|dc.description.abstract||During recent years, Autonomous Vehicle Storage and Retrieval Systems (AVS/RS) have been widely applied in distribution centers and production sites to meet the increasing demand for rapid and flexible large-scale warehousing activities. As the core subsystem of the bigger warehousing system, in AVS/RS horizontal devices (vehicles) and vertical devices (lifts) are applied for storage and retrieval operations to fulfill customer orders. The main topic of this study, Shuttle-based Storage and Retrieval System (SBS/RS), is one representative class in AVS/RS category. Recognizing the complex service dynamics due to the use of different types of S/R devices, both the configuration design problem and operational control problem need to be studied in order to improve efficient, sustainable and robust performance of the system. We identified critical decisions and factors of SBS/RS-based warehousing systems and studied their complexities and correlations, and proposed a comprehensive and consistent methodology for both the design configuration and the operational control practices.
In the first step, an animated, data-driven and data-generated simulation model is developed to support the development of both the design and configuration approach and the operational control strategy of SBS/RS-based warehouse systems. The model enables detailed analysis of different technology options including tier-captive and tier-to-tier configurations, multi-deep rack designs, multi-capacity lifts, etc., and provides visualized tracking of accurately simulated service processes of the S/R devices and performance evaluation under configurable demand scenarios.
In the second step, the research focuses on the conceptual design problem in which alternative SBS/RS designs and configurations are evaluated. A three-stage design methodology based on queuing analysis is proposed to provide rapid evaluation and screening for large number of alternative design options. The methodology considers not only design configuration parameters including number of aisles, tiers, columns, and shuttles, but also different technology options as well as control policies to improve estimation quality.
In the third step, we focus on the control aspect which involves the development of various operational control approaches for storage assignment and device scheduling. Mathematical programming techniques and dynamic dispatching approaches are explored to provide in-depth analysis of the control decisions. An operational control strategy framework that systematically integrates the control policies is developed and illustrated in detailed charts and pseudocode for practical implementation.
The research work used in this dissertation is part of a research and development project of an SBS/RS product by Damon Group (http://www.damon-group.com/), a global logistics solution provider, which is also the sponsor of this research work. Thanks to the practical data and professional insights provided by our sponsor, this research work is examined and validated all the way along its development.||en_US