The performance of load-selection rules and pickup-dispatching rules for multiple-load AGVs

In this paper, we address the problem of load selection and pickup-dispatching of multiple-load AGVs. Various load-selection rules and pickup-dispatching rules are proposed and studied. The objective of this study is twofold. We want to understand not only the performance of load-selection rules and pickup-dispatching rules in two performance criteria-throughput and tardiness, but also the effects that pickup-dispatching rules and load-selection rules have on each other's performance. The simulation results indicate the load-selection rule with a selection criterion based on the destination similarity between loads has the best throughput and tardiness performance. Also, the pickup-dispatching rule that dispatches vehicles to the workstation with the greatest queue length has the best throughput and tardiness performance. The simulation results also indicate load-selection rules and pickup-dispatching rules affect each other's performance. For example, a load-selection rule's throughput and tardiness performance tends to improve if it is paired with a pickup-dispatching rule that shares similar logic. Furthermore, not all average-time-value-based pickup-dispatching rules are better (in throughput or tardiness) than their respective single-time-value-based pickup-dispatching rules under all load-selection rules. (C) 2009 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.