Micromachined gyroscopes with 2-DOF sense modes allowing interchangeable robust and precision operation

• US 8,549,915 B2
• Filed: 10/23/2009
• Issued: 10/08/2013
• Est. Priority Date: 10/23/2009
• 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: Schofield, Adam, Trusov, Alexander, Shkel, Andrei
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): Redmann, Gregory J
• Application Number:
  US12/605,178
• Publication Number:
  US 20110094302A1
• Time in Patent Office: 1,446 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 19/5733 Structural details or topology

Abstract

A z-axis gyroscope design is presented with a 2-degree of freedom (DOF) sense mode allowing interchangeable operation in either precision (mode-matched) or robust (wide-bandwidth) modes. This is accomplished using a complete 2-DOF coupled system which allows for the specification of the sense mode resonant frequencies and coupling independent of frequency. By decoupling the frame connecting the sense system to a central anchor, x-y symmetry is preserved while enabling a fully coupled 2-DOF sense mode providing control over both the bandwidth and the amount of coupling independent of operational frequency. The robust mode corresponds to operation between the 2-DOF sense mode resonant frequencies providing a response gain and bandwidth controlled by frequency spacing. Precision mode of operation, however, relies on mode-matching the drive to the second, anti-phase sense mode resonant frequency which can be designed to provide a gain advantage over a similar 1-DOF system.

Claims

1. A micromachined z-axis vibratory rate gyroscope comprising:

a first 1-DOF drive subsystem restrained to oscillate substantially only in the drive mode, and having a drive suspension and drive mass, and wherein the 1-DOF drive subsystem further comprises;

an outer anchor;

an inner anchor;

an outer decoupling frame coupled to the outer anchor by at least one drive suspension that constrains the motion of the outer decoupling frame to substantially only the drive axis; and

an inner decoupling frame coupled to the inner anchor and at least one drive suspension that constrains the motion of the outer decoupling frame to substantially only the drive axis; and

a 2-DOF sense subsystem restrained to oscillate substantially only in the sense mode, having at least two sense mode resonant frequencies, and resiliently coupled to the 1-DOF drive subsystem, where the 1-DOF drive subsystem has a drive frequency independent of the at least two sense mode resonant frequencies, which drive frequency is determined by selection of dynamic parameters for the drive suspension and drive mass, and wherein the 2-DOF sense subsystem further comprises;

a first sense mass m_a coupled to one of either the inner decoupling frame or the outer decoupling frame and restrained to oscillate substantially only in the sense direction;

a second sense mass m_b coupled to the other one of either inner decoupling frame or outer decoupling frame and restrained to oscillate substantially only in the sense direction; and

an independent flexure coupling the first and second sense masses to allow relative motion of the first and second sense masses ma and mb in substantially only in the sense direction.

2. The gyroscope of claim 1 where the 1-DOF drive subsystem further comprises a drive electrostatic comb electrode for the actuation, detection and control of the inner and outer decoupling frames in the drive axis.

3. The gyroscope of claim 1 where the 2-DOF sense subsystem further comprises a sense electrostatic electrode for the actuation, detection of the motion induced by the Coriolis acceleration and for tuning of the resonant frequencies of the first and second sense masses.

4. The gyroscope of claim 1 where the 2-DOF sense subsystem further comprises means for independently controlling both peak spacing of the at least two sense mode resonant frequencies and the amount of coupling between the first and second sense masses.

5. The gyroscope of claim 1 where the dynamic parameters of the 2-DOF sense subsystem are selected so that the at least two resonant sense frequencies having a peak spacing with a predetermined bandwidth and where the dynamic parameters of the 1-DOF drive subsystem are selected to establish the drive frequency within the predetermined bandwidth for a robust operational mode.

6. The gyroscope of claim 1 where the dynamic parameters of the 2-DOF sense subsystem are selected so that the at least two resonant sense frequencies are predetermined and where the dynamic parameters of the 1-DOF drive subsystem are selected to establish the drive frequency on or near at least one of the at least two resonant sense frequencies for a precision operational mode.

7. The gyroscope of claim 1 further comprising first means:

for adjusting the dynamic parameters of the 1-DOF subsystem and/or 2-DOF subsystem during operation for a precision operational mode where the dynamic parameters of the 2-DOF sense subsystem are selected so that the at least two resonant sense frequencies are predetermined and where the dynamic parameters of the 1-DOF drive subsystem are selected to establish the drive frequency on or near at least one of the at least two resonant sense frequencies;

or

for adjusting the dynamic parameters of the 1-DOF subsystem and/or 2-DOF subsystem during operation for a robust operational mode where the dynamic parameters of the 2-DOF sense subsystem are selected so that the at least two resonant sense frequencies having a peak spacing with a predetermined bandwidth and where the dynamic parameters of the 1-DOF drive subsystem are selected to establish the drive frequency within the predetermined bandwidth.

8. The gyroscope of claim 1 further comprising a second 1-DOF drive subsystem restrained to oscillate substantially only in the drive mode, and having a corresponding drive suspension and corresponding drive mass and a second 2-DOF sense subsystem restrained to oscillate substantially only in the sense mode, having at least two corresponding sense mode resonant frequencies, and resiliently coupled to the second 1-DOF drive subsystem, where the second 1-DOF drive subsystem has a drive frequency independent of the at least two corresponding sense mode resonant frequencies, which corresponding drive frequency is determined by selection of dynamic parameters for the corresponding drive suspension and corresponding drive mass, where the first and second 1-DOF subsystems are resiliently coupled to each in the drive mode, but capable of being driven in antiphase to reject common mode inputs.

9. The gyroscope of claim 8 where the second 1-DOF drive subsystem further comprises a corresponding drive electrostatic comb electrode for the actuation, detection and control of the inner and outer decoupling frames in the drive axis.

10. The gyroscope of claim 9 where the second 2-DOF sense subsystem further comprises a corresponding sense electrostatic electrode for the actuation, detection of the motion induced by the Coriolis acceleration and for tuning of the resonant frequencies of the first and second sense masses.

11. The gyroscope of claim 10 further comprising corresponding second means:

for adjusting the dynamic parameters of the second 1-DOF subsystem and/or second 2-DOF subsystem during operation for a precision operational mode where the dynamic parameters of the second 2-DOF sense subsystem are selected so that the at least two corresponding resonant sense frequencies are predetermined and where the corresponding dynamic parameters of the second 1-DOF drive subsystem are selected to establish the corresponding drive frequency on or near at least one of the at least two corresponding resonant sense frequencies;

or

for adjusting the dynamic parameters of the second 1-DOF subsystem and/or second 2-DOF subsystem during operation for a robust operational mode where the corresponding dynamic parameters of the second 2-DOF sense subsystem are selected so that the at least two corresponding resonant sense frequencies having a peak spacing with a predetermined bandwidth and where the dynamic parameters of the second 1-DOF drive subsystem are selected to establish the corresponding drive frequency within the predetermined corresponding bandwidth.