-loop control in which the Coriolis output rate signal is based on a Coriolis sense signal and a feedback signal is provided to the accelerometer based on the Coriolis sense signal;

measuring a resonator signal path quality factor (Q); and

compensating for variations in gyroscope sensitivity based on variations in the resonator signal path quality factor while the gyroscope is operating.

19. The method according to claim 18, wherein compensating for variations in gyroscope sensitivity based on variations in the resonator signal path quality factor while the gyroscope is operating comprises:

combining the measured resonator signal path quality factor and the Coriolis output rate signal to produce a compensated Coriolis output rate signal.

20. The method according to claim 18, further comprising:

adjusting a resonator drive signal based on the measured resonator signal path quality factor to reduce variations in the resonator signal path quality factor.

21. The method according to claim 18, further comprising:

evaluating performance parameters of the resonator mass in response to different drive forces while the gyroscope is operational.