Dynamic prioritized motion coordination of multi-AGV systems

Abstract

The motion coordination problem for a fleet of Autonomous Guided Vehicles (AGVs) in a confined industrial facility is addressed. The working scenario involves a group of AGVs that is tasked to transport without collisions to predefined locations within the industrial facility. We introduce a centralized motion coordination controller that utilizes a dynamic priority logic to resolve motion conflicts between AGVs as they appear. The controller relies on the implementation of a predefined, virtual transportation network that is comparable to a conventional right-handed bidirectional traffic system. The construction of the transportation network considers the physical and motion characteristics of the AGVs (dimensions and maximum speed). The high-level function of the controller is to detect imminent collisions and determine the right-of-way of conflicting AGVs in same-directional routes and intersection junctions of the transportation network. The priority update logic is inspired by the traffic control of conventional four-way stop-controlled intersections. Based on the updated priorities, the motion coordinator adjusts the advancement of the AGVs to eliminate collisions. The proposed formulation combines a high-level event-driven logic for collision avoidance with low-level feedback control laws for guidance and navigation. As a result, the controller relies only on real-time measurements, removing the need for computationally demanding look-ahead predictions (heuristics) of the AGVs’ motion. It is shown that the proposed method ensures collision- and blockage-free motion of a large number of AGVs. Extensive numerical simulations validate the performance of the motion coordination algorithm.