The robotic welding has been adapted positively in many welding shops for the purpose of improving the welding efficiency and liberating operators from the severe working atmosphere.
But for a large-size structure with thick plates like ship-building and every kind of plants manufacturing, the application of the arc welding robots is not established yet. The reason is assumed that the conventional arc welding robots are not adaptive for multi-pass welding of thick plates whoose grooves are not so accurate. As one solution to this problem, the author developed a guidance system which uses the welding arc itself as a sensor.
In this thesis the velocity controller which changes the tip to workpiece distance for regulating the weld current was applied to guarantee the quality of a weld joint. To do this, a model using the relationship between welding current and tip to workpiece distance was proposed. The propotional and integral gains of velocity controller were determined by using the computer simulation of the control system, and the simulation results were compared with the experimental ones.
It was revealed that the control system which using the proposed arc sensor principle has a good capability for tracking the weld joint though some more studies for refining the model was needed.
