Frequency domain triangulation for full-field 3D operating-deflection-shape identification

Gorjup, Domen; Slavič, Janko

doi:10.1016/j.ymssp.2019.106287

Cited by 43 publications

(19 citation statements)

References 35 publications

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“…For a utility‐scale WTB within a test facility, the use of a standard stereo‐photogrammetry to measure the entire blade may be limited by the camera separation or the required working distance to capture the area of interest. Therefore, larger FOVs can be obtained by stitching together in a global coordinate system the images recorded using the two adjacent sets of cameras as demonstrated in several prior studies 39,40,58,59 . Thus, to perform a 3D‐DIC measurement, it is desirable to couple several pairs of cameras to simultaneously monitor the distributed strain, deflections, and deformations within the line of sight of each stereo‐vision system.…”

Section: Edgewise Fatigue Testmentioning

confidence: 99%

“…In this research, a multicamera measurement system, employing a stereo‐photogrammetry technique in conjunction with dynamic spatial data stitching, is used to evaluate the static and dynamic characteristics of a utility‐scale WTB subjected to static and dynamic loadings. Alternative approaches include image stitching operations performed in the frequency domain 39 and a single moving camera for multiview 3D reconstruction 40 . Figure 1 shows the conceptual setup of a multicamera system made of five synchronized stereo‐vision systems recording adjacent views of the low pressure side of a WTB.…”

Section: Introductionmentioning

confidence: 99%

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Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

et al. 2020

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Wind turbine blade certification requires static and fatigue testing at a large-scale facility similar to the Wind Technology Testing Center (WTTC) located in Charlestown, Massachusetts. Usually, these tests are conducted by using wire-based sensors such as strain gages, accelerometers, and string potentiometers. These systems are expensive, require a time-consuming installation (e.g., up to 3 weeks and $35 k-$50 k for a strain gage system on a 55-m-long blade), are difficult to deploy on large-sized structures, require additional instrumentations (e.g., power amplifiers and data acquisition systems), and produce results only at a handful of a discrete number of measurement points. In this study, a multicamera measurement system is implemented and experimentally evaluated to obtain full-field displacement and strain over a~12-m-long portion of a~60-m utility-scale wind turbine blade. The proposed system has the potential to streamline the certification process by reducing the blade's preparation and sensor installation cost and time to a few hundreds of dollars (for painting equipment) and a few days for preparing the surface of the blade for the test. Furthermore, operational modal analysis was used in conjunction with the multicamera system to estimate the natural frequencies and mode shapes of the wind turbine blade. The obtained results have shown that the proposed approach can detect in-plane displacement as low as 0.2 mm, mechanical strain with an error below 3% when compared with measurement performed using strain gages, and the first five natural frequencies with an error below 2% when compared with data recorded using traditional wire-based accelerometers. This paper presents these results and provides a summary of the strengths and weaknesses of the proposed optical measurement approach in the context of streamlining the blade certification/testing process and performing vision-based structural dynamic measurements on large-scale structures. K E Y W O R D Sdigital image correlation, fatigue tests, operational modal analysis, stitched field of view, structural health monitoring, wind turbine blades

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Section: Edgewise Fatigue Testmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

et al. 2020

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“…Moreover, a new single-camera method for steady-state vibration measurement was proposed newly. Gorjup et al [30] utilized a moving high-speed camera, extending the image-based vibration measurement method. Spatial small harmonic motion can be identified in the frequency domain.…”

Section: Introductionmentioning

confidence: 99%

Vibration Measurement of a Metal Sheet Using Single-Camera Digital Image Correlation with Projection Components

Liang

Lin

2022

Shock and Vibration

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Digital image correlation has emerged as a popular method for the dynamic performance measurement of metallic and polymer sheets, owing to the benefits of being a noncontact, full-field, and high-precision method. Two or more high-speed cameras are required for full-field vibration measurements with three-dimensional digital image correlation, which is generally costly. Perpendicular view to the specimen surface is conventional in two-dimensional digital image correlation, and the out-of-plane displacement is regarded as a part of systematic errors. In this study, a single view method was implemented with no complex optical settings. The full-field vibration displacement of the metal sheet was measured with projection components, and the first four orders of displacement modes were identified. Finite element analysis and traditional experimental modal analysis were then implemented to validate the effectiveness and accuracy of the proposed approach. The results show that the dynamic parameters, including the natural frequencies and mode shapes, were well consistent. Meanwhile, there is a significant difference in the length of mode shape vectors. The number of measurement points in the proposed method is 2016, which is far more than the number of measurement points in the traditional experimental modal analysis. This would be convenient and beneficial for damage identification towards thin-wall parts including turbine blade with the continuum hypothesis of mode shapes and a single-camera DIC system. It is worth noting that this is effective with conditions of small deformation vibration and no rigid-body rotation.

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“…Nevertheless, in last years, the use of non-contact imagebased measurement techniques in structural dynamics applications has grown. In fact, displacements, deformations and mode shapes can be measured with cameras operating in the visible spectrum by applying both Digital Image Correlation and other computer-vision methods [28]- [30]. One of the more promising approach for displacement and motion detection involves markers, either they are physical or virtual.…”

Section: Introductionmentioning

confidence: 99%

Thermoelasticity and ArUco marker-based model validation of polymer structure: application to the San Giorgio’s bridge inspection robot

et al. 2021

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<p>Experimental procedures are often involved in the numerical models validation. To define the behaviour of a structure, its underlying dynamics and stress distributions are generally investigated. In this research, a multi-instrumental and multi-spectral method is proposed in order to validate the numerical model of the Inspection Robot mounted on the new San Giorgio's Bridge on the Polcevera river. An infrared thermoelasticity-based approach is used to measure stress-concentration factors and, additionally, an innovative methodology is implemented to define the natural frequencies of the Robot Inspection structure, based on the detection of ArUco fiducial markers. Established impact hammer procedure is also performed for the validation of the results.</p>

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Frequency domain triangulation for full-field 3D operating-deflection-shape identification

Cited by 43 publications

References 35 publications

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

Multicamera measurement system to evaluate the dynamic response of utility‐scale wind turbine blades

Vibration Measurement of a Metal Sheet Using Single-Camera Digital Image Correlation with Projection Components

Thermoelasticity and ArUco marker-based model validation of polymer structure: application to the San Giorgio’s bridge inspection robot

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