Vibrating Inertial Rate Sensor Utilizing Split or Skewed Operational Elements

• US 20070256495A1
• Filed: 03/29/2007
• Published: 11/08/2007
• Est. Priority Date: 04/18/2006
• Status: Active Grant

• Current Assignee: Watson Industries, Inc.
• Original Assignee: Watson Industries, Inc.
• Inventors: Watson, William
• Granted Patent: US 7,617,727 B2
• Time in Patent Office: Days
• US Class Current: 73/504.120
• 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 19/5691 of essentially three-dimensional vibrators, e.g. wine glass-type vibrators

Abstract

A vibrating inertial rate sensor has operational elements that define axes that are rotationally offset or “skewed” from a node or anti-node reference axis. The skew may be relative to separate node or anti-node reference axes, or take the form of an element that is “split” about the same node axis. Both the drive signal and the sense signal may be resolved from a common set of sensing elements. The drive elements may also operate on a skewed axis angle to rotationally offset the vibration pattern to affect active torquing of the gyroscope. Skewed drive elements may be combined with skewed or split elements on the same device. The skewed sensing scheme may be applied to vibratory systems having one or more node axes. The skewed drive scheme may be applied to vibratory systems having two or more node axes to affect active torquing.

Claims

1. A vibratory inertial rate sensor comprising

a vibratory resonator comprising a continuous body that forms a closed loop on a cross-section that is orthogonal to a centerline axis;

a plurality of operational element pairs operatively coupled to said continuous body, the operational elements of each of said operational element pairs being positioned about said centerline axis to define a plurality of operational element axes, said plurality of operational element pairs being arranged in a non-uniform distribution about said centerline axis, said non-uniform distribution characterized by a mirrored symmetry about a plane inclusive of said centerline axis.

2. The vibratory inertial rate sensor of claim 1 wherein said continuous body is an axisymmetric body being symmetrical about said centerline axis.

3. The vibratory inertial rate sensor of claim 1 wherein a number of said operational element pairs are drive element pairs that generate an oscillation pattern on said vibratory resonator.

4. The vibratory inertial rate sensor of claim 3 wherein said drive element pairs are arranged in a non-uniform distribution about said centerline axis to enable dynamic rotation of said oscillation pattern relative to said centerline axis with said drive elements.

5. An inertial sensor for sensing a rate of angular rotation, comprising:

a vibratory resonator comprising a continuous body having a centerline axis;

means for generating an oscillation pattern on said vibratory resonator, said oscillation pattern defining a plurality of node pairs and anti-node pairs, each being positioned about said centerline axis, said plurality of node pairs and anti-node pairs defining a plurality of reference axes, each passing through a corresponding one of said plurality of node pairs and anti-node pairs;

a plurality of operational elements operatively coupled with said continuous body and defining a plurality of operational element axes, each of said plurality of operational element axes passing through a corresponding one of said plurality of operational elements and intersecting said centerline axis,

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

6. The inertial sensor of claim 5 wherein said first rotational offset and said second rotational offset are of substantially equal magnitude.

7. The inertial sensor of claim 5 wherein said continuous body is axisymmetric.

8. The inertial sensor of claim 5 wherein at least some of said plurality of operational elements are in physical contact with a surface of said continuous body.

9. The inertial sensor of claim 8 wherein said physical contact is selected from the group consisting of a bonded join, a glued joint and a combination thereof.

10. The inertial sensor of claim 5 wherein said first of said operational elements and said second of said operational elements are sense elements.

11. The inertial sensor of claim 5 wherein said plurality of reference axes define a substantially uniform angular displacement between adjacent reference axes of said plurality of reference axes and said first rotational offset is less than half of said substantially uniform angular displacement.

12. The inertial sensor of claim 5 wherein at least one of said operational element axes passes through an additional corresponding one of said plurality of operational elements, said corresponding one and said additional corresponding one of said plurality of operational elements defining an operational element pair.

13. A method of measuring the drive oscillation amplitude and the rotation rate of a vibrating gyroscope comprising:

selecting a vibrating gyroscope having;

a first sensing element configured to sense a first vibration vector having a first drive oscillation component and a first rotational rate component,

a second sensing element configured to sense a second vibration vector having a second drive oscillation component and a second rotational rate component, said second drive oscillation being of opposite oscillation phase relative to said first drive oscillation component;

obtaining a first signal from said first sensing element and a second signal from said second sensing element;

determining said magnitude of said drive oscillation by performing at least one operation selected from the group consisting of a subtraction of said first and second signals and an addition of said first and second signals; and

determining a rotation rate of said vibrating gyroscope by performing an operation selected from the group consisting of an addition of said first and second signals and a subtraction of said first and second signals.

14. The method of claim 13 further comprising

determining said magnitude of said drive oscillation by multiplying said first signal by a constant;

and

determining said rotation rate of said vibrating gyroscope by multiplying said first signal by said constant.

15. An inertial sensor for sensing a rate of angular rotation, comprising:

a vibratory resonator;

at least one drive element operatively coupled with said vibratory resonator to create a vibration on at least a portion of said vibratory resonator;

a first sensing element operatively coupled with said resonator to sense a first vector of said vibration, said first vector including a first drive component; and

a second sensing element operatively coupled with said resonator to sense a second vector of said vibration, said second vector including a second drive component, said second drive component being of opposite oscillation phase relative to said first drive oscillation component.

16. The inertial sensor of claim 15 wherein said vibratory resonator is continuous.

17. The inertial sensor of claim 15 wherein said first drive component and said second drive component are of substantially equal magnitude.

18. An inertial sensor for sensing a rate of angular rotation, comprising:

a vibratory resonator continuous about a centerline axis;

means for generating an oscillation pattern on said vibratory resonator, said oscillation pattern defining a plurality of nodes; and

at least one pair of sensing elements operatively coupled with said vibratory resonator, each of said at least one pair of sensing elements being adjacent to one of said plurality of nodes, said one of said plurality of nodes being positioned between said at least one pair of sensing elements when said vibratory resonator is rotationally stationary.

19. The inertial sensor of claim 18 wherein said vibratory resonator is axisymmetric.

20. An intertial sensor for sensing a rate of angular rotation, comprising:

a vibratory resonator;

means for driving an oscillation pattern on said vibratory resonator, said oscillation pattern characterized by at least one anti-node, said at least one anti-node having an oscillation amplitude; and

means for determining a rotation rate of said vibratory resonator; and

means for determining said oscillation amplitude of said at least one anti-node.

21. The inertial rate sensor of claim 20 wherein a plurality of sensing elements are shared in said means for determining said rotation rate and said means for determining said oscillation amplitude

22. An inertial sensor for sensing a rate of angular rotation, comprising:

a continuous vibratory resonator;

means for generating an oscillation pattern on said continuous vibratory resonator; and

means for selectively dynamically rotationally displacing said oscillation pattern,

wherein said means for generating said oscillation pattern and said means for displacing said oscillation pattern utilize the same electrodes.

23. An inertial rate sensor having a pattern of operational elements comprising:

a pattern length defining a pattern axis and being divisible into a first half and a second half; and

at least a first and a second pair of operational elements, said operational elements selected from the group consisting of drive elements and sense elements, each operational element having a centroid,

said centroids of said first pair of operational elements being located on said first half of said pattern length and presenting a first span length parallel to said pattern axis, said centroids of said first pair and defining a first midpoint located equidistant therebetween,

said centroids of said second pair of operational elements being located on said second half of said pattern length and presenting a second span length parallel to said pattern axis, said centroids of said second pair defining a second midpoint located equidistant therebetween,

said first and second midpoints being separated by a distance substantially equal to one-half of said pattern length,

said first span length being substantially equal to said second span length and being substantially unequal to one quarter of said pattern length.

24. The inertial rate sensor of claim 23 wherein said pattern length is continuous.

25. The inertial rate sensor of claim 23 further comprising a plurality of signal contact tabs defining a series of spacings on said first half that is repeated on said second half.

26. The inertial rate sensor of claim 25 wherein at least one of said signal contact tabs is in electrical communication with a ground element.

27. A method of making an inertial rate sensor comprising:

selecting an arrangement having an overall length divisible into a first half and a second half and including at least two pairs of like-functioning operational element patterns, said like-functioning operational element patterns being selected from the group consisting of drive element patterns and sense element patterns, one pair having a midpoint located on said first half of said pattern, another pair having a midpoint centered on said second half of said arrangement, said midpoints presenting a distance therebetween that is substantially equal to half of said overall length of said arrangement, each like-functioning operational element pattern having a centroid, said centroids of each like-functioning operational element pattern pair being located a same distance apart, said same distance being substantially unequal to one-quarter of said overall length of said pattern;

transferring said pattern to a continuous resonator; and

converting said like-functioning operational element patterns into like-functioning operational elements.

28. The method of claim 27 wherein converting said like-functioning operational element patterns into like-functioning operational elements includes electrically isolating said like-functioning operational elements.

29. The method of claim 28 wherein converting said like-functioning operational element patterns into like-functioning operational elements includes converting said patterns into a conductive layer that is bonded to said continuous resonator.

30. A method of electrically interfacing with an inertial sensor that includes a vibratory resonator having an axis of symmetry and a plurality of operational elements situated about said axis of symmetry, the method comprising:

applying a first oscillation drive signal to a first set of at least one operational element and applying a second oscillation drive signal to a second set of at least one operational element that is different from said first set such that at least one of said first and second oscillation drive signals causes said vibratory resonator to vibrate in a vibration pattern about said axis of symmetry, said vibration pattern including a plurality of nodes situated in a first position in relation to said vibratory resonator; and

changing said vibration pattern such that said plurality of nodes are situated in a second position in relation to said vibratory resonator that is different from said first position by varying an amplitude of at least one of said first oscillation drive signal and said second oscillation drive signal.

31. The method of claim 30, wherein said varying of said amplitude of said at least one of said first oscillation drive signal and said second oscillation drive signal produces a rotational offset in said vibration pattern relative to said axis of symmetry.

32. The method of claim 30, wherein said varying of said amplitude of said at least one of said first oscillation drive signal and said second oscillation drive signal includes setting respective amplitudes of said first oscillation drive signal and said second oscillation drive signal such that:

a first ratio of said respective amplitudes produces a vibration pattern wherein said plurality of nodes are situated in said second position that is offset from said first position in a first direction by an amount that is generally proportional to said first ratio; and

an inverse of said first ratio of said respective amplitudes produces a vibration pattern wherein said plurality of nodes are situated in a third position that is offset from said first position in a direction that is opposite said first direction by an amount that is generally proportional to said first ratio.

33. The method of claim 30, wherein said applying of said first oscillation drive signal to said first set of at least one operational element includes applying said first oscillation drive signal to a first pair of operational elements situated on said vibratory resonator along a first reference axis that intersects with said axis of symmetry;

and

wherein said applying of said second oscillation drive signal to said second set of at least one operational element includes applying said second oscillation drive signal to a second pair of operational elements situated on said vibratory resonator along a second reference axis that intersects with said axis of symmetry and is oblique relative to said first axis of symmetry.

34. The method of claim 30, further comprising:

monitoring said vibration pattern using a third set of at least one operational element and a fourth set of at least one operational element, wherein said operational elements of said third and fourth sets each produces a sense signal representing a characteristic of said vibration pattern existing at a location relative to said vibratory resonator that corresponds to a location of that operational element; and

wherein when said at least one operational element of said third set produces a sense signal indicative of a node being present a location that corresponds to said location of said at least one operational element of said third set, said at least one operational element of said fourth set produces a sense signal indicative of an absence of a node present at a location that corresponds to said location of said at least one operational element of said fourth set.

35. The method of claim 34, wherein said monitoring of said vibration pattern using said third and said fourth sets includes obtaining a first sense signal that is electrically common to said at least one operational element of said third set, and obtaining a second sense signal that is electrically common to said at least one operational element of said fourth set;

wherein each of said first and said second sense signals includes a first amplitude component representing a rate of angular motion of said inertial sensor and a second amplitude component representing said first and said second oscillation drive signals; and

wherein said monitoring of said vibration pattern further includes combining said first and said second sense signals to produce at least one monitor signal selected from the group consisting of;

a rate sense signal representing said rate of angular motion, and a drive sense signal representing said first and said second oscillation drive signals.

36. A circuit that electrically interfaces with an inertial sensor that includes a vibratory resonator, the circuit comprising:

an excitation signal generator that applies a set of at least one excitation signal to said vibratory resonator that causes said vibratory resonator to vibrate in a vibration pattern;

a vibration pattern monitor that obtains a first signal indicative of a vibration characteristic of said vibration pattern present at a corresponding first location on said vibratory resonator, and a second signal indicative of a vibration characteristic of said vibration pattern present at a corresponding second location on said vibratory resonator that is different from said first location;

wherein each of said first and said second signals includes a first amplitude component associated with a rate of said angular motion of said inertial sensor, and a second amplitude component associated with said set of at least one excitation signal; and

wherein said vibration pattern monitor obtains at least one of said first and said second amplitude components from said first and said second signals.

37. The circuit of claim 36, wherein said vibration pattern monitor produces a rate signal representing said rate of angular motion by combining said first amplitude component of said first signal with said first amplitude component of said second signal inverted in polarity;

and

wherein said vibration pattern monitor produces a drive sense signal representing said set of at least one excitation signal by combining said second amplitude component of said first signal with said second amplitude component of said second signal.

38. The circuit of claim 36, wherein said vibration pattern monitor includes signal conditioning circuitry that performs at least one of buffering and weighting of said first and said second signals.

39. The circuit of claim 38, wherein a signal representing said rate of angular motion is obtained via a first adjustable mixer that applies weighting to said first and said second signals such that said second amplitude component is cancelled from each of said first and said second signals;

and

wherein a signal representing said set of at least one excitation signal is obtained via a second adjustable mixer that applies weighting to said first and said second signals such that said first amplitude component is cancelled from each of said first and said second signals.

40. The circuit of claim 36, further comprising a control circuit that adjusts an amplitude of said set of at least one excitation signal based on at least one of (a) and (b) as follows:

(a) a signal based substantially on a combination of said first amplitude component of said first signal and said first amplitude component of said second signal; and

(b) a signal based substantially on a combination of said second amplitude component of said first signal and said second amplitude component of said second signal.

41. The circuit of claim 40, wherein said control circuit includes an automatic gain controller that adjusts said set of at least one excitation signal based on said first amplitude component from said first and said second signal processed as a function of said second amplitude component of said first and said second signal.

42. The circuit of claim 40, wherein said vibration pattern monitor produces a rate signal representing said rate of angular motion based on said first and said second signals;

wherein a signal representative of an angular position change resulting from said angular motion is produced based on said rate signal;

wherein said set of at least one excitation signal includes a plurality of excitation signals applied at different portions of said vibratory resonator; and

wherein said control circuit adjusts a relative amplitudes of said excitation signals to reposition said vibration pattern along said vibratory resonator such that an amplitude of said rate signal is reduced, wherein said relative amplitudes of said excitation signals are adjusted based on said signal representative of said angular position change.

43. A method of electrically interfacing with an inertial sensor that includes a vibratory resonator, the method comprising:

applying an excitation signal that causes said vibratory resonator to vibrate in a vibration pattern;

monitoring said vibration pattern with a first operational element and a second operational element, wherein said first operational element produces a first signal indicative of a vibration characteristic of said vibration pattern present at a corresponding first location on said vibratory resonator, and said second operational element produces a second signal indicative of a vibration characteristic of said vibration pattern present at a corresponding second location on said vibratory resonator that is different from said first location such that, in response to an angular motion of said inertial sensor, said first signal undergoes a change in magnitude at a first rate of change and said second signal undergoes a change in magnitude at a second rate of change that is different than said first rate of change;

using a first relationship of respective amplitudes of said first signal and said second signal to measure a rate of said angular motion of said inertial sensor; and

using a second relationship of respective amplitudes of said first signal and said second signal to measure an amplitude of said excitation signal.

44. The method of claim 43, wherein using said first relationship to measure said rate of angular motion includes combining said first signal with an inverted polarity signal representing said second signal;

and

wherein using said second relationship to measure said amplitude of said excitation signal includes combining said first signal with said second signal.

45. The method of claim 43, further comprising:

conditioning said first signal and said second signal, including adjusting a ratio of said respective amplitudes of said first signal and said second signal.

46. The method of claim 43, wherein said monitoring of said vibration pattern further includes monitoring said vibration pattern with a third operational element electrically coupled to said first operational element, and monitoring said vibration pattern with a fourth operational element electrically coupled to said second operational element, wherein said first operational element and said third operational element collectively produce said first signal, and wherein said second operational element and said fourth operational element collectively produce said second signal.

47. The method of claim 43, wherein said vibration pattern includes a plurality of nodes situated along said vibratory resonator;

wherein said using said first relationship of said respective amplitudes of said first signal and said second signal to measure said rate of said angular motion of said inertial sensor produces a rate signal; and

wherein said method further comprises configuring said first relationship such that, in an absence of rotation of said inertial sensor, said rate signal represents a vibration pattern existing at a node.

48. The method of claim 43, wherein said applying of said excitation signal includes applying a first oscillation drive signal to a first set of at least one drive operational element, and applying a second oscillation drive signal to a second set of at least one drive operational element that is different from said first set.

49. The method of claim 43, further comprising:

adjusting an amplitude of said excitation signal in response to a change in relative amplitudes of said first signal and said second signal.

50. The method of claim 49, wherein said adjusting is performed such that said relative amplitudes of said first signal and said second signal are generally maintained while said inertial sensor undergoes angular motion.

51. A system for measuring angular motion, comprising:

a vibratory resonator having a plurality of operational elements that include a plurality of drive elements and a plurality of sensors; and

a drive circuit that applies excitation signaling to said plurality of drive elements such that said vibratory resonator oscillates according to a vibration pattern that includes a plurality of nodes and anti-nodes, said excitation signaling including a first excitation signal applied to a first set of at least one drive element and a second excitation signal applied to a second set of at least one drive element, wherein relative amplitudes of said first and said second excitation signals control a positioning of said nodes and anti-nodes of said vibration pattern.

52. The system of claim 51, further comprising:

a vibration monitoring circuit that obtains signaling produced by said plurality of sensors; and

a control system that adjusts said relative amplitudes of said first and said second excitation signals based on an output of said vibration monitoring circuit such that said vibration pattern is changed to reposition said plurality of nodes and anti-nodes relative to said vibratory resonator.

53. The system of claim 52, wherein a positioning of said nodes and anti-nodes along said vibratory resonator changes in response to angular motion of said vibratory resonator;

wherein said control system establishes an initial positioning of said nodes and anti-nodes relative to said vibratory resonator in an absence of angular motion; and

wherein said control system adjusts said relative amplitudes of said first and said second excitation signals in response to a detected angular motion such that said initial positioning of said nodes and anti-nodes is restored.

54. A method for repositioning a vibration pattern of an inertial sensor that includes a vibratory resonator including a centerline axis and a plurality of operational elements situated about said centerline axis, comprising:

applying a first drive signal to a first set of at least one operational element positioned along a first drive axis that intersects with said centerline axis to define a first orientation;

applying a second drive signal to a second set of at least one operational element positioned along a second drive axis that intersects with said centerline axis to define a second orientation having a rotational offset about said centerline axis from said first orientation,

wherein said applying of at least one of said first and second drive signals generates a vibration pattern that includes a plurality of anti-nodes having an angular distribution about said centerline axis, said angular distribution having an angle between adjacent ones of said plurality of anti-nodes, said angle having a magnitude that differs from said rotational offset between said first and second drive axes; and

adjusting relative amplitudes of said first and said second drive signals to rotate said anti-node pattern to an arbitrary angular orientation about said centerline axis.

55. The method of claim 54, wherein said applying said first and said second drive signals generates said angle between adjacent nodes at substantially 90 degrees.

56. The method of claim 54, wherein said adjusting of said of said relative amplitudes of said first and said second drive signal includes setting said first drive signal at an amplitude that has a negative polarity, and setting said second drive signal at an amplitude sufficient to sustain vibration of said vibratory resonator.

57. The method of claim 54 wherein said adjusting of said relative amplitudes of said first and said second drive signals substantially retains said angle between adjacent anti-nodes.

58. The method of claim 54, wherein said adjusting of said relative amplitudes of said first and said second drive signals to effect said change in said angular orientation of said anti-node pattern is limited to a range of adjustment less than or equal to 110% of said rotational offset.

59. The method of claim 58, wherein said range of adjustment is limited to 100% of said rotational offset.

60. A system for measuring angular motion, comprising:

a vibratory resonator having a centerline axis;

means for generating a vibration pattern on said vibratory resonator; and

means for controlling said angular orientation of said vibration pattern about said centerline axis.

61. The system of claim 60 further comprising:

means for monitoring said vibration pattern to produce an output that indicates said angular orientation of said vibration pattern, and wherein said means for controlling said angular orientation of said vibration pattern utilizes said output.

62. A circuit that electrically interfaces with an inertial sensor that includes a vibratory resonator, the circuit comprising:

means for causing said vibratory resonator to vibrate in an oscillation pattern;

means for obtaining signals having a drive component and an angular rate component; and

means for resolving said drive component and said angular rate component.