Quality factor compensation in microelectromechanical system (MEMS) gyroscopes

• US 10,578,435 B2
• Filed: 01/12/2018
• Issued: 03/03/2020
• Est. Priority Date: 01/12/2018
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Lin, James, Kapusta, Jr., Ronald A., Gao, Lijun
• Primary Examiner(s): Williams, Jamel E
• Application Number:
  US15/869,163
• Publication Number:
  US 20190219394A1
• Time in Patent Office: 781 Days
• Field of Search: 7351438
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5726 Signal processing

Abstract

Circuits and methods for compensating microelectromechanical system (MEMS) gyroscopes for quality factor variations are described. Quality factor variations arise when mechanical losses are introduced in the gyroscope'"'"'s resonator, for example due to thermoelastic damping or squeeze-film damping, which may hinder the gyroscope'"'"'s ability to accurately sense angular velocity. Quality factor compensation may be performed by generating a compensation signal having a time decay rate that depends on the quality factor of resonator. In this way, artifacts that may otherwise arise in gyroscope'"'"'s output are limited. Additionally, or alternatively, quality factor compensation may be performed by controlling the force with which the gyroscope'"'"'s resonator is driven. This may be achieved, for example, by controlling the average value of the drive signal.

Claims

1. A method comprising:

receiving, from a resonator of a microelectromechanical system (MEMS) gyroscope, a resonator signal generated in response to motion of the resonator;

determining a quality factor of the resonator using the resonator signal;

generating a compensation signal having at least one time characteristic determined using the quality factor of the resonator;

receiving, from a sensor of the MEMS gyroscope, a sense signal generated in response to angular motion of the MEMS gyroscope; and

generating a compensated sense signal using the sense signal and the compensation signal.

2. The method of claim 1, wherein generating a compensation signal having at least one time characteristic determined using the quality factor of the resonator comprises generating a compensation signal having a time decay rate determined using the quality factor of the resonator.

3. The method of claim 1, further comprising:

detecting a resonant frequency of the resonator using the resonator signal; and

driving the resonator with a drive signal determined using the resonant frequency and the quality factor.

4. The method of claim 3, wherein driving the resonator with a drive signal determined using the resonant frequency and the quality factor comprises varying an average of the drive signal based on the quality factor.

5. The method of claim 3, wherein driving the resonator with a drive signal determined using the resonant frequency and the quality factor comprises varying a pulse density of the drive signal based on the quality factor.

6. The method of claim 1, wherein generating a compensated sense signal using the sense signal and the compensation signal comprises generating a compensated sense signal by multiplying the sense signal with the compensation signal.

7. The method of claim 1, further comprising maintaining the compensation signal substantially constant during a predefined time period.

8. The method of claim 7, further comprising setting a duration of the predefined time period based on the quality factor.

9. A microelectromechanical systems (MEMS) apparatus comprising:

a gyroscope comprising a sensor and a resonator; and

control circuitry configured to;

receive, from the resonator, a resonator signal generated in response to motion of the resonator;

determine a quality factor of the resonator using the resonator signal;

generate a compensation signal having a time characteristic determined using the quality factor of the resonator;

receive, from the sensor, a sense signal generated in response to angular motion of the MEMS gyroscope; and

generate a compensated sense signal using the sense signal and the compensation signal.

10. The MEMS apparatus of claim 9, wherein the control circuitry is configured to generate a compensation signal having a time characteristic determined using the quality factor of the resonator at least in part by generating a compensation signal having a time decay rate determined using the quality factor of the resonator.

11. The MEMS apparatus of claim 9, wherein the control circuitry is further configured to:

detect a resonant frequency of the resonator based on the resonator signal; and

drive the resonator with a drive signal determined using the resonant frequency and the quality factor.

12. The MEMS apparatus of claim 11, wherein the control circuitry is configured to drive the resonator with a drive signal determined using the resonant frequency and the quality factor at least in part by varying an average of the drive signal based on the quality factor.

13. The MEMS apparatus of claim 11, wherein the control circuitry is configured to drive the resonator with a drive signal determined using the resonant frequency and the quality factor at least in part by varying a pulse density of the drive signal based on the quality factor.

14. The MEMS apparatus of claim 9, wherein the control circuitry is configured to generate a compensated sense signal using the sense signal and the compensation signal at least in part by generating a compensated sense signal by multiplying the sense signal with the compensation signal.

15. The MEMS apparatus of claim 9, wherein the control circuitry is further configured to maintain the compensation signal substantially constant during a predefined time period.

16. A microelectromechanical systems (MEMS) apparatus comprising:

a gyroscope comprising a sensor and a resonator;

a quality factor measuring circuit coupled to a motion detection electrode of the resonator;

a compensation circuit having an input terminal coupled to the quality factor measuring circuit and an output terminal, the compensation circuit comprising transient compensation circuitry; and

signal combination circuitry coupled to the sensor and the output terminal of the transient compensation circuitry.

17. The MEMS apparatus of claim 16, wherein the transient compensation circuitry comprises a filter.

18. The MEMS apparatus of claim 16, further comprising a pulse density modulator coupled to the transient compensation circuitry and the resonator.

19. The MEMS apparatus of claim 16, wherein the compensation circuit comprises a quality factor blanking circuit.

20. The MEMS apparatus of claim 16, wherein the sensor comprises a first mass and the resonator comprises a second mass elastically coupled to the first mass.