Method and system for control and readout of tuning fork gyroscope
AssigneeThe Charles Stark Draper Laboratory, Inc.
InventorsPaul A. Ward, Richard D. Elliott, III, Daniel Joseph Guyon
Life of this patent
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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.
Claims14
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.
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.
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.
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.
Dependencies are inferred from the claim text.