Extraction of Full-Field Structural Dynamics from Digital Video Measurements in Presence of Large Rigid Body Motion

Abstract

Video cameras offer a versatile high resolution alternative to traditional sensor apparatuses for full field structural dynamics analysis. Previous work has extended phase based motion magnification techniques to achieve state of the art results in vibrational and structural analysis. One limitation on the current approach is that it does not work very well in situations where substantial rigid body motion is present in the scene. The large rigid motion drowns out the tiny vibrations that are relevant for a full-field structural analysis. This work extends upon previous phase based motion algorithms in order to allow them to work even in cases with large rigid body motion present. Through a keypoint tracking and video cropping scheme rigid body motion is subtracted from video streams, while preserving the smaller motions of interest. After this preprocessing step, the new video stream can be passed into the full-field analysis scheme as usual, in order to get a full-field modal decomposition.