Model Properties for Efficient Synthesis of Nonblocking Modular Supervisors

TL;DR

This paper introduces a new method for synthesizing nonblocking modular supervisors efficiently by analyzing control problem dependency graphs to avoid computationally expensive synthesis steps.

Contribution

It proposes a format for control requirements and a graph-based method to ensure controllability and nonblockingness, reducing synthesis complexity.

Findings

Method effectively localizes blocking issues in cyclic graphs.

Application to case studies demonstrates improved scalability.

Reduces computational effort in supervisor synthesis.

Abstract

Supervisory control theory provides means to synthesize supervisors for systems with discrete-event behavior from models of the uncontrolled plant and of the control requirements. The applicability of supervisory control theory often fails due to a lack of scalability of the algorithms. The paper proposes a format for the requirements and a method to ensure that the crucial properties of controllability and nonblockingness directly hold, thus avoiding the most computationally expensive parts of synthesis. The method consists of creating a control problem dependency graph and verifying whether it is acyclic. Vertices of the graph are modular plant components, and edges are derived from the requirements. In case of a cyclic graph, potential blocking issues can be localized, so that the original control problem can be reduced to only synthesizing supervisors for smaller partial control problems. The strength of the method is illustrated on two case studies: a production line and a roadway tunnel.