Dynamic Spare Point Application Based Coordination Strategy for Multi-AGV Systems in a WIP Warehouse Environment

Multi Automated Guided Vehicle (multi-AGV) systems are widely used in Work-in-Process (WIP) warehouses to improve the efficiency of material transportation. However, collisions and deadlocks between AGVs are inevitable. Many algorithms have been proposed to solve these problems, but their performance is inefficient in the WIP warehouse due to the lack of consideration of its features. In this paper, to fill the gap between current research and real-world application requirement, we construct a collision and deadlock solving model for a multi-AGV system in a WIP warehouse (CDSMWW). Then we propose a coordination strategy based on dynamic spare point application (DSPA), aiming to improve the efficiency of solving AGV collisions and deadlocks in a WIP warehouse. In this method, the AGV records its predecessor, successor, and reserved points in its local controller and can only enter the set of sequential shared points if its application for spare points is successful. Otherwise, it has to stop to avoid causing an unresolvable deadlock. If a deadlock occurs while this AGV is in the sequential shared points, the AGV moves to the spare point to resolve it. Whenever an AGV leaves the set of consecutive shared points, it releases all its spare points. We apply the algorithm to both the central and local controllers to improve the calculation efficiency. Extensive simulation results demonstrate the feasibility of the DSPA scheme under realistic WIP warehouse environment and its higher efficiency compared to previous state-of-the-art methods.