基于边缘导向算子模板匹配的熔池轮廓提取方法

轮廓提取作为熔池的基本视觉形态特征，在焊接质量在线监测中起着重要作用. 文中建立了非熔化极惰性气体保护电弧焊(tungsten Inert gas welding, TIG)焊接工艺环境下的熔池视觉传感系统，采集了高质量的熔池图像. 针对TIG焊不锈钢熔池图像中弱边缘检测的难点提出了一种基于边缘导向算子模板匹配的熔池轮廓提取算法(operator template matching based on edge direction guidance, OTM-EDG)，算法中首先基于非线性灰度变换方法增强弱边缘. 之后利用4个方向的Sobel算子与熔池图像进行卷积操作来判断后端弱边缘的方向并计算梯度图. 最后对梯度图进行边缘连接操作以及基于数学形态学的边缘平滑操作，得到需要提取的熔池轮廓. 结果表明，文中算法能够提取到封闭完整且定位准确的TIG焊不锈钢熔池轮廓. 在实际焊接环境中具有较高的鲁棒性，有效解决了熔池区域弱边缘难以准确检测的问题.

Molten pool contour extraction method based on edge oriented operator template matching

As the basic visual morphological feature of molten pool, contour extraction plays an important role in on-line monitoring of welding quality. A molten pool visual sensing system under the environment of tungsten inert gas welding (TIG) welding process is established, and high-quality molten pool images are collected. Aiming at the difficulty of weak edge detection in TIG welding stainless steel molten pool image, a molten pool contour extraction algorithm based on operator template matching based on edge direction guidance (OTM-EDG) is proposed. Firstly, the algorithm enhances the weak edge based on the nonlinear gray transformation method. Then, the Sobel operator in four directions is used to convolute with the molten pool image to judge the direction of the back-end weak edge and calculate the gradient map. Finally, the edge connection operation and edge smoothing operation based on mathematical morphology are carried out on the gradient map to obtain the molten pool contour to be extracted. Experiments show that the algorithm can extract the closed, complete and accurate molten pool contour of TIG welding stainless steel. It has high robustness in the actual welding environment, and effectively solves the problem that the weak edge of the molten pool area is difficult to accurately detect.