Research On Vehicle Cooperative Merging Control Method At On-ramps In The Context Of Intelligent And Connected Vehicle Infrastructure

The merging area is a typical traffic congestion point where accidents frequently occur.The intelligent and connected vehicle infrastructure system realizes the dynamic and realtime information interaction between drivers,vehicles,roads and environment in a wide range and all-round way,which provides powerful technical support and guarantee for the vehicle cooperative control in the merging area.In order to systematically solve the problem of vehicle cooperative merging control,improve the traffic efficiency in the merging area,and realize safe,efficient and environmental friendly cooperative merging,this paper studies the systematic control architecture on different levels and the vehicle cooperative control methods from different perspectives.The main work includes the following aspects:(1)A hierarchical control architecture for vehicles cooperative merging in the merging area is designed by integrating different perspectives.This paper analyzes the characteristics and requirements of traffic control layer,vehicle upper layer and vehicle lower layer control from different perspectives,proposes a centralized-decentralized hierarchical cooperative control architecture,and systematically explains and verifies the control functions of different layers.(2)A cooperative game-based control strategy is proposed to achieve the global optimal merging sequence.From the perspective of roadside traffic management,aiming at minimizing the total cost of the merging area,a global optimal control problem is modeled based on cooperative multi-player games.By analyzing the scenario constraints in the merging area and the characteristics of the vehicle’s arrival time,multiplayer games can be decomposed into multiple two-player games,and the Pareto solution to multi-player cooperative game can be solved by the income matrix so as to determine the merging sequence.(3)Vehicle cooperative control strategy and method in weaving sections are proposed.Based on the analysis of the characteristics of the target road and terminal state of different types of vehicles in the weaving section,a cooperative classification control strategy for vehicles is proposed based on optimal control.The control process of on-ramp vehicles is divided into two parts: cooperative collision avoidance and cooperative merging,respectively.A lateral collision prediction algorithm by considering vehicle geometric characteristics is designed to predict vehicle collision avoidance terminal time.In the merging stage of on-ramp vehicles,a merging sequence model with safety constraints is proposed to determine the safe and effective merging terminal time.The intelligent driving car-following model(IDM)is used to predict the merging terminal state according to the upstream traffic flow state.The analytical solution to infinite time horizon optimal control problem with inactivated constraint is derived based on Pontryagin’s Minimum Principle.(4)A longitudinal and lateral cooperative motion trajectory planning method under activated constraint is proposed.The nonlinear vehicle kinematics model is linearized by means of the feedback linearization method.According to the terminal state requirements of the upper control information set,the longitudinal and lateral motion trajectory planning model aiming at optimizing fuel consumption and improving lateral comfort is presented.The analytical solutions to optimal control with activated and inactivated constraint are classified and solved.A calculation method of start-up time of lateral planning for collision avoidance is designed to determine the safe start-up time range of lateral trajectory planning.When the constraint is activated,the optimal "energy" control problem is transformed into the optimal "time-energy" problem.Based on the Pontryagin’s Minimum Principle,the optimal time and the allowable analytical solutions of the optimal control under different constraint activation states are derived.(5)A decoupled cooperative tracking control method considering vehicle dynamics is proposed.In view of the vehicle dynamics and nonlinear characteristics,the vehicle longitudinal and lateral control problems are decoupled into longitudinal speed tracking control and lateral trajectory tracking control.The vehicle longitudinal speed tracking control is controlled by PID controller.By reference to the theory of driving safety field,the index of driving safety risk and tracking error are used as the optimization objective function to avoid the collision and minimize the track error.A vehicle cooperative lateral tracking method based on decentralized nonlinear model predictive control is proposed,which realizes the safe and stable vehicle trajectory coordinated tracking.MATLAB simulation experiments have been conducted to verify the effectiveness of different layers of cooperative control methods from different perspectives.In order to validate the practicability and feasibility of the architecture and methods,a near real merging environment based on Car Sim/Simulink simulation is built.Under the influence of vehicle dynamics,nonlinearity and mechanical delay,the centralized decentralized hierarchical control architecture and cooperative control method proposed in this paper are systematically verified.The simulation results show that the hierarchical cooperative control architecture and methods can effectively improve the traffic efficiency,smooth the vehicle trajectory and reduce the fuel consumption in the merging area,as well as improving the driving comfort,and ensuring the safety and efficiency of vehicles merging.