Pulse width modulation drive signal for a MEMS gyroscope

• US 20030200803A1
• Filed: 04/30/2002
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Platt, William P.
• Granted Patent: US 6,718,823 B2
• Time in Patent Office: Days
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A MEMS gyroscope may be coupled to drive electronics that provide a pulse width modulation drive signal to the MEMS gyroscope. The pulse width modulation drive signal may be generated by comparing a pickoff signal and/or input signal to a direct current threshold level.

Claims

1. A system for measuring a rate of rotation of a microelectromechanical system (MEMS) gyroscope comprising in combination:

the MEMS gyroscope for measuring a rate of rotation; and

drive electronics coupled to the MEMS gyroscope,

wherein the drive electronics provide a pulse width modulation drive signal to the MEMS gyroscope.

2. The system of claim 1, wherein the MEMS gyroscope further comprises a proof mass operable to oscillate along a drive axis in response to the pulse width modulation drive signal.

3. The system of claim 2, wherein the pulse width modulation drive signal changes the voltage between proof mass electrodes and drive comb electrodes of the MEMS gyroscope.

4. The system of claim 2, wherein a Coriolis acceleration is generated in response to an oscillation of the proof mass and a rotation of the MEMS gyroscope, and wherein the Coriolis acceleration is utilized for measuring the rate of rotation of the MEMS gyroscope.

5. The system of claim 4, wherein the Coriolis acceleration is measured through a change in capacitance between the proof mass and a sense plate.

6. The system of claim 1, wherein the pulse width modulation drive signal is generated from a pickoff signal provided from a motor pickoff comb of the MEMS gyroscope.

7. The system of claim 6, wherein the pickoff signal is demodulated and filtered to create a direct current threshold level.

8. The system of claim 7, wherein the drive electronics further comprises an input signal generator that creates an input signal, and wherein the pulse width modulation drive signal is generated by comparing the direct current threshold level to the input signal.

9. The system of claim 8, wherein a level of the pulse width modulation drive signal changes when the input signal crosses the direct current threshold level.

10. The system of claim 8, wherein the input signal is a periodic waveform.

11. The system of claim 1, wherein the MEMS gyroscope is a tuning fork gyroscope.

12. A method for measuring the rate of rotation of a MEMS gyroscope comprising in combination:

creating a pulse width modulation signal for use in the MEMS gyroscope;

driving a proof mass at a drive velocity with the pulse width modulation drive signal;

rotating the MEMS gyroscope;

measuring a change in capacitance between the proof mass and a sense plate;

calculating a Coriolis acceleration from the change in capacitance between the proof mass and the sense plate; and

calculating a rate of rotation of the MEMS gyroscope from the Coriolis acceleration and the drive velocity.

13. The method of claim 12 further comprising creating a plurality of pulse width modulation drive signals having different phases.

14. The method of claim 12 further comprising obtaining a pickoff signal from the MEMS gyroscope and creating a direct current threshold level based on the pickoff signal.

15. The method of claim 14 further comprising amplifying at least one of the pickoff signal and the pulse width modulation drive signal.

16. The method of claim 14 further comprising comparing an input signal to the direct current threshold level and changing a level of the pulse width modulation signal when the input signal crosses the direct current threshold level.

17. The method of claim 14 further comprising comparing the pickoff signal to the direct current threshold level and changing a level of the pulse width modulation signal when the pickoff signal crosses the direct current threshold level.

18. A system for measuring a rate of rotation of a MEMS gyroscope comprising in combination:

the MEMS gyroscope including a motor pickoff comb that is operable to provide a pickoff signal, and wherein the pickoff signal is utilized for determining a direct current threshold level;

an input signal unit for generating an input signal; and

a pulse width modulation drive signal unit for generating a pulse width modulation drive signal based on the input signal and the direct current threshold level,

wherein the pulse width modulation drive signal is sent to the MEMS gyroscope.

19. The system of claim 18 further comprising a pickoff processing unit operable to amplify, filter, and demodulate the pickoff signal, wherein the pickoff processing unit creates the direct current threshold level.

20. The system of claim 18, wherein the MEMS gyroscope further comprises a motor drive comb, and the pulse width modulation drive signal is sent to the motor drive comb.