Symbolic State-Space Exploration and Guard Generation in Supervisory Control Theory

Supervisory Control Theory (SCT) is a model-based framework for automatically synthesizing a supervisor that minimally restricts the behavior of a plant such that given specifications is fulfilled. The main obstacle which prevents SCT from having a major industrial breakthrough is that the supervisory synthesis, consisting of a series of reachability tasks, suffers from the state-space explosion problem. To alleviate this problem, a well-known strategy is to represent and explore the state-space symbolically by using Binary Decision Diagrams. Based on this principle, an alternative symbolic state-space traversal approach, depending on the disjunctive partitioning technique, is presented in this paper. In addition, the approach is adapted to the prior work, the guard generation procedure, to extract compact propositional formulae from a symbolically represented supervisor. These propositional formulae, referred to as guards, are then attached to the original model, resulting in a modular and comprehensible representation of the supervisor.