Task scheduling for multiple forklift AGVs in distribution warehouses

Distribution warehouses are considered in this paper with the aim of scheduling the transportation of pallet and roll pallet loads from the storage area to the gates at which the trucks arrive. Transportation activities are carried out by forklift AGVs that can move freely along the warehouse´s aisles (guide paths are not considered). In this paper, an optimization procedure is proposed, which is based on three sequential phases. In the first phase, the number of AGVs to be allocated to each arrived truck is determined; in the second phase, an AGV-to-truck assignment problem is solved; in the third phase, the single tasks are assigned to and sequenced on the AGVs. All phases are based on the formalization and solution of a specific mathematical programming problem, and a heuristic procedure is also proposed to solve a part of the third phase.