Load volume considerations in the collision free route planning of material handling devices in FMS

Material handling is an important component of Flexible Manufacturing Systems (FMSs). Automated Guided Vehicles (AGVs) are commonly employed for this function. Efficient use of AGV systems requires proper routing and scheduling of vehicular traffic. The simultaneous routing of several AGVs to avoid collision is known to be an NP-Hard problem. In this research, we address the problem of optimal and efficient routing of AGVs through a guide path network.;Initially, we assume AGV size and load size are negligible. We present a sequential approach to plan routes for one vehicle at a time. Traffic constraints are put in the form of time windows. The routing of AGVs is formulated as a shortest time path problem in a network with time window constraints. A labeling algorithm is developed to solve this problem in polynomial time.;In the second part of this research, we explicitly consider the volume of AGVs and the volume of the loads to be transported. A configuration space obstacle approach is employed to calculate traffic constraints. A two level decomposition of the route planning problem is used to plan collision free routes. A global navigation step plans a shortest time route between two nodes in the guide path network. The translation of the vehicle on an arc connecting two nodes and rotation at a node joining two arcs are planned at a local level. The routing problem at both levels is formulated as a network model with time window constraints at the local level and with reachability window constraints at the global level. The labeling algorithm developed in the first part is modified to plan both local and global routes.;The algorithms are tested using extensive computer simulations. The simulation results indicate that the algorithms are computationally efficient and can be applied for both point load and volume load vehicle routing problems on uni-directional and bi-directional networks. Practical considerations such as disposition of idle AGVs, dispatching and rerouting are also studied using simulations. Finally, extensions of the algorithms to the case of cooperative material handling systems are discussed.