Intelligent cooperative control system in visual welding robot

Abstract

The quality of multi-layer welding depends on the welding in the first layer. In order to get high-quality welding, it is necessary to make a stable back-bead and to melt the base metals. In narrow-gap welding, it is difficult to control the bead height (deposited metal) and the back-bead (the melted area of the back side) simultaneously by using conventional welding. To improve this situation, the authors propose a cooperative control of the welding equipment, including the welding power source, the electrode wire feeder and the welding robot, i.e. the welding torch is not only oscillating on the groove but also moving back and forth. To control the heat input, the power source is controlled according to the torch motion (robot motion) too. In the forward process, the arc (the heat) is given to the root edges to get a wide back-bead. In backward process, a suitable bead height is obtained. The idea of this robot motion comes from the knowledge of skilled welding workers. The arc length must be kept short during the welding regardless of unexpected disturbances. Therefore, the weld pool and the arc position are observed by using a CCD camera. A personal computer processes image and adjusts the welding current and the torch motion. Welding experiments are carried out to verify the validity of the cooperative control method.