Analysis Of Stability And Fundamental Diagram Of Mixed Traffic Flow Of Connected And Automated Vehicles Considering Time Delay

With the development of Internet of Vehicles technology and the popularization of connected and automated vehicles(CAVs),the traffic flow on the road will be transformed into a mixed traffic flow composed of CAVs and human driven vehicles(HDVs)for a long period of time in the future.Since the driving behavior of CAVs is quite different from HDVs,its applications will have a certain impact on the original traffic flow.Then it may result in the changes of characteristics of such mixed traffic flow such as stability,fundamental diagram(FD),safety,etc.compared with the original traffic flow.In order to clarify such changes in traffic flow characteristics after the applications of CAVs,this paper draws on the existing research methods,and on the basis of which considers more comprehensive influencing factors,studies the stability and FD of such mixed traffic flow.In terms of stability research,the paper takes into considerations of both vehicle’s time delay and functional degradations of the CAVs when following the HDVs,which is regarded as the starting point and innovation point.And derive the linear string stability condition which consists of percentages of CAVs,vehicle’s time delay and tree different types of vehicles for mixed traffic flow.On this basis,the impacts of CAVs percentages,vehicle’s time delay and vehicle’s function degradations on stability are analyzed.The results show that the CAVs can enhance the stability while the vehicle’s time delay and the functional degradations of the CAVs have a destructive effect on the stability.In terms of FD research,the thesis takes into account the vehicle’s time delay,the functional degradations of CAVs and the platooning intensity at the same time as the starting point and innovation point,and derives the FD model of mixed traffic flow in equilibrium state.On this basis,the influencing factors of maximum flow of mixed traffic flow and optimal density are analyzed.The results show that: 1)the CAVs and platooning intensity can improve the maximum flow and optimal density of the mixed traffic flow;2)the vehicle’s time delay has a negative effect on both;3)the free flow speed has a positive effect on the maximum flow,but a negative effect on the optimal density;4)The minimum safety distance has a negative effect on both.Finally,by constructing the same scenario as the theoretical analysis in the SUMO software,the stability and the analysis conclusion of the FD were simulated and verified.Stability simulation results show that the direction of the influence of CAVs and vehicle’s time delay on stability is consistent with the theoretical analysis.The FD simulation results show that the simulated flow-density scatter points obtained in each situation are in high agreement with the corresponding theoretical curves,which proves the correctness of the theoretical model.The above-mentioned research results are conducive to the exploration of urban traffic signal adaptive control systems in the Internet of Vehicles environment,and further promote the intelligentization of urban traffic system management and control,and lay a theoretical foundation for future urban traffic signal control.