Timed Petri nets in modeling and analysis of simple schedules for manufacturing cells

It is shown that a large class of flexible manufacturing cells can be modeled using timed Petri nets. Net models of simple schedules (i.e. schedules in which exactly one part enters and one leaves the cell during each cycle) are conflict-free nets. Two complementary approaches to analysis of such models are presented: invariant analysis and throughput analysis. Invariant analysis provides analytic (or symbolic) solutions for the cycle time of a cell analyzing (invariant) subnets of the original net. Throughput analysis performs a series of performance-preserving net reductions to simplify the original model. Several directions for further research are indicated.