Deadlock-free Rescheduling in Flexible Manufacturing Systems

The dynamic nature of manufacturing makes rescheduling essential in todayʹs complex production environment, particularly in flexible and re-configurable systems. Research on optimizing schedules, that includes deadlock avoidance, is rather limited. Furthermore, the deadlock problem is mostly ignored in research on rescheduling. A rescheduling algorithm, that uses time Petri-Nets and the minimal siphons concept, was developed to deal with sources of disturbance such as machine breakdowns in real-time. It guarantees a deadlock-free new schedule. The existence of alternative routes, availability of material handling facilities, and the limitation of buffer capacities were taken into consideration. The developed algorithm modifies only the affected portion of the original schedule, rather than rescheduling all jobs, in order to limit changes to the original schedule and reduce the impact on the response time.