Synthesis of an Event Based Supervisor for Deadlock Avoidance in Semiconductor Manufacturing Systems

摘要

With the emerging of highly automated and flexible manufacturing systems in semiconductor fabrication, reliability and productivity of such systems require intelligent and complex control systems. Deadlock issue arises easily in these systems due to shared equipment usage and high production flexibility. This paper presents an event-based deadlock avoidance supervisor that is able to efficiently and smartly avoid the deadlock state space explosion problem. The method is built upon a directed graph model of process flows. Concepts such as compound events, generalized strings, operating strings and deadlock strings are introduced in the paper. Major features in the proposed method include: i) it enables optimal deadlock free operation of regular systems; and ii) it runs in polynomial time (fast online computation) provided that the set of deadlock strings is calculated offline. Examples are provided to show the effectiveness of the method.