Detection and mitigation of aerodynamic error sources for micromachined inertial sensors

• US 8,677,801 B1
• Filed: 02/22/2013
• Issued: 03/25/2014
• 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.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US13/774,129
• Publication Number:
  US 20140060186A1
• Time in Patent Office: 396 Days
• Field of Search: 73/13.7, 73/13.8, 735/041.2
• US Class Current: 73/1.37
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/097 by vibratory elements

Abstract

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 modulated error signals in the accelerometer that are induced by such modulation. Compensating signals may be provided to substantially cancel errors caused by such error sources.

Claims

1. A method of detecting at least one error source relating to aerodynamic effects of a resonator in an inertial sensor having a resonator and an accelerometer for measuring an acceleration signal, wherein at least one error source relating to aerodynamics of the resonator induces corresponding error signals in the accelerometer, the resonator supported by an underlying substrate, 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 while the resonator is resonating so as to induce corresponding modulated error signals in the accelerometer, wherein the modulated error signals are related to aerodynamic force changes resulting from modulation of the distance between the resonator and the underlying substrate while the resonator is resonating; and

sensing the modulated error signals in the accelerometer to detect at least one error source relating to aerodynamics of the resonator.

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

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

3. A method according to claim 1, 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;

or

a separate set of test electrodes.

4. A method according to claim 1, wherein sensing the modulated error signals in the accelerometer includes demodulating accelerometer signals based on a modulation signal used to modulate the test signal.

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

providing at least one compensating signal responsive to the sensed modulated error signals to substantially cancel errors relating to aerodynamics of the resonator.

6. A method according to claim 5, wherein providing at least one compensating signal to substantially cancel errors relating to aerodynamics of the resonator comprises:

providing at least one compensating signal to a set of in-phase compensating electrodes.

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

8. An inertial sensor comprising:

a resonator supported by a substrate;

an accelerometer for measuring an acceleration signal, wherein at least one error source relating to aerodynamics of the resonator induces corresponding error signals in the 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 while the resonator is resonating so as to induce corresponding modulated error signals in the accelerometer, wherein the modulated error signals are related to aerodynamic force changes resulting from modulation of the distance between the resonator and the underlying substrate while the resonator is resonating; and

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

9. An inertial sensor according to claim 8, wherein the test signal generator is configured to modulate the test signal using one of amplitude modulation, frequency modulation, on/off keying, or a spread spectrum modulation.

10. An inertial sensor according to claim 8, 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;

or

a separate set of test electrodes.

11. An inertial sensor according to claim 8, wherein the detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the test signal.

12. An inertial sensor according to claim 8, further comprising:

a servo configured to provide at least one compensating signal responsive to the sensed modulated error signals to substantially cancel errors relating to aerodynamics of the resonator.

13. An inertial sensor according to claim 12, wherein the servo is configured to provide the at least one compensating signal to set of in-phase compensating electrodes.

14. An inertial sensor according to claim 8, wherein the resonator includes a plurality of shuttles, and wherein the shuttles are coupled to resonate at a single resonance frequency.

15. 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 for measuring an acceleration signal, wherein at least one error source relating to aerodynamics of the resonator induces corresponding error signals in the 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 substrate while the resonator is resonating so as to induce corresponding modulated error signals in the accelerometer, wherein the modulated error signals are related to aerodynamic force changes resulting from modulation of the distance between the resonator and the underlying substrate while the resonator is resonating; and

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

16. A controller according to claim 15, wherein the test signal generator is configured to modulate the test signal using one of amplitude modulation, frequency modulation, on/off keying, or a spread spectrum modulation.

17. A controller according to claim 15, 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;

or

a separate set of test electrodes.

18. A controller according to claim 15, wherein the detector is configured to demodulate accelerometer signals based on a modulation signal used to modulate the test signal.

19. A controller according to claim 15, further comprising:

a servo configured to provide at least one compensating signal responsive to the sensed modulated error signals to substantially cancel errors relating to aerodynamics of the resonator.

20. A controller according to claim 19, wherein the servo is configured to provide at least one compensating signal to a set of in-phase compensating electrodes of the inertial sensor.

21. A controller according to claim 15, wherein the resonator includes a plurality of shuttles, and wherein the shuttles are coupled to resonate at a single resonance frequency.