Offset Detection and Compensation for Micromachined Inertial Sensors

• US 20110041609A1
• Filed: 08/21/2009
• Published: 02/24/2011
• Est. Priority Date: 08/21/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Clark, William A., Geen, John A.
• Granted Patent: US 8,783,103 B2
• Time in Patent Office: Days
• US Class Current: 73/514.29
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/097 by vibratory elements

Abstract

Error sources relating to the drive signal applied to the resonator of an inertial sensor, such as in-phase offset errors relating to the drive signal and/or electronic pass-through of the drive signal to accelerometer sense electronics, are detected by modulating the drive signal and sensing accelerometer signals that are induced by the modulated drive signal. Error sources related to aerodynamics of an inertial sensor resonator are detected by modulating the distance between the resonator and the underlying substrate and sensing accelerometer signals that are induced by such modulation. Compensating signals may be provided to substantially cancel errors caused by such error sources.

Claims

1. In an inertial sensor having a resonator and an accelerometer, a method of detecting at least one error source relating to a drive signal applied to the resonator, the method comprising:

providing a modulated drive signal to the resonator; and

sensing accelerometer signals induced by the modulated drive signal to detect the at least one error source.

2. A method according to claim 1, wherein providing the modulated drive signal to the resonator comprises:

modulating a drive signal using one of amplitude modulation, frequency modulation, on/off keying, and a spread spectrum modulation.

3. A method according to claim 1, wherein detecting accelerometer signals induced by the modulated drive signal includes demodulating accelerometer signals based on a modulation signal used to modulate the drive signal.

4. A method according to claim 1, further comprising:

providing at least one compensating signal to substantially cancel errors introduced by the at least one error source.

5. A method according to claim 1, wherein the at least one error source includes in-phase offset error.

6. A method according to claim 5, further comprising:

providing a compensating signal to a set of in-phase-compensating electrodes to substantially cancel the in-phase offset error.

7. A method according to claim 1, wherein the at least one error source includes electronic pass-through of the drive signal to the accelerometer.

8. A method according to claim 7, further comprising:

providing a compensating signal to the accelerometer to substantially cancel the pass-through.

9. A method according to claim 1, wherein the resonator includes a plurality of shuttles coupled to resonate at a single resonance frequency.

10. A method according to claim 1, wherein accelerometer includes at least one of:

an x-axis sensor;

a y-axis sensor; and

a z-axis sensor.

11. An inertial sensor comprising:

a resonator;

an accelerometer;

a resonator driver configured to provide a modulated drive signal to the resonator; and

an offset detector configured to sense accelerometer signals induced by the modulated drive signal to detect at least one error source relating to the drive signal applied to the resonator.

12. An inertial sensor according to claim 11, wherein the resonator driver is configured to modulate the drive signal using one of amplitude modulation, frequency modulation, on/off keying, and a spread spectrum modulation.

13. An inertial sensor according to claim 11, wherein the offset detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the drive signal to detect accelerometer signals induced by the modulated drive signal.

14. An inertial sensor according to claim 11, further comprising:

a servo configured to provide at least one compensating signal to substantially cancel errors introduced by the at least one error source.

15. An inertial sensor according to claim 11, wherein the at least one error source includes in-phase offset error.

16. An inertial sensor according to claim 15, further comprising:

a servo configured to provide a compensating signal to a set of in-phase-compensating electrodes to substantially cancel the in-phase offset error.

17. An inertial sensor according to claim 11, wherein the at least one error source includes electronic pass-through of the drive signal to the accelerometer.

18. An inertial sensor according to claim 17, further comprising:

a servo configured to provide a compensating signal to the accelerometer to substantially cancel the pass-through.

19. An inertial sensor according to claim 11, wherein the resonator includes a plurality of shuttles coupled to resonate at a single resonance frequency.

20. An inertial sensor according to claim 11, wherein accelerometer includes at least one of:

an x-axis sensor;

a y-axis sensor; and

a z-axis sensor.

21. A controller for detecting at least one error source relating to a drive signal applied to a resonator of an inertial sensor including the resonator and an accelerometer, the controller comprising:

a resonator driver configured to provide a modulated drive signal to the resonator; and

an offset detector configured to sense accelerometer signals induced by the modulated drive signal to detect at least one error source relating to the drive signal applied to the resonator.

22. A controller according to claim 21, further comprising:

a servo configured to provide at least one compensating signal to the inertial sensor to substantially cancel errors introduced by the at least one error source.

23. In an inertial sensor having a resonator and an accelerometer, the resonator supported by an underlying substrate, a method of detecting at least one error source relating to aerodynamics of the resonator, the method comprising:

providing a drive signal to cause resonance of the resonator;

providing a modulated test signal to modulate the distance between the resonator and the underlying substrate; and

sensing accelerometer signals induced by the modulated test signal to detect the at least one error source.

24. A method according to claim 23, wherein providing the modulated test signal comprises:

modulating the test signal using one of amplitude modulation, frequency modulation, on/off keying, and a spread spectrum modulation.

25. A method according to claim 23, wherein the modulated test signal is applied to at least one of:

a set of quadrature-compensating electrodes;

a set of in-phase compensating electrodes; and

a separate set of test electrodes.

26. A method according to claim 23, wherein detecting accelerometer signals induced by the modulated test signal includes demodulating accelerometer signals based on a modulation signal used to modulate the test signal.

27. A method according to claim 23, further comprising:

providing at least one compensating signal to substantially cancel errors introduced by the at least one error source.

28. An inertial sensor comprising:

a resonator supported by a substrate;

an accelerometer;

a resonator driver configured to provide a drive signal to the resonator to cause resonance of the resonator;

a test signal generator configured to provide a modulated test signal to modulate the distance between the resonator and the substrate; and

a detector configured to sense accelerometer signals induced by the modulated test signal to detect at least one error source relating to aerodynamics of the resonator.

29. An inertial sensor according to claim 28, wherein the test signal generator is configured to modulate the test signal using one of amplitude modulation, frequency modulation, on/off keying, and a spread spectrum modulation.

30. An inertial sensor according to claim 28, wherein the modulated test signal is applied to at least one of:

a set of quadrature-compensating electrodes;

a set of in-phase compensating electrodes; and

a separate set of test electrodes.

31. An inertial sensor according to claim 28, wherein the detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the test signal.

32. An inertial sensor according to claim 28, further comprising:

a servo configured to provide at least one compensating signal to substantially cancel errors introduced by the at least one error source.

33. A controller for detecting at least one error source relating to aerodynamics of a resonator of an inertial sensor including the resonator and an accelerometer, the resonator supported by a substrate, the controller comprising:

a resonator driver configured to provide a drive signal to the resonator to cause resonance of the resonator;

a test signal generator configured to provide a modulated test signal to modulate the distance between the resonator and the underlying substrate; and

a detector configured to sense accelerometer signals induced by the modulated test signal to detect at least one error source relating to aerodynamics of the resonator.

34. A controller according to claim 33, further comprising:

a servo configured to provide at least one compensating signal to the inertial sensor to substantially cancel errors introduced by the at least one error source.