Microgyroscope with electronic alignment and tuning

• US 6,675,630 B2
• Filed: 08/17/2001
• Issued: 01/13/2004
• Est. Priority Date: 08/17/2001
• Status: Active Grant

• Current Assignee: California Institute of Technology, The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Challoner, A. Dorian, Gutierrez, Roman C.
• Primary Examiner(s): MOLLER, RICHARD ALAN
• Application Number:
  US09/932,796
• Publication Number:
  US 20030101814A1
• Time in Patent Office: 879 Days
• Field of Search: 73/17.7, 73/18.2, 735/040.2
• US Class Current: 73/1.77
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

A micro-gyroscope having electronic alignment by performing an electronic coordinate transformation on control voltages (V_TX, V_Ty) through an attenuator network thereby canceling first and second harmonic signals from the output (V_thx, V_thy). The micro-gyroscope is tuned by automatic electronic compensation based on quadrature error that is applied to correct for variations in the gyroscope.

Claims

1. A micro-gyroscope having a resonator having mechanical x and y axes, said micro-gyroscope comprising:

a plurality of electrodes spaced about a central hub and having electrical outputs, at least two electrodes on one side of said mechanical x axis being drive electrodes, and at least two electrodes on the other side of said x axis being sense electrodes, said resonator spaced from and located above said plurality of electrodes, whereby motion of said resonator is induced by said drive electrodes and sensed by said sense electrodes; and

a control circuit for aligning said electrical output of said electrodes with said mechanical axes, said control circuit electronically transforms control and sense voltages for said micro-gyroscope to eliminate a first harmonic signal.

2. The micro-gyroscope as claimed in claim 1 wherein said control circuit further comprises a network of attenuators being adjustable for eliminating a first harmonic at a predetermined frequency.

3. The micro-gyroscope as claimed in claim 2 further comprising a least one attenuator on said drive signal and at least one attenuator on said sense signal.

4. The micro-gyroscope as claimed in claim 2 further comprising a least one attenuator for canceling a second harmonic on a drive signal.

5. The micro-gyroscope as claimed in claim 1 further comprising a control circuit for tuning two orthogonal rocking modes on said micro-gyroscope, said control circuit having an automatic gain control loop.

6. The micro-gyroscope as claimed in claim 5 wherein said control circuit further comprises a quadrature compensator for adjusting a phase of said automatic gain control loop to eliminate quadrature in said control circuit.

7. A method for electronically aligning a micro-gyroscope having a network of attenuators, said method comprising the steps of:

determining the natural frequencies of the drive and sense modes Z_x and Z_y aligned with the mechanical drive axis and the mechanical sense axis;

setting all attenuators to nominal values;

verifying that all sum and difference functions in the micro-gyroscope control circuit have no significant phase shifts at Z_x and Z_y;

aligning an electrical output of said drive electrodes by adjusting a predetermined attenuator in said network of attenuators; and

aligning an electrical output of said sense electrodes by adjusting a predetermined attenuator in said network of attenuators.

8. The micro-gyroscope as claimed in claim 7 wherein said step of aligning said electronic output of said drive electrodes further comprises the steps of:

exciting a first drive electrode with a sinusoidal voltage at frequency Z_y,

adjusting said predetermined attenuator until a first harmonic component of a sense signal is at a minimum;

exciting a second drive electrode with a sinusoidal voltage at a frequency Z_x; and

adjusting said predetermined attenuator until a first harmonic component of a second sense signal is at a minimum.

9. The method as claimed in claim 8 wherein said steps of exciting a first and second drive electrode and adjusting an attenuator are repeated for refined alignment.

10. The method as claimed in claim 8 wherein said step of aligning said sense electrodes further comprises the steps of:

exciting a first drive electrode with a sinusoidal voltage at frequency Z_x;

adjusting said predetermined attenuator until a first harmonic component of a sense signal is at a minimum;

exciting a second drive electrode with a sinusoidal voltage at a frequency Z_y; and

adjusting said predetermined attenuator until a first harmonic component of a second sense signal is at a minimum.

11. The method as claimed in claim 10 wherein said steps of exciting a first and second drive electrode and adjusting said predetermined attenuator are repeated for refined alignment.

12. The method as claimed in claim 7 further comprising the step of electronically canceling a second harmonic component on said first sense electrode.

13. The method as claimed in claim 12 wherein said step of electronically canceling a second harmonic component further comprises the steps of:

squaring the drive signal; and

subtracting a fraction of said squared signal from said sensed signal.