Material transport activities assume special importance in the content of automated manufacturing environments such as Flexible Manufacturing Systems (FMSs). The performance of the total system in terms of throughout and timeliness of order completions, and utilization of material transport and handling equipment depends on scheduling of material transport and handling activities. "Material transport", in the context of this paper, refers to inter-workstation movement, while "material handling" refers to handling activities within a workstation. We address the issue of scheduling material transport activities in the context of any FMS.
In order to address material transport in an FMS, in an integrated way, we need a unified generic scheme that provides appropriate links between subsystems in an FMS. Such a representation must also be based on some assumed architecture for an FMS; this is to ensure that algorithms and procedures developed are compatible with all other aspects of making an FMS operational. For example, the material transport schedules developed must be at a level of detail that interactions with processing stations can be evaluated. The architecture we assume here is that proposed in Smith, Hoberecht and Joshi, and consists of three levels: shop, workstation and equipment.
In this paper, we present a representation for a Material Transport System in an FMS. Based on the representation, we identify a few scheduling subproblems. We present some mathematical models and example problems for some of the scheduling subproblems.