The performance of alternative strategies for dealing with deadlocks in FMS

Deadlocks in flexible manufacturing systems (FMS) are caused by resources limitation and the diversity of routings. In the literature, we find different strategies for coping with deadlocks. However, the performance comparison between these strategies is not extensively studied. In this paper, we evaluate, using simulation techniques, the performances of two different strategies: the first is a detection/recovery method based on digraph representation and for which the phase detection is cheap; the second is a prevention method based on Petri nets structure theory results and for which the restriction on the resource usage is limited to local sections. Our simulation study confirms the idea that the class of detection/recovery methods are more efficient than prevention or avoidance methods only if the time corresponding to their recovery phase is negligible relative to processing time. Since this condition is implausible in an FMS environment, the deadlock detection/recovery strategies seem to be not appropriate in this context.