UAV video based vibration frequency detection for bridge stay cables

The phase based signal extraction method has been successfully used in the vibration measurement for bridge stay cables. However, this method is only applicable to videos that captured by stable cameras but UAV cameras. In order to solve this problem caused by UAV shaking, a new method for vibration measurement of the stay cable by using a motion analysis framework with spatial phase is proposed in this paper. According to the periodicity of target vibration signal and the disturbance characteristics of UAV shaking, the pure vibration signal is reconstructed from the phase difference sequence. Firstly, the spatial phase of each frame of the image is calculated using the complex controllable pyramid. Secondly, the vibration signal is extracted by using the phase filtering, which is carried out according to the spatial distribution characteristics of the stay cable vibration signal. Finally, the vibration interference of UAV shaking is removed by the interference adaptive singular spectrum analysis, and the pure vibration signal of stay cable was reconstructed to complete the frequency detection. In the field test, the proposed method shows a strong agreement with the measured results of the accelerometer, which verifies the accuracy and robustness of the proposed method.