Coriolis oscillating gyroscopic instrument

• US 6,481,283 B1
• Filed: 04/04/2000
• Issued: 11/19/2002
• Est. Priority Date: 04/05/1999
• Status: Expired due to Fees

• Current Assignee: Milli Sensor Systems & Actuators, Inc.
• Original Assignee: Milli Sensor Systems & Actuators, Inc.
• Inventors: Cardarelli, Donato
• Primary Examiner(s): KWOK, HELEN C
• Application Number:
  US09/542,605
• Time in Patent Office: 959 Days
• Field of Search: 735/040.2, 735/040.3, 735/040.8, 735/040.9, 735/041.1, 735/10, 735/041.2, 735/041.8, 735/140.1, 74/5.R, 74/53.4
• US Class Current: 73/504.02
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• 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 15/14 by making use of gyroscopes gyroscopes per se G01C19/00

Abstract

Disclosed is a Coriolis Oscillating Gyroscopic instrument, comprising: a Double Ended Tuning Fork (DETF) having two stems and two tines; a Torque Summing Member (TSM) rigidly coupled to the DETF stems; drives located at least partially on the TSM for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency and a phase; a case; a plurality of flexures connecting the TSM to the case, to allow the TSM and the DETF to rotationally oscillate together relative to the case about a second axis transverse to the first axis; and a sensor and associated instrumentation for resolving rotation of the TSM relative to the case.

Claims

1. A Coriolis Oscillating Gyroscopic instrument, comprising:

a Double Ended Tuning Fork (DETF) having two stems and two tines;

a Torque Summing Member (TSM) rigidly coupled to the DETF stems;

means located at least partially on the TSM for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency and a phase;

a case;

a plurality of flexures connecting the TSM to the case, to allow the TSM and the DETF to rotationally oscillate together relative to the case about a second axis transverse to the first axis; and

means for resolving rotation of the TSM relative to the case.

2. The instrument of claim 1 wherein the flexures are co-linear along the second axis that serves as the gyroscopic input and output axes.

3. The instrument of claim 2, wherein the TSM is mass imbalanced about the second axis, so that the TSM experiences a pendulous torque when accelerated along a third axis transverse to both the first and second axes, causing the TSM and the DETF to rotate together about the second axis.

4. The instrument of claim 3, further including means for rotationally sinusoidally oscillating the TSM and the DETF together about the second axis, the oscillation having a constant amplitude, a phase, and a frequency the same as the tines'"'"' vibrational frequency.

5. The instrument of claim 4, further including means for resolving the phase difference between the tines'"'"' vibration along the first axis and the TSM rotational oscillation about the second axis.

6. The instrument of claim 5, further including means for altering the phase relationship between the tines'"'"' motion and the TSM and DETF oscillation, to generate a gyroscopic torque that balances the pendulous torque.

7. The instrument of claim 5, further including means, responsive to the means for resolving the phase difference, for determining the instrument acceleration along the third axis.

8. The instrument of claim 7, wherein the first and second axes are orthogonal.

9. The instrument of claim 2, further including means, responsive to the means for resolving rotation, for determining the TSM oscillation amplitude.

10. The instrument of claim 9, further including means, responsive to the means for determining the TSM oscillation amplitude, for determining the rate of rotation of the instrument about the input axis.

11. The instrument of claim 2 wherein the first and second axes are mutually orthogonal.

12. The instrument of claim 1, wherein the flexures are spaced circumferentially about the TSM in a common plane, and allow the TSM and the DETF to together rotationally oscillate in the plane about the second axis that is normal to the plane and that serves as the gyroscopic input and output axes.

13. The instrument of claim 12, wherein the instrument has an acceleration input axis in the plane, and the TSM is mass imbalanced about the second axis, so that the TSM experiences pendulous torque when accelerated along the acceleration input axis, causing the TSM and the DETF to rotate together about the second axis.

14. The instrument of claim 13, further including means, responsive to the means for resolving, for rotationally sinusoidally oscillating the TSM and the DETF together about the second axis, the oscillation having a constant amplitude, a phase, and a frequency the same as the tines'"'"' vibrational frequency.

15. The instrument of claim 14, further including means for resolving the phase difference between the tines'"'"' vibration along the first axis and the TSM rotational oscillation about the second axis.

16. The instrument of claim 15, further including means for altering the phase relationship between the tines'"'"' motion and the TSM and DETF oscillation, to generate a gyroscopic torque that balances the pendulous torque.

17. The instrument of claim 15, further including means, responsive to the means for resolving the phase difference, for determining the instrument acceleration along the acceleration input axis.

18. The instrument of claim 16, wherein the first and second axes are orthogonal.

19. The instrument of claim 12, further including means, responsive to the means for resolving rotation, for determining the TSM oscillation amplitude.

20. The instrument of claim 19, further including means, responsive to the means for determining the TSM oscillation amplitude, for determining the rate of rotation of the instrument about the input axis.

21. The instrument of claim 20 wherein the first and second axes are mutually orthogonal.

22. The instrument of claim 1 wherein the means for resolving rotation of the TSM relative to the case is at least partially located on the case.

23. The instrument of claim 4, wherein the means for rotationally sinusoidally oscillating the TSM and the DETF together is at least partially located on the case.

24. The instrument of claim 14, wherein the means for rotationally sinusoidally oscillating the TSM and the DETF together is at least partially located on the case.

25. The instrument of claim 1, wherein the tines comprise parallel plates.

26. The instrument of claim 1 wherein the DETF, the TSM and the flexures are located in the same plane to define an essentially planar instrument.

27. The instrument of claim 1, wherein the TSM is essentially cylindrical to define a three dimensional instrument.

28. A Coriolis Oscillating Gyroscopic instrument, comprising:

a Double Ended Tuning Fork (DETF) having two stems and two tines;

means for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency and a phase;

a case;

flexures connecting the DETF to the case and spaced circumferentially about the DETF in a common plane, to allow the DETF to rotationally oscillate in the plane about a second axis that serves as the gyroscopic input and output axis, and that is orthogonal to the first axis; and

means for resolving rotation of the DETF about the second axis.

29. The instrument of claim 28, further including means, responsive to the means for resolving rotation, for determining the DETF oscillation amplitude.

30. The instrument of claim 29, further including means, responsive to the means for determining the DETF oscillation amplitude, for determining the rate of rotation of the instrument about the input axis.

31. A Coriolis Oscillating Gyroscopic instrument, comprising:

a Double Ended Tuning Fork (DETF) having two stems and two tines;

means for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency and a phase;

a case;

a plurality of flexures connecting the DETT to the case, to allow the DETF to rotationally oscillate relative to the case about a second axis transverse to the first axis;

wherein the DETF is mass imbalanced about the second axis, so that the DETF experiences a pendulous torque when accelerated along a third axis, causing the DETF to rotate about the second axis;

means for rotationally sinusoidally oscillating the DETF about the second axis, the oscillation having a constant amplitude, a phase, and a frequency the same as the tines'"'"' vibrational frequency;

means for resolving rotation of the DETF relative to the case;

means for resolving the phase difference between the tines'"'"' vibration along the first axis and the DETF rotational oscillation about the second axis;

means for altering the phase relationship between the tines'"'"' motion and the DETF oscillation, to generate a gyroscopic torque that balances the pendulous torque; and

means, responsive to the means for resolving the phase difference, for determining the instrument acceleration along the third axis.

32. A stacked Coriolis Oscillating Gyroscopic instrument, comprising:

a plurality of stacked, planar Coriolis Oscillating Gyroscopic instruments, each one comprising;

a Double Ended Tuning Fork (DETF) having two stems and two tines;

a Torque Summing Member (TSM) rigidly coupled to the DETF stems;

a case; and

a plurality of flexures connecting the TSM to the case, wherein the flexures are spaced circumferentially about the TSM in a common plane, and allow the TSM and the DETF to together rotationally oscillate in the plane about the second axis that serves as the gyroscopic input and output axes;

wherein the cases are mechanically coupled, and the TSMs are mechanically coupled, to create a unitary stacked design;

means located at least partially on each TSM for vibrating all of the tines sinusoidally in opposition, each vibrating along a first axis, the tines'"'"' motions all having the same frequency and phase; and

means for resolving rotation of each TSM relative to its respective case.

33. The instrument of claim 32, further including means for rotationally sinusoidally-oscillating each TSM and DETF together about the second axis.

34. An essentially planar inertial measurement unit for measuring motion in six degrees of freedom, comprising:

a) three planar gyroscopes, each for measuring rotations about one of three mutually orthogonal axes, each gyroscope comprising;

a Double Ended Tuning Fork (DETF) having two stems and two tines;

a Torque Summing Member (TSM) rigidly coupled to the DETF stems;

means located at least partially on the TSM for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency, and a phase;

a plurality of flexures connecting the DETF to the case, to allow the DETF to rotationally oscillate relative to the case about a second axis transverse to the first axis; and

means for resolving oscillation of the TSM relative to the case;

wherein for two of the gyroscopes the first and second axes are co-planar with the gyroscope, and for the third gyroscope the second axis is orthogonal to the gyroscope plane; and

b) three planar accelerometers, each for measuring acceleration along one of the three mutually orthogonal axes, each accelerometer comprising;

a Double Ended Tuning Fork (DETF) having two stems and two tines;

a Torque Summing Member (TSM) rigidly coupled to the DETF stems;

means located at least partially on the TSM for vibrating the tines sinusoidally in opposition along a first axis, the tines'"'"' motion having a constant amplitude, a frequency, and a phase;

a case;

a plurality of flexures connecting the TSM to the case, to allow the TSM and DETF to be rotationally oscillated relative to the case about a second axis transverse to the first axis;

wherein the TSM is mass imbalanced about the second axis, so that it experiences a pendulous torque when accelerated along a third axis transverse to both the first and second axes, causing non-oscillatory rotation of the TSM and the DETF together about the second axis;

means for driving the TSM in oscillation about the second axis at the same frequency as the tines'"'"' vibration, to generate gyroscopic torque that balances the pendulous torque; and

means for determining, from the phase of the tines'"'"' vibration and the phase of the TSM oscillation, acceleration along the third axis;

wherein for one of the accelerometers the first and second axes are co-planar with the accelerometer, and for the other two accelerometers the second axis is orthogonal to the accelerometer plane.