Process supervision by means of a hybrid model

The paper concerns process supervision tasks in which a continuous-variable system has to be moved into a globally de®ned ®nal state. A hybrid model is proposed that describes the discrete-event behaviour as well as the quantitative behaviour of the con- tinuous-variable system. The model consists of a Petri net and of di€erential equations whose validity depends on the marking of the net. The supervisory control task is solved by searching for a path within the Petri net from the current towards the ®nal state and by using the relevant quantitative models to determine the speed of the state transitions. The results are illustrated by means of a laboratory tank system.