A review of design and control of automated guided vehicle systems <s> Conclusions and further research <s> interest in automated material handling systems has been increasing in manufacturing and assembly facilities. Automated guided vehicle system (AGVS) is one such material handling system. One of the decisions in implementing an AGVS is to determine the number of vehicles required for a facility at the early planning stage. This paper undertakes the development of an analytical model using a regression technique to estimate the number of vehicles required by a facility. The model attempts to use characteristics of a facility for which an automated guided vehicle system is under consideration to determine the number of vehicles required. Although several facility characteristics were investigated, only a few were finally included in the model based on the statistical significance of their contributions to predicting vehicle requirements. The predictive abilities of several models hypothesized were compared with results obtained through simulation on some test facilities. Based on the results of the compariso... <s> BIB001 </s> A review of design and control of automated guided vehicle systems <s> Conclusions and further research <s> This paper describes the development of a minimum flow algorithm to determine the number of automated guided vehicles (AGVs) required at a semi-automated container terminal. At such a terminal the containers are transported by AGVs from the quay cranes to the automated stacking cranes and vice versa. A model and a strongly polynomial time algorithm are developed to solve the case in which containers are available for transport at known time instants. <s> BIB002
In this paper, we have discussed several key issues in AGV system design and implementation. These issues include guide-path design, estimating the required number of vehicles, vehicle scheduling (dispatching), idle vehicle positioning, battery management, vehicle routing, and conflict resolution. For every decision problem we have reviewed important literature and have classified decision problems. The first important issue when designing AGV systems is guide-path design. In general, we can divide guide-path systems into three categories: conventional, single-loop and tandem systems. Each of them has its own advantages and disadvantages (Table 3) and is suitable for specific applications. Next important issue is estimating the required number of vehicles. Main vehicle estimating models include travel time  , queueing , regression BIB001 and network BIB002 ) models. Obtaining a good estimation of the vehicle empty travel under some good dispatching rules is the key problem here. Another issue is how to manage an AGV system efficiently. This issue includes several subissues: vehicle scheduling, idle vehicle positioning, battery-charging, vehicle routing and conflict resolution. In practice, online scheduling and dispatching systems are much more popular than offline scheduling due to the stochastic nature of AGV systems. Generally, online scheduling systems perform better than simple dispatching systems (Yang et al., 1999) , however they are much more complex. The scheduling system also decides which route a vehicle should take to reach its destination without collisions. In cases where vehicle blocking and interference problems are likely, we need a good conflict resolution system. In addition, to better serve future jobs, the controller should guide idle vehicles to strategic parking locations. Vehicles are usually located in such a way that the mean or maximum response time of new requests is minimized. Most authors neglect AGV battery management problems. In the case of long travel distances, the battery charging becomes an issue and needs to be considered as well.