Directive Mode for the Semi-Heterarchical Control Architecture of a Flexible Manufacturing system

Abstract

Manufacturing industries are challenged of accomplishing effective operations regardless of perturbations during execution. For this reason, manufacturing control systems must be able to manage the scheduling of production towards the efficiency and reactivity of operations. For many approaches, the use of priority rules has proven to be a simple and efficient technique to address the efficiency and reactivity objectives, compared to other scheduling methods. Still, the use of this technique is focused on offline scheduling rather the online dynamic scheduling. For this reason, this paper proposed the use of priority rules for improving the reactivity features of a semi-heterarchical control system. Our proposal consists of a bi-level architecture where a high-level component proposes a set of priority rules that lower components follow. In a called directive mode, the high-level components optimize the set of priority rules in order that a more autonomous lower component chooses during execution. The directive mode is based on a set of simple and specific rules, as well as low complexity decision mechanisms pre-tested in a simulated environment. To show the contribution, we tested our approach in a simulated model of a real FMS in a simulation-based software. Experimental results demonstrate that the increase of autonomy given to the lower levels improves the efficiency after perturbations.