Systems and methods for determining resonant frequency and quality factor of overdamped systems

• US 8,464,571 B1
• Filed: 03/22/2010
• Issued: 06/18/2013
• Est. Priority Date: 03/20/2009
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Sparks, Andrew, Judy, Michael
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): Frank, Rodney T
• Application Number:
  US12/728,867
• Time in Patent Office: 1,184 Days
• Field of Search: 73/13.8, 73/10.1, 702/104, 702/107
• US Class Current: 73/1.38
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A calibration system for a MEMS system having at least one overdamped motion axis includes a measurement module for determining a location of a pole of a MEMS device in the overdamped motion axis, a closed-loop feedback system configured to change a first location of the pole to a second location of the pole, and a computation module for calculating a resonant frequency and/or a quality factor using the first and the second location of the pole as determined by the measurement module. The calibration system further includes a calibration module for calibrating the MEMS system based on the calculated resonant frequency and/or the calculated quality factor.

Claims

1. A calibration system for a MEMS system that is overdamped along at least one motion axis, the system comprising:

a measurement module for determining a location of a pole of a MEMS device along the at least one motion axis;

a closed-loop feedback system configured to change a first location of the pole to a second location of the pole;

a computation module for calculating a resonant frequency, a quality factor, or both using the first and the second location of the pole as determined by the measurement module; and

a calibration module for calibrating the MEMS system based on the calculated resonant frequency, the calculated quality factor, or both.

2. The calibration system of claim 1, wherein the closed-loop feedback system is configured to regulate position, velocity, or both.

3. The calibration system of claim 1, wherein the closed-loop feedback system is a positive feedback system, a negative feedback system, or both.

4. The calibration system of claim 1, wherein the MEMS device is a MEMS sensor.

5. The calibration system of claim 1, wherein the MEMS sensor is an accelerometer.

6. A method of calibrating a MEMS system, the method comprising:

providing a MEMS device that is overdamped along at least one motion axis;

determining a first location of a pole of the MEMS device along the at least one motion axis;

changing the first location to a second location;

determining the second location of the pole;

calculating a resonant frequency, a quality factor, or both using the first and the second location of the pole; and

calibrating the MEMS system based on the calculated resonant frequency, the calculated quality factor, or both.

7. The method of claim 6, wherein the first location of the pole is determined by performing a localized frequency sweep.

8. The method of claim 6, wherein changing the first location is accomplished by a closed-loop feedback system.

9. The method of claim 8, wherein the closed-loop feedback system includes regulating position, velocity, or both.

10. The method of claim 8, wherein the closed-loop feedback system is a positive feedback system, a negative feedback system, or both.

11. The method of claim 6, wherein the MEMS device is a MEMS accelerometer.

12. The method of claim 6, further comprising changing an initial location of the pole to the first location before determining the first location of the pole.

13. The method of claim 12, wherein changing the initial location is accomplished by a closed-loop feedback system.

14. The method of claim 13, wherein changing the first location is accomplished by the closed-loop feedback system.

15. The method of claim 6, wherein the MEMS device has two poles, one having a higher frequency and one having a lower frequency, wherein the first location and the second location are determined for the lower frequency pole.

16. A method of detecting a parameter with a MEMS system, the method comprising:

providing a MEMS device that is overdamped along at least one motion axis;

determining a first location of a pole of the MEMS device along the at least one motion axis;

measuring a change in the first location to a second location of the pole;

calculating a resonant frequency, a quality factor, or both using the first and the second location of the pole; and

determining the parameter based on the calculated resonant frequency, the calculated quality factor, or both.

17. The method of claim 16, further comprising providing a closed-loop feedback system in the MEMS system to change the first location to the second location.

18. The method of claim 17, wherein the closed-loop feedback system is a positive feedback system, a negative feedback system, or both.

19. The method of claim 16, wherein the MEMS device is a MEMS sensor.

20. The method of claim 16, further comprising changing an initial location of the pole to the first location before determining the first location of the pole.