Research On Platoon Driving And Fuel Consumption Characteristics Of Connected Autonomous Vehicles In Mixed Traffic Flow

With the development of economy and society,the rapid increase in the number of vehicles has brought convenience to people’s lives,but it also caused a series of problems such as traffic congestion,energy consumption and environmental pollution.Connected Autonomous Vehicles(CAVs)combine autonomous driving and V2V(Vehicle-to-vehicle)communication technology,which can coordinate with each other and drive synchronously with short spacing to form CAV platoons.CAV platoons are expected to increase road traffic capacity and reduce fuel consumption and emissions.Despite the rapid development in CAV technology,it will take a long time for the Market Pnenetration Rate(MPR)of CAVs to increase,so the mixed traffic flow consisting of CAVs and Human Driven Vehicles(HDVs)will exist for a long time.The traffic flow characteristics and vehicle fuel consumption characteristics will be affected by different MPRs of CAV.Investigating the traffic and fuel consumption characteristics of CAV platoon under mixed traffic flow and developing CAV platoon formation strategies have become hot issuesIn this dissertation,the fuel consumption characteristics and platoon formation of CAV is studied in depth from the following aspects:1.Research on transient fuel consumption model for hybrid electric vehicles(HEVs).The HEV fuel consumption model is usually adopted when modeling and simulating CAVs.First,the steady-state fuel consumption model of the engine was developed by using the engine bench test data.The steady-state fuel consumption model was modified to obtain the transient fuel consumption model based on the measured fuel consumption data under different driving cycles.And the transient fuel consumption model was verified by the Urban Dynamometer Driving Schedule(UDDS)and it was proved to be high accuracy.Then,for the operation of the internal combustion engine,the electric motor and the battery,a strategy for switching the power source according to the critical speed was proposed to obtain the energy consumption model of the HEV.Finally,the effect of driving factors on vehicle fuel consumption was quantified by the proposed fuel consumption model,such as road conditions(road gradient and wind speed)and traffic flow factors(congestion level).The results showed that HEVs can achieve better fuel savings in a variety of situations compared with conventional fuel vehicles,and as the critical speed of HEVs increases,the percentage of fuel savings can be up to 17.5%.2.Research on the impact of dedicated CAV lane on the traffic and fuel consumption characteristics of mixed traffic flow.First,the high-accuracy DivAer vehicle model developed at the Technical University of Munich was used to simulate the forces on different platoon sizes in the ambient airflow,and the relationship between platoon size and vehicle average air drag coefficient was obtained so as to any lyze the impact of platoon size on fuel efficiency.Then,a mixed CAV/HDV traffic flow model was constructed based on the cellular-automaton model to simulate three driving modes:Human-Driven Vehicle mode,Adaptive Cruise Control mode and Cooperated Adaptive Ccruise Control mode.And the traffic flow and fuel consumption characteristics under different lane function settings were investigated.In the scenario where CAVs and HD Vs can freely travel on all lanes,increasing the MPR of CAV can effectively increase traffic capacity,but in certain density zones it will cause additional fuel consumption.After setting up the dedicated CAV lane,the system’s traffic capacity was further improved,and the problem of high fuel consumption due to high CAV MPR was also solved.Compared with the free lane scenario,the percentage of fuel saving effect in the dedicated CAV lane with high CAV penetration is about 42.6%.3.Research on cooperative platoon forming strategy for CAVs in the same lane.Given the low penetration rate in the early stage of CAV development,setting up a dedicated CAV lane may cause a waste of road resources,so a novel cooperative platoon forming strategy for CAVs in the same lane is proposed.In this strategy,CAVs can coordinate their speed with each other through short-distance communication.When a CAV finds another CAV ahead in the same lane,it will send out a platoon formation request.And after the CAV ahead receives the request,it will slightly reduce speed for a period of time,allowing the following CAV to catch up and form a CAV platoon.Traffic flow simulation experiments showed that the cooperative platoon formation strategy can effectively promote more CAVs to form CAV platoons compared with the ad-hoc platoon formation strategy,thereby alleviating traffic congestion,improving traffic capacity,and reducing fuel consumption.The work of this dissertation is important for solving fuel economy problems of vehicles,and provide a theoretical basis for the setting of dedicated CAV lanes and the CAV platoon formation,which helps to achieve transportation efficiency optimization,energy saving and emission reduction.