System and method for image-based structural health monitoring suitable for structures having uncertain load conditions and support conditions

Patent metadata

Field	Value
Publication number	US-9734423-B2
Application number	US-201514827615-A
Country	US
Kind code	B2
Filing date	Aug 17, 2015
Priority date	Jan 29, 2015
Publication date	Aug 15, 2017
Grant date	Aug 15, 2017

Abstract

An image-based structural health monitoring system and method are disclosed herein. The image-based structural health monitoring system includes a marker image acquisition unit, a marker coordinate calculation unit, a shape function determination unit, and a structural health evaluation unit. The marker image acquisition unit acquires marker images of markers attached onto the surface of a structure. The marker coordinate calculation unit calculates the coordinates of the markers in the marker images. The shape function determination unit determines a shape function by performing spline interpolation based on the calculated marker coordinates. The structural health evaluation unit evaluates the structural health of the structure by calculating the strain or stress of the structure based on the radius of curvature calculated at each location on the determined shape function.

First claim

What is claimed is:

1. An image-based structural health monitoring system, comprising:
a marker image acquisition unit configured to acquire marker images of markers attached onto a surface of a structure;
a marker coordinate calculation unit configured to calculate coordinates of the markers in the marker images;
a shape function determination unit configured to determine a shape function by performing spline interpolation based on the calculated marker coordinates; and
a structural health evaluation unit configured to evaluate structural health of the structure by calculating strain or stress of the structure based on a radius of curvature calculated at each location on the determined shape function.

2. The image-based structural health monitoring system of claim 1 , wherein the shape function determination unit is operative to determine the shape function by performing cubic smoothing spline interpolation on the calculated marker coordinates.

3. The image-based structural health monitoring system of claim 1 , wherein the shape function determination unit is operative to, in order to determine a spline polynomial for each subsection between two neighboring sets of marker coordinates, obtain coefficients of the spline polynomial so that two spline polynomials for two neighboring subsections satisfy all conditions in which a first derivative is continuous, a second derivative is continuous, and values of second derivatives are 0 at two ends.

4. The image-based structural health monitoring system of claim 3 , wherein the shape function determination unit is operative to obtain the coefficients of the spline polynomial that additionally satisfy a condition in which a square error between the marker coordinate values and the spline polynomial is minimized and a condition in which a curvature of the spline polynomial is minimized, for each subsection.

5. The image-based structural health monitoring system of claim 4 , wherein the shape function determination unit is operative to obtain the coefficients of the spline polynomial that additionally satisfy a condition in which a weighted sum, of the square error between the marker coordinate values and the spline polynomial, and the curvature of the spline polynomial, is minimized, for each subsection.

6. The image-based structural health monitoring system of claim 5 , wherein the shape function determination unit is operative to apply the condition in which the weighted sum, of the square error between the marker coordinate values and the spline polynomial, and the curvature of the spline polynomial, is minimized, in accordance with an equation below:

minimize
⁢

⁢
p
⁢

∑

i
=
1

n

⁢

⁢

(

z
i

-

S
⁡

(

x
i

)

)

2

+

(

1
-
p

)

⁢

∫

(

S
n

⁡

(
x
)

)

2

⁢
dx

where p is a smoothing parameter having a value ranging from 0 to 1 and corresponds to p≃1/(1+H 3 /6), H is an average interval value between the passive markers, z i is a z axis coordinate value of an i-th marker coordinates of n marker coordinates, x i is an x axis coordinate value of the i-th marker coordinates, S(x) is the spline polynomial, S″(x) is the second derivative of the spline polynomial, an x axis is parallel to a neutral axis of an undeformed structure, and a z axis is parallel to a direction in which the structure is deformed and is perpendicular to the x axis.

7. The image-based structural health monitoring system of claim 1 , wherein the structural health evaluation unit is operative to calculate the radius of curvature at each location on the shape function in accordance with an equation below:

r
⁡

(

x
_

j

)

=

(

f
′

⁡

(

x
_

j

)

2

+
1

)

3
/
2

f
″

⁡

(

x
_

j

)

⁢

Assignees

• Industry-Academic Cooperation Foundation Yonsei Univ

Inventors

• Park Hyo Seon
• Park Jun Su
• Oh Byung Kwan
• Kim You Sok

Classifications

• G01M5/0058 Primary

  of elongated objects, e.g. pipes, masts, towers or railways · CPC title

• G01B11/16

  for measuring the deformation in a solid, e.g. optical strain gauge · CPC title

• G01L5/00

  Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes · CPC title

• G06F17/13

  Differential equations (using digital differential analysers G06F7/64) · CPC title

• G01B11/255 Primary

  for measuring radius of curvature {(measuring diameter G01B11/08)} · CPC title