Gyroscope self test by applying rotation on coriolis sense mass
A self-test method by rotating the proof mass at a high frequency enables testing the functionality of both the drive and sense systems at the same time. In this method, the proof mass is rotated at a drive frequency. An input force which is substantially two times the drive frequency is applied to the actuation structures to rotate the proof mass of the gyroscope around the sensitive axis orthogonal to the drive axis. An output response of the gyroscope at the drive frequency is detected by a circuitry and a self-test response is obtained.
1. A gyroscope comprising:
a proof mass vibrating along a drive axis;
a transducer for generating a drive motion signal, at a drive frequency, in response to the vibration of the proof mass along the drive axis;
a circuit for generating a self-test signal in response to the drive motion signal, the self-test signal having a frequency substantially twice the drive frequency, the self-test signal to be employed in a self-test or calibration of the gyroscope; and
an actuator configured to receive the self-test signal and to apply the self-test signal to the proof mass thereby inducing a rotation of the proof mass around a sensitive axis at substantially two times the drive frequency to generate a Coriolis force on the proof mass.
2. The gyroscope, as recited in claim 1 , wherein the actuator is an electrostatic parallel plate capacitor.
3. The gyroscope, as recited in claim 1 , further including a frame coupled to the proof mass and capable of rotating the proof mass about the sensitive axis.
4. The gyroscope, as recited in claim 3 , wherein the actuator is coupled to the frame.
5. The gyroscope, as recited in claim 3 , wherein the actuator is directly coupled to the frame.
6. The gyroscope, as recited in claim 3 , wherein the actuator is indirectly coupled to the frame.
7. The gyroscope, as recited in claim 3 , wherein the frame surrounds the proof mass.
8. The gyroscope as recited in claim 3 , wherein the frame comprises of one or more elements.
9. The gyroscope as recited in claim 1 , wherein the actuator is electrostatic comb type.
10. The gyroscope as recited in claim 1 , wherein the proof mass has a degree of freedom along the sensitive axis.
11. The gyroscope as recited in claim 1 , wherein the signal is a sine wave.
12. The gyroscope as recited in claim 1 , wherein the signal is a square wave.
13. The gyroscope as recited in claim 1 , wherein the signal is generated by a phase lock loop (PLL).
14. The gyroscope as recited in claim 1 , further comprising a demodulator to demodulate an output of the gyroscope to generate an output signal.
15. The gyroscope as recited in claim 14 , wherein the output signal is responsive to the self-test signal.
16. The gyroscope as recited in claim 1 , wherein the gyroscope is responsive to angular velocity.
17. The gyroscope, as recited in claim 1 , wherein the frequency of the self-test signal is greater than substantially two times the drive frequency.
18. The gyroscope, as recited in claim 1 , wherein the self-test signal is generated by multiplying a signal in-phase with the drive amplitude and a signal in-phase with the drive velocity.
19. The gyroscope, as recited in claim 1 , wherein the frequency of the self-test signal is greater than the drive frequency.