Research On Decision Making And Trajectory Planning Of Connected Autonomous Vehicles(CAV)Merging In Acceleration Lane Area

The merging area of expressway ramp is one of the main bottlenecks of expressway due to complex geometric linearity,frequent forced lane change and various driving behaviors.On the whole,connected autonomous vehicles(CAV)are expected to bring substantial improvement to ramp merging,which can partially or completely eliminate the uncertainty of human driving and reduce traffic conflicts and collisions.It is of great significance for the safety and operation efficiency of expressways in the future to construct a merging control strategy for vehicles in the on-ramp area in mixed traffic flow.In this study,firstly,the specific characteristics of subject vehicle in four different combination scenarios formed main line leading vehicles and following vehicles are analyzed.Based on two-person non-zero-sum incomplete information static game model and two-person non-zero-sum complete information static game model,the subject vehicle takes safety,lanechanging urgency and comfort as payoff functions,the following vehicle takes safety,driving efficiency and comfort as payoff functions respectively,and then the combined lane-changing decision-making model is established in different combination scenarios.In order to ensure the equilibrium solution of the model and the rationality of decision-making,a lane-changing penalty term is introduced into the game model established in the scene when the leading vehicle is CAV.Secondly,according to the merging subject position and driving state of the target vehicle,the merging trajectory is planned for the subject vehicle based on the quintic polynomial model.Linear trajectory planning models are established according to the possible driving behavior of the leading vehicle(uniform speed,acceleration,first acceleration and then uniform speed)and the possible driving behavior of the following vehicle(uniform speed,deceleration,first deceleration and then uniform speed)in different scenarios.Trajectory planning is also carried out for the first vehicle behind the following vehicle and the first vehicle in front of the leading vehicle participating in the merging.Then,a standard research scenario consisting of five vehicles participating in merging in the on-ramp area is constructed by using the Freeway C data set in City Sim.Based on the lanechanging decision-making and trajectory planning model,considering the constraints of minimum safe distance,maximum acceleration and lane-changing duration,this paper explores the merging decision-making ability of the target vehicle in four different combination scenarios when the distance between the leading vehicle and the following vehicle is decreasing by 10%of the effective distance,and effective distance between vehicles after merging.Finally,the effective distance between the leading vehicle and the following vehicle on the main line decreases by 40% as the research scenario.And the collision time,speed standard deviation and safety distance ratio are used to evaluate the safety of the target vehicle in four different vehicle combination scenarios.It is found that when there are CAV on the main line,the merging possibility of the subject vehicles can be effectively improved.Especially when the leading vehicle is CAV,proper acceleration to increase the merging gap without affecting the safety will effectively improve the merging capacity of the subject vehicle and the overall safety of the ramp area.This study can provide theoretical basis for the algorithm structure of CAV and highway safety management in the future.