MEMS gyroscope with parametric gain

• US 20030200804A1
• Filed: 04/25/2002
• Published: 10/30/2003
• Est. Priority Date: 04/25/2002
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Johnson, Burgess R.
• Granted Patent: US 6,715,353 B2
• Time in Patent Office: Days
• 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

Abstract

A microelectromechanical (MEMS) gyroscope has one or more proof masses mechanically coupled to a substrate by springs. A motor force drives the proof masses at their resonant frequency in one direction, 180 degrees out of phase with each other in the case of a dual proof mass gyroscope. Sense electrodes sense motion of the proof masses in response to a Coriolis force. The motion caused by the Coriolis force is perpendicular to the motion caused by the motor force. An AC pump voltage at twice the motor frequency is applied to the sense electrodes to provide parametric amplification of the Coriolis force. The AC pump voltage alters the mechanical and electrical gain of the gyroscope.

Claims

1. A microelectromechanical gyroscope comprising:

a proof mass;

a motor driver that oscillates the proof mass at its resonant frequency in a motor mode of oscillation;

a sense electrode positioned proximate the proof mass to detect oscillation of the proof mass in a sense mode of oscillation; and

a pump coupled to the sense electrode that provides a force at twice the resonant frequency of the motor mode of oscillation.

2. The microelectromechanical gyroscope of claim 1 and further comprising an output circuit coupled to the proof mass.

3. The microelectromechanical gyroscope of claim 2 wherein the output circuit comprises an operational amplifier having parallel resistive and capacitive feedback.

4. The microelectromechanical gyroscope of claim 1 wherein the force provided by the pump is caused by an electrical signal having a DC component and an AC component.

5. The microelectromechanical gyroscope of claim 4 wherein the voltage of the AC component is approximately twice the voltage of the DC component.

6. The microelectromechanical gyroscope of claim 1 and further comprising springs coupled to the proof mass.

7. The microelectromechanical gyroscope of claim 6 wherein the proof mass is suspended from a substrate by the springs.

8. The microelectromechanical gyroscope of claim 7 wherein the substrate is formed of silicon or pyrex.

9. The microelectromechanical gyroscope of claim 1 wherein the frequency of the motor mode of oscillation is greater than the frequency of the sense mode of oscillation.

10. A method of measuring Coriolis force, the method comprising:

oscillating a proof mass at its resonant frequency in a motor mode of oscillation;

providing a pumping force to a sense mode of oscillation of the proof mass at approximately twice the resonant frequency and substantially perpendicular to the motor mode of oscillation; and

detecting oscillation of the proof mass caused by the Coriolis force in the sense mode of oscillation.

11. The method of claim 10 and further comprising providing the detected oscillation to an output circuit coupled to the proof mass.

12. The method of claim 10 wherein the force provided by the pump is caused by an electrical signal having a DC component and an AC component.

13. The method of claim 12 wherein the voltage of the AC component is approximately twice the voltage of the DC component.

14. The method of claim 13 wherein the proof mass is formed of silicon.

15. The method of claim 10 wherein the proof mass is suspended from a substrate by springs.

16. The method of claim 10 wherein the frequency of the motor mode of oscillation is greater than the frequency of the sense mode of oscillation.

17. The method of claim 10 wherein the frequency of the motor mode of oscillation is approximately less than the frequency of the sense mode of oscillation.

18. A microelectromechanical gyroscope comprising:

a pair of proof masses suspended from a substrate by springs;

a motor driver that oscillates the proof masses at their resonant frequency in a motor mode of oscillation;

two pair of sense electrodes, each pair sandwiching a proof mass, which operates as a further sense electrode to form sense capacitors for each proof mass to detect oscillation of the proof masses in a sense mode of oscillation; and

a pump coupled to the sense electrodes that provides a force at approximately twice the resonant frequency of the motor mode of oscillation.

19. The microelectromechanical gyroscope of claim 18 wherein the force provided by the pump is caused by an electrical signal having a DC component and an AC component.

20. The microelectromechanical gyroscope of claim 18 wherein the voltage of the AC component is approximately twice the voltage of the DC component.

21. The microelectromechanical gyroscope of claim 18 wherein the proof mass is formed of silicon.

22. A method of measuring Coriolis force, the method comprising:

oscillating a proof mass suspended by a spring at its resonant frequency in a motor mode of oscillation;

providing a pumping force to a sense mode of oscillation of the proof mass at approximately twice the resonant frequency and substantially perpendicular to the motor mode of oscillation; and

detecting oscillation of the proof mass caused by the Coriolis force in the sense mode of oscillation.

23. A method of measuring Coriolis force, the method comprising:

oscillating a pair of proof masses suspended by springs at their resonant frequency in a motor mode of oscillation;

providing a pumping force to a sense mode of oscillation of the proof masses at approximately twice the resonant frequency and substantially perpendicular to the motor mode of oscillation; and

detecting oscillation of the proof masses caused by the Coriolis force in the sense mode of oscillation.