A review of design and control of automated guided vehicle systems <s> Vehicle routing <s> This paper presents an efficient algorithm for finding conflict-free shortest-time routes for automated guided vehicles moving in a bidirectional flow path network. The proposed algorithm is based on Dijkstra's shortest-path method. It maintains, for each node, a list of time windows reserved by scheduled vehicles and a list of free time windows available for vehicles to be scheduled. We introduce the concept of time window graph in which the node set represents the free time windows and the arc set represents the reachability between the free time windows. Then the algorithm routes the vehicles through the free time windows of the time window graph instead of the physical nodes of the flow path network. It requires O(v4n2) computations in the worst case, where v is the number of vehicles and n is the number of nodes. <s> BIB001 </s> A review of design and control of automated guided vehicle systems <s> Vehicle routing <s> An automated Guided Vehicle (AGV) System with a limited number of vehicles cannot perform all of the transportation requests on demand. When a capacitated AGV system is used, then it is possible for the material handling system to become the bottleneck. There are many factors that affect the efficiency of an AGV system including how vehicles are routed and schedules. This paper presents a new dynamic approach to AGV routing. Simulation is used to study the effectiveness of this approach. <s> BIB002 </s> A review of design and control of automated guided vehicle systems <s> Vehicle routing <s> This study addresses the issue of vehicle route planning in an AGV system. The two salient approaches to route planning static and dynamic are briefly discussed. The main thrust of the present work is development and testing of a proposed semi-dynamic time window constrained routeing strategy. Reserved time windows are placed on nodes indicating sequential crossing of nodes by the respective vehicles. Free time windows represent empty time slots available for vehicles to cross the nodes. Similarly, time windows representing the direction of traffic flow are placed on the bidirectional arcs. Based on these time windows, Dijkstra's algorithm is applied to find the least congested fastest routes for vehicles. A simulation study of a bidirectional flow path is then reported. The aim of the simulation experiment is to evaluate the system performance under the proposed routeing strategy vis-a-vis static routeing strategy. The results show that the proposed routeing strategy helps in reducing vehicle blocking ti... <s> BIB003 </s> A review of design and control of automated guided vehicle systems <s> Vehicle routing <s> Automated guided vehicles (AGVs) are now becoming popular in automated materials handling systems, flexible manufacturing systems and even container handling applications. In the past few decades, much research has been devoted to the technology of AGV systems and rapid progress has been witnessed. As one of the enabling technologies, scheduling and routing of AGVs have attracted considerable attention. Many algorithms for the scheduling and routing of AGVs have been proposed. However, most of the existing results are applicable to systems with a small number of AGVs, offering a low degree of concurrency. With a drastically increased number of AGVs in recent applications (e.g. in the order of a hundred in a container handling system), efficient algorithms are needed to resolve the increased contention of resources (e.g. path, loading and unloading buffers) among AGVs. This survey paper first gives an account of the emergence of the problem of AGV scheduling and routing. It then differentiates it from seve... <s> BIB004 </s> A review of design and control of automated guided vehicle systems <s> Vehicle routing <s> Automated Guided Vehicles (or AGVs for short) are now widely used in automated material handling systems. Much research has been done on developing path layout and algorithms for the optimal routing and scheduling of AGVs. However, with the drastically increased number of AGVs in some recent applications (e.g. in the order of a hundred in container terminals), algorithms that can achieve a high degree of concurrency of AGV moves are urgently needed. This paper presents a bi-directional path layout and an algorithm for routing AGVs. To route the vehicles without conflicts and to minimize the space requirement of the layout, critical conditions for certain key parameters of the path and vehicle are derived. We further show theoretically that a high degree of concurrency of AGV moves can be achieved, although the routing decision takes only a constant amount of time for each vehicle. The routing efficiency is analysed in terms of the distance traversed and the time requirement for AGVs to complete all pickup... <s> BIB005
The vehicle scheduling and routing problems are closely related and should be addressed concurrently. In tandem systems, the routing problem is very simple, but in conventional systems, it is more complicated. In the scheduling section (4.1), we supposed that a vehicle could reach its destination without blocking. However, to avoid blocking, the vehicle routing needs to be taken into account as well. BIB001 propose an algorithm based on Dijkstra's shortest-path method to schedule vehicles based on the nodes' time windows. This approach produces a conflict-free schedule. However, as noted by the authors, a small change in the schedule may destroy it completely. BIB002 introduce an incremental route planning and scheduling algorithm. Other approaches are introduced in BIB003 and BIB005 . More details about the vehicle routing issue can be found in BIB004 .