Digital angular rate and acceleration sensor

• US 20020166379A1
• Filed: 05/14/2001
• Published: 11/14/2002
• Est. Priority Date: 05/14/2001
• Status: Active Grant

• Current Assignee: Paroscientific Incorporated
• Original Assignee: Paroscientific Incorporated
• Inventors: Paros, Jerome M., Schaad, Theo P.
• Granted Patent: US 6,595,054 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719
• CPC Class Codes: G01P 15/0922 of the bending or flexing mode type
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 2015/0828 the mass being of the paddle type being suspended at one of its longitudinal ends

Abstract

A digital angular rate and acceleration sensor is constructed with force-sensitive resonators positioned longitudinally on one or both sides of the neutral bending plane of a cantilevered structure. The cantilevered structure has an inertial proof mass at its free end with a periodic velocity applied sideways to the bending plane. Rotation about the longitudinal axis, which produces periodic Coriolis acceleration, as well as inertial acceleration applied perpendicular to the bending plane, generate tensile and compressive forces on the resonators thereby altering the resonant frequencies that are thus a measure of angular rate of rotation and acceleration.

Claims

1. A transducer for providing one or more electrical signals having a frequency modulation indicative of angular rate of rotation about a longitudinal axis of the transducer, the transducer comprising:

at least one cantilevered structure having a base and a free end, the cantilevered structure having a neutral bending plane;

a drive mechanism to cause the cantilevered structure to periodically move back-and-forth along an axis parallel to the neutral bending plane; and

at least one force-sensitive resonator sensor mounted on the cantilevered structure at a location spaced apart from a neutral bending plane of the cantilevered structure such that bending of the cantilevered structure imparts a force to the resonator sensor.

2. The transducer of claim 1 wherein the force-sensitive resonator sensor comprises two force-sensitive resonators positioned longitudinally on opposite sides of the neutral bending plane such that bending moments produce tension in one resonator and produce compression in the other resonator.

3. The transducer of claim 2 wherein the resonators project from one end of the cantilevered structure, with a mount of each resonator attached to the cantilevered structure, and wherein the transducer further comprises a proof mass extending between and attached to another mount of each resonators so that the resonators create a virtual neutral bending plane positioned between the resonators.

4. The transducer of claim 3 wherein the resonators comprise struts extending between the mounts of each resonator in parallel with the resonators and in a plane in which the resonators resonate.

5. The transducer of claim 1 further comprising a proof mass mounted at a free end of the cantilevered structure.

6. The transducer of claim 1 wherein the cantilevered structure further comprises a stress concentrator flexure positioned in the neutral bending plane of the cantilevered structure.

7. The transducer of claim 1 wherein the cantilevered structure further comprises a transverse flexure about which the cantilevered structure is relatively compliant about an axis that is perpendicular to the neutral bending plane of the cantilevered structure.

8. The transducer of claim 1 wherein the cantilever structure comprises a fixed base, and wherein the drive mechanism is operable to flex the cantilevered structure back-and-forth along the axis parallel to the neutral bending plane.

9. The transducer of claim 1 wherein the at least one resonator is integral to the cantilevered structure to form a monolithic assembly.

10. The transducer of claim 1 wherein the cantilevered structure and the at least one resonator are each fabricated from the same material.

11. The transducer of claim 1 wherein the cantilevered structure is fabricated from quartz.

12. The transducer of claim 1 wherein the at least one resonator is fabricated from quartz.

13. The transducer of claim 1 wherein the cantilevered structure is fabricated from silicon.

14. The transducer of claim 1 wherein the at least one resonator is fabricated from silicon.

15. The transducer of claim 1 further comprising at least one sensor that measures the sideways velocity of the cantilevered structure imparted by the drive mechanism.

16. The transducer of claim 1 further comprising at least one sensor that measures the sideways displacement of the cantilevered structure imparted by the drive mechanism.

17. The transducer of claim 1 further comprising at least one sensor that measures the sideways acceleration of the cantilevered structure imparted by the drive mechanism.

18. The transducer of claim 1 further comprising at least one force-sensitive sensor positioned at a location spaced apart from the bending plane of the sideways motion of the levered structure such that sideways motion of the cantilevered structure imparts a force to the force-sensitive sensor.

19. The transducer of claim 18 where in the at least one force-sensitive sensor comprises a force-sensitive resonator.

20. A transducer for providing one or more electrical signals indicative of angular rate of rotation about a longitudinal axis of the transducer, the transducer comprising:

at least one cantilevered structure having a base and a free end, the cantilevered structure having a neutral bending plane;

a drive mechanism to cause the cantilevered structure to periodically move back-and-forth along an axis parallel to the neutral bending plane; and

at least one force-sensitive sensor positioned at a location spaced apart from a neutral bending plane of the cantilevered structure such that bending of the cantilevered structure imparts a strain-induced force to the force-sensitive sensor.

21. The transducer of claim 20 wherein the force-sensitive sensor comprises a force-sensitive resonator.

22. The transducer of claim 20 further comprising at least one force-sensitive sensor positioned at a location spaced apart from the bending plane of the sideways motion of the cantilevered structure such that sideways motion of the cantilevered structure imparts a force to the force-sensitive sensor.

24. The system of claim 23 wherein the electronic interface device is further operable to generate a second output indicative of acceleration along a second axis that is perpendicular to the neutral bending plane, the electronic interface device being operable to generate the second output by determining the resonant frequency of the resonator as the resonant frequency changes responsive to acceleration of the cantilevered structure along the second axis.

25. The system of claim 24 wherein the force sensitive resonator sensor comprises two force-sensitive resonators positioned longitudinally on opposite sides of the neutral bending plane such that bending moments produce tension in one resonator and produce compression in the other resonator.

26. The system of claim 25 wherein the resonators project from one end of the cantilevered structure, with a mount of each resonator attached to the cantilevered structure, and wherein the transducer further comprises a proof mass extending between and attached to another mount of each resonators so that the resonators create a virtual neutral bending plane positioned between the resonators.

27. The system of claim 26 wherein the resonators comprise struts extending between the mounts of each resonator in parallel with the resonators and in a plane in which the resonators resonate.

28. The system of claim 24 further comprising a proof mass mounted at a free end of the cantilevered structure.

29. The system of claim 24 wherein the cantilevered structure further comprises a stress concentrator flexure positioned in the neutral bending plane of the cantilevered structure.

30. The system of claim 24 wherein the cantilevered structure further comprises a transverse flexure about which the cantilevered structure is relatively compliant about an axis that is perpendicular to the neutral bending plane of the cantilevered structure.

31. The system of claim 24 wherein the cantilever structure comprises a fixed base, and wherein the drive mechanism is operable to flex the cantilevered structure back-and-forth along the axis parallel to the neutral bending plane.

32. The system of claim 24 wherein the at least one resonator is integral to the cantilevered structure to form a monolithic assembly.

33. The system of claim 24 wherein the cantilevered structure and the at least one resonator are each fabricated from the same material.

34. The system of claim 24 wherein the cantilevered structure is fabricated from quartz.

35. The system of claim 24 wherein the at least one resonator is fabricated from quartz.

36. The system of claim 24 wherein the cantilevered structure is fabricated from silicon.

37. The system of claim 24 wherein the at least one resonator is fabricated from silicon.

39. The system of claim 38 wherein the electronic interface device is further operable to generate a second output indicative of acceleration along a second axis that is perpendicular to the neutral bending plane, the electronic interface device being operable to generate the second output based on the output signal generated by the force-sensitive sensor.

40. The system of claim 38 wherein the force-sensitive sensor comprises two force-sensitive sensors positioned on opposite sides of the neutral bending plane such that bending moments produce tension in one sensor and produce compression in the other sensor.

41. The system of claim 38 wherein the force-sensitive sensor comprises a force-sensitive resonator.

42. The transducer of claim 38 further comprising at least one force-sensitive sensor positioned at a location spaced apart from the bending plane of the sideways motion of the cantilevered structure such that sideways motion of the cantilevered structure imparts a force to the force-sensitive sensor.

23. A system for providing an output indicative of angular rate of rotation about a first axis, the system comprising:

at least one cantilevered structure having a base and a free end, the cantilevered structure having a neutral bending plane;

a drive mechanism to cause the cantilevered structure to periodically move back-and-forth along an axis parallel to the neutral bending plane; and

at least one force-sensitive resonator sensor mounted on the cantilevered structure at a location spaced apart from a neutral bending plane of the cantilevered structure such that bending of the cantilevered structure imparts a force to the resonator sensor; and

an electronic interface device coupled to the resonator, the electronic interface device being operable to generate the output indicative of angular rate of rotation by determining the magnitude of variation in the resonant frequency of the resonator as the resonant frequency periodically varies responsive to rotation of the cantilevered structure about the first axis.

38. A system for providing an output indicative of angular rate of rotation about a first axis, the system comprising:

at least one cantilevered structure having a base and a free end, the cantilevered structure having a neutral bending plane;

a drive mechanism to cause the cantilevered structure to periodically move back-and-forth along an axis parallel to the neutral bending plane;

at least one force-sensitive sensor positioned at a location spaced apart from a neutral bending plane of the cantilevered structure, the force sensitive sensor being operable to generate an output signal indicative of a force imparted to the force-sensitive sensor resulting from bending of the cantilevered structure; and

an electronic interface device coupled to the force-sensitive sensor, the electronic interface device being operable to generate the output indicative of angular rate of rotation based on the output signal generated by the force-sensitive sensor.

43. A transducer for providing one or more electrical signals having a frequency modulation indicative of angular rate of rotation about a longitudinal axis of the transducer, the transducer comprising:

at least one pair of cantilevered structures, each cantilevered structure having a fixed base, a free end, and a neutral bending plane, the cantilevered structures in each pair being mass-balanced to each other so that the momentum of one cantilevered structure is substantially cancelled by the other;

a drive mechanism to cause the cantilevered structures to periodically flex back-and-forth along an axis parallel to the neutral bending plane; and

at least one force-sensitive resonator mounted on at least one of the cantilevered structures at a location spaced apart from a neutral bending plane of the cantilevered structure on which it is mounted such that bending of the cantilevered structure imparts a force to the resonator.

44. The transducer of claim 43 wherein the force-sensitive resonator sensor comprises two force-sensitive resonators positioned longitudinally on opposite sides of the neutral bending plane such that bending moments produce tension in one resonator and produce compression in the other resonator.

45. The transducer of claim 43 wherein the resonators project from one end of the cantilevered structure, with a mount of each resonator attached to the cantilevered structure, and wherein the transducer further comprises a proof mass extending between and attached to another mount of each resonators so that the resonators create a virtual neutral bending plane positioned between the resonators.

46. The transducer of claim 45 wherein the resonators comprise struts extending between the mounts of each resonator in parallel with the resonators and in a plane in which the resonators resonate.

47. The transducer of claim 43 further comprising a proof mass mounted at a free end of the cantilevered structure.

48. The transducer of claim 43 wherein the cantilevered structure further comprises a stress concentrator flexure positioned in the neutral bending plane of the cantilevered structure.

49. The transducer of claim 43 wherein the cantilevered structure further comprises a transverse flexure about which the cantilevered structure is relatively compliant about an axis that is perpendicular to the neutral bending plane of the cantilevered structure.

50. The transducer of claim 43 wherein the at least one resonator is integral to the cantilevered structure to form a monolithic assembly.

51. The transducer of claim 43 wherein the cantilevered structure and the at least one resonator are each fabricated from the same material.

52. The transducer of claim 43 wherein the cantilevered structure is fabricated from quartz.

53. The transducer of claim 43 wherein the at least one resonator is fabricated from quartz.

54. The transducer of claim 43 wherein the cantilevered structure is fabricated from silicon.

55. The transducer of claim 43 wherein the at least one resonator is fabricated from silicon.

56. The transducer of claim 43 wherein multiple resonators are mounted on at least one pair of cantilevered structures, and wherein the resonators are mounted on opposite sides of the respective neutral bending planes of the cantilevered structures.

57. The transducer of claim 43 wherein multiple resonators are mounted on at least one pair of cantilevered structures, and wherein the resonators are mounted on the same side of the respective neutral bending planes of the cantilevered structures.

58. The transducer of claim 43 wherein a pair of resonators is mounted on each of the cantilevered structures in at least one pair of cantilevered structures, and wherein the resonators are mounted on each cantilevered structure on opposite sides of the respective neutral bending planes of the cantilevered structures.

59. The transducer of claim 43 further comprising a sensor that measures the sideways velocity of the cantilevered structure imparted by the drive mechanism.

60. The transducer of claim 43 further comprising a sensor that measures the sideways displacement of the cantilevered structure imparted by the drive mechanism.

61. The transducer of claim 43 further comprising a sensor that measures the sideways acceleration of the cantilevered structure imparted by the drive mechanism.

62. The transducer of claim 43 further comprising a force-sensitive sensor positioned at a location spaced apart from the bending plane of the sideways motion of the cantilevered structure such that sideways motion of the cantilevered structure imparts a force to the force-sensitive sensor.

63. The transducer of claim 62 wherein the force-sensitive sensor comprises a force-sensitive resonator.

64. A system for providing an output indicative of angular rate of rotation about a first axis, the system comprising:

at least one pair of cantilevered structures, each cantilevered structure having a fixed base, a free end, and a neutral bending plane, the cantilevered structures in each pair being mass-balanced to each other so that the momentum of one cantilevered structure is substantially cancelled by the other;

a drive mechanism to cause the cantilevered structures to periodically flex back-and-forth along an axis parallel to the neutral bending plane;

at least one force-sensitive resonator mounted on at least one of the cantilevered structures at a location spaced apart from a neutral bending plane of the cantilevered structure on which it is mounted such that bending of the cantilevered structure imparts a force to the resonator; and

an electronic interface device coupled to the resonator, the electronic interface device being operable to generate the output indicative of angular rate of rotation by determining the magnitude of variation in the resonant frequency of the resonator as the resonant frequency periodically varies responsive to rotation of the cantilevered structure about the first axis.

65. The system of claim 64 wherein the electronic interface device is further operable to generate a second output indicative of acceleration along a second axis that is perpendicular to the neutral bending plane, the electronic interface device being operable to generate the second output by determining the resonant frequency of the resonator as the resonant frequency changes responsive to acceleration of the cantilevered structure along the second axis.

66. The system of claim 65 wherein the force-sensitive resonator sensor comprises two force-sensitive resonators positioned longitudinally on opposite sides of the neutral bending plane such that bending moments produce tension in one resonator and produce compression in the other resonator.

67. The system of claim 66 wherein the resonators project from one end of the cantilevered structure, with a mount of each resonator attached to the cantilevered structure, and wherein the transducer further comprises a proof mass extending between and attached to another mount of each resonators so that the resonators create a virtual neutral bending plane positioned between the resonators.

68. The system of claim 67 wherein the resonators comprise struts extending between the mounts of each resonator in parallel with the resonators and in a plane in which the resonators resonate.

69. The system of claim 65 further comprising a proof mass mounted at a free end of the cantilevered structure.

70. The system of claim 65 wherein the cantilevered structure further comprises a stress concentrator flexure positioned in the neutral bending plane of the cantilevered structure.

71. The system of claim 65 wherein the cantilevered structure further comprises a transverse flexure about which the cantilevered structure is relatively compliant about an axis that is perpendicular to the neutral bending plane of the cantilevered structure.

72. The system of claim 65 wherein the at least one resonator is integral to the cantilevered structure to form a monolithic assembly.

73. The system of claim 65 wherein the cantilevered structure and the at least one resonator are each fabricated from the same material.

74. The system of claim 65 wherein the cantilevered structure is fabricated from quartz.

75. The system of claim 65 wherein the at least one resonator is fabricated from quartz.

76. The system of claim 65 wherein the cantilevered structure is fabricated from silicon.

77. The system of claim 65 wherein the at least one resonator is fabricated from silicon.

78. The system of claim 65 wherein multiple resonators are mounted on at least one pair of cantilevered structures, and wherein the resonators are mounted on opposite sides of the respective neutral bending planes of the cantilevered structures.

79. The system of claim 65 wherein multiple resonators are mounted on at least one pair of cantilevered structures, and wherein the resonators are mounted on the same side of the respective neutral bending planes of the cantilevered structures.

80. The system of claim 65 wherein a pair of resonators is mounted on each of the cantilevered structures in at least one pair of cantilevered structures, and wherein the resonators are mounted on each cantilevered structure on opposite sides of the respective neutral bending planes of the cantilevered structures.