Cloverleaf microgyroscope with electrostatic alignment and tuning

• US 20030033850A1
• Filed: 08/09/2001
• Published: 02/20/2003
• Est. Priority Date: 08/09/2001
• Status: Abandoned Application

• Current Assignee: California Institute of Technology, The Boeing Co.
• Original Assignee: California Institute of Technology
• Inventors: Gutierrez, Roman C., Challoner, A. Dorian, Tang, Tony K.
• Application Number:
  US09/927,858
• Publication Number:
  US 20030033850A1
• Time in Patent Office: Days
• US Class Current: 73/1.77
• 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
• CPC Class Codes: G01C 25/00 Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass testing, calibrating or compensating compasses G01C17/38
• CPC Class Codes: G01P 2015/084 the mass being suspended at more than one of its sides, e.g. membrane-type suspension, so as to permit multi-axis movement of the mass
• CPC Class Codes: G01P 2015/0842 the mass being of clover leaf shape

Abstract

A micro-gyroscope (10) having closed loop operation by a control voltage (V_ty), that is demodulated by an output signal of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis). The present invention provides independent alignment and tuning of the micro-gyroscope by using separate sensors and actuators to detect and adjust alignment and tuning. A quadrature amplitude signal is used to detect misalignment, that is corrected to zero by an electrostatic bias adjustment. A quadrature signal noise level, or a transfer function test signal, is used to detect residual mistuning, that is corrected to zero by a second electrostatic bias adjustment.

Claims

1. A method for aligning a micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of:

detecting misalignment of said micro-gyroscope; and

correcting misalignment to zero by an electrostatic bias adjustment.

2. The method as claimed in claim 1 wherein said step of detecting misalignment further comprises detecting misalignment by way of quadrature signal amplitude obtained by demodulation of a signal of said output axis using a signal in quadrature to rate signal for said drive axis.

3. The method as claimed in claim 1 further comprising the step of nulling an in-phase bias.

4. The method as claimed in claim 3 wherein said step of nulling an in-phase bias further comprises nulling by electronically coupling a torque component of said drive axis with said output axis.

5. A method for tuning a cloverleaf micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of:

detecting residual mistuning by way of a signal; and

correcting said residual mistuning to zero by way of electrostatic bias adjustment.

6. The method as claimed in claim 5 wherein said step of detecting residual mistuning further comprises detecting by way of a quadrature signal noise level.

7. The method as claimed in claim 5 wherein said step of detecting residual mistuning further comprises detecting by way of a transfer function test signal.

8. A method for independently aligning and tuning a cloverleaf micro-gyroscope having closed loop control of drive, output and sense axes, said method comprising the steps of:

detecting misalignment of said micro-gyroscope by way of a quadrature signal amplitude;

correcting said misalignment to zero by way of an electrostatic bias adjustment;

detecting residual mistuning by way of a signal; and

correcting said residual mistuning by way of an electrostatic bias adjustment.

9. The method as claimed in claim 8 wherein said step of detecting a residual mistuning further comprises detecting a residual mistuning by way of a quadrature signal noise level.

10. The method as claimed in claim 8 wherein said step of detecting a residual mistuning further comprises detecting a residual mistuning by way of a transfer function test signal.

11. The method as claimed in claim 8 further comprising the step of nulling in-phase bias.

12. The method as claimed in claim 11 wherein said step of nulling further comprises electronically coupling a torque component of said drive axis with said output axis.

13. The method as claimed in claim 8 wherein said micro-gyroscope closed loop control further comprises:

using separate sensors and actuators for said step of correcting said misalignment and said step of correcting said residual mistuning.

14. The method as claimed in claim 8 wherein said step of correcting said misalignment further comprises the step of introducing an electrostatic cross-coupling spring, K^e_xy for canceling said misalignment.

15. The method as claimed in claim 14 further comprising the step of applying a bias voltage to a drive electrode on said drive axis that is different from a bias voltage to another drive electrode on said drive axis.

16. The method as claimed in claim 8 further comprising the step of introducing a relative gain mismatch, δ

_T≈

0, to each drive electrode on said drive axis.

17. The method as claimed in claim 8 further comprising the step of maximizing a stiffness matrix K.

18. The method as claimed in claim 8 wherein said step of correcting said residual mistuning to zero further comprises adjusting a total stiffness of said micro-gyroscope.