On maximal permissiveness of hierarchical and modular supervisory control approaches for discrete event systems

Recently, several efficient modular and hierarchical approaches for the control of discrete event systems (DES) have been proposed. Although these methods are very suitable for dealing with the state space explosion problem, their common limitation is that either maximal permissiveness is not addressed or unnecessarily restrictive conditions are required in order to ensure maximally permissive control. In this paper we develop a unified framework for the investigation of maximal permissiveness of modular control in multi-level hierarchies.We identify a set of conditions that is met by several approaches, and prove its sufficiency for maximally permissive control.