Supervision of multiple industrial robots: optimal and collision free work cycles

A method for automatic generation of collision free, blocking free and work cycle time optimized supervisors for industrial robot cells has been implemented. The individual robots´ tasks are specified as a set of targets that the robot should visit in arbitrary order. Finite automaton models of allocation and release of critical spatial volumes that the robots share, as well as models of the robots´ possible movements are automatically extracted from a 3D simulation environment. This includes explicitly calculating the intersection between the robots´ work envelopes, the spatial volumes where collisions may occur, and simulating the robots´ collisions with these. Each robot´s different sequences of operations of factorial complexity in the number of states are efficiently represented as a set of automata using a polynomial number of states. The automatically generated system model is analyzed using the Ramadge-Wonham supervisory control theory to verify nonlocking and to synthesize supervisors. The method guarantees collision freeness, nonblocking and a flexible coordination function. The model is also used to find the time optimal work cycle for completion of the robots´ tasks. To meet market demands of mass customization and shorter time to market, more flexible manufacturing systems are needed. The method presented here aims to automatize robot coordination programming which, being a tedious manual task in today´s industry, is a bottleneck in the development of old and new production lines.