Systems and methods for controlling oscillation of a gyroscope

• US 9,645,166 B2
• Filed: 06/26/2015
• Issued: 05/09/2017
• Est. Priority Date: 06/26/2014
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Lumedyne Technologies Incorporated (Alphabet Inc.)
• Inventors: Waters, Richard Lee, Jacobs, John David, Brayshaw, Jeffrey Alan, Chisum, Brad Wesley, Fralick, Mark Steven, Tally, IV, Charles Harold, Huang, Xiaojun
• Primary Examiner(s): Patel, Harshad R
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US14/751,727
• Publication Number:
  US 20150377622A1
• Time in Patent Office: 683 Days
• CPC Class Codes: G01C 19/5705 using masses driven in reciprocating rotary motion about an axis
• CPC Class Codes: G01C 19/5726 Signal processing
• CPC Class Codes: G01C 19/5747 each sensing mass being connected to a driving mass, e.g. driving frames
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

Systems and methods are disclosed herein for determining rotation. A gyroscope includes a drive frame and a base, the drive frame springedly coupled to the base. The gyroscope includes a drive structure configured for causing a drive frame to oscillate along a first axis. The gyroscope includes a sense mass springedly coupled to the drive frame. The gyroscope includes a sense mass sense structure configured for measuring a displacement of the sense mass along a second axis orthogonal to the first axis. The gyroscope includes measurement circuitry configured for determining a velocity of the drive frame, extracting a Coriolis component from the measured displacement, and determining, based on the determined velocity and extracted Coriolis component, a rotation rate of the gyroscope.

Claims

1. A system for controlling oscillation of a gyroscope, comprising:

a drive frame springedly coupled to a base of the gyroscope, wherein;

the drive frame comprises a first plurality of equally spaced teeth, and

the base comprises a second plurality of equally spaced teeth;

a drive structure that causes the drive frame to oscillate relative to the base by applying an oscillation voltage between the drive frame and the base; and

a sense structure that measures an analog signal corresponding to displacement of the drive frame due to the oscillation, wherein monotonic motion of the first plurality of equally spaced teeth relative to the second plurality of equally spaced teeth causes a non-monotonic change in the analog signal,

an analog front end that converts the analog signal to a voltage;

a comparator that determines times at which the voltage crosses a threshold;

a time to digital converter that determines respective time intervals between the times, wherein the respective time intervals are based on motion of the first plurality of equally spaced teeth past an aligned position with the second plurality of equally spaced teeth;

drive velocity detection circuitry that determines, based on the respective time intervals, an amplitude of the oscillation of the drive frame; and

a controller that;

compares the amplitude to a setpoint that is based on a predetermined value, and

controls the oscillation of the gyroscope by adjusting the oscillation voltage between the drive frame and the base, based on the comparing of the amplitude and the setpoint.

2. The system of claim 1, wherein the controller comprises a digital controller.

3. The system of claim 1, wherein the analog front end comprises a transimpedance amplifier.

4. The system of claim 3, wherein the controller further adjusts the oscillation by adjusting a common mode output voltage of the transimpedance amplifier.

5. The system of claim 1, wherein the controller controls the oscillation by adjusting a common mode output voltage of an amplifier used to apply the oscillation voltage between the drive frame and the base.

6. The system of claim 5, wherein the amplifier is a fixed gain amplifier.

7. The system of claim 1, wherein the analog front end comprises a charge amplifier.

8. The system of claim 1, wherein the analog front end comprises a switched capacitor.

9. The system of claim 1, comprising:

a variable gain amplifier configured for applying the oscillation voltage between the drive frame and the base; and

wherein the controller is configured for adjusting a gain of the variable gain amplifier.

10. The system of claim 9, wherein the variable gain amplifier is a transconductance amplifier.

11. The system of claim 1, wherein the analog front end further comprises:

a full-wave rectifier configured for rectifying the analog signal; and

a low-pass filter configured for filtering the rectified signal;

wherein the analog front end converts the analog signal to the voltage by converting the filtered signal to the voltage.

12. The system of claim 11, wherein the controller comprises an analog controller.

13. A method for controlling oscillation of a gyroscope, comprising:

causing a drive frame of the gyroscope to oscillate relative to a base of the gyroscope by applying an oscillation voltage between the drive frame and the base, wherein;

the drive frame comprises a first plurality of equally spaced teeth, and

the base comprises a second plurality of equally spaced teeth;

measuring an analog signal corresponding to displacement of the drive frame due to the oscillation, wherein monotonic motion of the first plurality of equally spaced teeth relative to the second plurality of equally spaced teeth causes a non-monotonic change in the analog signal;

converting the analog signal to a voltage;

determining respective time intervals between times at which the voltage crosses a threshold, wherein the respective time intervals are based on motion of the first plurality of equally spaced teeth past an aligned position with the second plurality of equally spaced teeth,

determining, based on the respective time intervals, an amplitude of the oscillation of the drive frame;

comparing the amplitude to a setpoint that is based on a predetermined value; and

controlling the oscillation of the gyroscope by adjusting the oscillation voltage between the drive frame and the base, based on the comparing of the amplitude to the setpoint.

14. The method of claim 13, wherein controlling the oscillation comprises adjusting, with a digital controller, the oscillation voltage between the drive frame and the base.

15. The method of claim 13, wherein converting the analog signal to the voltage comprises using a transimpedance amplifier to convert the analog signal to the voltage.

16. The method of claim 15, wherein adjusting the oscillation voltage between the drive frame and the base comprises adjusting a common mode output voltage of the transimpedance amplifier.

17. The method of claim 13, wherein adjusting the oscillation voltage between the drive frame and the base comprises adjusting a common mode output voltage of an amplifier used to cause the drive frame to oscillate.

18. The method of claim 17, wherein the amplifier is a fixed gain amplifier.

19. The method of claim 13, wherein converting the analog signal to the voltage comprises using a charge amplifier to convert the analog signal to the voltage.

20. The method of claim 13, wherein converting the analog signal to the voltage comprises using a switched capacitor to convert the analog signal to the voltage.

21. The method of claim 13, wherein adjusting the oscillation voltage between the drive frame and the base comprises adjusting a gain of a variable gain amplifier used to cause the drive frame to oscillate.

22. The method of claim 21, wherein the variable gain amplifier is a transconductance amplifier.

23. The method of claim 13, wherein converting the analog signal to the voltage comprises:

rectifying, with a full-wave rectifier, the analog signal;

filtering, with a low-pass filter, the rectified signal; and

converting the rectified signal to the voltage.

24. The method of claim 23, wherein adjusting the oscillation voltage between the drive frame and the base comprises adjusting, with an analog controller, the oscillation voltage between the drive frame and the base.

25. A system for controlling oscillation of a gyroscope, comprising:

a drive frame springedly coupled to a base of the gyroscope, wherein;

the drive frame comprises a first plurality of equally spaced teeth, and

the base comprises a second plurality of equally spaced teeth; and

means for;

causing the drive frame to oscillate relative to the base by applying an oscillation voltage between the drive frame and the base,

measuring an analog signal corresponding to displacement of the drive frame due to the oscillation, wherein monotonic motion of the first plurality of equally spaced teeth relative to the second plurality of equally spaced teeth causes a non-monotonic change in the analog signal,

converting the analog signal to a voltage,

determining respective time intervals between times at which the voltage crosses a threshold, wherein the respective time intervals are based on motion of the first plurality of equally spaced teeth past an aligned position with the second plurality of equally spaced teeth,

determining, based on the respective time intervals, an amplitude of the oscillation of the drive frame,

comparing the amplitude to a setpoint that is based on a predetermined value, and

controlling the oscillation of the gyroscope by adjusting the drive voltage between the drive frame and the base, based on the comparing of the amplitude and the setpoint.