Title: Variance-based approximations of transaction waiting times in autonomous vehicle storage and retrieval systems

Authors: Li Zhang, Ananth Krishnamurthy, Charles J. Malmborg, Sunderesh S. Heragu

Addresses: Royal Bank of Scotland Group, Inc., Bridgeport, Connecticut, USA. ' Department of Industrial and Systems Engineering, ME 3258, University of Wisconsin, 1513 University Avenue, Madison, Wisconsin, USA. ' Department of Decision Sciences and Engineering Systems, Rensselaer Polytechnic Institute, Troy, New York, USA. ' Department of Industrial Engineering, University of Louisville, Louisville, Kentucky, USA

Abstract: Approximation strategies for transaction waiting times are proposed for use in Autonomous Vehicle Storage and Retrieval Systems (AVS/RSs) with non-Poisson arrival rates and non-exponential service times. The proposed modelling tools dynamically adjust approximations based on the variance of the transaction inter-arrival times observed in a system. Simulation-based validation studies indicate that this strategy can reduce the magnitude of errors in estimated transaction waiting times by approximately 80% relative to static approximations. The design conceptualisation applications of the proposed technique are demonstrated over a series of realistically sized demonstration problems. [Received 8 April 2008; Revised 20 July 2008; Accepted 2 August 2008]

Keywords: autonomous vehicles; autonomous vehicle storage and retrieval systems; AVS/RSs; non-Poisson queuing approximations; transaction waiting times; modelling; simulation; automated storage and retrieval systems; AS/RS.

DOI: 10.1504/EJIE.2009.023603

European Journal of Industrial Engineering, 2009 Vol.3 No.2, pp.146 - 169

Published online: 02 Mar 2009 *

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