Cable Force Determination Using Phase-Based Video Motion Magnification and Digital Image Correlation

2021 ◽  
Author(s):  
Wenbing Chen ◽  
Banfu Yan ◽  
Jingbo Liao ◽  
Lei Luo ◽  
You Dong
Keyword(s):  
Mode Shape ◽  
Digital Image ◽  
Time History ◽  
Identification Accuracy ◽  
Image Correlation ◽  
Mode Shapes ◽  
Cable Model ◽  
Study Results ◽  
Cable Force ◽  
Motion Magnification

The mode shape-aided method provides a simple and effective way for cable force determination, which, however, requires accurate parameter identification of the cable structure. This paper proposes a phase-based video motion magnification to process the image sequences of a cable. Digital image correlations were engaged to measure the dynamic displacement–time history, through tracking the surface characteristic features of the cable. Thereafter, a frequency–domain decomposition technique was applied to extract the natural frequency and mode shape of the cable from the displacement–time history measurements. The identified cable mode shapes, along with a tensioned pinned-pinned cable model, were used to estimate the cable force. The accuracy of the proposed methodology was subsequently verified through laboratory testing on an inclined cable model and field testing on a typical hanger cable of a real-world arch bridge. Overall, the study results indicated that the proposed methodology could expediently and cost-effectively estimate the tension forces of a cable with reasonably acceptable identification accuracy.

Mode shape–aided cable force determination using digital image correlation

2020 ◽  
pp. 147592172095216
Author(s):  
Banfu Yan ◽  
Derui Li ◽  
Wenbing Chen ◽  
Lu Deng ◽  
Xiaomo Jiang
Keyword(s):  
Digital Image Correlation ◽  
Mode Shape ◽  
Digital Image ◽  
Image Correlation ◽  
Effective Length ◽  
Estimation Methods ◽  
Mode Shapes ◽  
Correlation Technique ◽  
Remote Measurement ◽  
Cable Force

Assuming the distance between two nodal points of a specific cable vibration mode as the effective length of a pinned–pinned cable, mode shape–aided cable tension estimation methods are employed to estimate the cable force. This article proposes a framework based on digital image correlation technique for remote measurement of the dynamic displacement time history of cables in cable structures. Frequency domain decomposition technique is then used to extract the cable natural frequencies and mode shapes. Identified cable mode shapes are used along with a tensioned pinned–pinned cable model to estimate the cable force. Accuracy of the proposed methodology is investigated using the experimental data coming from a laboratory-scale test setup and hanger cables of a real-world arch bridge.

scholarly journals Comparisons of Differential Filtering and Homography Transformation in Modal Parameter Identification from UAV Measurement

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5664
Author(s):  
Jiqiao Zhang ◽  
Zhihua Wu ◽  
Gongfa Chen ◽  
Qiang Liang
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Time History ◽  
Reference Points ◽  
Image Correlation ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Modal Parameter ◽  
Filtering Method ◽  
Homography Transformation

This paper proposes a differential filtering method for the identification of modal parameters of bridges from unmanned aerial vehicle (UAV) measurement. The determination of the modal parameters of bridges is a key issue in bridge damage detection. Accelerometers and fixed cameras have disadvantages of deployment difficulty. Hence, the actual displacement of a bridge may be obtained by using the digital image correlation (DIC) technology from the images collected by a UAV. As drone movement introduces false displacement into the collected images, the homography transformation is commonly used to achieve geometric correction of the images and obtain the true displacement of the bridge. The homography transformation is not always applicable as it is based on at least four static reference points on the plane of target points. The proposed differential filtering method does not request any reference points and will greatly accelerate the identification of the modal parameters. The displacement of the points of interest is tracked by the DIC technology, and the obtained time history curves are processed by differential filtering. The filtered signals are input into the modal analysis system, and the basic modal parameters of the bridge model are obtained by the operational modal analysis (OMA) method. In this paper, the power spectral density (PSD) is used to identify the natural frequencies; the mode shapes are determined by the ratio of the PSD transmissibility (PSDT). The identification results of three types of signals are compared: UAV measurement with differential filtering, UAV measurement with homography transformation, and accelerometer-based measurement. It is found that the natural frequencies recognized by these three methods are almost the same. This paper demonstrates the feasibility of UAV-differential filtering method in obtaining the bridge modal parameters; the problems and challenges in UAV measurement are also discussed.

An Investigation of the Temperature Influence on a Shift of Natural Frequencies Using Digital Image Correlation

2014 ◽  
Vol 611 ◽  
pp. 506-510 ◽  
Author(s):  
Martin Hagara ◽  
Martin Schrötter ◽  
Pavol Lengvarský
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
High Speed ◽  
Natural Frequencies ◽  
Damping Ratio ◽  
Indicator Function ◽  
Image Correlation ◽  
Mode Shapes ◽  
Temperature Influence ◽  
Air Gun

The contribution describes an original optical measuring technique serving for the investigation of temperature influence on the shift of investigated objects natural frequencies. The mentioned method uses a modified high-speed digital image correlation system with original program Modan 3D created in Matlab, by which it is possible to non-contactly determine the natural frequencies using complex mode indicator function (CMIF) or normal mode indicator function (NMIF), the mode shapes as well as the damping ratio. Influence of the temperature on the shift of natural frequencies was analyzed at the planar steel specimen of circular shape with three holes. To the excitation a modal hammer was used. The specimen heating was realized by a hot-air gun, whereby the influence of the elevated temperature on the shift of natural frequencies was investigated by three temperatures distinguishing the room temperature 50° C, 75° C and 100° C.

scholarly journals Integrating a Hive Triangle Pattern with Subpixel Analysis for Noncontact Measurement of Structural Dynamic Response by Using a Novel Image Processing Scheme

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Yung-Chi Lu ◽  
Shih-Lin Hung ◽  
Tzu-Hsuan Lin
Keyword(s):  
Image Processing ◽  
Digital Image Correlation ◽  
Dynamic Response ◽  
Digital Image ◽  
Time History ◽  
Image Correlation ◽  
Estimation Accuracy ◽  
Structural Dynamic ◽  
Processing Scheme ◽  
Noncontact Measurement

This work presents a digital image processing approach with a unique hive triangle pattern by integrating subpixel analysis for noncontact measurement of structural dynamic response data. Feasibility of proposed approach is demonstrated based on numerical simulation of a photography experiment. According to those results, the measured time-history displacement of simulated image correlates well with the numerical solution. A small three-story frame is then mounted on a small shaker table, and a linear variation differential transformation (LVDT) is set on the second floor. Experimental results indicate that the relative error between data from LVDT and analyzed data from digital image correlation is below 0.007%, 0.0205 in terms of frequency and displacement, respectively. Additionally, the appropriate image block affects the estimation accuracy of the measurement system. Importantly, the proposed approach for evaluating pattern center and size is highly promising for use in assigning the adaptive block for a digital image correlation method.

Full-field strain prediction using mode shapes measured with digital image correlation

Measurement ◽  
2019 ◽  
Vol 139 ◽  
pp. 326-333 ◽  
Author(s):  
Kedar Bharadwaj ◽  
Azadeh Sheidaei ◽  
Arash Afshar ◽  
Javad Baqersad
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Image Correlation ◽  
Field Strain ◽  
Mode Shapes ◽  
Full Field

scholarly journals Subpixel Matching Using Double-Precision Gradient-Based Method for Digital Image Correlation

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 3140
Author(s):  
Gang Liu ◽  
Mengzhu Li ◽  
Weiqing Zhang ◽  
Jiawei Gu
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Search Algorithm ◽  
Spline Interpolation ◽  
Speckle Pattern ◽  
Identification Accuracy ◽  
Image Correlation ◽  
Bending Test ◽  
Double Precision ◽  
Gradient Based

Digital image correlation (DIC) for displacement and strain measurement has flourished in recent years. There are integer pixel and subpixel matching steps to extract displacement from a series of images in the DIC approach, and identification accuracy mainly depends on the latter step. A subpixel displacement matching method, named the double-precision gradient-based algorithm (DPG), is proposed in this study. After, the integer pixel displacement is identified using the coarse-fine search algorithm. In order to improve the accuracy and anti-noise capability in the subpixel extraction step, the traditional gradient-based method is used to analyze the data on the speckle patterns using the computer, and the influence of noise is considered. These two nearest integer pixels in one direction are both utilized as an interpolation center. Then, two subpixel displacements are extracted by the five-point bicubic spline interpolation algorithm using these two interpolation centers. A novel combination coefficient considering contaminated noises is presented to merge these two subpixel displacements to obtain the final identification displacement. Results from a simulated speckle pattern and a painted beam bending test show that the accuracy of the proposed method can be improved by four times that of the traditional gradient-based method that reaches the same high accuracy as the Newton–Raphson method. The accuracy of the proposed method efficiently reaches at 92.67%, higher than the Newton-Raphon method, and it has better anti-noise performance and stability.

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