Research On Lateral-Longitudinal Cooperative Control Method For Intelligent Driving Vehicles

Intelligent vehicle is a comprehensive product integrating multi-functional functions such as environment perception,decision planning,intelligent control and execution,and is also an essential part of constructing future urban intelligent transportation system.Among them,lateral-longitudinal cooperative control,as a key link for intelligent vehicles to realize autonomous driving,mainly regulates the speed,steering,braking and other parameters of vehicles to enable them to run safely and smoothly under complex road conditions.This paper addresses the issues of trajectory tracking accuracy and speed tracking stability in complex operating conditions.Considering the intelligent vehicle as a multi-input-multi-output nonlinear time-varying system that is susceptible to external disturbances,solutions are proposed for the lateral control,longitudinal control,and lateral-longitudinal coupled control of the vehicle.The main contents of the work are as follows:(1)Establish the vehicle system model.It takes into account vehicle kinematics,lateral and longitudinal dynamics,and tire characteristics,to provide a model basis for the subsequent controller design and simulation.(2)Design the lateral controller based on the combination of far and near points.Aiming at the trajectory tracking accuracy in the lateral control process,the far and near point control modules are designed respectively by using the pre-scanning following theory and LQR control method.The far and near point controllers calculate the respective desired turning angles and output the optimal front wheel turning angle in a weighted summation.Among them,the near-point controller is designed based on vehicle dynamics to build a trajectory tracking model,and the lateral controller is designed using a linear quadratic optimal control algorithm,while feedforward control is introduced to compensate for the system steady-state error.The far-point controller is designed based on the pre-targeting following model,and the desired front wheel rotation angle is solved based on the “minimum error principle”.(3)The longitudinal controller design uses a hierarchical structure to solve the speed tracking problem.Firstly,the upper controller is designed using finite state machine to solve for the desired acceleration;then,the lower controller uses PI control method based on acceleration feedback to control the throttle or brake to achieve desired speed tracking;finally,the effectiveness of the longitudinal controller is verified using software simulation.(4)Design the lateral-longitudinal cooperative control system and perform experimental verification.Considering the complexity of the vehicle operating environment,separate transverse or longitudinal control cannot meet the needs,speed is chosen as the entry point to couple lateral motion with longitudinal motion to establish the intelligent vehicle cooperative control system.Meanwhile,the proposed lateral-longitudinal cooperative control algorithm is verified using both simulation and real vehicle testing under different operating conditions.