FREQUENCY MODULATED MICRO GYRO

• US 20100095770A1
• Filed: 10/16/2009
• Published: 04/22/2010
• Est. Priority Date: 10/21/2008
• Status: Active Grant

• Current Assignee: Ying W. Hsu
• Original Assignee: Ying W. Hsu
• Inventors: Hsu, Ying W.
• Granted Patent: US 8,443,665 B2
• Time in Patent Office: Days
• 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, comprising:

a proof mass resonator; and

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.

2. The device of claim 1, 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.

3. 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 and a first connecting beam coupled to both the first actuator and the proof mass resonator, the first connecting beam operating as a support spring.

4. The device of claim 3, wherein the actuator and the connecting beam of the first detector resonator being oscillated 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.

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 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 actuated to oscillate the first detector resonator and the second detector resonator.

7. The device of claim 3, wherein the second detector resonator comprises a second connecting beam coupled to both the proof mass resonator and the second detector resonator.

8. The device of claim 1 being fabricated on a substrate.

9. The device of claim 8 further comprising:

a stationary element raised above the substrate;

a plurality of ring structures;

a first support spring coupled to the stationary element and a first ring structure of the plurality of ring structures; and

a second support spring coupled to the stationary element and a second ring structure of the plurality of ring structures.

10. The device of claim 9, wherein both the first support spring and the second support spring are further coupled to an edge forming part of an inside diameter of the proof mass resonator.

11. A sensing device, comprising:

a proof mass resonator; and

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.

12. The sensing device of claim 11 further comprising a second detector resonator being oscillated at a second resonant frequency, the second resonant frequency being different than the first resonant frequency and changed in response to the resultant force produced by the angular rotation of the proof mass resonator.

13. The sensing device of claim 11, wherein the first detector resonator comprises a first actuator and a first connecting beam coupled to both the first actuator and the proof mass resonator, the first connecting beam operating as a support spring.

14. The sensing device of claim 13, wherein the first actuator and the connecting beam of the first detector resonator are oscillated at a resonant frequency that is substantially different than a resonant frequency of the proof mass resonator.

15. The sensing device of claim 11 further comprising means for oscillating the first detector resonator.

16. The sensing device of claim 12 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 actuated to oscillate the first detector resonator and the second detector resonator.

17. The sensing device of claim 11 being fabricated on a substrate and 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.

18. The sensing device of claim 17 further comprising:

a stationary element raised above the substrate;

a plurality of ring structures;

a first support spring coupled to the stationary element and a first ring structure of the plurality of ring structures; and

a second support spring coupled to the stationary element and a second ring structure of the plurality of ring structures.

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

oscillating a detector resonator at a first frequency;

oscillating a proof mass resonator at a resonant frequency substantially different from the first frequency;

changing a frequency for the detector resonator to a second 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.

20. The method of claim 19, wherein the rate of motion being angular motion of the proof mass resonator.