A motion magnification application in video-based vibration measurement
In the field of non-destructive testing (NDT) and Structural Health Monitoring (SHM), physical properties of objects’ are studied and their states evaluated through the measurement of vibration response and subsequent analysis with a use of physical models. The usual way of obtaining a vibration data are contact sensors placed on the structure. However, an application of these methods may be difficult and take a lot of time. Measurements are limited to a finite, usually small, set of points. The main advantage of cameras in vibration measurement is a possibility of having a dense grid of measurement points. However, a practical use of these methods is difficult, mainly because of the limited spatial resolution and image noise. An application of motion estimation using phased-based optical flow makes it possible to have a vision-based measurement of small amplitude vibrations. It may be used to magnify or attenuate motion amplitude in a given frequency band which may find an application in Structural Health Monitoring systems.
In the paper, an experimental investigation of phase-based motion magnification for non-contact vibration measurement is presented. Estimation of vibration frequencies of a free-free beam structure based on high-speed camera video signal has been carried out. Next, an application of motion magnification algorithm for restoration of band-limited video signal by increasing spatial magnitude of motion is shown. Finally, a preliminary test of single frequency component extraction based on video sequence of a structure excited by a white noise signal which may find an application in direct visualization of mode shapes has been presented.
KeywordsMotion Magnification Non-contact Measurements Vibration Measurements Image and Video Processing
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This research was financed within the scope of the project LIDER/0103/L-9/2017 supported by the National Centre for Research and Development.
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