Coriolis vibratory accelerometer system

Patent metadata

Field	Value
Publication number	US-11073391-B2
Application number	US-201916584332-A
Country	US
Kind code	B2
Filing date	Sep 26, 2019
Priority date	Sep 26, 2019
Publication date	Jul 27, 2021
Grant date	Jul 27, 2021

Abstract

A CVA system includes a sensor system including a pendulous element that rotates about a first axis via first flexures in response to an input acceleration provided along a second axis that is orthogonal with respect to the first axis. A torque-summing gimbal is coupled to the pendulous element via the first flexures and coupled to a housing via second flexures. The system further includes an accelerometer controller that monitors a pickoff signal of the rotation of the pendulous element from a first electrode coupled to the pendulous element and to provide a forcer signal to at least one second electrode coupled to the torque-summing gimbal to force the torque-summing gimbal to rotate about the second axis via the second flexures based on the pickoff signal to provide Coriolis force-rebalance of the pendulous element. The accelerometer controller can determine the input acceleration based on the rotation of the torque-summing gimbal.

First claim

What is claimed is:

1. A Coriolis Vibratory Accelerometer (CVA) system comprising:
a sensor system comprising a pendulous element configured to rotate about a first axis via first flexures in response to an input acceleration provided along a second axis that is orthogonal with respect to the first axis, the sensor system further comprising a torque-summing gimbal coupled to the pendulous element via the first flexures and coupled to a housing via second flexures; and
an accelerometer controller configured to monitor a pickoff signal associated with the rotation of the pendulous element from at least one first electrode coupled to the pendulous element and to provide a forcer signal to at least one second electrode coupled to the torque-summing gimbal to force the torque-summing gimbal to rotate about the second axis via the second flexures based on the pickoff signal to provide Coriolis force-rebalance of the pendulous element, the accelerometer controller being further configured to determine the input acceleration based on the rotation of the torque-summing gimbal.

2. The system of claim 1 , wherein the sensor system further comprises a plurality of oscillating-masses that are driven by an oscillating-mass forcer signal via at least one third electrode to provide in-plane oscillatory motion of the plurality of oscillating-masses, wherein the accelerometer controller is configured to provide the forcer signal to force the torque-summing gimbal to rotate in an oscillatory manner about the second axis at a same frequency as the in-plane oscillatory motion of the plurality of oscillating-masses, such that the in-plane oscillatory motion of the plurality of oscillating-masses and the rotation of the torque-summing gimbal in the oscillatory manner generates a Coriolis force to provide the Coriolis force-rebalance of the pendulous element.

3. The system of claim 2 , wherein the oscillating-mass forcer signal is generated by the accelerometer controller as a triangular wave to provide for a substantially constant velocity anti-parallel periodic motion of the plurality of oscillating-masses.

4. The system of claim 2 , wherein the at least one first electrode comprises a first planar pair of electrodes coupled to the pendulous element and a first opposing pair of planar electrodes coupled to a housing on a surface opposite a surface of the pendulous element, wherein the at least one second electrode comprises at least one first set of comb-drive electrodes coupled to the torque-summing gimbal and at least one second set of comb-drive electrodes coupled to the housing on each of opposite sides of the housing, with the at least one second set of comb-drive electrodes on each opposite side of the housing being interdigitated with the respective first pair of comb-drive electrodes, wherein the at least one third electrode comprises a first set of tooth-drive electrodes coupled to each of the plurality of oscillating-masses and a second set of tooth-drive electrodes coupled to the housing on a surface opposite a surface of each of the respective plurality of oscillating-masses.

5. The system of claim 2 , wherein the accelerometer controller is configured to determine the input acceleration based on a velocity of the plurality of oscillating-masses and based on an angular velocity of the torque-summing gimbal.

6. The system of claim 5 , further comprising an optical velocity detector configured to determine the velocity of the plurality of oscillating-masses and to determine the angular velocity of the torque-summing gimbal.

7. The system of claim 1 , wherein the second flexures occupy a first plane that includes a center of gravity associated with the sensor system, and wherein the first flexures are offset from the first plane by a predetermined distance to provide pendulosity of the pendulous element in response to the input acceleration in-plane with the first plane and to substantially mitigate pendulosity of the torque-summing gimbal in response to any acceleration in-plane with the first plane.

8. The system of claim 1 , wherein the accelerometer controller is further configured to monitor a displacement of the torque-summing gimbal and to provide self-integration of the determination of the input acceleration based on the monitored displacement of the torque-summing gimbal.

9. The system of claim 1 , wherein the accelerometer controller comprises an angular rate servo configured to provide a force-rebalance signal to the first set of electrodes in response to the pickoff signal to substantially mitigate errors associated with angular rotation of the pendulous element in response to rotation of the sensor system.

10. The system of claim 9 , wherein the angular rate servo is further configured to calculate the rotation of the sensor system based on the amplitude of the force-rebalance signal.

11. A method for measuring an input acceleration along a sensitive axis via a Coriolis Vibratory Accelerometer (CVA) system, the method comprising:
providing an oscillating-mass forcer signal to at least one first electrode to drive an in-plane oscillatory motion of a plurality of oscillating-masses associated with a pendulous element of a sensor system;
monitoring a pickoff signal from at least one second electrode to determine a rotation of the pendulous element about a first axis via first flexures in response to an input acceleration provided along a second axis that is orthogonal with respect to the first axis;
generating a forcer signal based on the pickoff signal;
providing the forcer signal to at least one third electrode associated with a torque-summing gimbal of the sensor system to force the torque-summing gimbal to rotate in response to the pickoff signal to provide Coriolis force-rebalance of the pendulous element via the rotation of the torque-summing gimbal and the in-plane oscillatory motion of the oscillating-masses; and
determining an input acceleration based on a velocity of the in-plane oscillatory motion of the oscillating-masses and an angular velocity of the rotation of the torque-summing gimbal.

12. The method of claim 11 , further comprising generating the oscillating-mass forcer signal as a triangular wave to provide for a substantially constant velocity motion of the plurality of oscillating-masses.

13. The method of claim 11 , further comprising determining the velocity of the in-plane oscillatory motion of the oscillating-masses and determining the angular velocity of the rotation of the torque-summing gimbal via an optical detection system.

14. The method of claim 11 , further comprising:
determining a displacement of the torque-summing gimbal in response to rotation of the torque-summing gimbal; and
integrating the determination of the input acceleration based on the monitored displacement of the torque-summing gimbal.

15. The method of claim 11 , further comprising:
generating an angular rate force-rebalance signal in response to the pickoff signal;
providing the angular rate force-rebalance signal to the at least one second electrode to substantially mitigate errors in the determination of the input acceleration based on angular rotation of the pendulous element in response to rotation of the sensor system; and
calculating an angular rate of the rotation of the sensor system based on the amplitude and polarity of the angular rate force-rebalance signal.

16. A Coriolis Vibratory Accelerometer (CVA) system comprising:
a sensor system comprising:
a pendulous element configured to rotate about a first axis via first flexures in response to an input acceleration provided along a second axi

Assignees

• Stewart Robert E
• Northrop Grumman Systems Corp

Inventors

• Stewart Robert E

Classifications

• G01C19/5733 Primary

  Structural details or topology · CPC title

• G01P15/093

  by photoelectric pick-up · CPC title

• G01C19/5726

  Signal processing · CPC title

• G01P15/125

  by capacitive pick-up · CPC title

• G01P15/097 Primary

  by vibratory elements · CPC title