Research On Measurement Method Of Tip Deflection Of Wind Turbine Blade Static Loading Test Based On Binocular Vision

With the development of China’s wind power industry,more and more attention has been paid to the research of the full-scale structure test of wind turbine blade.The static loading test is a test step in which the turbine blade must pass after a new development or a major technological change.In the static loading test,the deformation date of blade is recorded by applying load to blade,so as to test the bearing capacity of the blade under ultimate load,and the deflection of blade tip is the key parameter in the test.The traditional measurement method is to use draw-wire displacement sensor or laser distance sensor,but both of these methods have the problems of theoretical error,so the measurement accuracy is not high.In order to solve the above problems,a method for measuring the deflection of wind turbine blade tip based on binocular vision is proposed.By setting up a multi-group binocular vision measurement system and using visual measurement and image processing technology to analyze the blade tip image,the tip deflection during static loading can be measured more accurately.The specific research contents of this paper are as follows:Firstly,the principle of camera imaging model and Zhang Z Y camera calibration method is analyzed.Aiming at the optimization of camera calibration parameters,Gauss-Newton method is proposed to replace LM method in MATLAB camera calibration toolbox,the convergence speed of the camera intrinsic parameters optimization algorithm is improved,and the experiment is set up.Secondly,the edge detection effect of the traditional morphological edge detection operator is analyzed and compared.According to the image characteristics of the marker circle used in this paper,an improved anti-noise composite mathematical morphological edge detection operator is constructed and used to extract the edge image of the marker circle in the blade tip.Then,in order to locate the center point of the marker circle,the ellipse detection algorithm based on least square fitting and Hough transform is analyzed.An improved ellipse detection algorithm based on Chord midpoint Hough transform based ellipse detection method is proposed,which can prevent the occurrence of anomalous solutions by setting threshold,and locating of the center point of the marker circle precisely is realized.Finally,a complete wind turbine blade tip deflection measurement system based on binocular vision is constructed,and the measurement scheme by segmentation measurement is designed and field experiment is carried out.The deflection of the blade tip is calculated by triangulation and global calibration which based on unified intermediate coordinate method.The experimental results validate the feasibility of the proposed method for measuring the tip deflection.At the same time,it shows that the accuracy of the method in this paper has a great improvement compared with the traditional methods.