Robust six degree-of-freedom micromachined gyroscope with anti-phase drive scheme and method of operation of the same

• US 8,113,050 B2
• Filed: 01/25/2006
• Issued: 02/14/2012
• Est. Priority Date: 01/25/2006
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Acar, Cenk, Shkel, Andrei, Schofield, Adam R., Costlow, Lynn E., Madni, Asad M.
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US12/279,174
• Publication Number:
  US 20090272189A1
• Time in Patent Office: 2,211 Days
• Field of Search: 735/041.2, 735/040.4, 735/041.4, 735/041.6, 735/040.2, 735/10, 735/11
• US Class Current: 73/504.04
• CPC Class Codes: G01C 19/574 the devices having two sensing masses in anti-phase motion
• CPC Class Codes: G01P 15/14 by making use of gyroscopes gyroscopes per se G01C19/00
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: Y10T 74/1225 with rotor drives

Abstract

A method of operating an anti-phase six degree-of-freedom tuning fork gyroscope system comprises the steps of driving a first three degree-of-freedom gyroscope subsystem, and driving a second three degree-of freedom gyroscope subsystem in an anti-phase mode with the first gyroscope subsystem at an anti-phase resonant frequency. Acceleration or an angular rate of motion is sensed by the first and second three degree-of-freedom gyroscope subsystems operating in a flat frequency response range where the anti-phase resonant frequency is designed. Response gain and phase are stable and environmental and fabrication perturbations are avoided by such operation. A anti-phase six degree-of-freedom tuning fork gyroscope system which operates as described is also characterized.

Claims

1. An apparatus with six degrees of freedom and driven in anti-phase for passive relaxation of sense mode phase matching requirements comprising:

a first and second three degree-of-freedom (3-DOF) subsystem coupled with each other in a drive-mode and driven into anti-phase oscillation to substantially reject common-mode stimuli,

where each of the first and second 3-DOF subsystems comprise two proof masses and a decoupling frame, the two proof masses in each 3-DOF subsystem being collectively arranged and configured to function as both a 1-DOF drive oscillator and 2-DOF sense oscillator,

where in each of the first and second 3-DOF subsystems the 1-DOF drive oscillator and 2-DOF sense oscillator are mechanically decoupled from each other and a substrate via the decoupling frame,

where the two 1-DOF drive oscillators in the first and second 3-DOF subsystems are coupled with each other to collectively function as a 2-DOF coupled system and to provide a common anti-phase drive-mode resonant frequency at which the first and second 3-DOF subsystems oscillate in opposite directions,

and where the two 2-DOF sense-mode oscillators in the first and second 3-DOF subsystems each provide a flat range in frequency response where the response gain and phase are stable to provide robustness to imperfections and environmental influences, and to provide matching of sense-mode amplitude and phase of the first and second 3-DOF subsystems.

2. The apparatus of claim 1 further comprising a mechanical flexure and where the two 1-DOF drive oscillators in the first and second 3-DOF subsystems are coupled with each other through the mechanical flexure.

3. The apparatus of claim 1 where the two 1-DOF drive oscillators in the first and second 3-DOF subsystems are coupled with each other through regulation of the two 1-DOF drive oscillators.

4. The apparatus of claim 1 further comprising sense electrodes in each of the first and second 3-DOF subsystems and where the sense electrodes are positioned in a central location within the first and second 3-DOF subsystems.

5. The apparatus of claim 1 further comprising a substrate with an edge, where the first and second 3-DOF subsystems are disposed on the substrate, further comprising sense electrodes in each of the first and second 3-DOF subsystems, and where the sense electrodes are positioned proximate the substrate edge.

6. The apparatus of claim 1 where the two 2-DOF sense-mode oscillators in the first and second 3-DOF subsystems are arranged configured so that the flat range in the frequency response of the two 2-DOF sense-mode oscillators have overlapping frequency ranges.

7. The apparatus of claim 6 where the common anti-phase drive-mode resonant frequency of the two 1-DOF drive oscillators in the first and second 3-DOF subsystems, functioning as a 2-DOF coupled system, is within the overlapping frequency ranges of the two 2-DOF sense-mode oscillators in the first and second 3-DOF subsystems.

8. An anti-phase six degree-of-freedom tuning fork gyroscope system comprising:

a first three degree-of-freedom gyroscope subsystem; and

a second three degree-of-freedom gyroscope subsystem,

where the first and second gyroscope subsystems each comprise two proof masses mechanically coupled together and mechanically restrained in each gyroscope subsystem to form a two degree-of-freedom sense mode oscillator in each gyroscope subsystem, and each of the two proof masses mechanically restrained in the first and second gyroscope subsystems to function as a one degree-of-freedom drive mode oscillator so that the four proof masses function overall as a two degree-of-freedom drive mode oscillator having two primary resonance modes, namely an in-phase and anti-phase mode;

drive means for driving the two degree-of-freedom drive mode oscillator in the anti-phase mode at an anti-phase resonant frequency, and

where each of the two degree-of-freedom sense mode oscillators is characterized by a flat frequency response range and where the anti-phase resonant frequency is within the flat frequency response ranges of the sense mode oscillators where response gain and phase are stable.

9. The system of claim 8 further comprising:

a first frame mechanically coupled to at least one of the two proof masses in the first gyroscope subsystem;

a second frame mechanically coupled to at least one of the two proof masses in the second gyroscope subsystem,

where the first and second frames are mechanically coupled to a substrate and mechanically restrained in the first and second gyroscope subsystems respectively.

10. The system of claim 9 where the two proof masses in the first and second gyroscope subsystems are mechanically restrained to move only in a sense direction, and where the first and second frames are mechanically restrained to move only in a drive direction.

11. The system of claim 10 where the sense direction and drive direction are in orthogonal directions in a common plane.

12. The system of claim 8 where the flat frequency response ranges of the two degree-of-freedom sense mode oscillators overlap.

13. The system of claim 12 where the flat frequency response ranges of the two degree-of-freedom sense mode oscillators are substantially identical.

14. The system of claim 8 where the first and second gyroscope subsystems are fabricated in a common plane and where drive or sense oscillations are directed out-of-plane for out-of-plane gyroscope implementations.

15. The system of claim 8 further comprising additional gyroscope subsystems mechanically serially coupled to the first subsystem, second subsystem or to each other in order to improve the frequency response or amplify anti-phase motion.

16. The system of claim 8 where each two degree-of-freedom sense mode oscillator comprises additional proof masses to enhance sense mode frequency response characteristics, all of the proof masses being at least indirectly coupled together.

17. The system of claim 8 where each one degree-of-freedom drive mode oscillator and two degree-of-freedom sense mode oscillator comprises additional proof masses, all of the proof masses being at least indirectly coupled together.

18. The system of claim 8 further comprising accelerometer means for coupled to the two degree-of-freedom sense mode oscillators for generating a measurement of acceleration.

19. The system of claim 18 where the accelerometer means comprises separate acceleration sense electrodes coupled to at least one of the proof masses in each two degree-of-freedom sense mode oscillator.

20. The system of claim 18 where the accelerometer means comprises a circuit for adding responses of the two degree-of-freedom sense mode oscillators and generating a measure of acceleration therefrom.

21. A method of operating a gyroscope with six degrees of freedom comprising:

driving a 1-DOF drive oscillator in each of a first and second three degree-of-freedom (3-DOF) gyroscope systems, which 1-DOF drive oscillators in the first and second 3-DOF systems are coupled with each other to collectively function as a 2-DOF coupled system and to provide a common anti-phase drive-mode resonant frequency at which the first and second 3-DOF subsystems oscillate in opposite directions to substantially reject common-mode stimuli,

sensing a rate of angular rotation by means of a 2-DOF sense oscillator in each of a first and second three degree-of-freedom (3-DOF) gyroscope systems, each 2-DOF sense oscillator providing a flat range in its frequency response where the response gain and phase are stable to provide robustness to imperfections and environmental influences, and to provide matching of sense-mode amplitude and phase of the first and second 3-DOF subsystems; and

decoupling the 1-DOF drive oscillator and the 2-DOF sense oscillator from each other and from a substrate in each of the first and second three degree-of-freedom (3-DOF) gyroscope systems.

22. The method of claim 21 where driving the coupled 1-DOF drive oscillators in each of the first and second three degree-of-freedom (3-DOF) gyroscope systems comprises driving the 1-DOF drive oscillators coupled together by a mechanical flexure.

23. The method of claim 21 where driving the coupled 1-DOF drive oscillators in each of the first and second three degree-of-freedom (3-DOF) gyroscope systems comprises driving the 1-DOF drive oscillators coupled with each other through regulation of the two 1-DOF drive oscillators.

24. The method of claim 21 where sensing the rate of angular rotation comprises sensing the rate of angular rotation by means of sense electrodes in each of the first and second 3-DOF systems positioned in a central location within the first and second 3-DOF systems.

25. The method of claim 21 where the gyroscope is fabricated on a substrate with at least one edge and where sensing the rate of angular rotation comprises sensing the rate of angular rotation by means of sense electrodes in each of the first and second 3-DOF systems positioned proximate the substrate edge.

26. The method of claim 21 where sensing the rate of angular rotation comprises providing the 2-DOF sense-mode oscillators with a flat range in frequency response and sensing in the flat range in the frequency response of the 2-DOF sense-mode oscillators.

27. The method of claim 26 where driving the 1-DOF drive oscillator in each of the first and second three degree-of-freedom (3-DOF) gyroscope systems comprises driving the 1-DOF drive oscillator at the common anti-phase drive-mode resonant frequency within overlapping flat frequency ranges of the 2-DOF sense-mode oscillators.

28. A method of operating an anti-phase six degree-of-freedom tuning fork gyroscope system comprising:

driving a first three degree-of-freedom gyroscope subsystem; and

driving a second three degree-of-freedom gyroscope subsystem in an anti-phase mode with the first three degree-of-freedom gyroscope subsystem at an anti-phase resonant frequency; and

sensing motion by means of the first and second three degree-of-freedom gyroscope subsystems in a flat frequency response range where the anti-phase resonant frequency is within the flat frequency response ranges where response gain and phase are stable.

29. The method of claim 28 further comprising mechanically decoupling sensing motion from driving the first and second three degree-of-freedom gyroscope subsystems.

30. The method of claim 29 where sensing motion comprises mechanically restraining two proof masses in the first and second gyroscope subsystems to move only in a sense direction, and driving the first and second gyroscope subsystems comprises mechanically restraining the first and second gyroscope subsystems to move only in a drive direction.

31. The method of claim 30 where mechanically restraining two proof masses in the first and second gyroscope subsystems to move only in a sense direction, and driving the first and second gyroscope subsystems comprises mechanically restraining the first and second gyroscope subsystems to move only in a drive direction comprises mechanically restraining motion in the sense direction and the drive direction to orthogonal directions in a common plane.

32. The method of claim 28 where sensing motion in the flat frequency response ranges of the first and second three degree-of-freedom gyroscope subsystems comprises sensing motion in a range of overlap in the frequency response ranges of the first and second three degree-of-freedom gyroscope subsystems.

33. The method of claim 32 where sensing motion in a range of overlap comprises sensing motion in a range of substantially identical frequency response ranges.

34. The method of claim 28 where the first and second gyroscope subsystems are fabricated in a common plane and where driving the first and second gyroscope subsystems or sensing motion is directed out-of-plane for out-of-plane gyroscope implementations.

35. The method of claim 28 further comprising driving additional gyroscope subsystems mechanically serially coupled to the first subsystem, the second subsystem or to each other in order to improve the frequency response or amplify anti-phase motion.

36. The method of claim 28 where sensing motion comprises sensing motion by means of additional three degree-of-freedom gyroscope subsystems to enhance sense mode frequency response characteristics, all of the three degree-of-freedom gyroscope subsystems being at least indirectly coupled together.

37. The method of claim 28 further comprising sensing acceleration by means of adding output response signals from each gyroscope subsystem.

38. The method of claim 37 where sensing acceleration comprises sensing the output response signals through separate acceleration sense electrodes coupled to at least one proof mass in each gyroscope subsystem.

39. The method of claim 37 where sensing acceleration comprises adding responses of a plurality of sense mode oscillators in a detection circuit and generating a measure of acceleration therefrom.