A New DES Control Synthesis Approach Based on Structural Model Properties

This work proposes a novel approach for controller synthesis on the shop-floor level for discrete-event systems. The approach is based on a modular modeling formalism and structural properties of models of uncontrolled plant behavior that are designed using this modeling formalism. The approach takes advantage of the transition invariants of the underlying Petri net components of the model and uses the event interconnections of transitions that are part of the transition invariants. The result is the so-called transition invariant graph that represents a new structural property of the modeled system. The synthesis procedure takes models of the uncontrolled plant behavior and formal specifications of the desired cyclic plant behavior under control and forbidden states as well. From these ingredients, the transition invariant graph is computed from which the admissible trajectories are extracted. This is performed by partial reachability analysis. An example taken from a lab-scaled manufacturing system illustrates the methodology and shows the application. The complexity of the synthesis procedure is significantly reduced. That makes it feasible to be used for even larger systems of real industrial scale.