Binocular photogrammetric vibration measurement method introducing character recognition and tracking
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Abstract:
Coded targets are widely used in photogrammetry for large-scale structures. A coded target based on a circled character is designed and applied in vibration measurement through binocular vision system,in which English or Chinese characters are used for coding information and the circle is used for positioning. Weiner filter method is employed to de-noise image. Further, character feature is segmented using adaptive local threshold method.Character information is identified through BP neural network. Target position is calculated with gray value gravity center method. The vibration responses of the coded targets position are measured by the binocular vision system. A 3 kW wind turbine blade was tested with the presented method. The first three natural frequencies were identified and the relative errors were less than 0.9% compared with those from hammer impact experiment.The results show that the method is reliable and feasible.
