Machine scheduling with transportation considerations

In most manufacturing and distribution systems, semi-finished jobs are transferred from one processing facility to another by transporters such as automated guided vehicles and conveyors, and finished jobs are delivered to customers or warehouses by vehicles such as trucks. Most machine scheduling models assume either that there are an infinite number of transporters for delivering jobs or that jobs are delivered instantaneously from one location to another without transportation time involved. In this paper, we study machine scheduling problems with explicit transportation considerations. Models are considered for two types of transportation situations. The first situation involves transporting a semi-finished job from one machine to another for further processing. The second appears in the environment of delivering a finished job to the customer or warehouse. Both transportation capacity and transportation times are explicitly taken into account in our models. We study this class of scheduling problems by analysing their complexity. We show that many problems are computationally difficult and propose polynomial or psuedo-polynomial algorithms for some problems.