A novel centerline extraction algorithm for a laser stripe applied for turbine blade inspection
A novel centerline extraction algorithm for a laser stripe applied for turbine blade inspection
复制标题
一种新颖的用于涡轮叶片检测的激光条纹中心线提取算法
DOI：
10.1088/1361-6501/ab8971
复制
发表时间：
2020
影响因子：
2.4
通讯作者：
Yu Wen-yong
中科院分区：
文献类型：
--
作者：
Jiang Cheng;Li Wen-long;Wu An;Yu Wen-yong
线激光三维扫描技术是一种新型的涡轮机叶片自动检测技术。线激光三维扫描中的一个关键问题是激光条纹中心线的提取。在某些区域，存在由高曲率引起的线轮廓的不对称性，例如叶片的前缘和后缘。针对非对称高斯分布的激光条纹轮廓，提出了一种基于亚像素边界提取和中轴变换的激光条纹中心线提取算法。利用过零法提取激光条纹的候选边界点。基于泰勒展开和插值，可以准确估计边界的灰度梯度分布。然后，利用灰度梯度极值提取精确边界点，并对精确边界点进行中轴变换计算中心线。该方法可以有效地减少高曲率区域中由于线条轮廓不对称而引起的误差。仿真和测量实验验证了该方法的有效性。实验结果表明，非对称高斯线轮廓的提取误差在± 0.15像素以内，测量精度实验的均方根误差不超过0.015 mm。
Line-laser 3D scanning is a novel and promising automation technique for turbine blade inspection. One key task encountered in line-laser 3D scanning is centerline extraction of the laser stripes. In some regions, there is asymmetry of the line profiles caused by high curvature, such as the leading and trailing edges of a blade. According to the asymmetric Gaussian distribution line profile, this paper presents a new algorithm to extract the centerline of a laser stripe based on sub-pixel boundary extraction and medial axis transformation. The candidate boundary points of the laser stripe are extracted by zero crossing. Based on Taylor expansion and interpolation, the gray gradient distribution of the boundary can be estimated accurately. Following this, the accurate boundary points are extracted by extreme values of the gray gradient, and the centerline is calculated by medial axis transformation of the accurate boundary points. The proposed method can effectively reduce errors caused by the asymmetry of line profiles in areas of high curvature. The effectiveness of this method is verified using simulation and measuring experiments. The experiment results show that the extraction error of the asymmetric Gaussian line profile is within ± 0.15 pixels, and the root mean square error in measurement accuracy experiments does not exceed 0.015 mm.