An algorithm for routeing control of a tandem automated guided vehicle system

A tandem AGV (automated guided vehicle) system is composed of several non-overlapping closed loops. Stations within each loop are served by a single dedicated vehicle. The transit area located between two adjacent loops serves as an interface and allows loads to be transferred from one loop to another. If a load needs to be delivered to a station not located within the same loop, the load needs more than one vehicle to carry it to its destination. We regard this routeing problem as a problem of finding the shortest travel time. After a command to deliver a load is issued, finding a route from the source to the destination as rapidly as possible without disrupting other active travel schedules was the objective of this study. A task-list time-window algorithm to find a shortest travel time based on the current status to route a load from point A to point B is presented. Two idle-vehicle managements are considered: circulating (CIRC) and STAY policies. Experiments showed that the STAY policy is more efficient than the CIRC policy in routeing control.