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Communication Dans Un Congrès Année : 2022

Joint Order Batching and Picker Routing Problem including congestion

Résumé

Warehouse management at the operational level is mainly focused on the efficient execution of the picking process. Picking activities consist in collecting all the products of a given set of customer orders. In this presentation, we consider a rectangular warehouse composed by a set of parallel cross and vertical aisles. A sub-aisle is a piece of a vertical aisle delimited by the intersection with two consecutive cross aisles. Products are stored in racks located in the sub-aisles. Pickers walk around the warehouse pushing a capacitated trolley to collect the products. Order picking tasks represent the majority of the total operational cost, and managers have to take two main decisions: (1) assign and group the orders to be collected by the available pickers, and (2) define the exact route to be followed by each picker to pick the items of its assigned orders. Several pickers are simultaneously moving around the warehouse to collect the products. Several pickers must likely compete to use the space, producing an undesirable effect named congestion. This occurs when two or more pickers are located in the same space simultaneously, producing a delay in the nominal travel times. This delay is directly related to the number of pickers located in the same zone. In a real scenario with human pickers, it is impossible to exactly coordinate them, so we propose to divide the planning horizon into time intervals, and then define a situation of congestion when several pickers are using the same sub-aisle during the same time interval. We propose a Mixed Integer Linear Program formulation that considers the integrated batching and picker routing decisions and minimizes the total completion time (travel, picking, and delay). We propose an approximation using a piecewise linear function to quantify the delay. A time delay is imposed each time several pickers are in a situation of congestion. Since we need to decide the arrival of the pickers at each picking location, we developed a transformation of the warehouse graph. The model allows obtaining optimal solutions in small instances. To achieve optimal so- lutions on larger instances, we develop two-step solution procedure in which the first step solves the batching and picker routing without considering congestion, and then the second step solves the scheduling problem minimizing congestion. Computational results will be presented and the relevance of the model will be discussed.
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Dates et versions

hal-03771620 , version 1 (07-09-2022)

Identifiants

  • HAL Id : hal-03771620 , version 1

Citer

Pablo Torrealba-González, Dominique Feillet, Maxime Ogier, Frédéric Semet. Joint Order Batching and Picker Routing Problem including congestion. VeRoLog 2022 - Workshop of the EURO Working Group on Vehicle Routing and Logistics optimization, Jun 2022, Hamburg, Germany. ⟨hal-03771620⟩
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