Method and system for control and readout of tuning fork gyroscope

Patent metadata

Field	Value
Publication number	US-12163787-B2
Application number	US-202218067044-A
Country	US
Kind code	B2
Filing date	Dec 16, 2022
Priority date	Oct 16, 2018
Publication date	Dec 10, 2024
Grant date	Dec 10, 2024

Abstract

A tuning fork sensor system places a controlled bias on the proof-mass drive-axis electrodes to cancel the quadrature charge. Also, its charge amplifiers employ a field-effect transistor biased slightly into the triode region so that it behaves as a very large value resistor. In addition, it uses a phase-locked loop having a special loop filter in order to optimize performance by rejecting off-frequency drive feedthrough to the motor pick-off while resulting in very low phase wander for the demodulation references.

First claim

What is claimed is:

1. A tuning-fork sensor, comprising:
proof-masses;
comb drives for driving the proof masses;
a motor drive system for driving the comb drives with a drive signal having a drive axis resonance frequency;
a motor bias system for providing a bias voltage on the comb drives for quadrature nulling;
wherein a signal containing Coriolis information is digitally filtered to produce the quadrature nulling,
wherein a first half-resonance frequency square wave has a fixed amplitude, and a second half-resonance frequency square wave has an amplitude that is automatically adjusted to adjust an amplitude of the drive signal, and
wherein the drive signal is a sum of the first and second half-resonance frequency square waves.

2. The sensor as claimed in claim 1 , wherein the motor bias system comprises a digital demodulator for demodulating the digitally-filtered signal containing Coriolis information.

3. The sensor as claimed in claim 2 , wherein the demodulated signal containing Coriolis information is filtered by a comb filter.

4. The sensor as claimed in claim 1 , wherein a bandwidth of a quadrature nulling loop is equal to or greater than a bandwidth of an inertial rate measurement.

5. The sensor as claimed in claim 1 , wherein an off-frequency drive method provides the drive signal.

6. The sensor as claimed in claim 1 , further comprising an off-frequency drive that produces a drive force at a drive-axis resonance frequency, while electrical feedthrough artifacts are at a frequency different from the drive-axis resonance frequency.

7. The sensor as claimed in claim 1 , wherein the motor drive system includes a phase locked loop that rejects off-frequency artifacts in a motor pick-off signal.

8. The sensor as claimed in claim 7 , wherein the phase locked loop has low loop gain at a frequency equal to a frequency of the off-frequency drive artifacts.

9. The sensor as claimed in claim 7 , wherein a loop filter of the phase locked loop has a START and a RUN mode.

10. A method of operation of a tuning-fork sensor, comprising:
driving proof-masses;
detecting Coriolis information from the proof-masses;
providing, from a motor bias system, a motor bias voltage on comb drives of the proof-masses for quadrature nulling; and
digitally filtering a signal containing Coriolis information to generate the motor bias voltage;
wherein the proof-masses are driven with a drive signal having a drive-axis resonance frequency, and
wherein a first half-resonance frequency square wave has a fixed amplitude, and a second half-resonance frequency square wave has an amplitude that is automatically adjusted to adjust an amplitude of the drive signal, and
wherein the drive signal is a sum of the first and second half-resonance frequency square waves.

11. The method as claimed in claim 10 , wherein a bandwidth of a quadrature nulling loop of the motor bias system is equal to or greater than a bandwidth of an inertial rate measurement.

12. The method as claimed in claim 10 , further comprising demodulating the digitally filtered signal containing Coriolis information.

13. A tuning-fork sensor, comprising:
a first proof-mass and a second proof-mass;
a first sense plate disposed under the first proof-mass;
a second sense plate disposed under the second proof-mass;
a third sense plate disposed over the first proof-mass;
a fourth sense plate disposed over the second proof-mass;
comb drives for oscillating the first and second proof masses along a drive axis;
a motor drive system for driving the comb drives and operating at a drive-axis resonance frequency; and
a motor bias system for providing a bias voltage on the comb drives for quadrature nulling;
wherein the first and fourth sense plates are biased with a DC bias having a first polarity,
wherein the second and third sense plates are biased with the DC bias in an opposite polarity; and
wherein a signal containing Coriolis information is digitally filtered to produce the quadrature nulling;
wherein the proof-masses are driven with a drive signal having a drive-axis resonance frequency,
wherein a first half-resonance frequency square wave has a fixed amplitude, and a second half-resonance frequency square wave has an amplitude that is automatically adjusted to adjust an amplitude of a drive signal, and
wherein the drive signal is a sum of the first and second half-resonance frequency square waves.

14. A tuning-fork sensor, comprising:
proof-masses;
comb drives for driving the proof masses; and
a motor drive system for driving the comb drivers with a drive signal having a drive-axis resonance frequency;
wherein a first half-resonance frequency square wave has a fixed amplitude, and a second half-resonance frequency square wave has an amplitude that is automatically adjusted to adjust an amplitude of the drive signal, and
wherein the drive signal is a sum of the first and second half-resonance frequency square waves.

Assignees

• Charles Stark Draper Laboratory Inc

Inventors

• Ward Paul A
• Elliott Iii Richard D
• Guyon Daniel Joseph

Classifications

• H03F1/08

  Modifications of amplifiers to reduce detrimental influences of internal impedances of amplifying elements (wide-band amplifiers with inter-stage coupling networks incorporating these impedances H03F1/42) · CPC title

• G01C19/574

  the devices having two sensing masses in anti-phase motion · CPC title

• G01C19/5726

  Signal processing · CPC title

• G01C19/5621

  the devices involving a micromechanical structure · CPC title

• H03F3/70

  Charge amplifiers · CPC title