Research On Key Technologies Of Connected And Automated Vehicles Platoon Control In Expressway Environment

In the field of connected and automated vehicles,the platoon control technology has received extensive attention in the research field due to its safety,stability and efficiency.When vehicles are driving in platonn,the characteristics of low spacing and high following stability can reduce the air resistance and improve the space utilization rate.Thereby,the platoon can greatly improving the road traffic capacity,improving the efficiency of traffic,avoiding traffic congestion and reducing fuel consumption,which plays a positive role in the energy and economy of the entire society.Due to the relatively simple traffic environment,the high traffic efficiency and the large traffic flow,freeways will become an ideal application scenario for the connected automated vehicle platoon control technology.However,in the actual development and application of this technology,the external disturbance factors such as vehicle-to-vehicle communication delay and platoon merging have brought certain challenges to the operational safety,stability and overall operational efficiency of the platoon.In response to the problems above,this thesis starts with communication delay and platoon merging,which can affect the operation performance at the same time,and builds the "Minimum Safe Distance Modeling under Communication Delay-Constructing a Platonn Control Method Considering Stability and Security-Platoon Merging Sequence Optimization Based on Cooperative Game-Horizontal and Vertical Control Method of Platoon Merging Process" technical route.The main innovative work includes the following aspects:(1)Aiming at the safety problem of connected and automated vehicle platoons caused by communication delay,a minimum safe distance model of platoon based on communication delay is proposed.DSRC communication protocol is taken as the basis of inter-vehicle communication,and the maximum communication delay of DSRC under normal conditions is obtained through the field test and analysis and calculation of the packet loss of the communication protocol.At the same time,the error caused by the mechanical response delay of the vehicle is considered,by establishing the minimum safe distance model based on the communication delay,the acceptable standard of the minimum safe distance of platoon under the DSRC communication protocol is determined,and the simulation experiment verifies the reliability of the minimum safety distance under different motion states.(2)For the string stability requirements of CAV platoon under the condition of communication delay,a platoon control method under multiple constraints is proposed.By using the Udwadia-Kalaba method,the dynamic model of the vehicle under Lagrangian mechanics is established,and the multi-vehicle dynamic system is got.The equality constraints and bilateral inequality constraints,including the minimum safe distance constraint proposed by the previous research,are incorporated into the dynamic system.The former part ensures that the gap error between the current platoon state and the final state converges to zero,and the latter part makes the distance between vehicles is limited to an appropriate range and cannot be lower than the minimum safe distance during the whole process.The differential homeomorphism method is applied to release the inequality constraints by transforming the bounded state into an unbounded state,so that the control strategy of inequality constraints can be used,and the performance of the proposed control strategy is verified by Lyapunov stability theory and simulation experiments.(3)In order to meet the strategy level sequence planning requirements in the process of platoon merging,a cooperative game-based optimization method of expressway vehicle platoon merging sequence is proposed.Aiming at the platoon merging problem caused by the reduction of the number of lanes,the game method is used to maximize the merging efficiency,and the game between platoons is transformed into the game problem between multiple two vehicles.The minimum cost determining the optimal merging sequence,and allowing vehicles to reach the merging point through the proposed platoon control method.It is verified by simulation experiments that the optimization method can effectively reduce the overall energy consumption of the system and improve passenger comfort.(4)To make the management and control requirements of the control layer in the process of vehicle platoon merging,a trajectory planning method for vehicle lane change cooperative control is suggested.Based on the previous work,which using the combined sequence optimization method to determine the vehicle sequence,applying the acceleration in the platoon control algorithm proposed by the previous study,and introducing a sine function,a dynamic lane-changing trajectory planning model is established to make the trajectory smooth,increase the vehicle’s agility and improve passenger comfort in the process of lane change.The feasibility and effectiveness of the trajectory planning method are verified by simulation experiments.(5)In view of the application capability analysis requirements of the method proposed in this study for the real traffic environment,the thesis constructs a numerical simulation environment of heterogeneous traffic flow,and tests the traffic shock propagation suppression capability of the longitudinal and merging control of platoon.Through simulation experiments,the effectiveness of vehicle queuing in improving the stability of traffic flow is verified under different penetration rates of CAVs,and the effectiveness of the new platoon control algorithm for the speed disturbance attenuation in traffic flow is also verified.This thesis analyzes and verifies the longitudinal and merging control characteristics of the CAVs platoon in the highway environment through progressive researches.The results show that the expressway vehicle platoon control methods can take advantage of the cooperative control characteristics of connected and automated vehicles,improve the stability of traffic flow,optimize vehicle trajectories,and improve traffic efficiency and safety.