基于改进NCC算法的大尺寸原位风机叶片可见光图像拼接

Visible image stitching of large in-situ wind turbine blade based on improved NCC

风机叶片的原位检修与维护对保证风电机组的安全运行起着至关重要的作用,目前主流的无人机巡检方式需要对风机叶片图像进行全景拼接以进一步定位分析叶片的微小缺陷和评估叶片的整体状态。针对风机叶片结构单一纹理稀疏难以拼接的问题,提出一种改进归一化互相关NCC算法的图像拼接技术,利用Canny边缘检测算法提取叶片边缘并进行筛选去重得到边界坐标,将NCC算法沿叶片边界坐标搜索匹配以简化搜索路径加快运算速度,同时增加关键信息的权重提高拼接准确率,并结合图像金字塔粗-精匹配思想对算法进行进一步加速,最终根据得到的最佳匹配位置获取空间对应关系实现图像拼接。实验结果表明,所提方法的匹配耗时约为原始NCC算法的6%,其他经典灰度匹配算法的3%~10%,同时也低于其他改进的NCC算法。其拼接成功率为94.74%,高于所有对比方法,最终成功获取了风机叶片可见光全景图像,表明该方法对大尺寸风机叶片可见光图像全景拼接具有良好的稳定性。

In-situ inspection and maintenance of wind turbine blades play a crucial role in ensuring the safe operation of wind turbines.Currently,the mainstream UAV inspection method requires panoramic stitching of wind turbine blade images to further locate and analyze minor blade defects and assess the overall blade condition.An improved image stitching technology based on NCC algorithm is proposed to solve the problem of difficult stitching caused by single structure and sparse texture of wind turbine blades.Canny edge detection algorithm is used to extract the blade edge and filter the duplication to get the boundary coordinates,NCC algorithm traverses the blade boundary coordinates for searching and matching to optimize the search strategy and speed up computation while increasing the weight of key information to improve the stitching accuracy,and combining image pyramid coarse-fine matching thoughts to further speed up the algorithm.Finally,the spatial corresponding relation is obtained according to the optimal matching position to achieve stitching.The experimental results show that the matching time of the proposed method is about 6%of the original NCC algorithm and 3%~10%of other classical gray matching algorithms,and lower than other improved NCC algorithms.The stitching success rate is 94.74%,which is higher than all comparison methods,and finally,the visible panoramic image of the wind turbine blade is obtained successfully,demonstrating its good stability in panoramic stitching of large-size wind turbine blades visible images.