Hybrid Cooperative Coevolution for Fuzzy Flexible Job Shop Scheduling Problems

Abstract

In this paper we consider a variant of the flexible job shop scheduling problem with uncertain task durations modelled as fuzzy numbers. We propose a cooperative coevolutionary algorithm to minimise the schedule's makespan, with two di fferent populations evolving the two main aspects that conform a solution: machine assignment and task relative order. Additionally, we incorporate a specifi c local search method for each population. The resulting hybrid algorithm, called CELS, is then evaluated on existing benchmark instances, comparing favourably with the state-of-the-art methods.