Multi-robot spot-welding cells for car-body assembly: Design and motion planning

Multi-robot cells for spot welding use coordinated robots to assemble metal panels via spot welding by coordinated robots, for instance in the construction of car doors. The design of multi-robot cells for spot welding required both cell design and off-line motion planning. Cell design involves resource selection (such as robots and welding guns) and resource configuration, while considering cell productivity, costs, flexibility and reconfigurability. Motion planning involves allocating welding points to each resource and calculating collision-free motion plan for each robot. Currently, cell design and motion planning are sequential and manual activities, managed by different and separate industrial functional units. This results in several cycles before the design converges to a feasible final solution. The proposed approach introduces a unified methodology, aiming at optimizing the holistic cell design and motion planning, that reduces design time and errors. The feasibility of the proposed approach has been demonstrated in several ad-hoc basic replicable cases and in one industrial case. The outcome of this research improves state of the art, reducing design and motion planning time over current technology. Moreover, the method has been integrated into a computerized approach which has the potential to accelerate the whole cell design and motion planning processes and to reduce human efforts.