Petri Net Supervisors for DES in the Presence of Uncontrollable and Unobservable Transitions

This paper describes a computationally eecient method for synthesizing feedback controllers for plants modeled by Petri nets which may contain uncontrollable transitions. The controller, a Petri net itself, computed using the concept of Petri net place invariants, enforces a set of linear constraints on the plant. It is shown how the original set of plant behavioral constraints can be transformed into a new set that will yield a controller which enforces the original constraints without directly innuencing any of the uncontrollable transitions. Previous researchers have shown that this constraint transformation can be performed by solving a linear integer programming problem; the method presented in this paper is simpler computationally, but, depending on the structure of the uncontrollable part of the plant, maximal permissiveness may not be guaranteed.