Modeling Uncertainty for a Vision System Applied to Vibration Measurements

Lavatelli, Alberto; Zappa, Emanuele

doi:10.1109/tim.2016.2541359

Cited by 38 publications

(14 citation statements)

References 40 publications

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“…In fact, motion blur itself is generated by the target moving during exposure. As demonstrated in previous works [27], [35], [36], this phenomenon is driven by the peaks in the instantaneous speed of the measurand. So, if we compare two possible excitation signals, the one that develops higher velocity peaks in the measurand is more prone to produce an under-estimation of resonant amplitude in the H1 estimator (when using vision based measurement system).…”

Section: Managing the Structural Excitation During Testssupporting

confidence: 68%

“…For sure it is possible to simulate more modern and sophisticated methods (i.e. pattern matching, digital image correlation), however the effects of motion blur are expected to behave similarly: motion blur is able to degrade all the geometrical features nested in an image, so that all the existing segmentation methods suffer from the presence of motion blur [34], [35]. The simulated blob consists in a bright circle on a black background.…”

Section: Imaging Technique and Investigation Pathmentioning

confidence: 99%

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Uncertainty in vision based modal analysis: probabilistic studies and experimental validation

Lavatelli

Zappa

2016

ACTA IMEKO

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This paper analyses the issues related with the application of photogrammetric methods in the context of modal analysis. In this field of mechanical testing, the vibrations of the measurand are monitored. The possibility to measure displacement of several monitored points without directly instrumenting those, pushes the interest toward the application of an image based measurement system. However, the process of acquiring a moving target with a camera is complex due to the motion blur phenomenon. The effects of this particular phenomenon on uncertainty generation and propagation are discussed in parallel with Monte Carlo simulation and experimental approach. The case study here proposed focuses on the estimation of the main modal parameters (first two resonant frequencies and amplitudes) of a structure with the help of 2D Blob Analysis, with particular focus in comparing the performances of photogrammetry with the ones of classic motion transducers. The results of both the approaches confirm that the choice of using photogrammetry as an input for modal analysis should be made carefully, since the actual behavior of a structure can be distorted. Nonetheless, the results show that particular care should be made in the choice of structural excitation when using vision based techniques.

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Section: Managing the Structural Excitation During Testssupporting

confidence: 68%

Section: Imaging Technique and Investigation Pathmentioning

confidence: 99%

Uncertainty in vision based modal analysis: probabilistic studies and experimental validation

Lavatelli

Zappa

2016

ACTA IMEKO

Self Cite

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“…The effect of shaking frequency is investigated by imposing a sinusoidal acceleration a ( t ) of constant amplitude A 0 = 0.125 g onto the modified DIC rig at different frequencies. Exposure time, t sh , is fixed, while camera velocity amplitude, V 0 , and motion‐blur amplitude, w , vary according to Equation

({, \begin{array}{l} a ((), t) = italicRe ({}, A_{0} \cdot e^{jωt}) \\ V_{0} = \frac{A_{0}}{ω} \\ w \propto V_{0} \cdot t_{sh} \propto \frac{A_{0}}{ω} \cdot t_{sh} \end{array})

…”

Section: Influence On Shape Reconstructionmentioning

confidence: 99%

“…Exposure time, t sh , is fixed, while camera velocity amplitude, V 0 , and motion-blur amplitude, w, vary according to Equation 1. [23,24]…”

Section: Influence Of Shaking Frequencymentioning

confidence: 99%

Impact of motion blur on stereo‐digital image correlation with the focus on a drone‐carried stereo rig

Balcaen

Lavatelli

Jiménez-Peña

et al. 2018

Strain

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Stereo‐digital image correlation (DIC) is a wide‐spread technique in the field of experimental mechanics for measuring shape, motion, and deformation and it is frequently used for material identification by using inverse methods (e.g., virtual fields method and finite element model updating). New applications emerge due to the reached maturity level of the technique, which poses new challenges towards reaching a desired level of accuracy in operating conditions. In this work, the possibility of a drone carrying an in‐house‐made portable DIC setup is explored, and the effect of the drone‐induced vibrations on the accuracy of stereo‐DIC for shape and strain measurement is evaluated. During acquisition, the relative motion between the camera system and the measured item generates motion‐blurred images. The effect of this phenomenon on the precision of stereo‐DIC is further evaluated in this paper.

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“…To sum up, DIC is a valuable measurement technology to solve complex problems in the field of experimental mechanics, but in the context of dynamic measurements uncertainty is still hard to manage. More in details, the sources of uncertainty are related both to static factors [8] and dynamic phenomena [11,12].…”

Section: Introductionmentioning

confidence: 99%

Experimental Modal Analysis on Vibration Data Measured by Digital Image Correlation

Castellini

Chiariotti

Martarelli

et al. 2017

Shock &Amp; Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics &Amp; Optics, Volume 9

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This paper discusses the application of 3D vision-based techniques to recover the Operational Deflection Shapes of a reference specimen consisting in a rectangular section cantilever beam. The research work focuses on the analysis of the accuracy of this measuring approach and discusses the strong points and the limitation of the photogrammetric approaches to experimental modal analysis. Two different types of area-based matching techniques are considered here: the former is based on incremental displacement estimation of subsets of subsequent images. This technique works the approach of Particle Image Velocimetry (PIV), with an Eulerian approach. The second technique considered here is on the contrary based on the estimation of the absolute displacement, considering the first acquired image as the reference for all the subsequent ones. In this last case a Lagrangian approach is used and the applied algorithm is the Digital Image Correlation (DIC). The main advantage of Eulerian (i.e. PIV) approach is that it is possible to analyse also the vibration of a moving object (like in belt dynamic characterization), where the reference region imaged in the first acquired picture, comes out of the field of view much before the end of the test. On the other hand, the Lagrangian approach shows some accuracy problems in the applications where the estimation of the displacement is request instead of velocity. In these cases, the incremental displacement estimated at each new image has to be composed with all the previously estimated ones to obtain the overall motion. Experimental tests were done using a cantilever beam as a case study. The excitation of the beam is done by means of an electromagnetic shaker, while the reference transducer used to validate the output of vision-based techniques is a Scanning Laser Doppler Vibrometry. Results show that the two image-based methodologies have similar performances when estimating natural frequencies, loss factors and ODSs. Keywords Digital image correlation • Particle image velocimetry • Laser doppler vibrometry • Experimental modal analysis • Folded optics IntroductionVibration measurement plays an essential role in the operative monitoring and characterization of mechanical systems. During the last two decades, it has been possible to develop several non-contact methodologies able to measure vibration remotely, thanks to the continuous improvement of the hardware, in terms of calculation power and size. For instance, with reference to the problem of characterizing the dynamics of timing belt, non-contact approaches (mainly Scanning Laser Doppler Vibrometry [1][2][3][4]) have proven their efficacy. This dissertation will focus onto the application of imaging techniques to analyse the modal behaviour of a test specimen.The use of imaging devices as displacement transducers was firstly proposed in almost-static applications, where the effect of target motion during the exposure time can be neglected. Thanks to technology improvements, the applications of vision-based measu...

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Modeling Uncertainty for a Vision System Applied to Vibration Measurements

Cited by 38 publications

References 40 publications

Uncertainty in vision based modal analysis: probabilistic studies and experimental validation

Uncertainty in vision based modal analysis: probabilistic studies and experimental validation

Impact of motion blur on stereo‐digital image correlation with the focus on a drone‐carried stereo rig

Experimental Modal Analysis on Vibration Data Measured by Digital Image Correlation

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