C. Núñez del Toro, E. Fernández, J. Kalcsics, S. Nickel
In this work we consider a multi-period problem with the following characteristics. We are given a set of customers where items are produced at a given rate per period, for example commodities, raw materials, or waste. Each customer can only store a certain number of items. Such items have to be collected from time to time with appropriate vehicles, and transported to some facility, e.g., to a warehouse, factory, or recycling center. The task is to determine when to visit each customer such that the storage limitations at the customers are adhered to as few vehicles as possible are needed. This problem is motivated in the context of collection and recycling of waste electrical and electronic equipment (WEEE). We focus on tactical level modelling aspects aimed at reducing the fleet size and, hence, maximizing the utilization of vehicles. Thus, we do not consider the actual routing of the vehicles which can be addressed at an operational level. This objective coincides with the current trend in scheduling and vehicle routing problems, not only for economic savings but also due the environmental benefits. In particular, two alternative policies for scheduling customer visits are considered. In the first one, a customer is visited just on time, i.e., in the period where he or she has a demand for service. The second policy allows visits ahead of time. Linear integer formulations are presented for both collection policies. The numerical experiments show the reduction in number of vehicles when the second collection policy is considered.
Keywords: multi-period problems, scheduling, heuristicsScheduled
F4 Combinatorial Optimization 3
October 2, 2015 3:30 PM
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