Comparing deadlock detection and avoidance policies in automated storage and retrieval systems

This paper focuses on real time control of automated storage and retrieval systems (AS/RS) that is in charge of making decisions on resource allocation and scheduling choices. In these systems deadlock conditions may occur when parts require a set of resources in a circular wait situation. We model a generic multi-product AS/RS serviced by rail guided vehicles as a discrete event system. Next, we compare two different real time deadlock solution strategies for AS/RS: a deadlock avoidance strategy previously proposed by one of the authors and a deadlock detection/recovery strategy, proposed in the related literature. The considered control strategies are compared by means of a simulation of a case study.