performance of AVS/RS

We perform a simulation based experimental design for automated unit-load (UL) storage and retrieval systems based on autonomous vehicle technology to identify factors affecting their performance. First, we select the best combination of numbers of lifts and vehicles from pre-defined scenarios that are the key components of the system. Then, we apply design of experiment (DOE) for a system with this combination of lifts and vehicles and for various arrival rates. The factors considered in the DOE include: dwell point policy, scheduling rule, input/output (I/O) locations and interleaving rule. Three different responses, the average cycle time for storage and retrieval transactions, average vehicle utilization, and average lift utilization, are considered. However, because the ANOVA assumptions are not met for the average cycle time response, an inverse transformation method is applied on this response. The results show that there is three-way interaction effect on each response at a 95% confidence level. After determining the main and the interaction effects, a Tukey's test analysis is completed on the responses. We utilize data from a warehouse in France that utilizes the autonomous vehicle storage and retrieval system. (C) 2009 Elsevier Ltd. All rights reserved

A new technology for unit-load automated storage system: Autonomous vehicle storage and retrieval system

Material handling is a growing, $80 billion industry that is central to the nation's economic competitiveness and national defense. A major segment of this industry is unit load (UL) storage and retrieval (S/R) systems which form a critical link in global supply chains. The first step in UL S/R system design is the configuration from which subsequent design details are derived. Most UL S/R system life cycle costs and capabilities are established during the selection of S/R device technology, UL throughput rates, storage capacity and system configuration. The crane-based automation technologies were introduced in the 1970s. Automated storage and retrieval system (AS/RS) has been widely used in distribution and production environments to store and retrieve loads (Roodbergen KJ, Vis IFA (2009) A survey of literature on automated storage and retrieval systems. Eur J Oper Res 194:343-362). An AS/RS usually consists of conveyors, racks and automated S/R devices (cranes). The cranes are fully automated and can travel in aisles between the racks to pick up and drop off loads. Between 1994 and 2004, there has been a significant increase in the number of AS/RSs used in distribution environments in the United States (Roodbergen KJ, Vis IFA (2009) A survey of literature on automated storage and retrieval systems. Eur J Oper Res 194:343-362). The most important advantages of using AS/RSs over non-automated systems are: savings in labour costs and floor space, increased reliability and reduced error rates. However, it has significant disadvantages including the high investment cost, less flexibility and higher investments in control systems (Zollinger H (1999) AS/RS application, benefits and justification in comparison to other storage methods: a white paper automated storage retrieval systems. Production Section of the Material Handling Industry of America). © 2012 Springer-Verlag London Limited