Gyroscope sensitivity calibration
An in-situ calibration system, method and apparatus is disclosed that uses test electrodes to stimulate a proof-mass of a MEMS based gyroscope at a drive frequency as quasi-Coriolis forces to extract the electromechanical gain, and uses a non-resonant carrier signal on the proof-mass to extract the additional changes in the sense and drive capacitance. Additionally, an in-situ calibration system, method and apparatus is disclosed that uses quadrature electrodes to apply a known force stimulus to the proof-mass as part of a calibration procedure, where the known force is applied again after installation into a system or further into the life of the gyroscope. Differences in the proof-mass response to the force are proportional to changes in sensitivity, which allows the sensitivity to be corrected in-field.
1. A method of calibrating sensitivity of a micro-electrical-mechanical system (MEMS) based gyroscope, comprising:
driving a proof-mass of the MEMS based gyroscope using signals from a drive capacitance-to-voltage (C2V) converter output to generate quasi-Coriolis forces on the proof-mass;
extracting electromechanical gain from the MEMS based gyroscope; and
using the gain to recalibrate a sensitivity of the MEMS based gyroscope.
2. The method of claim 1 further comprising:
injecting a non-resonant carrier signal into the proof-mass of the MEMS based gyroscope to extract additional changes in a sense capacitance and a drive capacitance of the MEMS based gyroscope; and
using the gain and the additional changes to recalibrate sensitivity of the MEMS based gyroscope.
3. A method of calibrating sensitivity of a micro-electrical-mechanical system (MEMS) based gyroscope, comprising:
at a first time:
driving, by quadrature test electrodes, a proof-mass of the MEMS based gyroscope at a drive frequency to apply a known force stimulus to the proof-mass;
determining a first response of the proof-mass to the known force stimulus;
at a second time after the first time:
driving, by the quadrature test electrodes, the proof-mass of the MEMS based gyroscope at the drive frequency to apply the known force stimulus to the proof-mass;
determining a second response of the proof-mass to the known force stimulus;
determining a difference in first and second responses of the proof-mass to the know force stimulus; and
using the difference to recalibrate sensitivity of the MEMS based gyroscope.
4. The method of claim 3 further comprising:
injecting a non-resonant carrier signal into the proof-mass of the MEMS based gyroscope to extract additional changes in a sense capacitance and a drive capacitance of the MEMS based gyroscope; and
using the difference and the additional changes to recalibrate sensitivity of the MEMS based gyroscope.
5. A gyroscope sensitivity calibration system, comprising:
a micro-electrical-mechanical system (MEMS) based gyroscope including:
a drive mass;
a sense mass disposed within an opening of the drive mass and configured to move within the opening in response to the drive mass moving along a drive axis;
test electrodes configured to excite the drive mass during a calibration mode of operation;
a drive system configured to generate quasi-Coriolis excitation signals and apply the excitation signals to the test electrodes, wherein the quasi-Coriolis excitation signals excite the drive mass with quasi-Coriolis forces to induce quasi-Coriolis excitation forces on the sense mass; and
a sense system configured to extract a varying capacitance due to displacement of the sense mass in response to the induced quasi-Coriolis excitation forces, and to determine a mechanical sensitivity of the MEMS based gyroscope based on the varying capacitance.