Fleet sizing of laser guided vehicles and pallet shuttles in automated warehouses

The paper deals with emerging automation technologies for pallet handling in warehouses characterized by multiple-depth rack storage systems. In particular, this studyaddresses the adoption of Pallet Shuttles (PSs) for material handling within the rack structure, i.e., for put-away and retrieval operations from the rack face to the specific pallet location and viceversa. PSs are used in combination with Laser Guided Vehicles (LGVs) so as to obtain a fully automated warehousing system. The study develops an analytical model for the joint LGV–PS fleet sizing problem, also taking into consideration stochastic phenomena and queueing implications. This enables the analyst to compute the utilization of LGVs and PSs as a function of sizes of the two fleets. Then, a queueing model can be applied to estimate the cycle time of the orders in the warehousing system. An example to clarify the application of the method is also provided.