Date of Graduation

8-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Industrial Engineering

Advisor/Mentor

Haitao Liao

Committee Member

John A White, Jr.

Second Committee Member

Manuel D. Rossetti

Third Committee Member

Jennifer A. Pazour

Keywords

Chebysheve Travel, MIAPP, Order Picking System, Queue Model, Rectilinear Travel, Storage Policies

Abstract

The development of probability density functions (pdfs) for travel time of a narrow aisle lift truck (NALT) and an automated storage and retrieval (AS/R) machine is the focus of the dissertation. The multiple in-the-aisle pick positions (MIAPP) order picking system can be modeled as an M/G/1 queueing problem in which storage and retrieval requests are the customers and the vehicle (NALT or AS/R machine) is the server. Service time is the sum of travel time and the deterministic time to pick up and deposit a pallet (TPD).

Our first contribution is the development of travel time pdfs for retrieval operations in an MIAPP order picking system supported by a narrow aisle lift truck (MIAPP-NALT); storage operations are assumed to occur when order picking is not being performed. A rectilinear travel metric is used for the NALT; pdfs are derived and finite population queueing and infinite population queueing models are used to analyze the retrieval operations under stochastic conditions.

Our second contribution is the development of travel time pdfs for retrieval operations in an MIAPP order picking system supported by an AS/R machine (MIAPP-AS/RS); storage operations are assumed to occur when order picking is not being performed. A Chebyshev travel metric is used for the AS/R machine. For the MIAPP-AS/RS operation, pick positions are located at floor level and on a mezzanine. The pdfs for four scenarios are derived and finite population and infinite population queueing models are used to analyze the retrieval operation under stochastic conditions.

Our final contribution is the development of travel time pdfs for storage and retrieval operations in an MIAPP-NALT system with two classes of stock keeping units (skus): fast movers and slow movers. A rectilinear travel metric is used and two levels of pick positions are considered. Non-preemptive priority queueing and non-priority queueing models are used to analyze storage and retrieval requests in the MIAPP-NALT system. Retrieval requests are given a higher priority than storage requests; alternately, storage and retrieval requests are served using a first come, first serve (FCFS) discipline.

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