Timed Petri net models of flexible manufacturing cells

It is shown that a class of flexible manufacturing cells can be conveniently modeled and evaluated by timed Petri nets. For simple schedules, the modeling nets are covered by conflict-free invariant subnets, so the performance of the model is determined by the performance of its subnets. For composite schedules, the invariant subnets are free-choice, so a more elaborate approach to evaluating the performance of the model must be used