Closed loop resonant rotation rate sensor

• US 5,850,035 A
• Filed: 04/11/1997
• Issued: 12/15/1998
• Est. Priority Date: 06/07/1995
• Status: Expired due to Fees

• Current Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Original Assignee: BEI Sensors & Systems Company Incorporated (Schneider Electric SE)
• Inventors: Hilby, Timothy R., Newell, G. Richard, Layton, Michael R.
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/827,836
• Time in Patent Office: 613 Days
• Field of Search: 73/504.16, 73/504.12, 73/504.13, 73/504.14, 73/504.15, 73/504.04, 310/329, 310/370
• US Class Current: 73/504.16
• CPC Class Codes: G01C 19/5614 Signal processing

Abstract

A closed loop sensor that utilizes a piezoelectric structure. In one embodiment, drive/non-control electrodes apply drive voltages to the piezoelectric structure and drive/control electrodes apply drive/control voltages to the piezoelectric structure to cause drive mode displacement of the piezoelectric structure and cancel motion induced pickup mode and quadrature displacements of the piezoelectric structure. In another embodiment, pickup/control electrodes detect a pickup signal from the piezoelectric structure corresponding to the motion induced pickup mode and quadrature displacements and apply a control signal to the piezoelectric structure so as to cancel these displacements. In still another embodiment of the invention, an optical sensing device optically senses the motion induced pickup mode and quadrature displacements and control electrodes apply a control signal to the piezoelectric structure so as to cancel them.

Claims

1. A sensor comprising:

a piezoelectric structure;

a sensor circuit to generate an AC drive signal and an AC control signal; and

drive electrodes coupled to the sensor circuit and configured on the piezoelectric structure so that (a) all of the drive electrodes together apply the AC drive signal to the piezoelectric structure to cause drive mode displacement of the piezoelectric structure, and (b) at least some of the drive electrodes also together apply the AC control signal to the piezoelectric structure to cancel motion induced pickup mode and quadrature displacements of the piezoelectric structure.

2. A sensor as recited in claim 1 further comprising:

means for producing an AC pickup signal corresponding to the motion induced pickup mode and quadrature displacements of the piezoelectric structure;

wherein the sensor circuit includes

pickup/control electronics responsive to the produced AC pickup signal to generate the AC control signal.

3. A sensor as recited in claim 2 wherein the producing means comprises:

pickup electrodes configured on the piezoelectric structure to detect an AC pickup charge signal from the piezoelectric structure in response to charges induced in the piezoelectric structure from the motion induced pickup mode and quadrature displacements of the piezoelectric structure; and

a charge amplifier in the sensor circuit to generate the produced AC pickup signal in response to the AC pickup charge signal.

4. A sensor as recited in claim 2 wherein the producing means comprises an optical sensing device to optically sense the motion induced pickup mode and quadrature displacements of the piezoelectric structure and generate in response the produced AC pickup signal.

5. A sensor as recited in claim 1 wherein:

the AC drive signal comprises the difference between a first drive voltage and a second drive voltage;

the AC control signal comprises the difference between a first control voltage and a second control voltage;

the at least some of the drive electrodes include drive/control electrodes that apply drive/control voltages to the piezoelectric structure, each of the drive/control voltages having a drive component that is one of the first and second drive voltages and a control component that is one of the first and second control voltages.

6. A sensor as recited in claim 5 wherein the drive electrodes include drive/non-control electrodes that only apply the first and second drive voltages to the piezoelectric structure.

7. A sensor as recited in claim 5 wherein:

the drive/control voltages include;

a first drive/control voltage whose drive component is the first drive voltage and whose control component is the first control voltage;

a second drive/control voltage whose drive component is the first drive voltage and whose control component is the second control voltage;

a third drive/control voltage whose drive component is the second drive voltage and whose control component is the first control voltage; and

a fourth AC drive/control voltage whose drive component is the second drive voltage and whose control component is the second control voltage;

the piezoelectric sensor has first opposite surfaces and second opposite surfaces;

the drive/control electrodes include;

first electrodes and second electrodes that are opposingly configured on the first opposite surfaces to respectively apply the first and second drive/control voltages to the piezoelectric structure; and

third electrodes and fourth electrodes that are opposingly configured on the second opposite surfaces to respectively apply the third and fourth drive/control voltages to the piezoelectric structure.

8. A rotation rate sensor comprising:

a piezoelectric tuning fork having drive tines and pickup tines;

a sensor circuit to generate an AC drive signal and an AC control signal; and

drive electrodes coupled to the sensor circuit and configured on the drive tines so that (a) all of the drive electrodes together apply the AC drive signal to the drive tines to cause drive mode vibration of the drive tines, and (b) at least some of the drive electrodes also together apply the AC control signal to the drive tines to cancel rotation induced pickup mode and quadrature vibrations of the pickup tines.

9. A rotation rate sensor as recited in claim 8 further comprising:

means for producing an AC pickup signal corresponding to the rotation induced pickup mode and quadrature vibrations of the piezoelectric structure;

wherein the sensor circuit includes pickup/control electronics responsive to the produced AC pickup signal to generate the AC control signal.

10. A rotation rate sensor as recited in claim 9 wherein the producing means comprises:

pickup electrodes configured on the pickup tines to detect an AC pickup charge signal from the pickup tines in response to charges induced in the pickup tines from the rotation induced pickup mode and quadrature vibrations of the pickup tines; and

a charge amplifier in the sensor circuit to generate the produced AC pickup signal in response to the AC pickup charge signal.

11. A rotation rate sensor as recited in claim 9 wherein the producing means comprises an optical sensing device to optically sense the rotation induced pickup mode and quadrature vibrations of the pickup tines and generate in response the produced AC pickup signal.

12. A rotation rate sensor as recited in claim 8 wherein:

the AC drive signal comprises the difference between a first drive voltage and a second drive voltage;

the AC control signal comprises the difference between a first control voltage and a second control voltage;

the at least some of the drive electrodes include drive/control electrodes that apply drive/control voltages to the drive tines, each of the drive/control voltages having a drive component that is one of the first and second drive voltages and a control component that is one of the first and second control voltages.

13. A rotation rate sensor as recited in claim 12 wherein the drive electrodes include drive/non-control electrodes that only apply the first and second drive voltages to the drive tines.

14. A rotation rate sensor as recited in claim 12 wherein:

the drive/control voltages include;

a first drive/control voltage whose drive component is the first drive voltage and whose control component is the first control voltage;

a second drive/control voltage whose drive component is the first drive voltage and whose control component is the second control voltage;

a third drive/control voltage whose drive component is the second drive voltage and whose control component is the first control voltage; and

a fourth AC drive/control voltage whose drive component is the second drive voltage and whose control component is the second control voltage;

the drive tines include a first drive tine and a second drive tine that each have opposite surfaces;

the drive/control electrodes include;

first electrodes and second electrodes that are opposingly configured on the opposite surfaces of the first drive tine to respectively apply the first and second drive/control voltages to the first drive tine; and

third electrodes and fourth electrodes that are opposingly configured on the opposite surfaces of the second drive tine to respectively apply the third and fourth drive/control voltages to the second drive tine.

15. A rotation rate sensor as recited in claim 8 wherein the drive electrodes are each disposed on a corresponding drive tine of the drive tines and each extend along a majority of the corresponding drive tine'"'"'s length.

16. A sensor comprising:

a piezoelectric structure; and

drive electrodes configured on the piezoelectric structure so that (a) drive mode displacement of the piezoelectric structure is caused when all of the drive electrodes together apply an AC drive signal to the piezoelectric structure, and (b) motion induced pickup mode and quadrature displacements of the piezoelectric structure are canceled when at least some of the drive electrodes together also apply an AC control signal to the piezoelectric structure.

17. A sensor as recited in claim 16 wherein:

the AC drive signal comprises the difference between a first drive voltage and a second drive voltage;

the AC control signal comprises the difference between a first control voltage and a second control voltage;

the at least some of the drive electrodes include drive/control electrodes that apply drive/control voltages to the piezoelectric structure, each of the drive/control voltages having a drive component that is one of the first and second drive voltages and a control component that is one of the first and second control voltages.

18. A sensor as recited in claim 17 wherein the drive electrodes include drive/non-control electrodes that only apply the first and second drive voltages to the piezoelectric structure.

19. A sensor as recited in claim 17 wherein:

the drive/control voltages include;

a first drive/control voltage whose drive component is the first drive voltage and whose control component is the first control voltage;

a second drive/control voltage whose drive component is the first drive voltage and whose control component is the second control voltage;

a third drive/control voltage whose drive component is the second drive voltage and whose control component is the first control voltage; and

a fourth AC drive/control voltage whose drive component is the second drive voltage and whose control component is the second control voltage;

the piezoelectric sensor has first opposite surfaces and second opposite surfaces;

the drive/control electrodes include;

first electrodes and second electrodes that are opposingly configured on the first opposite surfaces to respectively apply the first and second drive/control voltages to the piezoelectric structure; and

third electrodes and fourth electrodes that are opposingly configured on the second opposite surfaces to respectively apply the third and fourth drive/control voltages to the piezoelectric structure.

20. A rotation rate sensor comprising:

a piezoelectric tuning fork having drive tines and pickup tines; and

drive electrodes configured on the piezoelectric structure so that (a) drive mode vibration of the drive tines is caused when all of the drive electrodes together apply an AC drive signal to the drive tines, and (b) motion induced pickup mode and quadrature vibrations of the pickup tines are canceled when at least some of the drive electrodes together also apply an AC control signal to the drive tines.

21. A rotation rate sensor as recited in claim 20 wherein:

the AC drive signal comprises the difference between a first drive voltage and a second drive voltage;

the AC control signal comprises the difference between a first control voltage and a second control voltage;

the at least some of the drive electrodes include drive/control electrodes that apply drive/control voltages to the drive tines, each of the drive/control voltages having a drive component that is one of the first and second drive voltages and a control component that is one of the first and second control voltages.

22. A rotation rate sensor as recited in claim 21 wherein the drive electrodes include drive/non-control electrodes that only apply the first and second drive voltages to the drive tines.

23. A rotation rate sensor as recited in claim 21 wherein:

the drive/control voltages include;

a first drive/control voltage whose drive component is the first drive voltage and whose control component is the first control voltage;

a second drive/control voltage whose drive component is the first drive voltage and whose control component is the second control voltage;

a third drive/control voltage whose drive component is the second drive voltage and whose control component is the first control voltage; and

a fourth AC drive/control voltage whose drive component is the second drive voltage and whose control component is the second control voltage;

the drive tines include a first drive tine and a second drive tine that each have opposite surfaces;

the drive/control electrodes include;

first electrodes and second electrodes that are opposingly configured on the first opposite surfaces to respectively apply the first and second drive/control voltages to the drive tines; and

third electrodes and fourth electrodes that are opposingly configured on the second opposite surfaces to respectively apply the third and fourth drive/control voltages to the drive tines.

24. A rotation rate sensor as recited in claim 20 wherein the drive electrodes are each disposed on a corresponding drive tine of the drive tines and each extend along a majority of the corresponding drive tine'"'"'s length.