Multi-axis, single mass accelerometer

Patent metadata

Field	Value
Publication number	US-11204365-B2
Application number	US-201916569764-A
Country	US
Kind code	B2
Filing date	Sep 13, 2019
Priority date	Sep 13, 2018
Publication date	Dec 21, 2021
Grant date	Dec 21, 2021

Abstract

A multi-axis, single mass acceleration sensor includes a three-dimensional frame, a test mass, a plurality of transducers, and a plurality of struts. The test mass may have three principal axes disposed within and spaced apart from the frame. The transducers are mechanically coupled to the frame. The struts are configured to couple to the central mass at each of the three principal axes, respectively, and to couple with respective sets of the transducers, thereby suspending the test mass within the frame. The sensor is thus responsive to translational motion in multiple independent directions and to rotational motion about multiple independent axes.

First claim

What is claimed is:

1. A multi-axis, single mass acceleration sensor comprising:
a three-dimensional frame;
a test mass disposed within and spaced apart from the frame;
a plurality of transducers mechanically coupled to the frame at a plurality of respective locations on the frame; and
a plurality of struts coupled to the test mass at a plurality of respective positions and coupled to respective sets of the transducers at the plurality of respective locations, thereby suspending the test mass within the frame, wherein the struts connect the transducers to the test mass;
wherein the sensor is responsive to translational motion in multiple independent directions and to rotational motion about multiple independent axes.

2. The sensor of claim 1 , wherein:
each set of transducers comprises a pair of the transducers positioned on opposing sides of a respective face of the frame; and
lateral ends of respective struts connect to each pair of transducers on the opposing sides of each respective face of the frame.

3. The sensor of claim 1 , wherein each strut is stiffer along a longitudinal sensing axis than along axes perpendicular to the longitudinal sensing axis.

4. The sensor of claim 1 , wherein:
the plurality of struts is arranged in pairs with the struts in each pair arranged parallel to each other;
each strut of each pair of struts is positioned on an opposite side of the test mass from the other strut in the pair; and
each strut is positioned normal to one of a plurality of principal axes of the sensor.

5. The sensor of claim 4 , wherein:
the plurality of principal axes of the sensor are orthogonal to each other;
a plurality of planar coupling surfaces are formed on an outer surface of the test mass and each of the planar coupling surfaces is positioned normal to one of the principal axes; and
a center portion of each of the struts is attached to a respective planar coupling surface of the test mass.

6. The sensor of claim 5 , wherein:
each planar coupling surface is parallel to a plane defined by two orthogonal axes centered within the test mass and is a first distance away from the plane;
an attachment surface of the frame to which a respective transducer is coupled to the frame is a second distance from the plane; and
the first distance is greater than the second distance.

7. The sensor of claim 5 , wherein a rigid insulator is positioned between each of the struts and the respective planar coupling surface of the test mass.

8. The sensor of claim 1 , wherein a rigid insulator is positioned between each of the transducers and the frame.

9. The sensor of claim 1 , wherein the test mass is a hollow sphere with walls of uniform thickness.

10. The sensor of claim 1 , wherein the test mass is formed of brass.

11. The sensor of claim 1 , wherein the transducers are oriented with respect to respective struts to respond primarily to acceleration parallel to a longitudinal sensing axis of each respective strut.

12. The sensor of claim 1 , wherein the transducers are responsive to shear stress and are oriented with respect to respective struts to respond primarily to shear stress in a plane defined by a longitudinal sensing axis of each respective strut and a corresponding axis extending outward from a center of mass of the test mass normal to the longitudinal sensing axis of each respective strut.

13. The sensor of claim 1 , wherein for each set of transducers and a corresponding one of the struts coupled with the respective set of transducers:
each transducer is coupled to a respective attachment surface on the frame;
each attachment surface is parallel to and spaced apart from a plane defined by two orthogonal axes centered in the test mass; and
a first distance measured between each attachment surface and the plane is less than a second distance measured between a point at which the corresponding one of the struts couples with the test mass and the plane.

14. The sensor of claim 13 , wherein the second distance is less than a radius of the test mass.

15. The sensor of claim 1 , wherein a distance measured between a point at which the corresponding one of the struts couples with the test mass and a center of the test mass is less than a radius of the test mass.

16. A multi-axis, single mass acceleration sensor comprising:
a three-dimensional frame;
a hollow, substantially spherical test mass disposed within and spaced apart from the frame;
six pairs of shear crystals mechanically coupled to the frame; and
six suspension blades each coupled at a center portion to the test mass normal to opposite ends of each of the three orthogonal principal axes, respectively, and coupled with a respective pair of shear crystals at each lateral end of the suspension blades, thereby suspending the test mass within the frame;
wherein the sensor is oriented with respect to three orthogonal principal axes that each pass through a center of mass of the test mass; and
wherein the sensor is responsive to translational motion parallel to the three orthogonal principal axes and to rotational motion about the three orthogonal principal axes.

17. The sensor of claim 16 , wherein a mass distribution of the test mass is symmetric.

18. The sensor of claim 16 , wherein the six suspension blades are arranged in three pairs with the suspension blades in each pair arranged parallel to each other on opposing sides of the test mass.

19. The sensor of claim 16 , wherein the suspension blades are conductive and an electrical connection is formed between each pair of shear crystals and the corresponding suspension blade.

20. The sensor of claim 16 , wherein a rigid insulator is positioned between each of center portions of the suspension blades and the test mass.

21. The sensor of claim 16 , wherein the suspension blades are made of beryllium copper.

22. The sensor of claim 16 , wherein the suspension blades are formed as flat plates with two apertures formed between a center section and respective lateral end sections.

23. The sensor of claim 16 , wherein each suspension blade is stiffer along a longitudinal sensing axis than along axes perpendicular thereto.

24. The sensor of claim 23 , wherein the longitudinal sensing axis of each suspension blade is parallel to one of the orthogonal principal axes and is perpendicular to a second one of the orthogonal principal axes.

25. The sensor of claim 16 , wherein:
a plurality of planar coupling surfaces is formed on an outer surface of the test mass and each of the planar coupling surfaces is positioned normal to one of the three principal axes; and
a center portion of each of the suspension blades is attached to a respective planar coupling surface of the test mass.

26. The sensor of claim 25 , wherein a rigid insulator is positioned between each of the suspension blades and the respective planar coupling surface of the test mass.

27. The sensor of claim 25 , wherein a distance, measured between a respective planar coupling surface at which a corresponding one of the suspension blades couples with the test mass and the center of mass of the test mass, is less than a radius of the test mass.

28. The sensor of claim 25 , wherein:
each planar coupling surface is parallel to a plane defined by two of the orthogonal principal axes and is a first distance away from the plane;
the frame is defined by twelve beams and e

Assignees

• Ion Geophysical Corp

Inventors

• Olivier André W
• Behn Lawrence Philip
• Greco Matthew
• Faber Cornelis A M

Classifications

• G01P15/18 Primary

  in two or more dimensions · CPC title

• G01V1/164

  Circuits therefore · CPC title

• G01V1/3852

  to the seabed · CPC title

• G01V1/184

  Multi-component geophones · CPC title

• G01V2210/1427

  Sea bed · CPC title