Gyroscope

Patent metadata

Field	Value
Publication number	US-11243077-B2
Application number	US-201916679521-A
Country	US
Kind code	B2
Filing date	Nov 11, 2019
Priority date	Dec 21, 2018
Publication date	Feb 8, 2022
Grant date	Feb 8, 2022

Abstract

A vibrating structure gyroscope includes a permanent magnet, a structure arranged in a magnetic field of the permanent magnet and arranged to vibrate under stimulation from at least one primary drive electrode and a drive system that includes: one primary drive electrode arranged at least one primary sense electrode arranged to sense motion in the vibrating structure and a drive control loop controlling the primary drive electrode dependent on the primary sense electrode. The structure also includes a compensation unit arranged to receive a signal from the drive system representative of a gain in the drive control loop and arranged to output a scale factor correction based on that signal. As the magnet degrades (e.g. naturally over time as the material ages), the magnetic field weakens. To compensate for this, the primary drive control loop will automatically increase the gain.

First claim

The invention claimed is:

1. A vibrating structure gyroscope, comprising:
a permanent magnet;
a vibrating structure arranged in a magnetic field of the permanent magnet and arranged to vibrate under stimulation from at least one primary drive electrode;
a drive system arranged to vibrate the vibrating structure at a resonance frequency, the drive system comprising:
the at least one primary drive electrode arranged to induce motion in the vibrating structure,
at least one primary sense electrode arranged to sense motion in the vibrating structure; and
a drive control loop controlling the primary drive electrode dependent on the primary sense electrode; and
a compensation unit arranged to receive a signal from the drive system representative of a gain in the drive control loop and arranged to output a scale factor correction, for application to a rate signal of the gyroscope based on the signal.

2. The vibrating structure gyroscope as claimed in claim 1 , wherein the signal from the drive system comprises one or more of:
the amplitude of the drive signal for the primary drive electrode;
the amplitude of the signal from the primary sense electrode; and
the gain of the drive control loop.

3. The vibrating structure gyroscope as claimed in claim 1 , wherein the compensation unit is arranged to output the scale factor correction based on the signal from the drive system and a stored reference value, wherein the stored reference value is a value of a signal from the drive system obtained during a calibration procedure.

4. A vibrating structure gyroscope as claimed in claim 3 , wherein the compensation unit is arranged to output the scale factor correction further based on a known relationship between a signal level of the signal from the drive system, magnetic field strength and scale factor error.

5. The vibrating structure gyroscope as claimed in claim 1 , wherein the compensation unit includes a lookup table that is arranged to provide a scale factor correction value according to the input signal from the drive system.

6. The vibrating structure gyroscope as claimed in claim 1 , wherein the compensation unit is arranged to receive a temperature signal and to output the scale factor correction based on both the signal from the drive system and the temperature signal.

7. The vibrating structure gyroscope as claimed in claim 6 , wherein the compensation unit includes a lookup table that is arranged to provide a scale factor correction value according to both the signal from the drive system and the temperature signal.

8. The vibrating structure gyroscope as claimed in claim 1 , further comprising:
a sensing system arranged to sense the vibrations of the vibrating structure and arranged to output an angular rate signal based on the sensed vibrations;
wherein the vibrating structure gyroscope is arranged to apply the scale factor correction to the angular rate signal to provide an output of the vibrating structure gyroscope.

9. A method of calibrating a gyroscope, comprising:
providing a gyroscope as claimed in claim 1 ;
evaluating a strength of a signal from the drive system in a test environment while the gyroscope is not rotating; and
storing in the compensation unit information based on the evaluation of the drive system that allows determination of the scale factor correction from the signal from the drive system.

10. The method of as claimed in claim 9 , further comprising storing in the compensation unit information on a relationship between the strength of the signal from the drive system and the magnetic field of the permanent magnet.

11. The method as claimed in claim 9 , wherein evaluating comprises evaluating the strength of the signal from the drive system across a range of temperatures.

12. The method as claimed in claim 9 , wherein storing comprises storing the information in a lookup table.

Assignees

• Atlantic Inertial Systems Ltd

Inventors

• Williamson Matthew
• Sheard John Keith
• Gregory Christopher M

Classifications

• G01C19/5684 Primary

  the devices involving a micromechanical structure · CPC title

• G01C19/5677 Primary

  of essentially two-dimensional [2D] vibrators, e.g. ring-shaped vibrators · CPC title

• G01C19/5726 Primary

  Signal processing · CPC title

• G01C19/5776 Primary

  Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719 · CPC title

• B81B2201/0242

  Gyroscopes · CPC title