Gyroscope that compensates for fluctuations in sensitivity

• US 9,869,552 B2
• Filed: 03/20/2015
• Issued: 01/16/2018
• Est. Priority Date: 03/20/2015
• Status: Active Grant

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Gregory, Jeffrey A.
• Primary Examiner(s): Laballe, Clayton E
• Assistant Examiner(s): Butler, Kevin
• Application Number:
  US14/664,034
• Publication Number:
  US 20170023364A1
• Time in Patent Office: 1,033 Days
• Field of Search: 7350412
• 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 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: G01C 19/5642 using vibrating bars or beams
• CPC Class Codes: G01C 19/5649 Signal processing
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/13 by measuring the force required to restore a proofmass subjected to inertial forces to a null position
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A method compensates for a sensitivity of an inertial sensor having a resonator and an accelerometer. The method includes adding a test signal to a quadrature tuning voltage applied to the resonator of the inertial sensor. The method also includes receiving a quadrature error signal from the accelerometer of the inertial sensor. The method also includes detecting a phase difference between the quadrature error signal and the test signal. The method also includes determining a bandwidth of the accelerometer based on the detected phase difference, the bandwidth indicating the sensitivity of the accelerometer.

Claims

1. A method of compensating a gyroscope for bandwidth sensitivity, the method comprising:

generating a test signal;

generating a quadrature error signal using a received Coriolis sense signal;

detecting a phase difference between the quadrature error signal and the test signal;

determining a bandwidth of the gyroscope based on the detected phase difference; and

compensating the gyroscope for bandwidth sensitivity by using the Coriolis sense signal and the bandwidth of the gyroscope.

2. The method of claim 1, wherein determining the bandwidth of the gyroscope comprises:

determining a time constant τ

of the gyroscope and determining the bandwidth based on the time constant τ

.

3. The method of claim 1, wherein determining the bandwidth of the gyroscope comprises adjusting a frequency of the test signal until the phase difference is equal to a predetermined value.

4. The method of claim 3, wherein adjusting the frequency of the test signal comprises:

adjusting the frequency of the test signal until the phase difference is equal to 45 degrees.

5. The method of claim 1, wherein detecting the phase difference between the quadrature error signal and the test signal comprises:

demodulating the quadrature error signal with the test signal;

determining a direct current (DC) component of the demodulated quadrature error signal; and

detecting the phase difference based on the DC component.

6. The method of claim 5, wherein determining the bandwidth of the gyroscope comprises:

adjusting a frequency of the test signal until the direct current (DC) component of the demodulated quadrature error signal is zero (0).

7. The method of claim 1, wherein detecting the phase difference between the quadrature error signal and the test signal comprises:

demodulating the quadrature error signal with the test signal;

determining an alternating current (AC) component of the demodulated quadrature error signal; and

detecting the phase difference based on the AC component.

8. The method of claim 1,

wherein generating the test signal comprises generating a dither signal, and

wherein detecting the phase difference between the quadrature error signal and the test signal comprises detecting a phase difference between the quadrature error signal and the dither signal.

9. The method of claim 1, wherein generating the quadrature error signal using the received Coriolis sense signal comprises demodulating the Coriolis sense signal with a quadrature reference signal generated by the gyroscope.

10. The method of claim 1, wherein compensating the gyroscope for bandwidth sensitivity by using the Coriolis sense signal and the bandwidth of the gyroscope comprises:

generating a rate signal by demodulating the Coriolis sense signal with an in-phase reference signal generated by a resonator of the gyroscope; and

multiplying the rate signal by a value indicative of the bandwidth of the gyroscope.

11. An apparatus for compensating a gyroscope for bandwidth sensitivity, the apparatus comprising:

the gyroscope; and

circuitry including;

a test signal generator configured to generate a test signal;

a phase difference detector configured to detect a phase difference between the test signal and a quadrature error signal generated using a Coriolis sense signal obtained from the gyroscope,

a sensitivity gauge configured to determine a bandwidth of the gyroscope based on the phase difference; and

a compensating circuit configured to compensate the gyroscope for bandwidth sensitivity by using the Coriolis sense signal and the determined bandwidth of the gyroscope.

12. The apparatus of claim 11, wherein the phase difference detector is configured to detect the phase difference at least in part by demodulating the quadrature error signal with the test signal.

13. The apparatus of claim 11, wherein the test signal generator is configured to adjust a frequency of the test signal until the quadrature error signal and the test signal are 45 degrees out of phase.

14. The apparatus of claim 11, wherein the test signal generator is configured to adjust a frequency of the test signal until a direct current (DC) component of the phase difference is zero (0).

15. The apparatus of claim 11, wherein the sensitivity gauge comprises a proportional-integrator (PI) controller.

16. The apparatus of claim 11, wherein the test signal generator comprises a voltage-controlled oscillator (VCO).

17. An apparatus, comprising:

a gyroscope; and

circuitry coupled to the gyroscope, the circuitry comprising;

a phase difference detector coupled to an output of the gyroscope;

an oscillator;

a bandwidth detector coupled to an output of the oscillator and an output of the phase difference detector; and

a compensating circuit coupled to the output of the gyroscope and to an output of the bandwidth detector.

18. The apparatus of claim 17, wherein the oscillator comprises a voltage-controlled oscillator (VCO).

19. The apparatus of claim 17, wherein the bandwidth detector comprises a proportional-integrator (PI) controller.

20. The apparatus of claim 17, wherein the compensating circuit comprises a multiplying unit.