Stability Characterization Method And Influencing Factor Simulation Analysis Of Connected And Autonomous Mixed Platoon

Platoon stability is one of the key points to analyze the mechanism of vehicle interaction which is significant to enhance traffic control performance,with huge value on theoretical research and practical application.Recently,the vigorous development of connected and autonomous vehicles technology has gradually made connected and autonomous vehicle a reality.Multiple vehicle types may exist at the same time and form a mixed platoon,which raises new questions for stability research while brings opportunities for improving stability of the platoon.In this context,understanding stability characteristics of the mixed platoon and its characterization method in a connected environment is of great significance for making a better road traffic environment in the future.The mixed platoon is composed of human drive platoons and connected and autonomous platoons,which both have an important impact on the stability of the mixed platoon.Therefore,the stability of these two platoons is analyzed,based on which,the stability and its characterization of the mixed platoon are studied,and factors affecting stability are discussed.First,the stability of human drive platoon is characterized and analyzed based on the car following model.The stability conditions based on the general form of traditional human drive vehicle(HDV)and connected human drive vehicle(CHDV)combined with transfer function theory are derived.And the calibrated intelligent driver model are selected to describe human driving behavior.Accordingy,this thesis characterizes the stability domain of HDV and CHDV platoon,investigates and compares their stability.The results reflect that the CHDV platoon has better traffic stability than the HDV platoon.Second,the car following model of autonomous vehicles are constructed and the stability of the connected and autonomous platoon are analyzed.Considering that the constant time headway is inefficiency and easily leads to the instability of traffic flow,this thesis selects variable time headways combined with sliding mode control method to construct adaptive cruise control(ACC)car following model in the non-connected environment and cooperative adaptive cruise control(CACC)car following model in the connected environment,then its stability domain is characterized.Then,model parameters are determined,and simulation experiments are used to analyze safety and stability of the two platoons.The results show that both the two platoons can maintain stability under disturbances,and ensure a safety distance between vehicles under emergency braking.Also,the CACC platoon performs better than the ACC platoon in terms of stability.Third,on the basis of the aforementioned model and stability analysis,characteristics of the vehicles in the mixed platoon are studied,and proportion estimation method of each mode of the vehicle in the mixed platoon is derived.Then,the stability domains of the local mixed platoon and the overall mixed platoon are characterized and analyzed respectively.It can be concluded that stability of the mixed platoon is related to proportion of vehicles under different modes,vehicle spacing strategy and speed of the platoon.Furthermore,the stability region boundary can be accurately determined through analytical conditions and characterization methods.Finally,in order to figure out factors affecting stability of the mixed platoon,several numerical simulation experiments are designed in Matlab,which verifies the theoretical analysis and stability characterization results above.