BDD-Based Synthesis of Fail-Safe Supervisory Controllers for Safety-Critical Discrete Event Systems

Sophisticated hardware/software and harsh environment in safety-critical discrete event systems may cause system failures that can lead to catastrophic consequences. Therefore, keeping the system in a safe mode even after the occurrence of a fault is critically important. This paper addresses the problem by first extending net condition/event systems with uncontrollable transitions that allows one to well represent controllable and uncontrollable events and cater for modeling normal and abnormal events in safety-critical systems. A binary decision diagram-based symbolic supervisor synthesis method is proposed to ensure time and space efficiency when dealing with a practical supervisory control problem. As a case study, a high-speed railway station is used to illustrate the proposed concepts and method.