Sensing and digital control of weld pool with visual welding robot

Quality of a multi-layer welding depends on a welding in first layer. In order to get a high quality of the welding, it is necessary to make a stable back bead and to melt the base metals. In narrow gap of which groove angle is over 16°, an arc discharges from top of an extension wire to surface of the groove and cannot creep up the electrode wire. If the arc length becomes long, heat is given to upper side of the base metal. It is difficult to get the wide back bead. Weaving width is shorter than gap to avoid the creeping of the arc. In order to get a good back bead and suitable bead height, the authors try to carry out cooperative control of the welding power source, a wire feeder unit and a robot manipulator. Weld pool is observed by using a CCD camera. A personal computer processes image of the weld pool. By using the result of the image processing, a simulation model of the welding system is prepared to make a digital controller. Welding speed and wire feed rate are controlled to get the desired bead height and arc position