Integrated Scheduling of Machines and AGVs in Flexible Manufacturing System

Nowadays, with the general application of Flexible Manufacturing System (FMS), Automated Guided Vehicles (AGV) have been broadly used for material handling in many manufacturing organisations, as they offer great routing flexibility to support diversified manufacturing processes
for producing high variety of products. For these organisations, the effectiveness in scheduling and using AGVs for material handling would significantly affect the smoothness and efficiency of their production systems in operational level. However, scheduling problems in manufacturing system conventionally focus on production resources, i.e., production machines, only, which generally assume material handling amongst production machines have fixed and known parameters (i.e., processing time and cost) and readily available, but does not take into account of the capacity constraints of material handling resources. This paper therefore investigates the scheduling of machines and AGVs in a FMS environment in an integrated manner. In doing so, an integrated scheduling problem is defined in this paper, in which a set of simultaneous jobs with alternative process plans are to be scheduled on resource constrained machines and AGVs with the view to
minimising their total makespan. A hybrid one-phase approach is developed to solve the problem defined. In the integrated scheduler, jobs are allocated and scheduled on machines by using a bistring Genetic Algorithm (GA) and the heuristic of “Vehicle Assignment Algorithm” developed by experiential studies to allocate and schedule jobs on AGVs. Performance of the proposed approach is tested through numerical experiments.