Connected and automated vehicles have shown great potential in improving traffic mobility and reducing emissions, especially at unsignalized intersections. Previous research has shown that vehicle passing order is the key influencing factor in improving intersection traffic mobility. In this paper, we propose a graph-based cooperation method to formalize the conflict-free scheduling problem at an unsignalized intersection. Based on graphical analysis, a vehicle's trajectory conflict relationship is modeled as a conflict directed graph and a coexisting undirected graph. Then, two graph-based methods are proposed to find the vehicle passing order. The first is an improved depth-first spanning tree algorithm, which aims to find the local optimal passing order vehicle by vehicle. The other novel method is a minimum clique cover algorithm, which identifies the global optimal solution. Finally, a distributed control framework and communication topology are presented to realize the conflict-free cooperation of vehicles. Extensive numerical simulations are conducted for various numbers of vehicles and traffic volumes, and the simulation results prove the effectiveness of the proposed algorithms.

翻译：以往的研究显示,车辆通行顺序是改善交叉交通流动的关键影响因素。在本文件中,我们提议采用基于图表的合作方法,将无冲突时间安排问题正式确定在一个无信号十字路口。根据图形分析,车辆的轨迹冲突关系模型是冲突引导图和不定向图。然后,建议采用两种基于图表的方法来找到车辆通行顺序。第一个是改进的深度第一横贯树算法,目的是找到当地最佳车辆通行顺序。另一个新颖方法是一种最低分类覆盖算法,确定了全球最佳解决办法。最后,提出了一个分散控制框架和通信结构,以实现车辆的无冲突合作。对各种车辆和交通量进行了广泛的数字模拟,模拟结果证明了拟议算法的有效性。