Robot tasks sequence planning using Petri nets

The automatic programming of robots to assemble products must cope with assembly planning and task planning problems. These problems are not independent, since an assembly operation may be performed by a different robot task depending on the previous assembly operations performed. Therefore, the cost of assembly operations vary depending on the assembly sequence. This paper deals with the problem of finding the optimum sequence of robot tasks taking into account this variable cost of assembly operations. The proposed approach can cope with products with AND/OR/XOR relations and uses Petri nets as a modelling methodology. The search of a near-optimum sequence of robot tasks is done with an heuristic search of the reachability tree of the Petri net.