| Intersection is one of the necessary elements of urban traffic environment,but it is also a serious area of traffic accidents and traffic jam.At present,most of the intersections set up traffic lights to guide vehicles through the intersection area.However,when the traffic flow is low,this method is prone to a large number of idle traffic resources at the intersection,which reduces the traffic efficiency.Therefore,many studies on multivehicle cooperation at driverless intersections focus on intersections without traffic lights.The three key problems in intersection multi-vehicle cooperation are deadlock avoidance,efficiency improvement in different traffic flow density conditions and vehicle waiting time cost reduction.The existing intersection multi-vehicle cooperation methods aren’t capable of solving all the three problems at the same time,so this paper combines the priority concept,the movement parameters,the back-pressure control and lane changing dispatch,so that the method proposed can solve these three key problems.Firstly,aiming at the problem of traffic efficiency at intersections,this paper proposes a multi-vehicle traffic strategy based on priority graph,which transforms the multi-vehicle traffic problem into a multi-layered system efficiency improvement problem.In this system,the strategy layer needs only do the priority assignment task,and the motion planning process is distributed to the vehicle individual behavior layer.These two layers communicate with requests from vehicles and priorities assigned by the strategy layer.This designing has lowered the system complexity and made the vehicles have kind of free behaviors.Secondly,using the tool of priority graph,we managed to design a priority system with acyclic priorities,and proved its property of deadlock avoidance.According to the movement characteristics of vehicle multiagent,this paper adopts priority planning method,which combines priority graph with vehicle movement,and improves the efficiency of intersection system on the premise of considering traffic safety in all the traffic density situations.Aiming at the problem of vehicle over-waiting in pure prioritybased system,back pressure control method is applied to reduce the waiting time cost of the system.The simulation experiments prove that the method proposed in this paper can achieve a larger intersection throughput capacity and a less vehicle waiting time cost than the classic method.Thirdly,a vehicle dispatch method using lane changing and overtaking is proposed.When an ego vehicle slowing down or a long queue is detected,the vehicle can make a lane changing or overtaking to reach the intersection control area faster,which improves the utilization efficiency of road resources and intersection transportation efficiency.The simulation experiments prove that the method with lane changing dispatch can achieve a larger intersection throughput capacity and a less vehicle waiting time cost than the method without the lane changing dispatch.Finally,based on the above theoretical research,the multi-vehicle traffic strategy at the intersection is simulated using software tools in Intelligent Transportation Simulation Platform,which proves its feasibility,stability and efficiency.Meanwhile,a field experiment is carried out on the microvehicle experimental platform to prove this strategy’s feasibility on different platforms. |
