Analytical foundations for autonomous vehicle storage and retrieval systems using load transfer station based dwell point strategies

Autonomous vehicle storage and retrieval systems (AVSRS's) utilize rail-guided vehicles moving in rectilinear paths within and between the aisles of unit load storage racks. These systems represent an alternative to crane based automated storage and retrieval systems for which an extensive literature on analytical design methods is available. Most of the models in this literature exploit the fact that aisle captive cranes yield highly efficient travel patterns owing to their simultaneous horizontal and vertical movement. However, AVS/RS technology offers other advantages including lower cost and greater flexibility to adjust capacity to the throughput demand of a system. In this thesis, computationally practical analytical methodologies to evaluate AVSR systems are developed based on the movement kinematics peculiar to this technology. These methodologies are focused on decision making in the early pre-engineering or "conceptualization" phase of system design where the levels of key design variables driving the majority of system life cycle costs are determined. The research also addresses more general problems in the design and analysis of unit load storage and retrieval systems including the cycle time effects of coupling random storage policies with closest open location load dispatching.