Joint recognition and tracking for robotic arc welding

An automatic joint guidance system was developed as part of a project to develop an expert welding robot. The apparatus consists of a servo-robot laser scanner mounted on a conventional CLOOS model ROMAT 75/76 industrial welding robot. The computer vision system is able to recognize and track the joint to be welded without external information by using range data obtained from scanning the workpiece. An approach and some experiments related to achieving this ultimate goal are discussed. Three different joint types are identified. Tracking of the joint geometry is done by building, online, a three-dimensional model of the joint during the welding process. This approach is attractive because of its complete autonomy for joint recognition and its ability to trace the geometry while at the same time avoiding an elaborate teaching pass prior to the process. The algorithms used have been tested in a simulation using real laser data. The results indicate that it is possible to recognize automatically the joint type and then to track the joint during the process of welding