Frequency modulated micro gyro

• US 8,443,665 B2
• Filed: 10/16/2009
• Issued: 05/21/2013
• Est. Priority Date: 10/21/2008
• Status: Expired due to Fees

• Current Assignee: Ying W. Hsu
• Original Assignee: Ying W. Hsu
• Inventors: Hsu, Ying W.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US12/581,003
• Publication Number:
  US 20100095770A1
• Time in Patent Office: 1,313 Days
• Field of Search: 735/041.2
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A micro gyro consisting of a vibrating micro scale structure produces a signal whose characteristic frequency shifts in proportion to the applied angular velocity. The vibrating structure consists of a suspended proof mass resonator supported on springs and connected to at least one detector resonator. The structure can be made with multiple semiconductor materials such as silicon, poly-silicon, silicon dioxide, and silicon nitride, using one of many MEMS fabrication processes. The proof mass resonator is designed to have two closely coupled resonant frequencies, with one resonant mode for the drive motion and the second resonant mode for the sense motion. Detector resonators are connected to the vibrating structure such that when the proof mass resonator oscillates due to the Coriolis force in its sense mode, the connections to the detector resonators are stressed by the proof mass resonator, thus changing the resonant frequency of the detector resonators. By measuring the shift in the resonant frequency of the detectors, the applied angular rate can be determined.

Claims

1. A device for measuring angular rate fabricated on a substrate, comprising:

a proof mass resonator;

at least one detector resonator coupled to the proof mass resonator, the at least one detector resonator being oscillated at a first resonant frequency and being altered to oscillate at a second resonant frequency in response to a resultant force produced by rotating the proof mass resonator at an angular rate;

a stationary element raised above the substrate;

a first ring structure; and

a first support spring coupled between the stationary element and an edge forming part of an inside diameter of the proof mass resonator, the first support spring supporting the first ring structure.

2. The device of claim 1, wherein the at least one detector resonator comprises a first detector resonator and a second detector resonator, the first detector resonator comprises a first actuator coupled to the proof mass resonator.

3. The device of claim 2, wherein the at least one detector comprises a means for oscillating the first actuator at the second resonant frequency that is higher than the first resonant frequency, the second resonant frequency being caused by the resultant force being a Coriolis force.

4. The device of claim 2, wherein the second detector resonator comprises a second actuator coupled to the proof mass resonator.

5. The device of claim 1 further comprising means for oscillating the at least one detector resonator.

6. The device of claim 1 further comprising (i) a plurality of electrodes each uniquely corresponding to the at least one detector resonator, wherein the at least one detector being one of a first detector resonator and a second detector resonator, and (ii) a plurality of traces each coupled to one of the plurality of electrodes, the plurality of electrodes and the plurality of traces being energized to oscillate the first detector resonator and the second detector resonator.

7. The device of claim 1 further comprising:

a second ring structure; and

a second support spring coupled between the stationary element and the proof mass resonator, the second support spring supporting the second ring structure.

8. The device of claim 1, wherein the proof mass resonator is operable in a drive resonant mode and sense resonant mode with the drive resonant mode being a mode of operation with a rotation of the proof mass resonator about a first axis and the sense resonant mode being a mode of operation with a rotation of the proof mass resonator being about a second axis that is orthogonal to the first axis.

9. The device of claim 8, wherein the first axis is parallel to a plane of the substrate and the second axis is perpendicular to the plane of the substrate.

10. The device of claim 8, where in the angular rate to be measured is applied about an axis that is orthogonal both to the first axis and the second axis.

11. The device of claim 1 further comprising means for oscillating the at least one detector resonator at a resonant frequency that is higher than the resonant frequency of the proof mass resonator.

12. A sensing device fabricated on a substrate, comprising:

a proof mass resonator;

a first detector resonator coupled to and substantially surrounded by the proof mass resonator, the first detector resonator being oscillated at a first resonant frequency, the first resonant frequency being changed in response to a resultant force produced by angular rotation of the proof mass resonator;

a stationary element raised above the substrate;

a first ring structure; and

a first support spring coupled between the stationary element and the proof mass resonator, the first support spring supporting the first ring structure,

wherein the sensing device being operable in a drive resonant mode and a sense resonant mode with the drive resonant mode being a mode of operation with a rotation of the proof mass resonator about a first axis parallel to a plane of the substrate and the sense resonant mode being a mode of operation with a rotation of the proof mass resonator being about a second axis perpendicular to the plane of the substrate so that the angular rate is applied along an axis that is orthogonal to both the first axis and the second axis.

14. The sensing device of claim 12 further comprising means for oscillating the first detector resonator at the first resonant frequency that is higher than a resonant frequency of the proof mass resonator.

15. The sensing device of claim 12 further comprising a second detector resonator being oscillated at a second resonant frequency, the second resonant frequency being changed in response to the resultant force produced by the angular rotation of the proof mass resonator.

16. The sensing device of claim 15 further comprising (i) a plurality of electrodes each corresponding to one of the first detector resonator and the second detector resonator, and (ii) a plurality of traces each coupled to one of the plurality of electrodes, the plurality of electrodes and the plurality of traces being energized to oscillate the first detector resonator and the second detector resonator.

17. The sensing device of claim 12, wherein the first detector resonator comprises a first actuator coupled to the proof mass resonator.

18. The sensing device of claim 17, wherein the first detector resonator comprises a means for oscillating the first actuator at a resonant frequency that is substantially different than a resonant frequency of the proof mass resonator.

19. The sensing device of claim 12 further comprising means for oscillating the first detector resonator.

13. A device for measuring angular rate fabricated on a substrate, comprising:

a proof mass resonator;

at least one detector resonator coupled to the proof mass resonator, the at least one detector resonator being oscillated at a first resonant frequency and being altered to oscillate at a second resonant frequency in response to a resultant force produced by rotating the proof mass resonator at an angular rate;

a stationary element raised above the substrate;

a first ring structure; and

a first support spring coupled between the stationary element and the proof mass resonator, the first support spring supporting the first ring structure,

wherein the proof mass resonator is a ring shaped element that is suspended above a substrate by a plurality of support springs, each of the plurality of support springs being coupled at one end to an inside edge of the proof mass resonator.

20. A method of measuring changes in motion using a micro gyro, comprising:

oscillating a detector resonator at a first resonant frequency;

oscillating rotationally a proof mass resonator at a resonant frequency substantially different from the first resonant frequency, wherein the proof mass resonator being coupled to the detector resonator;

changing a frequency for the detector resonator to a second resonant frequency in response to a Coriolis force produced by a change of motion of the proof mass resonator; and

measuring a rate of motion of the proof mass resonator based on a shift in the resonant frequency of the detector resonator from the first resonant frequency to the second resonant frequency.

21. The method of claim 20, wherein the rate of motion being angular motion of the proof mass resonator.