Sensor system for indirect sensing of deformation of flexible structures

Patent metadata

Field	Value
Publication number	US-10488183-B1
Application number	US-201715852059-A
Country	US
Kind code	B1
Filing date	Dec 22, 2017
Priority date	Dec 30, 2016
Publication date	Nov 26, 2019
Grant date	Nov 26, 2019

Abstract

A sensor system for sensing deformation of a flexible structure includes a beam structure that will be coupled to a surface of the flexible structure having a natural frequency fs, an axial strain εaxialstructure, and a shear strain εxystructure associated therewith. The beam structure has an axial strain εaxialbeam and a shear strain εxybeam associated therewith. The beam structure satisfies criteria defined by minimization of a root mean square difference between εaxialstructure and εaxialbeam and minimization of a root mean square difference between εxystructure and εxybeam. Fiber optic strain sensors are coupled to and distributed in a spaced-apart fashion along the beam structure. The beam structure is more flexible than the flexible structure such that a combination of the beam structure, the fiber optic sensors, and the flexible structure has a natural frequency fc defined by (0.95)fs≤fc≤(1.05)fs.

First claim

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A sensor system for sensing deformation of a flexible structure, comprising:
a beam structure adapted to be coupled to a surface of a flexible structure, wherein the flexible structure has a natural frequency f s , an axial strain ε axial structure , and a shear strain ε xy structure associated therewith, said beam structure having an axial strain ε axial beam and a shear strain ε xy beam associated therewith, wherein said beam structure satisfies a criteria defined by minimization of a root mean square difference between ε axial structure and ε axial beam and minimization of a root mean square RMS difference between ε xy structure and ε xy beam ; and
a plurality of fiber optic strain sensors coupled to and distributed in a spaced-apart fashion along said beam structure,
said beam structure being more flexible than the flexible structure wherein a combination of said beam structure, said fiber optic sensors, and the flexible structure has a natural frequency f c defined by (0.95)f s ≤f c ≤(1.05)f s .

2. A sensor system as in claim 1 , wherein said beam structure is solid.

3. A sensor system as in claim 1 , wherein said beam structure is hollow.

4. A sensor system as in claim 1 , wherein said beam structure is rectangular in cross-section.

5. A sensor system as in claim 1 , wherein said beam structure has a longitudinal axis, and wherein said sensors are arranged along at least one line that is parallel to said longitudinal axis.

6. A sensor system as in claim 1 , wherein said beam structure has a longitudinal axis, wherein each of said sensors has a sensing axis, and wherein each said sensing axis is one of parallel to said longitudinal axis and oriented at an acute angle relative to said longitudinal axis.

7. A sensor system as in claim 1 , wherein said beam structure has a longitudinal axis, wherein each of said sensors has a sensing axis, wherein said sensing axis associated with a portion of said sensors is parallel to said longitudinal axis, and wherein said sensing axis associated with a remainder of said sensors lies at an acute angle relative to said longitudinal axis.

8. A sensor system as in claim 7 , wherein said portion of said sensors is interleaved with said remainder of said sensors.

9. A sensor system as in claim 1 , wherein a number of said sensors and positions of said sensors on said beam structure are based on an estimation of bending curvature and twist of the structure.

10. A sensor system as in claim 1 , wherein said beam structure comprises N longitudinally-extending planar faces, and wherein said plurality of fiber optic sensors are coupled to N−1 of said longitudinally-extending planar faces.

11. A sensor system as in claim 1 , wherein said beam structure comprises a plurality of flat plates.

12. A sensor system for sensing deformation of a flexible cylindrical structure, comprising:
a plurality of beam structures, each of said beam structures adapted to be coupled to a surface of a flexible cylindrical structure, wherein the flexible structure has a natural frequency f s , an axial strain ε axial structure , and a shear strain ε xy structure associated therewith, each of said beam structures being more flexible than the cylindrical structure, each of said beam structures having an axial strain ε axial beam and a shear strain ε xy beam associated therewith, wherein each of said beam structures satisfies a criteria defined by minimization of a root mean square difference between ε axial structure and ε axial beam and minimization of a root mean square difference between ε xy structure and ε xy beam , each of said beam structures having a beam axis that is parallel to a longitudinal axis of the cylindrical structure, said beam structures distributed evenly about a radial circumference of the cylindrical structure; and
a plurality of fiber optic strain sensors coupled to and distributed in a spaced-apart fashion along outside surfaces of each of said beam structures,
each of said beam structures being more flexible than the flexible cylindrical structure wherein a combination of said beam structures, said fiber optic sensors, and the flexible cylindrical structure has a natural frequency f c defined by (0.95)f s ≤f c ≤(1.05) f s .

13. A sensor system as in claim 12 , wherein each of said beam structures is solid.

14. A sensor system as in claim 12 , wherein each of said beam structures is hollow.

15. A sensor system as in claim 12 , wherein each of said beam structures is rectangular in cross-section.

16. A sensor system as in claim 12 wherein, for each of said beam structures, said sensors are arranged along at least one line that is parallel to said beam axis associated therewith.

17. A sensor system as in claim 12 , wherein each of said sensors has a sensing axis, and wherein each said sensing axis is one of parallel to said beam axis associated with a corresponding one of said beam structures and oriented at an acute angle relative to said beam axis associated with said corresponding one of said beam structures.

18. A sensor system as in claim 12 , wherein each of said sensors has a sensing axis and wherein, for at least one of said beams elements, said sensing axis associated with a portion of said sensors is parallel to said beam axis, and said sensing axis associated with a remainder of said sensors lies at an acute angle relative to said beam axis.

19. A sensor system as in claim 18 , wherein said portion of said sensors is interleaved with said remainder of said sensors.

20. A sensor system as in claim 12 , wherein a number of said sensors and positions of said sensors on each of said beam structures are based on an estimation of bending curvature and twist of the cylindrical structure.

21. A sensor system as in claim 12 , wherein each of said beam structures comprises N planar faces extending parallel to said beam axis thereof, and wherein said plurality of fiber optic sensors are coupled to N−1 of said planar faces for each of said beam structures.

22. A sensor system as in claim 12 , wherein each of said beam structures comprises a plurality of flat plates.

23. A sensor system for sensing deformation of a flexible structure, comprising:
at least one rigid mount adapted to be rigidly coupled to a surface of a flexible structure, wherein the flexible structure has a natural frequency f s , an axial strain ε axial structure , and a shear strain ε xy structure associated therewith;
a beam structure coupled to said at least one rigid mount wherein said beam structure is offset from the surface of the structure, said beam structure having an axial strain ε axial beam and a shear strain ε xy beam associated therewith, wherein said beam structure satisfies a criteria defined by minimization of a root mean square difference between ε axial structure and ε axial beam and minimization of a root mean square difference between ε xy structure and ε xy beam ; and
a plurality of fiber optic strain sensors coupled to and distributed in a spaced-apart fashion along outside surfaces of said beam structure,
said beam structure being more flexible than the flexible structure wherein a combination of said beam structure, said fiber optic sensors, and the flexible structure has a natural frequency f c defined by (0.95)f s ≤f c ≤(1.05)f s .

24. A sensor system as in c

Assignees

• Nasa

Inventors

• Wolf Michael G
• Suhey Jeffrey D
• Stanley James E
• Griffin Edwin D
• Gutierrez Hector
• Kirk Daniel
• Lapilli Gabriel
• Su Weihua
• Tsushima Natsuki
• Van Der Veek Bartel

Classifications

• G01M5/0041

  by determining deflection or stress · CPC title

• G01M5/0025

  of elongated objects, e.g. pipes, masts, towers or railways (G01M5/0058 takes precedence) · CPC title

• G01M5/0016

  of aircraft wings or blades · CPC title

• G01L1/246

  using integrated gratings, e.g. Bragg gratings · CPC title

• G01B5/0004

  Supports (G01B5/025 takes precedence) · CPC title