In the automatic pipeline welding systems, the welding properties are varied regarding to the robot angle variations around the pipe. In this paper, a modified dynamic model—presented for the free-flight mode [1]—is extended to include the short-circuit mode. Consequently, a complete dynamic model is introduced including some modifications in characteristics equations. Some events and phenomena, like frequency jumping and combined transfer mode—caused by angle variations—are illustrated using time-frequency representation through the simulation and experimental examples.
