Order Picking Problem: Its Variations and Integration

Saylam, Serhat
Order picking is the most costly and labour-intensive warehouse activity. The objective of order picking problem is to collect the items on the pick list in a sequence to ensure a route that minimizes the travel time. In both manual and automated warehouses, a combination of efficient zoning, batching and picker routing plays an important role in improving travel time, congestion, workload balancing and system throughput. In this thesis, we study single-picker and multi-picker order picking problems on single-block, two-block and multi-block warehouse layouts by also considering synchronised dynamic zone-picking and batch-picking decisions. For this end, we present (1) mathematical models for the optimal solutions of some of these problems, (2) exact dynamic programming approaches to find the optimal solution for some other cases, and (3) simple but effective heuristics for the remaining more complex forms. Computational experiments on randomly generated instances in line with those in the literature show that the proposed approaches can find optimal and near-optimal solutions in negligible computational times. The comparisons of the resulting objective function values with the ones in the related literature also show that our approaches perform at least as strongly as the models in the state-of-the-art literature. We also contribute to the literature by introducing the arc routing perspective into the solution methodologies of order picking problems, by also introducing disconnectivity elimination constraints instead of sub-tour elimination constraints and by studying zone-picking and batch-picking decisions as operational level problems integrated with picker routing and workload balancing problems.


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Citation Formats
S. Saylam, “Order Picking Problem: Its Variations and Integration,” Ph.D. - Doctoral Program, Middle East Technical University, 2022.