Method of canceling quadrature error in an angular rate sensor

• US 20010039834A1
• Filed: 03/19/2001
• Published: 11/15/2001
• Est. Priority Date: 03/17/2000
• Status: Active Grant

• Current Assignee: Nytell Software LLC (Intellectual Ventures LLC)
• Original Assignee: Irvine Sensors Corp.
• Inventors: Hsu, Ying W.
• Granted Patent: US 6,370,937 B2
• Time in Patent Office: Days
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis

Abstract

Disclosed is a method of correcting quadrature error in a dynamically decoupled micro-gyro (100, 200) having a drive mass (110, 210) that is vibrated relative to a drive axis (Y, Z) and a sense mass (111, 211) that responds to the drive mass (110, 210) in the presence of an angular rate and associated coriolis force by vibrating relative to a sense axis (X, Y). The method includes the steps of providing a first static force element (121, 221) for applying a first steady-state force to a first region of the drive mass (110, 210); providing a second static force element (122, 222) for applying a second steady-state force to a second region of the drive mass (210), and applying a corrective steady-state force to the drive mass (110, 210) with the first and second static force elements (121, 122; 221, 222), the corrective steady-state force making the drive axis (Y, Z) of the drive mass (110, 210) orthogonal to the sense axis (X, Y) of the sense mass (111, 211). In the rotational embodiment, the static force elements are located at +Y and −Y directions.

Claims

1. A method of correcting quadrature error in a micro-gyro having a drive mass that is vibrated relative to a drive axis and a sense mass that responds to the drive mass in the presence of an angular rate about a rate axis and a corresponding coriolis force by vibrating relative to a sense axis, the method comprising the steps of:

providing a first static force element for applying a first steady-state force to a first region of the drive mass; and

applying a corrective steady-state force to the drive mass with the first static force element, the corrective steady-state force re-orienting the drive mass to make the drive axis of the drive mass orthogonal to the sense axis of the sense mass.

2. The method of

claim 1

wherein the corrective steady-state force re-orients the drive mass by repositioning the drive mass about the rate axis.

3. The method of

claim 1

comprising the further step of providing a second static force element for applying a second steady-state force to a second region of the drive mass and wherein the applying step is accomplished by selectively applying a corrective steady-state force to one of the first and second static force elements.

4. The method of

claim 1

wherein the first and second static force elements comprise first and second electrodes that provide an electrostatic force.

5. The method of

claim 4

comprising the further steps of:

connecting the drive mass to a ground voltage;

holding one of the first and second electrodes at the ground voltage; and

setting the other of the first and second electrodes to a voltage that is different than the ground voltage such that a corrective steady-state force of suitable direction and magnitude is applied to the drive mass.

6. The method of

claim 5

comprising the further steps of establishing a direction and magnitude for the corrective steady-state force in the absence of an angular rate of rotation.

7. The method of

claim 6

wherein the step of establishing a direction and magnitude for the corrective steady-state force in the absence of an angular rate of rotation is accomplished by:

detecting a quadrature signal associated with a vibration of the sense mass in the absence of an angular rate of rotation;

integrating the quadrature signal to produce a control voltage; and

applying the control voltage to the first and second electrodes.

8. The method of

claim 1

wherein the micro-gyro is linear in operation in that the drive mass is vibrated along the drive axis and the sense mass is vibrated along a sense axis.

9. The method of

claim 1

wherein the micro-gyro is rotary in operation in that the drive mass is vibrated about the drive axis and the sense mass is vibrated about a sense axis.

10. The method of

claim 9

wherein the drive mass is ring-shaped;

wherein the sense mass is disk-shaped; and

wherein the first static force element is located below the ring-shaped drive mass.

11. The method of

claim 10

further comprising the step of providing a second static force element for applying a second steady-state force to a second region of the ring-shaped drive mass, wherein the second static force element is located below the ring-shaped drive mass, and wherein the applying step is accomplished by selectively applying a corrective steady-state force to one of the first and second static force elements.

12. The method of

claim 10

wherein the micro-gyro comprises:

a substrate defining an XY plane with an X axis and Y axis and with a Z axis extending perpendicularly therefrom;

wherein the ring-shaped drive mass is supported above the substrate by flexures that permit the ring-shaped drive mass to vibrate about a drive axis that is ideally aligned with the Z-axis and to tip and tilt relative to the XY plane;

wherein the disk-shaped drive mass is supported above the substrate by flexures that substantially constrain it to rocking about the Y axis; and

wherein the first and second static force elements are located at +Y and −

Y locations below the ring-shaped drive mass in order to correct for the mechanical imperfection that would otherwise causes the drive axis of the drive mass to deviate from the Z axis by some angle about the X-axis.

13. The method of

claim 1

wherein the first static force element comprises a thermal element that provides a thermally-induced force.

14. The method of

claim 1

wherein the first static force element comprises a magnetic element that provides a magnetically-induced force.

15. The method of

claim 1

wherein the micro-gyro is a dynamically decoupled micro-gyro.