A new welding robot system with visual sensors is developed in order to realize a full automatic welding of thin mild steel plates, such as automatic seam tracking and automatic control of welding conditions. Especially, in this study, a system to detect the dimension of molten pool using CCD camera and a penetration control system in gas tungsten arc welding (GTAW) of mild steel plates are investigated. In order to increase the robustness of the sensing system, some new methods, such as self-arc-lighting method, application of pulse current and etc., are proposed and the effectiveness of these methods is shown. As the results of the automatic welding experiments applied the control system with visual sensor, it is confirmed that the system constructed is effective for penetration control in automatic butt welding of thin mild steel plates.
Recently, mechanization androbotization of welding has been investigated widely, and many types of intelligent welding robots which have some sensors, such as arc-sensor 1) and vision sensor2–8), are developed Especially, the adaptive control of welding conditions, in which the welding arc phenomena and the molten pool condition are observed during welding and furthermore the welding conditions are controlled in real-time, are remarked. For instance, a method to control the penetration of weld, in which the shape and dimensions of the molten pool are visually detected and welding conditions are controlled so as to keep them optimum, is remarked and investigated by some researchers8). On the other hand, in automatic butt welding of relatively thin plates, it is important to control welding conditions to obtain a soundfull penetration weld. Especially, it is difficult to obtain a full penetration weld, because the optimum welding condition changes with change of various welding situations, such as gap of groove, shape of groove welding speed.
