Observations on the interactions among deadlock avoidance policies and dispatching rules in automated manufacturing systems

In automated manufacturing systems, deadlock avoidance policies guarantee deadlock-free operation while performance controllers, such as dispatching rules, attempt to achieve performance thresholds. In an automated system, dispatching rules must work within the constraints imposed by the deadlock avoidance policy in order to assure continuing system operation, and thus, the deadlock avoidance logic defines the decision space over which the dispatching rule can work. This paper investigates the interactions that arise between deadlock avoidance flexibility and the effectiveness of dispatching rules in achieving good system performance. Two major findings are that the positive effects of intelligent dispatching are highly influenced by the flexibility of the deadlock avoidance policy, and that a nayve dispatching rule can sometimes achieve better system performance under an inflexible deadlock avoidance policy.