Phase-based measurement and control of a gyroscope

• US 10,030,976 B2
• Filed: 05/13/2015
• Issued: 07/24/2018
• Est. Priority Date: 05/13/2015
• Status: Active Grant

• Current Assignee: ROHM Co., Ltd.
• Original Assignee: Kionix Incorporated (ROHM Co., Ltd.)
• Inventors: DeWall, Jonah
• Primary Examiner(s): Kwok, Helen
• Application Number:
  US14/710,991
• Publication Number:
  US 20160334213A1
• Time in Patent Office: 1,168 Days
• CPC Class Codes: G01C 19/5684 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5712 the devices involving a micromechanical structure
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

A gyroscope includes a resonator, a transducer, and a comparator. The comparator is designed to receive an input signal from the transducer and compare the input signal with a reference signal to produce an output signal. Rising and falling edge transitions of the output signal are substantially synchronized with a motion of the resonator along a sense-axis of the transducer.

Claims

1. A gyroscope comprising:

a mechanical resonator;

a first transducer;

a comparator configured to;

receive an input signal from the transducer, and

compare the input signal with a reference signal to produce an output signal, wherein rising and falling edge transitions of the output signal are substantially synchronized with a motion of the mechanical resonator along a sense-axis of the transducer, and wherein the comparator is powered off during a period of time between subsequent rising and falling edge transitions; and

a first switch configured to open or close an electrical pathway between the transducer and an input of the comparator.

2. The gyroscope of claim 1, wherein the output signal is a mixed signal waveform (MSW).

3. The gyroscope of claim 1, wherein the sense-axis of the first transducer is aligned with a drive mode of the mechanical resonator.

4. The gyroscope of claim 1, wherein the sense-axis of the first transducer is aligned with a sense mode of the mechanical resonator.

5. The gyroscope of claim 1, wherein the reference signal includes at least one common-mode error shared with the input signal.

6. The gyroscope of claim 5, wherein the common-mode error is a voltage supply noise.

7. The gyroscope of claim 5, wherein the common-mode error is caused by a temperature variation.

8. The gyroscope of claim 1, wherein the comparator receives the reference signal from a reference source external to the comparator.

9. The gyroscope of claim 1, wherein the comparator receives the reference signal from a reference source within the comparator.

10. The gyroscope of claim 1, further comprising:

a second switch configured to open or close an electrical pathway between an actuator of the gyroscope and an external signal source.

11. The gyroscope of claim 10, wherein the first switch is controlled via a first control signal such that the first switch is closed during the rising and falling edge transitions of the output signal, and the first switch is open during a period of time when the output signal has a substantially constant voltage.

12. The gyroscope of claim 10, wherein the second switch is controlled via a second control signal such that the second switch is open during the rising and falling edge transitions of the output signal, and the second switch is closed during a period of time when the output signal has a substantially constant voltage.

13. The gyroscope of claim 12, wherein the external signal source produces a signal configured to cause motion of the mechanical resonator via the actuator when the second switch is closed.

14. The gyroscope of claim 1, wherein the reference signal is received from a second transducer of the gyroscope at a second input of the comparator.

15. The gyroscope of claim 14, wherein the first transducer and the second transducer are configured to sense motion about nominally anti-parallel sense axes.

16. The gyroscope of claim 1, wherein the output signal is a first output signal, and the gyroscope further comprises:

a second transducer; and

a second comparator configured to;

receive a second input signal from the second transducer,

compare the second input signal with a second reference signal to produce a second output signal,

wherein rising and falling edge transitions of the second output signal are substantially synchronized with a motion of the mechanical resonator along a sense-axis of the second transducer, and

wherein a phase shift between the first output signal and the second output signal is proportional to an externally applied angular rate.

17. The gyroscope of claim 16, further comprising a phase detect module configured to receive the first output signal and the second output signal and to produce one or more additional output signals having pulse widths that are proportional to the phase shift between the first output signal and the second output signal.

18. The gyroscope of claim 17, further comprising a signal processing module configured to:

receive the one or more additional output signals;

perform signal processing functions on the received one or more additional output signals; and

produce a processed output signal proportional to the externally applied angular rate.

19. The gyroscope of claim 17, wherein the one or more additional output signals comprise complementary output signals, wherein pulse widths of a first complementary output signal are proportional to the phase of the first output signal with respect to the phase of the second output signal, and pulse widths of a second complementary output signal are proportional to the phase of the second output signal with respect to the phase of the first output signal.

20. The gyroscope of claim 16, where the first transducer is aligned with a sense-axis of the mechanical resonator and the second transducer is aligned with a drive-mode of the mechanical resonator.

21. The gyroscope of claim 16, where the first and second transducers are configured to sense motion about nominally anti-parallel sense axes, and to sense common-mode motion.

22. The gyroscope of claim 21, where the common-mode motion is a drive-mode motion.

23. The gyroscope of claim 21, where the common-mode motion is the motion of an auxiliary resonator mode.

24. A gyroscope comprising:

a mechanical resonator;

an actuator;

a transducer;

a comparator configured to;

receive an input signal from the transducer, and

compare the input signal with a reference signal to produce an output signal, wherein rising and falling edge transitions of the output signal are substantially synchronized with a motion of the mechanical resonator along a sense-axis of the transducer, and wherein the comparator is powered off during a period of time between subsequent rising and falling edge transitions;

a driver module configured to receive the output signal and produce a driving signal that is applied to the actuator; and

a first switch configured to open or close an electrical pathway between the transducer and an input of the comparator.

25. The gyroscope of claim 24, wherein the driver module is configured to produce a driving signal that toggles between a first voltage and a second voltage.

26. The gyroscope of claim 24, further comprising a gain control module configured to:

receive a peak-amplitude signal from the comparator,

compare the peak-amplitude signal with a target value, and

produce a driving amplitude signal received by the driver module and configured to control an amplitude of the driving signal.

27. The gyroscope of claim 24, further comprising:

a second switch configured to open or close an electrical pathway between the actuator and the driver module.

28. A gyroscope comprising:

a mechanical resonator;

a first transducer and a second transducer, the first transducer being aligned to a first axis of the resonator and the second transducer being aligned to a second axis of the mechanical resonator;

a phase detect circuit configured to detect a phase shift between an output of the first transducer and an output of the second transducer, wherein the phase shift is proportional to an externally applied angular rate;

a feedback control circuit configured to produce a feedback signal based on the detected phase shift, wherein the feedback signal counteracts the detected phase shift by suppressing motion of the mechanical resonator; and

a first actuator configured to receive the feedback signal and counteract the phase shift by producing an oscillatory force onto the mechanical resonator.

29. The gyroscope of claim 28, wherein the output of the first transducer is a first electrical signal, substantially synchronized with motion along the first axis of the mechanical resonator, and the output of the second transducer is a second electrical signal, substantially synchronized with motion along the second axis of the mechanical resonator.

30. The gyroscope of claim 29, where the first axis is nominally aligned with a sense-axis of the mechanical resonator, and the second axis is nominally aligned with a drive-mode of the mechanical resonator.

31. The gyroscope of claim 29, where the first and second axes are primarily aligned to anti-parallel sense axes and partially aligned to a common-mode axis of the mechanical resonator.

32. The gyroscope of claim 31, where the common-mode axis is a drive-mode of the mechanical resonator.

33. The gyroscope of claim 31, where the common-mode axis is an auxiliary mode of the mechanical resonator.

34. The gyroscope of claim 28, wherein the actuator is configured to counteract the phase shift by producing an electrostatic damping onto the mechanical resonator.

35. The gyroscope of claim 28, wherein the actuator is configured to counteract the phase shift by producing an electrostatic stiffness onto the mechanical resonator.

36. The gyroscope of claim 28, further comprising:

a third transducer aligned with a drive mode of the mechanical resonator;

a second phase detect circuit configured to detect a second phase shift based on the outputs of the first and second transducers, and an output of the third transducer; and

a second feedback control circuit configured to produce a second feedback signal based on the detected second phase shift, wherein the second feedback signal maintains a substantially constant frequency separation between the drive-mode and a sense-mode of the mechanical resonator.

37. The gyroscope of claim 36, wherein the second feedback signal also maintains a constant phase shift between the drive-mode and the sense-mode.

38. The gyroscope of claim 36, further comprising a second actuator configured to receive the second feedback signal.

39. The gyroscope of claim 38, wherein the second actuator is configured to produce an oscillatory force onto the mechanical resonator, based on the second feedback signal.

40. The gyroscope of claim 38, wherein the second actuator is configured to produce an electrostatic stiffness onto the mechanical resonator, based on the second feedback signal.