Abstract– Stock Keeping Unit (SKU) assignmentis an essential problem for the design and operation of Automated PickingSystem (APS), which is mainly composed of Horizontal Dispenser (HD) andA-frame. The challenge is to develop an effective measurement to evaluate thesku and the efficient assignment procedure in practice. Based on fluid model, the optimal number ofchannels allottedto each sku to minimize the total restocking cost of Horizontal Dispenser is presentedand extended to A-frame.Greedy heuristic algorithmto assign skus to Horizontal Dispenser andA-framefor a given period is then developed based on the equivalent two-tier, three-mode inventory system. In order to evaluate skus over multi-period, sequence viscosity is formulated byminimizingthe total cost of picking, restocking, andreslotting.And the best-sequenceheuristic is adopted to assign skus to Horizontal Dispenser and A-framein the equivalent inventory system of APS over multiple periods. Computational result for real-life instances shows that the proposedmethod generates a savings of over 14% referring to the total restocking cost.
Index Term- automated picking system, forward-reserveproblem, restocking, reslotting
I. Introduction
The fast-picking area of a warehousefunctions as a “warehouse within the warehouse”: Many of the most popular skusare stored there in relatively small amounts, so that most picking can beaccomplished within a relatively small area. This means that pickers do lessunproductive travel and may be more easily supervised. The trade-off is thatthe fast-picking area may require replenishment from bulk storage area, or socalled reserve area [1]. The simplest configuration of the commonly knownforward-reserve inventory system includes single reserve area and fast-pickingarea.
In practice, a warehouse that picks some skus with one ormore automatic picking devices has a more complicated inventory system. AutomatedPicking System (APS), a kind of automated order picking system for thepiece/unit of cigarette that combines the Horizontal Dispenser (HD) and A-frametogether, is often used in the order fulfillment area of the tobacco warehouse toincrease the picking efficiency, accuracy and reduce the labor intensity. As itis shown in Fig. 1, the general inventory system of APS is a four-tier,six-mode inventory system. The first tier is Back Warehouse (BW) which may bepallet racks or stacks. Its main responsibility is to provide restocks to thenext tier. The second tier is Pallet Storage Area (PSA) which only receivespallets of skus from BWand provides restocks to the next tier.