Experimental Modal Analysis Using Phase Quantities from Phase-Based Motion Processing and Motion Magnification
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S.I. : COMPUTER VISION AND SCANNING LASER VIBROMETRY METHODS
Experimental Modal Analysis Using Phase Quantities from Phase-Based Motion Processing and Motion Magnification D.P. Rohe1
· P.L. Reu1
Received: 7 April 2020 / Accepted: 4 August 2020 © Sandia National Laboratories 2020
Abstract Phase-based motion processing and the associated Motion Magnification that it enables has become popular not only for the striking videos that it can produce of traditionally stiff structures visualized with very large deflections, but also for its ability to pull information out of the noise floor of images so that they can be processed with more traditional optical techniques such as digital image correlation or feature tracking. While the majority of papers in the literature have utilized the Phasebased Image Processing approach as a pre-processor for more quantitative analyses, the technique itself can be used directly to extract modal parameters from an image, noting that the extracted phases are proportional to displacements in the image. Once phases are extracted, they can be fit using traditional experimental modal analysis techniques. This produces a mode “shape” where the degrees of freedom are phases instead of physical motions. These phases can be scaled to produce onimage visualizations of the mode shapes, rather than operational shapes produced by bandpass filtering. Modal filtering techniques can also be used to visualize motions from an environment on an image using the modal phases as a basis for the expansion. Keywords Phase-based processing · Experimental modal analysis · Optical · Motion magnification · Modal filtering
Introduction Phase-based motion processing [1] has become a popular technique for analyzing optical data from structural dynamic tests due to its ability to magnify small, imperceptible displacements in the images. These magnified displacement images can give the viewer a more intuitive look at
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology, Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DENA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. D.P. Rohe
[email protected] 1
Sandia National Laboratories, P.O. Box 5800 - MS0557, Albuquerque, NM 87123, USA
what is going on in a test. Several researchers have utilized phase-based motion processing as a way to extract quantitative information on the dynamics of the part. Chen et al. used the phase-based processing and motion magnification approach to amplify motions in a series of images and then used edge detection to extract pixel displacements, which are multiplied by a calibration factor to produce physical displacements [2]. Other authors have utilized th
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