In: Proceedings of the 4th International Workshop on Discrete Event Systems, pages 79-84. August 1998.
Abstract: This paper treats feedback control design for discrete event systems, modeled as Petri nets, with avoidance of forbidden states as specification of the control goal. It has been shown before that for calculating maximally permissive feedback controls attention can be limited to the marking of a subnet, the influencing net. We first show that the influencing net can be described algorithmically using min-plus algebra. Next we introduce a general approach for calculating state feedback controls by decomposing the set of places and the set of transitions in the uncontrolled net in a number of layers. These layers are used to construct a min-plus polynomial which has to be maximized to obtain the maximal value of the expressions specifying the control goal. An example shows that in many interesting cases it is possible to eliminate most of the variables, allowing efficient control design for general Petri net models.
Keywords: Petri net, supervisory control, min-plus algebra, influencing net.