Chair: René de Koster (Erasmus University Rotterdam)

Title: The average tour length in warehouses
Speaker: Kees Jan Roodbergen (RUG)

Authors: Arjan S. Dijkstra, Gerlach van der Heide, Kees Jan Roodbergen

Abstract: To design warehouses properly, it is essential that the effects of design choices on operational efficiency can be adequately quantified. We consider the setting in which order pickers travel through a warehouse to retrieve products from storage locations. To determine operational efficiency in this setting, we seek for the average length of the traveling salesperson problem in a warehouse layout. Literature provides several approximations for this, both for the general traveling salesperson problem as well as for warehousing problems. We present, however, formulations that provide the exact average tour length. The applicability of the approach is demonstrated by the case of assigning products to storage locations.
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Title: Manual order picking in a warehouse
Speaker: Ivo Adan (Eindhoven University of Technology)

Abstract: We consider manual order-picking in a rectangular warehouse consisting of multiple parallel aisles. The routing heuristic of the picker is the mid-point strategy. Through use of generating functions we determine closed-form expressions for mean and variance of the travel time.
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Title: Increasing the practical applicability of order picking planning
Speaker: Sarah Vanheusden (Univerity Hasselt)

Abstract: Managing order picking operations is a complex task. Trends such as e-commerce, globalisation,  and increased customer expectations pose new challenges on warehouse management and increase the need for efficient order picking systems (Marchet et al., 2015). Scientific research focusses on the design and control of individual warehouse operations and more recently on the interaction or integration of multiple order picking planning problems and policies (van Gils et al., 2018). Despite the valuable contribution of these research papers, the application of the proposed solution algorithms in practice is rather limited due to insufficient attention for practical factors in real-life warehouse settings.

This study aims to increase the practical applicability of research in manual order picking by accounting for perspectives of practitioners. Warehouse managers emphasize the increased difficulties in managing warehouse operations due to changing CLP regulations (Classification, Labelling and Packaging of substances and mixtures) for storing products. Accounting for CLP regulations in storage assignment is highly important as these regulations aim to limit the risk on chemical reactions in the warehouses (e.g. situations in which goods are damaged during handling) and make sure that products can be handled safely without harming people or the environment. A mixed integer linear programming (MIP) model is developed to formulate the problem. Furthermore, existing policies for storage assignment, batching and routing are simulated in a real-life order picking system subject to CLP regulations with the aim of reducing order picking time.

In cooperation with:
van Gils, K. Ramaekers and A. Caris Hasselt University, research group logistics

References
Marchet, G., Melacini, M., Perotti, S., 2015. Investigating order picking system adoption: a casestudy