Deadlock avoidance for manufacturing systems with partially ordered process plans

Deadlock avoidance policies guarantee deadlock-free resource allocation to concurrent competing processes in flexible manufacturing systems. Most deadlock avoidance work in manufacturing deals with systems where each part requires a fired sequence of operations. In contrast, this paper deals with those systems that support sequencing flexibility, that is, the operations required by the part are partially ordered. In this setting, the order in which operations are performed is not predetermined, but becomes a real-time decision. Specifically, the paper characterizes the deadlock detection and avoidance problems for these systems, presents a sub-optimal deadlock avoidance approach, and addresses two relevant special structures on the partial orders for which optimal deadlock avoidance is of polynomial complexity.