Solving the Problem of Forbidden States by Feedback Control Logical Synthesis

Uncontrollable transitions in discrete event systems is the cause of forbidden states in supervisory control. This paper concerns the problem of forbidden states in safe Petri net (PN). It is possible to use conditions or predicates to prevent the forbidden states. Generally, there are many forbidden states, thus many complex conditions are associated with the transitions. In this paper, a systematic method is presented to calculate simpler conditions for the controllable transitions. This method is applicable for safe Petri nets. Using this method, we can construct a maximally permissive controller. The implementation of this approach is considered using the Grafcet model