On a selection and scheduling problem in automatic storage and retrieval warehouses

Warehousing is one of the main components of the supply chain and its optimisation is crucial to achieve global efficiency. Warehouse operations involve receiving, shipping, storing and order picking, among other things, and the coordinated optimisation of all these different operations is highly complex. This paper examines a real selection and scheduling problem that arises in an automatic storage/retrieval warehouse system involving the scheduling of forklift pickup operations. The objective is to minimise the total loading time of the vehicles performing transportation, while respecting their departure due dates. This complex problem is approached via a two-phase decomposition method, combining both exact and heuristic procedures. The performance of the proposed solution method is evaluated using extensive computational results from several scenarios from a real case study using data from a real mattress warehouse.