| The construction of an intelligent connected transportation system brings changes in automatic driving technology,traffic environment,management and control technology and other factors.The transportation system presents the mixed coexistence of connected and autonomous vehicle(CAV)and human-driven vehicle(HV),and new traffic behavior characteristics have emerged on the whole.Facing the development trend of CAV and HV hybrid coexistence,focusing on the dynamic coupling characteristics of single lane networked hybrid vehicles,following the physical law that "force is the reason for changing the motion state of objects",this paper makes an in-depth study on HV car following,CAV car following,CAV queue formation and control,and speed optimization of networked hybrid vehicle clusters.The specific contents include:(1)In order to make up for the defect that the traditional car following model ignores the difference between the driver’s psychological characteristics and the acceleration and deceleration performance of the vehicle itself,the similarity between the vehicle following behavior and the motion of inert molecules is analyzed from the perspective of molecular dynamics,and a sub car following model is established based on Lennard-Jones potential function,The model can better explain the driver’s asymmetry in the process of following cars at different distances and acceleration and deceleration.The numerical simulation results show that under the molecular car following model,the acceleration of vehicle acceleration and deceleration is not fixed,but the sensitivity to the deceleration of the leading vehicle is stronger than that of acceleration,and the sensitivity to the acceleration / deceleration of close distance is stronger than that of long-distance acceleration / deceleration.The simulation results can be better analyzed from the interaction between molecules.Compared with the classical OV model,the model fits the measured data better and can describe the driver’s car following characteristics more accurately.(2)In order to systematically describe the safety risks faced by CAV during driving,a safety potential field model including lane line potential field,road boundary potential field and vehicle action potential field is established.In the process of establishing the model,aiming at the defect that the existing vehicle potential field function has the independent segmentation of the expression of gravity and repulsion,a unified vehicle interaction potential field function based on Lennard-Jones potential is established by referring to the interaction relationship between molecules,and the acceleration parameters of the front vehicle are introduced,The change of acceleration directly affects the distribution of vehicle action potential field,which can effectively reflect the dynamic change trend of vehicle safety potential field under different operating states.The safety potential field model is applied to CAV car following behavior decision-making.The model parameters are calibrated through Shanghai natural driving data set.Compared with the existing classical IDM and VTH models,the model has a smoother response curve in different traffic scenes to improve car following safety and efficiency,and the effectiveness of the model is verified.(3)Aiming at CAV with different spatial distribution,how to maintain CAV formation and queue without any collision,a queue formation and control strategy combining graph theory and security potential field theory is proposed.Graph theory is used to describe the information topology between CAV and plan the trajectory in the process of queue formation.At the same time,the safety potential field is used to characterize the driving risk of vehicles in the process of queue formation,and a 4-step strategy for the whole process is formulated to realize the initial formation and maintenance of the queue.The effectiveness of the strategy is verified by designing three different CAV distribution scenarios.The simulation results show that the strategy can merge the vehicles distributed in different lanes into the lane where the leading vehicle is located according to the information between vehicles in a short time without collision.In addition,by introducing multi front vehicle acceleration information,CAV queue has significantly improved traffic safety and efficiency compared with two typical VTH and IDM methods.(4)In the process of CAV queue tracking and controlling the output results of the upper controller,it will be affected by factors such as vehicle dynamics,communication delay and external interference,which will reduce the accuracy and stability of queue tracking control.In view of this,an adaptive robust controller is designed.The driving and braking switching strategy is designed through the reasonable vehicle longitudinal dynamics model and inverse dynamics model.The adaptive term is added to the controller,and the robustness condition of the controller is solved by using Lyapunov stability theory.Simulation results show that compared with robust control method and linear quadratic optimal control method,this method can not only accurately track the expected value of the upper controller,but also greatly reduce the impact of communication delay on the performance of the controller,and has better anti-interference and robustness.(5)In order to reduce the traffic oscillation of expressway,a speed coordinated control strategy of single lane hybrid vehicle cluster based on running track is proposed.Using the information collected by the road test traffic sensor,combined with the wave speed of the traffic wave and the driver’s reaction time,offset and modify the CAV track in the downstream vehicle cluster to predict the running track of the tail vehicle HV,and plan the speed distribution of the first CAV in the upstream vehicle cluster at different time points according to the predicted track,Guide CAV to suppress the propagation of speed oscillation by changing speed in a small range for a long time instead of a large range for a short time,so that the upstream CAV vehicle cluster can gradually merge into the downstream vehicle flow at a more reasonable and smooth speed.The numerical simulation results show that within the designed CAV permeability of 0% ～25% and the starting position of the bottleneck of 575 m ～ 975 m,the higher the permeability,the farther the starting position of the bottleneck and the smoother the speed guidance curve selected by the CAV,the stronger the inhibition of speed oscillation.At the same time,it is proved that the speed coordinated control strategy can effectively reduce the fluctuation of traffic flow,Improve driver comfort and overall traffic efficiency of vehicle queue. |
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