Petri net control using event observers and timing information

The use of an observer in Petri net control may significantly reduce the performance of the closed-loop system because of the incomplete knowledge of the net marking. In this paper we present an algorithm that uses the information on the timing structure associated to the net to improve the marking estimate. This procedure may be invoked not only when the controlled system has entered a blocking condition (as in a previous work) but also whenever a transition has not fired for a time larger than its expected delay. The algorithm requires solving a number of integer linear programming problems and helps us to detect partial deadlocks and to accelerate the convergence of the marking estimation procedure.