Vibrating rate gyro with slaving of detection frequency to excitation frequency

• US 20060117849A1
• Filed: 12/18/2003
• Published: 06/08/2006
• Est. Priority Date: 12/20/2002
• Status: Active Grant

• Current Assignee: Thales SA
• Original Assignee: Thales SA
• Inventors: Chaumet, Bernard, Gallon, Pierre
• Granted Patent: US 7,159,461 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• 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 19/574 the devices having two sensing masses in anti-phase motion

Abstract

The invention relates to a gyroscope comprising at least one mass capable of vibrating along an x axis at a resonant excitation frequency F_x capable of vibrating along a y axis perpendicular to the x axis, at a resonant detection frequency F_y, under the effect of a Coriolis force generated by a rotation about a z axis perpendicular to the x and y axes. It includes, connected to the mass or masses, a feedback control loop for controlling the resonant frequency F_y so that F_y is equal or practically equal to F_x throughout the duration of use of the gyroscope.

Claims

1. A gyroscope comprising at least one mass capable of vibrating along an x axis at a resonant excitation frequency F_x and capable of vibrating along a y axis perpendicular to the x axis, at a resonant detection frequency F_y, under the effect of the Coriolis force generated by a rotation about a z axis perpendicular to the x and y axes, comprising connected to the mass, a signal generator for generating a signal that disturbs the vibration of the mass along y, and a feedback control loop for controlling the resonant frequency F_y so that F_y is equal or practically equal to F_x throughout the duration of use of the gyroscope, the feedback control loop comprising:

means for modifying the resonant detection frequency F_y;

means for detecting the variation induced by the disturbing signal on the vibration of the mass along y, an error signal e representative of the difference between F_x and F_y being deduced from this variation; and

control means for controlling the F_y-modifying means, the control being established on the basis of the error signal e.

2. The gyroscope as claimed in claim 1, wherein the disturbing-signal generator is connected to the mass via the F_y-modifying means.

3. The gyroscope as claimed in claim 1, wherein the disturbing-signal generator is connected to the F_y-modifying means via the feedback control loop.

4. The gyroscope as claimed in claim 2, wherein the disturbing-signal generator is an oscillator of predetermined reference frequency F₀.

5. The gyroscope as claimed in claim 2, wherein, since the gyroscope has a predetermined bandwidth, the disturbing signal is a periodic signal of frequency F₀, where F₀ is above the bandwidth of the gyroscope but below F_x.

6. The gyroscope as claimed in claim 1, comprising:

excitation means for exciting the mass along y, with the aim of counterbalancing the vibration along y generated by the Coriolis force, wherein the disturbing-signal generator is connected to the mass via these excitation means.

7. The gyroscope as claimed in claim 1, comprising:

a y excitation loop and wherein the disturbing-signal generator is connected to the excitation means via the y excitation loop.

8. The gyroscope as claimed in claim 6, wherein the disturbing-signal generator is a voltage-controlled oscillator.

9. The gyroscope as claimed in claim 6, wherein, since the gyroscope has a predetermined bandwidth, the disturbing signal is a periodic signal, the frequency of which varies between F_x−

Δ

F and F_x+Δ

F according to a frequency F₀, where F₀ is above the bandwidth of the gyroscope but below F_x, Δ

F being equal to about 10% of F_x.

10. The gyroscope as claimed in of claim 6, wherein the excitation means comprise electrodes.

11. The gyroscope as claimed in claim 1, wherein the feedback control loop further comprises:

connected in series, means for shaping the signal output by the detection means, an amplitude detection device, an F₀-centered band-pass filter, a synchronous demodulator for synchronizing with the reference frequency F₀, and an integrator/corrector that is connected to the means for modifying the frequency F_y.

12. The gyroscope as claimed in claim 1, wherein, since the mass is connected to a rigid frame by means of springs along x and y, of respective stiffness K_x and K_y, the means for modifying the resonant frequency F_y comprise electrodes for controlling the stiffness K_y.

13. The gyroscope as claimed in claim 1, wherein the means for detecting the variation induced in the vibration of the mass along y comprise electrodes.

14. The gyroscope as claimed in claim 1, wherein, when the disturbing signal is a periodic signal of predetermined frequency F₀, the disturbing signal is a sinusoidal or triangular signal.

15. The gyroscope as claimed in claim 1, wherein the gyroscope is a micromachined gyroscope having a plane structure and in that the x and y axes lie in the plane of the plane structure.

16. The gyroscope as claimed in claim 1, wherein the gyroscope is a micromachined gyroscope having a plane structure and in that the x axis lies in the plane of the plane structure and the y axis does not lie in the plane of the plane structure.

17. The gyroscope as claimed in claim 1, wherein the gyroscope has a three-dimensional structure.