Date on Master's Thesis/Doctoral Dissertation

12-2020

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Industrial Engineering

Degree Program

Industrial Engineering, PhD

Committee Chair

Gue, Kevin

Committee Co-Chair (if applicable)

Gentili, Monica

Committee Member

Bai, Lihui

Committee Member

Altiparmak, Nihat

Author's Keywords

Warehousing; order picking; goods-to-person systems; modern logistics

Abstract

In recent years, there has been an increased growth in e-commerce, which is a special case of a business-to-customer model. Among all the operations for fulfilling online orders, order picking has been the concern of many researchers and practitioners in the field of warehousing and material handling. This is due to very different technical assumptions and service expectations for online retailers compared to the case of business-to-business models. The most fundamental change in order processing, imposed by business-to-customer models, is shipping individual items or “eaches,” instead of cases and pallets, which is typical of business-to-business models. As a result, the methods and equipment used to serve orders for store replenishment are not suitable for online retailers. This dissertation investigates new design ideas, at different stages of an order fulfillment process, to improve the throughput in goods-to-person order picking systems. These ideas focus on reducing the item interarrival time in workstations by improving the item retrieval operation in both the storage and the pick side. In Chapter II, we propose a design for a grid-based goods-to-person order picking system that overcomes the barriers to assign the workstations to different sides of a grid, employing an existing path planning method in the literature. We also address some specific design questions to explore this design’s potentials to maximize the throughput by reducing the expected interarrival time, for the requested items at workstations. Given a high retrieval rate from the storage side, the focus of Chapter III is on designing the pick interfaces in goods-to-person order picking systems. At this step of our research, we investigate how to manage the material flow in the interface and how to sequence the items to be processed by the picker to maximize the system throughput, under different scenarios for the picker’s picking and traveling speed. To further accelerate the order fulfillment process, the focus of Chapter IV is on designing a “dynamic order picking” system. This design aims at overcoming the restrictions on the minimum size of the pick area, utilizing the available replenishment capacity for required item replacements, in a timely manner. This design exploits the opportunities provided by a continuous synchronization between picking and replenishing operations.

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