Filter-based method and system for measuring angular speed of an object

• US 6,742,389 B2
• Filed: 01/23/2002
• Issued: 06/01/2004
• Est. Priority Date: 01/24/2001
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: Demirci, Mustafa U., Nguyen, Clark T.-C.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US10/055,210
• Publication Number:
  US 20030037614A1
• Time in Patent Office: 860 Days
• Field of Search: 735/041.2, 735/041.4, 735/041.6
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details

Abstract

A method and system for measuring angular speed of an object uses a micromechanical filter apparatus and allows Q-multiplication in both drive and sense modes. The invention takes advantage of the constant amplitude region of a filter spectrum within a passband of the filter apparatus to sense with a constant scaling factor that is independent of frequency variations with the passband. Thus, the system has much less sensitivity to drive mode resonance frequency shifts due to temperature variations, fabrication non-idealities and aging. The system senses angular rate or speed at resonance, which results in a great improvement over conventional gyroscopes operated off-resonance.

Claims

1. A method for measuring angular speed of an object, the method comprising:

providing a micromechanical filter apparatus including a first resonator having a first resonance frequency formed on a substrate, a second resonator and a third resonator comprising platform resonators, and means for coupling the second and third resonators so that the filter apparatus has a filter response in a sense mode with a substantially constant amplitude region for a passband of frequencies and the filter apparatus having a drive mode response in a drive mode;

coupling the substrate to the object so that the filter apparatus rotates with the object about a first axis;

driving the first resonator in the drive mode so that the first resonator vibrates along a second axis at a reference vibration and generates a Coriolis force which causes the second resonator to vibrate along a third axis at an induced vibration; and

sensing the induced vibration in the sense mode to obtain a corresponding output signal which represents the angular speed of the object about the first axis wherein the passband of frequencies includes the first resonance frequency in the sense mode.

2. The method as claimed in claim 1 wherein the second resonator has a second resonance frequency and wherein the resonance frequencies are substantially the same in the drive and sense modes.

3. The method as claimed in claim 2 wherein the passband of frequencies includes the resonance frequencies and wherein the filter response of the filter apparatus in the sense mode is substantially constant about the resonance frequencies.

4. The method as claimed in claim 1 wherein the first resonator is comb-driven.

5. The method as claimed in claim 1 wherein the step of sensing is performed capacitively.

6. The method as claimed in claim 1 wherein Q-amplification is attained at a higher level in the drive mode than in the sense mode at the first resonance frequency.

7. The method as claimed in claim 1 wherein the resonators are polysilicon resonators.

8. The method as claimed in claim 1 wherein the means for coupling includes a mechanical spring for coupling the second and third resonators together.

9. The method as claimed in claim 1 wherein the filter apparatus is a wide passband filter apparatus and wherein the filter response is wider than the drive mode response.

10. The method of claim 1, wherein the passband of frequencies is substantially larger than a bandwidth of the first resonator so that frequency shifts in the first resonance frequency stay within the passband of frequencies.

11. The method of claim 1, wherein the filter apparatus includes a resistor coupled to the second resonator to obtain a desired filter response.

12. A system for measuring angular speed of an object, the system comprising:

a substrate;

a micromechanical filter apparatus including a first resonator having a first resonance frequency formed on the substrate, a second resonator and a third resonator comprising platform resonators, and means for coupling the second and third resonators so that the filter apparatus has a filter response in a sense mode with a substantially constant amplitude region for a passband of frequencies and having a drive mode response in a drive mode wherein the filter apparatus rotates with the object about a first axis when the substrate is coupled to the object and the object is rotated;

means for driving the first resonator in the drive mode so that the first resonator vibrates along a second axis at a reference vibration and generates a Coriolis force which causes the second resonator to vibrate along a third axis at an induced vibration; and

means for sensing the induced vibration in the sense mode to obtain a corresponding output signal which represents the angular speed of the object about the first axis wherein the passband of frequencies includes the first resonance frequency in the sense mode.

13. The system as claimed in claim 12 wherein the second resonator has a second resonance frequency and wherein the resonance frequencies are substantially the same in the drive and sense modes.

14. The system as claimed in claim 13 the passband of frequencies includes the resonance frequencies and wherein the filter response of the filter apparatus in the sense mode is substantially constant about the resonance frequencies.

15. The system as claimed in claim 12 wherein the first resonator is comb-driven.

16. The system as claimed in claim 12 wherein the means for sensing includes a capacitor for capacitively sensing the induced vibration.

17. The system as claimed in claim 12 wherein Q-amplification is attained at a higher level the drive mode than in the sense mode at the first resonance frequency.

18. The system as claimed in claim 12 wherein the resonators are polysilicon resonators.

19. The system as claimed in claim 12 wherein the means for coupling include a mechanical spring for coupling the second and third resonators together.

20. The system as claimed in claim 12 wherein the filter apparatus is a wide passband filter apparatus and wherein the filter response is wider than the drive mode response.

21. The system of claim 12, wherein the passband of frequencies is substantially larger than the bandwidth of the first resonator so that frequency shifts in the first resonance frequency stay within the passband of frequencies.

22. The system of claim 12, wherein the filter apparatus includes a resistor coupled to the second resonator to obtain a desired frequency response.