347 / 2021-07-07 19:37:12

A Node-Antinode Searching Method for Spatial Filtering in Camera based Vibration Modal Analysis

full-field vibration measurement,camera-based modal analysis,optimization-based spatial filtering,nodes and antinodes

Video camera-based vibration measurement is increasingly used for modal analysis, because of its superior merits in noncontact and full-field measurement. Recently, spatial filtering-based methods have been found to be effective in improving signal to noise ratio (SNR) of vibration signal to a higher level. In comparison with conventional methods, the spatial filtering method needs mode shapes to be the weight vectors of filter during computation, even though it is unknown at beginning. For this reason, a fast and reliable solution of optimization problem defined by spatial filtering method is proposed in this study. The weight vector is firstly constructed by a piecewise function with parameters of node/antinode locations. Then, the spatial filtering is applied to video footages from a high-speed camera to calculate the output signal of modal displacement. Finally, the undetermined parameters are optimized one by one through maximizing the power of output signal. The simulation study shows the proposed method allows the weight vector to converge to modal shapes with fast iterations, confirming the optimization problem defined in spatial filtering method is solvable with high accuracy.