Order release and deadlock avoidance interactions in counter-flow system optimization

Supervisory controllers for automated manufacturing systems must assure goo d system performance and guarantee deadlock-free operation. Order release m echanisms are performance control policies that order and schedule the rele ase of work into the system, while deadlock avoidance policies are control policies that inhibit enabled events that might lead to deadlock. Because n either policy explicitly considers the objectives of the other, their decis ions often conflict. To guarantee continuing system operation, these confli cts must be resolved in favour of the deadlock avoidance policy, and as a r esult, the intended beneficial effects of the order release mechanism can b e significantly undermined. The goals of this paper are: (i) to demonstrate how deadlock avoidance and order release can be integrated to form a contr ol policy that ensures continued system operation and improved performance with regard to performance measures; and (ii) to experimentally investigate the important interactions that can arise between these two types of contr ol.