Penetration control of GTAW process for aluminum alloy using vision sensing

Unpredictable and inevitable perturbations during welding have adverse effects on the uniformity of weld penetration degree. Hence feedback control of weld penetration is necessary for assuring the welding quality. The backside weld bead width, regarded as a representation of penetration state, is measured usually by a structured-light sensor during the welding process. However, the structured-light method can only measure the width of the solidified weld behind the weld pool, but not the weld pool width, owing to the specular weld pool surface, thermal radiation and the possible arc light. It will introduce a time delay into the penetration control system. A novel low-cost visual technique of acquiring the backside weld pool width is developed in this paper, and the closed-loop control of weld penetration is achieved during gas tungsten arc welding (GTAW) for aluminum alloy. The parallel light is projected onto the weld pool backside, and the outline of the weld pool is highlighted because of the different reflection from the plate's flat surface and the weld pool's convex surface. Changes in the plate geometry are introduced during the experiments to perturb the welding process. Results show that stable penetration is maintained despite the perturbation.