A review of design and control of automated guided vehicle systems <s> Workload-based dispatching rules take queue sizes (or workloads of workstations) into <s> Abstract The problem of organizing and controlling the material handling activity in an AGV-based material handling system for a flexible manufacturing system involves several decisions such as the number of vehicles required for the system, the layout of the tracks, the dispatching rules for the vehicles and the provision of control zones and buffers. This paper demonstrates the use of a two-stage approach for solving the problem. The required number of vehicles is estimated using an analytical model in the first stage. In the next stage, the effects of AGV failures and AGV dispatching rules on the system performance are observed through simulation studies based on which the AGV dispatching rule can be chosen. <s> BIB001 </s> A review of design and control of automated guided vehicle systems <s> Workload-based dispatching rules take queue sizes (or workloads of workstations) into <s> Abstract In this paper we present a general-purpose analytical model to compute die approximate throughput capacity of a trip-based material handling system used in a manufacturing setting. A wide variety of handling systems, including freight elevators, cranes, microload automated storage/retrieval (AS/R) systems, industrial lift trucks, and automated guided vehicle (AGV) systems can be modeled as trip-based handling systems. To our knowledge, this model is one of the few analytical models that explicitly considers an empty device dispatching rule. The model is first developed for a single-device system (such as a crane) and subsequently, with a simple modification, it is extended to multiple-device systems (such as lift trucks and AGVs). Using this model one can rapidly evaluate a wide range of handling and layout alternatives for given flow data. Hence, die model would be most effective when used early in the design phase to narrow down die set of alternative handling systems and configurations prior t... <s> BIB002 </s> A review of design and control of automated guided vehicle systems <s> Workload-based dispatching rules take queue sizes (or workloads of workstations) into <s> This study examines the effects of scheduling rules on the performance of flexible manufacturing systems (FMSs). Several machine and AGV scheduling rules are tested against the mean flowtime criterion. In general, scheduling rules are widely used in practice ranging from direct applications as a stand-alone scheduling scheme to indirect application as a part of complicated scheduling systems. In this paper, we compare the rules under various experimental conditions by using an FMS simulation model. Our objective is to measure sensitivity of the rules to changes in processing time distributions, various levels of breakdown rates, and types of AGV priority schemes. A comprehensive bibliography is also presented in the paper. <s> BIB003 </s> A review of design and control of automated guided vehicle systems <s> Workload-based dispatching rules take queue sizes (or workloads of workstations) into <s> Guided vehicles (GVs) are commonly used for the internal transportation of loads in warehouses, production plants and terminals. These guided vehicles can be routed with a variety of vehicle dispatching rules in an attempt to meet performance criteria such as minimizing the average load waiting times. In this research, we use simulation models of three companies to evaluate the performance of several real-time vehicle dispatching rules, in part described in the literature. It appears that there is a clear difference in average load waiting time between the different dispatching rules in the different environments. Simple rules, based on load and vehicle proximity (distance-based) perform best for all cases. The penalty for this is a relatively high maximum load waiting time. A distance-based rule with time truncation, giving more priority to loads that have to wait longer than a time threshold, appears to yield the best possible overall performance. A rule that particularly considers load-waiting time performs poor overall. We also show that using little pre-arrival information of loads leads to a significant improvement in the performance of the dispatching rules without changing their performance ranking. <s> BIB004
account. In  and BIB003 , several queue-size rules are introduced, such as the maximum-outgoing-queue-size (MOQS) rule and the minimumremaining-outgoing-queue-space (MROQS) rule. The MOQS rule dispatches a vehicle to the workstation with the largest number of loads waiting to be picked up in its outgoing queue. MROQS dispatches vehicles to the workstation with the minimum remaining space in its outgoing queue. The aim of this rule is to reduce the possibility of queue overflowing or workstation blocking. In addition, several rules based on vehicle utilization (such as select the least utilized vehicle) are proposed by  and BIB001 . Time-based dispatching rules dispatch vehicles based on jobs' waiting time. These rules include the first-come-first-served (FCFS) rule and two modified first-come-first-served rules (MFCFS, MODFCFS) (see  BIB002 . Under the MFCFS rule, a station places only one move request at a time, so it can have at most one "active" move request. The MODFCFS rule differs from the MFCFS rule as it attempts to reduce unnecessary empty travel time by allowing the vehicle to override the FCFS rule whenever it finds an unassigned move request at the destination point.  provides an analytical analysis of AGV systems using FCFS dispatching policies. De BIB004 have carried out extensive simulation experiments with several commonly used dispatching rules such as NVF, for three real cases. They experimented with different operating conditions for AGV systems and point out that for environments where the queue space is critical, the distance-based dispatching rules (NWF, NVF) outperform other rules. However, when it is not the case, the time-based (MODFCFS) or workload-based dispatching rules might perform better.