Multiseam tracking with a portable robotic welding system in unstructured environments

Most welding manufacturing in heavy industries, such as shipbuilding and construction, is conducted in unstructured workspaces, indicating that the production environment is irregular, changeable, and unmodeled. In this case, changeable workpiece position/shape and environmental background/illumination should be carefully considered. Owing to these complicated characteristics, welding currently relies on manual operation, resulting in high cost, low efficiency, and inconsistent quality. This study proposes a portable robotic welding system and a novel seam-tracking method. Compared with existing methods, it can track more general and complex spatial weld seams. First, the tracking pose of the robot was modeled using a proposed dual-sequence tracking strategy. On this basis, the working parameters can be adjusted to avoid robot-workpiece collision around the workpiece corners during tracking processes. By associating the forward direction of a welding torch with the viewpoint direction of a camera, the problem that the weld seam feature points are prone to lost during tracking processes can be solved by conventional methods. Point cloud registration is adopted to locate the multi-segment weld seams in the workpiece globally because the system deployment location is not fixed. Various experiments on single or multiple weld seams under different environmental conditions show that even if the robot was deployed in different positions, it could reach the initial points of the seams smoothly and accurately track along them.