High-speed Video Measurement Method of Attitude Angle Applied to Floating Offshore Wind Turbine Model Wind-Wave Tank Test

During the wind-wave tank model test of floating offshore wind turbine (FOWT), acquiring the model attitude angles is one of the key objectives. Due to the environment of the wind-wave tank, there are inevitable shortcomings of traditional contact sensors, such as difficult installation, increased model weight, limited sampling frequency, and incomplete data acquisition. In this paper, a vision-based technology is presented, which mainly consists of (1) construct a high-speed video acquisition network; (2) identify, track and match the circular landmarks on the sequence image, and obtain three-dimensional coordinates of the spatial points using the spatial point reconstruction algorithm; (3) propose a method for computing model attitude angles in sequence images to obtain the pose of the model in each frame; (4) deduce the theoretical accuracy of attitude angle from the obtained accuracy of landmarks, and propose a way to improve the accuracy of landmarks. The model attitude angle acquisition method is verified by experimental measurements of a wind-wave tank model with a 1:50 Spar-type floating wind turbine model, the results show that the point measurement accuracy can reach sub-millimeter level, and the difference between the attitude angle measurement value and the theoretical value is less than 2.34′, which meets the testing requirements. The method proposed can be further extended to the attitude angle measurement in various wind tunnel pool tests.