Research On Optimal Control Method Of Vehicles At Unsignalized Intersections Based On Cooperative Vehicle Infrastructure System

As an important part of intersections,unsignalized intersections mainly exist in urban branch roads and small streets.Because there are no restrictions of traffic signal lights,unsignalized intersections have become the multiple areas of traffic problems such as traffic safety and traffic jams.Therefore,the research on finding a safe and efficient traffic method of vehicles at unsignalized intersections has become one of the hotspots of urban road traffic research at home and abroad.As a new type of traffic environment,Cooperative Vehicle Infrastructure System(CVIS)connects pedestrians,vehicles and roads as an integral whole based on real-time information exchange between vehicles and vehicles and between vehicles and roads,and provide a solution for the safe and efficient driving of vehicles at unsignalized intersections.In this paper,the unsignalized intersection is taken as the research object.Aiming at the problem of vehicle driving safety and efficiency,combined with the Cooperative Vehicle Infrastructure System and the control theory of unsignalized intersections,an optimal control method for vehicles at unsignalized intersections is proposed,taking the overall travel time of the traffic flow through unsignalized intersections as the optimization objective.Specific research contents are as follows:Firstly,the optimal control scenario of unsignalized intersections under Cooperative Vehicle Infrastructure environment is built,and optimal control strategies of vehicles at unsignalized intersections are proposed,including:(1)Coordinating strategy of opposite traffic flow based on speed guidance.By collecting the speed and position data of vehicles,this strategy analyzes the conflict relationship of traffic flows in different directions at the intersection,and develops the appropriate control strategy for the following vehicle to pass the intersection.(2)The strategy of following the same direction of traffic flow based on the SVS idea.Based on the analysis of the "supply and demand" relationship between the change of the distance between the neighboring vehicles and the change of the critical safety distance demand of the rear vehicle,the SVS safe distance discrimination model is proposed to judge whether the rear vehicle could obtain the right of way and develop the corresponding control strategy.(3)Vehicle sequencing strategy based on dynamic programming-CPS.This strategy combines the idea of dynamic programming and CPS algorithm to determine the order of right of way allocation by comparing the travel time of different schemes.Secondly,based on the vehicles optimization control strategy proposed in the previous paper,according to the behavior characteristics of vehicles in the actual traffic environment,combined with the greedy algorithm,taking the shortest travel time as the objective function,the Greedy-like algorithm is proposed and the optimization control model of unsignalized intersections is established.In addition,an unsignalized intersection of Dezheng Road-Municipal Government Central Road in Dezhou City is selected as the optimization scenario to solve the optimization control model of unsignalized intersections,proving the effectiveness of the optimization control model of unsignalized intersections and the optimization effect of the Greedy-like algorithm.Finally,based on VISSIM and Matlab,the co-simulation of unsignalized intersections under Cooperative Vehicle Infrastructure environment is designed.The total travel time,average travel time,average number of stops and average speed are taken as evaluation parameters,and compared with the traditional control mode of unsignalized intersections,different traffic flow parameters are set for simulation.The results prove that the optimal control method of unsignalized intersection proposed in this paper is correct and feasible.