Monitoring mechanical properties of structures such as bridges, buildings, or wind turbines, is important to detect early stage failures. Operational modal analysis is a testing method to estimate these properties from vibration measurements. Taking advantage of works on motion estimation, several video modal analysis methods have emerged in the last decade. This paper compares two strategies about subpixel phase-based motion estimations thanks to multi-scale decomposition. Synthetic videos of a vibrating cantilever beam are generated to assess the robustness of these methods against motion amplitude, gray scale quantization, white noise, and blurring.
Vibration study, also called modal analysis, plays an important role in the structural health monitoring of mechanical structures. During the last decade, video-based modal analysis methods have emerged to provide dense vibration estimation using each pixel as a contactless sensor. Dense subpixel motion is estimated and is then processed by a modal analysis algorithm to extract the modal basis composed of natural frequencies, damping ratios, and mode shapes. This paper introduces a new single-subband phase-based method for subpixel motion estimation. It is compared with state-of-the-art motion estimation method on synthetic and experimental videos of a cantilever beam.
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