A bi-directional path layout for conflict-free routing of automated guided vehicles

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 and drop-off (or P/D for short) jobs. Results of this study could form a basis for more complicated path layouts and routing algorithms.