Avoidance of deadlocks in flexible manufacturing systems using a capacity-designated directed graph

Deadlocks in flexible manufacturing systems (FMSs) refer to the stop state of job flow that may often occur while operating the systems. This state should be avoided to provide the efficient way of job flow and to achieve full utilization of high-capital resources. In this paper, we developed a capacity-designated directed graph (CDG) representing machine resources and job routeings in FMSs. Using the CDG, a deadlock-avoidance method is proposed to prevent the system from satisfying the necessary condition for deadlocks. This deadlock-avoidance method is implemented into static and dynamic strategies. A simulation study demonstrates the applicability of the two strategies to an FMS.