Vibrating structural gyroscope with quadrature control

• US 8,661,898 B2
• Filed: 10/14/2009
• Issued: 03/04/2014
• Est. Priority Date: 10/14/2008
• Status: Expired due to Fees

• Current Assignee: Watson Industries, Inc.
• Original Assignee: Watson Industries, Inc.
• Inventors: Watson, William S.
• Primary Examiner(s): Macchiarolo, Peter
• Assistant Examiner(s): Shah, Samir M
• Application Number:
  US12/579,098
• Publication Number:
  US 20100089158A1
• Time in Patent Office: 1,602 Days
• Field of Search: 735/041.2, 735/033, 735/040.8, 735/041.8, 735/40, 73/13.7
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5691 of essentially three-dimensional vibrators, e.g. wine glass-type vibrators

Abstract

An apparatus and/or method that corrects for tuning errors in vibrating structure gyroscopes that are configured to be driven along a plurality of axes without the need for dedicated torque elements. The correction is accomplished by introducing a phase offset in the drive signal of one or more of the drive elements relative to other drive elements to minimize or reduce the quadrature signal. The tuning may be accomplished as a one time “set and forget” adjustment, as a manual adjustment performed at the discretion of the user, or as a closed loop active correction system. The technique improves the tuning of the resonator assembly, rather than merely compensating for the mistuning. Accordingly, for various embodiments of the invention, the destructive interference between the plurality of drive axes is reduced. Conservation of vibrational energy present in the resonator is thus enhanced, with less vibrational energy transferred to the support structure.

Claims

1. A method for controlling a quadrature signal of a vibrating structure gyroscope, comprising:

providing a resonator assembly including an axisymmetric resonator defining a

central axis, a plurality of drive elements operatively coupled with said axisymmetric resonator and adapted to sustain a resonant oscillation pattern on said axisymmetric resonator, a first of said drive elements adapted to be driven along a first drive axis, a second of said plurality of drive elements adapted to be driven along a second drive axis, and at least one sense element operatively coupled with said axisymmetric resonator, said at least one sense element being adapted to detect a rotation rate;

driving said resonator assembly along said first drive axis with said first of said drive elements and in accordance with a first drive signal;

driving said resonator assembly along said second drive axis with said second of said drive elements and in accordance with a second drive signal;

measuring a rotation rate signal from said at least one sense element while said resonator assembly is driven along said first drive axis and said second drive axis;

inferring the quadrature signal from said rotation rate signal;

imposing a combined phase offset between said first drive signal and said second drive signal so that said quadrature signal is maintained at a desired level.

2. The method of claim 1, wherein imposing said combined phase offset is performed such that said quadrature signal is maintained at a minimum magnitude.

3. The method of claim 1 wherein imposing said combined phase offset between said first drive signal and said second drive signal includes imposing a first phase offset on the first drive signal and a second phase offset on the second drive signal, said second phase offset being an opposite of and substantially equal to said first phase offset.

4. The method of claim 1 further comprising:

providing at least one drive sensor adapted to sense a driving oscillation of the resonator assembly;

providing a phase-locked loop driving system having an input operatively coupled with said at least one drive sensor and having outputs operatively coupled to said first and said second of said plurality of drive elements;

causing said phase-locked loop driving system to output said first drive signal and said second drive signal, said first drive signal and said second drive signal having a frequency that substantially matches the frequency of said driving oscillation.

5. The method of claim 1 wherein said at least one sense element provided in the step of providing is adapted to sense a driving oscillation of the resonator assembly, the method further comprising:

providing a phase-locked loop driving system having an input operatively coupled with at least one driving sensor and having outputs operatively coupled to said first and said second of said plurality of drive elements;

causing said phase-locked loop driving system to output said first drive signal and said second drive signal, said first drive signal and said second drive signal having a frequency that substantially matches the frequency of said driving oscillation.

6. The method of claim 1:

wherein said drive elements of said resonator assembly provided in said step of providing are adapted to sustain said resonant oscillation pattern to include a plurality of anti-node pairs that define a plurality of reference axes when said resonator assembly is rotationally at rest, each of said anti-node pairs being diametrically opposed about said central axis, each of said plurality of reference axes passing through a corresponding one of said plurality of anti-node pairs;

wherein said first drive axis of said resonator assembly provided in said step of providing is offset by a first rotational offset relative to a first of said plurality of reference axes, said first drive axis being other than coincident with any of said plurality of reference axes; and

wherein said second drive axis of said resonator assembly provided in said step of providing is offset by a second rotational offset relative to a second of said plurality of reference axes, said second drive axis being other than coincident with any of said plurality of reference axes, said second rotational offset being in a direction opposite from said first rotational offset.

7. The method of claim 1, wherein said first drive as and said second drive axis that are driven in said steps of driving are offset with respect to each other.

8. The method of claim 1, wherein said first and second drive axes that are driven in said steps of driving are substantially coincident.

9. The method of claim 1 further comprising obtaining a phase demodulation error.

10. A quadrature controlled vibrating structure gyroscope, comprising:

a resonator assembly including;

an axisymmetric resonator defining a central axis,

a plurality of drive elements operatively coupled with said axisymmetric resonator, a first of said plurality of drive elements adapted to be driven along a first drive axis in accordance with a first drive signal, a second of said plurality of drive elements adapted to be driven along a second drive axis in accordance with a second drive signal, and

at least one sense element operatively coupled with said axisymmetric resonator, said at least one sense element being adapted to detect a rotation rate; and

a control system operatively coupled with said plurality of drive elements and adapted to sustain said a resonant oscillation pattern on said axisymmetric resonator and to infer a quadrature component from said rotation rate signal measured from said at least one sense element, said control system being further adapted to control a combined phase offset between said first drive signal and said second drive signal for control of the magnitude of said quadrature component.

11. The quadrature controlled vibrating structure gyroscope of claim 10, wherein said first drive axis and said second drive axis are rotationally offset relative to said central axis.

12. The quadrature controlled vibrating structure gyroscope of claim 11,

wherein said control system and said drive elements are adapted to sustain said oscillation pattern to include a plurality of anti-node pairs that define a plurality of reference axes when said resonator assembly is rotationally at rest, each of said plurality of anti-node pairs being diametrically opposed about said central axis, each of said plurality of reference axes passing through a corresponding one of said plurality of anti-node pairs;

wherein said first drive axis is offset by a first rotational offset relative to a first of said plurality of reference axes, said first drive axis being other than coincident with any of said plurality of reference axes; and

wherein said second drive axis is offset by a second rotational offset relative to a second of said plurality of reference axes, said second drive axis being other than coincident with any of said plurality of reference axes, said second rotational offset being in a direction opposite from said first rotational offset.

13. The quadrature controlled vibrating structure gyroscope of claim 10 wherein said second drive axis is rotationally offset with respect to said first drive axis.

14. The quadrature controlled vibrating structure gyroscope of claim 10 wherein said control system is operatively coupled with said at least one sense element, said control system being a closed loop control system that utilizes said quadrature signal as a feedback signal.

15. The quadrature controlled vibrating structure gyroscope of claim 10 wherein said first drive element is adapted to be driven by a first drive signal defined by

K SIN(ω

t)+Kα

COS(ω

t)

and said second drive element is adapted to be driven by a second drive signal defined by

Kα

COS(ω

t)−

K SIN(ω

t)

where K is an amplitude of said drive signal, α

is a phase offset, ω

is a drive frequency and t is a time parameter.

16. The quadrature controlled vibrating structure gyroscope of claim 15 wherein said control system further comprises:

an automatic gain control adapted to provide said amplitude of said drive signal;

a quadrature phase adjustment source adapted to provide said phase offset;

a sine wave reference adapted to provide the SIN(ω

t) function; and

a cosine wave reference adapted to provide the COS(ω

t) function.

17. The quadrature controlled vibrating structure gyroscope of claim 10 wherein said first drive element is adapted to be driven by a first drive signal defined by

K SIN(ω

t)+Kα

COS(ω

t)

and said second drive element is adapted to be driven by a second drive signal defined by

Kα

SIN(ω

t)−

Kα

COS(ω

t)

where K is an amplitude of said drive signal, α

is a phase offset, ω

is a drive frequency and t is a time parameter.

18. The quadrature controlled vibrating structure gyroscope of claim 17 wherein said control system further comprises:

an automatic gain control adapted to provide said amplitude of said drive signal;

a quadrature phase adjustment source adapted to provide said phase offset;

a sine wave reference adapted to provide the SIN(ω

t) function; and

a cosine wave reference adapted to provide the COS(ω

t) function.

19. The quadrature controlled vibrating structure gyroscope of claim 10 wherein said resonator assembly comprises an axisymmetric resonator selected from the group consisting of a cup resonator, a hemispherical resonator, a ring resonator, a two-tine fork resonator and a four-tine fork resonator.

20. A method for controlling a quadrature controlled vibrating structure gyroscope, comprising:

providing a resonator assembly, said resonator assembly including;

an axisymmetric resonator defining a central axis;

a plurality of drive elements operatively coupled with said axisymmetric resonator and adapted to sustain a resonant oscillation pattern on said axisymmetric resonator, a first of said drive elements adapted to be driven along a first drive axis, a second of said plurality of drive elements adapted to be driven along a second drive axis, said second drive axis being offset with respect to said first drive axis, and

at least one sense element operatively coupled with said axisymmetric resonator, said at least one sense element being adapted to detect a rotation rate;

providing a central microprocessor operatively coupled to said axisymmetric resonator; and

providing a computer-readable medium operatively coupled with said central microprocessor and including instructions for control of said quadrature controlled vibrating structure gyroscope, said instructions comprising;

driving said resonator assembly along said first drive axis in accordance with a first drive signal,

driving said resonator assembly along said second drive axis in accordance with a second drive signal,

measuring a rotation rate signal from said at least one sense element while said resonator assembly is driven along said first and second drive axes,

inferring a quadrature signal from said rotation rate signal, and

imposing a combined phase offset between said first drive signal and said second drive signal so that said quadrature signal is maintained at a desired level.

21. The method of claim 20 wherein said second drive axis is rotationally offset with respect to said first drive axis.

22. The method of claim 21, further comprising:

configuring said control system and said drive elements to sustain said oscillation pattern to include a plurality of anti-node pairs that define a plurality of reference axes when said resonator assembly is rotationally at rest, each of said plurality of anti-node pairs being diametrically opposed about said central axis, each of said plurality of reference axes passing through a corresponding one of said plurality of anti-node pairs;

arranging said first drive axis to be offset by a first rotational offset relative to a first of said plurality of reference axes, said first drive axis being other than coincident with any of said plurality of reference axes; and

arranging said second drive axis to be offset by a second rotational offset relative to a second of said plurality of reference axes, said second drive axis being other than coincident with any of said plurality of reference axes, said second rotational offset being in a direction opposite from said first rotational offset.

23. The method of claim 20, further comprising operatively coupling said control system with said at least one sense element, said control system being a closed loop control system that utilizes said quadrature signal as a feedback signal.

24. The method of claim 20 further comprising configuring said control system to drive said first drive element with a first drive signal defined by

K SIN(ω

t)+Kα

COS(ω

t)

and configuring said control system to drive said second drive element with a second drive signal defined by

Kα

COS(ω

t)−

K SIN(ω

t)

where K is an amplitude of said drive signal, α

is a phase offset, ω

is a drive frequency and t is a time parameter.

25. The method of claim 20 further comprising configuring said control system to drive said first drive element with a first drive signal defined by

K SIN(ω

t)+Kα

COS(ω

t)

and configuring said control system to drive said second drive element with a second drive signal defined by

K SIN(ω

t)−

Kα

COS(ω

t)

where K is an amplitude of said drive signal, α

is a phase offset, ω

is a drive frequency and t is a time parameter.