Forbidden State Avoidance Controller Synthesis for a Class of DES

This paper describes a synthesis method of forbidden state controller for a class of discrete-event systems (DES) with generalized mutual exclusion constraints (GMEC). The system models are a class of restricted Petri nets named forward-synchronization and backward-conflict free (FSBCF) nets. The properties of FSBCF nets, in which each place has at most one output transition and each transition has at most one input place, is studied and used to analyze the reachable state space of the system. An efficient controller synthesis algorithm that is able to deal with the so-called precedence path condition is then proposed to avoid the forbidden state represented by GMEC. One example is provided for illustration.