Structural Modal Identification Through High Speed Camera Video: Motion Magnification

Video cameras offer the unique capability of collecting high density spatial data from a distant scene of interest. They could be employed as remote monitoring or inspection sensors because of their commonplace use, simplicity, and relatively low cost. The difficulty is in interpreting the video data into a usable format, such as displacement, that is familiar to engineers. A methodology called motion magnification, developed for visualizing exaggerated versions of small displacements, is extended to modal identification in structures. Experiments in a laboratory setting on a cantilever beam were performed to verify the method against accelerometer and laser vibrometer measurements. Motion magnification is used for modal analysis of cantilever beams to visualize mode shapes and calculate mode shape curvature as a basis for damage detection. Suggestions for applications of this methodology and challenges in real-world implementations are given.