Coloured Petri net scheduling models: Timed state space exploration shortages

The paper deals with the problem of timed state space generation and exploration in the frame of simulation–optimization approach for discrete-event systems. Coloured Petri net representation of a system is considered and corresponding techniques of timed state space generation and timed simulation are addressed. It is shown that the established simulation techniques do not perform adequately in some application relevant examples since in general, only a subset of a timed state space of a simulated system is represented. Two examples are provided to illustrate the effect of timed state space reduction. While the optimal solution is preserved within the reduced state space in one example, in the second example this is not the case and the optimum is missed. This indicates that the timed simulation technique has to be carefully designed in order to be suitable for the simulation–optimization approach.