Angular rate sensor misalignment correction

• US 5,866,816 A
• Filed: 11/13/1997
• Issued: 02/02/1999
• Est. Priority Date: 05/30/1995
• Status: Expired due to Fees

• Current Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Original Assignee: Alliedsignal Inc. (Honeywell International Inc.)
• Inventors: Hulsing, Rand H. II
• Primary Examiner(s): Williams, Hezron
• Assistant Examiner(s): Moller, Richard A.
• Application Number:
  US08/969,968
• Time in Patent Office: 446 Days
• Field of Search: 73/504.12, 73/504.14, 73/504.15, 73/504.16, 310/314, 310/315, 310/316, 310/317, 310/318
• US Class Current: 73/504.16
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719

Abstract

An angular rate sensor includes a plurality of spaced apart vibrating beams, for example, four beams, defining a pair of outer beams and a pair of inner beams. Each outer beam is mechanically coupled to an inner beam by way of an interconnecting member. The outer beams are excited to cause them to vibrate in the plane of the beams and 180 degrees out of phase with the inner beams. In order to compensate for bias errors due to geometric mismatches between the beams, electrode patterns are deposited on the beams up to the point of inflection of the beam during vibration. The electrodes enable an electric field to be applied either parallel or normal to the longitudinal axis of the drive beams, which, in turn, cause the beams to twist about their longitudinal axis. Such twisting forces the quadrature acceleration components to cancel and thus electrically compensates for such bias errors due to quadrature acceleration components.

Claims

1. An angular rate sensor for providing a signal representative of angular motion relative to a predetermined axis, the angular sensor comprising:

a predetermined plurality of vibrating beams formed from a predetermined substrate, said vibrating beams spaced apart and connected together at opposing ends;

means for exciting said vibrating beams to cause said beams to vibrate in the plane of the substrate,

means for sensing the vibration frequency of one or more of said vibrating beams and providing an output signal representative of the angular rate relative to said predetermined axis; and

means for electrically compensating for bias errors in said output signal resulting from any geometric mismatch of said beams, said electrically compensating means including

first and second electrodes disposed on opposing surfaces of said vibrating beams,

a first signal having a first polarity applied to said first electrode, and

a second signal having a polarity opposite said first signal applied to said second electrode.

2. An angular rate sensor as recited in claim 1, wherein said predetermined plurality of vibrating beams is four.

3. An angular rate sensor as recited in claim 1, wherein said predetermined substrate is formed from a predetermined piezoelectric material.

4. An angular rate sensor as recited in claim 3, wherein said predetermined piezoelectric material is quartz.

5. An angular rate sensor as recited in claim 1, wherein said predetermined substrate is formed from a predetermined silicon material.

6. An angular rate sensor as recited in claim 1, wherein said electrically compensating means includes twisting means for causing one or more of said vibrating beams to twist relative to the longitudinal axis of the beams.

7. An angular rate sensor for providing a signal representative of angular motion relative to a predetermined axis, the angular sensor comprising:

predetermined plurality of vibrating beams formed from a predetermined substrate, said vibrating beams spaced apart and connected together at opposing ends;

means for exciting said vibrating beams to cause said beams to vibrate in the plane of the substrate;

means for sensing the vibration frequency of one or more of said vibrating beams and providing an output signal representative of the angular rate relative to said predetermined axis; and

means for applying an electrical signal to at least one of said vibrating beams to electrically compensate for bias errors in said output signal resulting from any geometric mismatch of the beams;

wherein said electrically compensating means includes twisting means for causing one or more of said vibrating beams to twist relative to the longitudinal axis of the beams; and

wherein said twisting means includes means for generating opposing electrical fields on opposing sides of said one or more beams, said generating means being disposed between one or both ends of said one or more beams and predetermined nodal points on said beams.

8. An angular rate sensor as recited in claim 7, wherein said predetermined nodal points are the points of inflection of said beams when said beams are in an excited state.

9. An angular rate sensor as recited in claim 7, wherein said twisting means further includes a plurality of electrodes to enable said opposing electrical fields to be generated between the ends of said one or more beams and said nodal points on opposing sides of said one or more beams.

10. An angular rate sensor as recited in claim 9, wherein the polarity of said opposing electrical fields is generally parallel to the longitudinal axis of the beams.

11. An angular rate sensor as recited in claim 9, wherein the polarity of said opposing electrical fields is generally normal to the longitudinal axis of the beams.

12. An angular rate sensor for providing a signal representative of angular motion relative to a predetermined axis, the angular rate sensor comprising:

a first, a second, a third, and a fourth vibrating beams, generally parallel, spaced apart and connected together at opposing ends, formed from a predetermined substrate, defining, a pair of inner beams and a pair of outer beams;

means for exciting said inner pair of beams and said outer pair of beams;

means for sensing the vibration frequency and providing an output signal representative of the angular rate relative to said predetermined axis;

means for electrically compensating said sensor for any bias errors in the output signal resulting from any geometric mismatch of said beams, said electrically compensating means including

first and second electrodes disposed on opposing surfaces of said vibrating beams,

a first signal having a first polarity applied to said first electrode, and

a second signal having a polarity opposite said first signal applied to said second electrode.

13. An angular rate sensor as recited in claim 12, wherein said predetermined substrate is formed from a crystalline material.

14. An angular rate sensor as recited in claim 12, further including means for interconnecting said inner beams and said outer beams such that each outer beam is interconnected with an inner beam.

15. An angular rate sensor as recited in claim 14, wherein said exciting means includes means for exciting one or the other of said inner pair of vibrating beams or said outer pair of vibrating beams.

16. An angular rate sensor as recited in claim 14, wherein said sensing means includes means for sensing one or the other of said inner pair of vibrating beams or said outer pair of vibrating beams.

17. An angular rate sensor as recited in claim 12, wherein said electrically compensating means includes twisting means for causing one or more of said vibrating beams to twist relative to their longitudinal axis.

18. An angular rate sensor for providing a signal representative of angular motion relative to a predetermined axis, the annular rate sensor comprising:

a first, a second, a third, and a fourth vibrating beams, generally parallel, spaced apart and connected together at opposing ends, formed from a predetermined substrate, defining a pair of inner beams and a pair of outer beams;

means for exciting said inner pair of beams and said outer pair of beams;

means for sensing the vibration frequency and providing an output signal representative of the angular rate relative to said predetermined axis;

means for applying an electrical signal to at least said first beam to electrically compensate said sensor for any bias errors in the output signal resulting from any geometric mismatch of the beams;

wherein said electrically compensating means includes twisting means for causing one or more of said vibrating beams to twist relative to their longitudinal axis;

wherein said twisting means includes means for generating opposing electrical fields on opposing sides of at least said first beam, said generating means being disposed between one or both ends of at least said first beam and predetermined nodal points of said first beam; and

wherein said twisting means further includes a plurality of electrodes to enable said opposing electrical fields to be generated between the ends of at least said first beam and said nodal points on opposing sides of said first beam.

19. An angular rate sensor as recited in claim 18, wherein the polarity of said opposing electrical fields is generally parallel to the longitudinal axis of the beams.

20. An angular rate sensor as recited in claim 18, wherein the polarity of said opposing electrical fields is generally normal to the longitudinal axis of the beams.

21. An angular rate sensor for providing a signal representative of angular motion relative to a predetermined axis, the angular sensor comprising:

a plurality of beams comprising first and a second vibrating beams formed from a substrate, said vibrating beams spaced apart and connected together at opposing ends;

means for exciting said first and said second vibrating beams to cause said beams to vibrate in the plane of the substrate;

means for sensing the vibration frequency of one or more of said vibrating beams and providing an output signal representative of the angular rate relative to said predetermined axis; and

means, coupled to said means for exciting, for electrically compensating for bias errors in said output signal resulting from any geometric mismatch of the beams wherein said means for electrically compensating includes;

a first drive circuit operating at a first substantially constant drive amplitude for exciting said first vibrating beam to cause said first vibrating beam to vibrate in the plane of said substrate at a first drive frequency;

a second drive circuit operating at a second substantially constant drive amplitude for exciting said second vibrating beam to cause said second vibrating beam to vibrate in the plane of said substrate at a second drive frequency substantially identical to said first drive frequency; and

an electrode pattern disposed over the plurality of beams and configured to enable an electric field to cause at least one of the beams of the plurality of beams to twist about its longitudinal axis.

22. An angular rate sensor providing a signal representative of angular motion relative to a predetermined axis, the angular rate sensor comprising

at least a first and a second vibrating beam formed from a substrate, said vibrating beams spaced apart and connected together at opposing ends;

means for exciting said first and said second vibrating beams to cause said beams to vibrate in the plane of the substrate;

means for sensing the vibration frequency of one or more of said vibrating beams and providing an output signal representative of the angular rate relative to said predetermined axis; and

a circuit coupled to at least said first vibrating beam for generating opposing electric fields on opposing surfaces of said vibrating beam to compensate for bias errors in said output signal resulting from any geometric mismatch of the beams.