Application of timed Petri nets to modeling the schedules of manufacturing cells

Abstract

Timed Petri nets are proposed as models of simple and composite schedules for a large class of manufacturing cells. Net models of simple schedules can easily be derived from the possible sequences of robot actions. Models of composite schedules can be obtained by different compositions of simple schedules. Timed net models can be evaluated using one of typical methods developed for analysis of timed Petri nets, for example, invariant analysis. Performance characterization (the cycle time or the throughput) obtained in this way can be used for maximization of the cell's performance. Because the number of different schedules grows very quickly with the number of machines as well as the length of the (composite) schedule, colored Petri nets are proposed as a uniform representation of entire classes of schedules. Simple examples illustrate the proposed approach.