Lane Keeping Algorithm And Stability Control For In-wheel Motors Electric Vehicle Based On Finite Time Control

Driving safety is always the primary factor for automobile design.As an intelligent active security system,lane keeping assist system(LKA)has become one of the hotspots in the field of automobile research.When the car is driving,the environment condition is complex,the road may be bend or straight,and the quality of the lane lines identified by camera may not be good.In lane departure warning(LDW)algorithm,low complexity and high accuracy are difficult to get at the same time.The existing algorithms can’t simultaneously get high accuracy and real-time performance.When the lane line quality is poor,the effect of lane keeping will decline because of the lack of reasonable measures.In addition,when vehicle is running at high speed,active corrective action by lane keeping actuator may cause the car to lose its stability.In order to solve these problems,based on previous studies,a lane keeping algorithm and driving stability control algorithm of four-wheel-independent-drive electric vehicle(4WID-EV)is studied in this paper.The main research contents are as follows:(1)In order to solve the problem that high accuracy and real-time performance are difficult to get at the same time,two different algorithms are proposed to deal with straight lane line and curved lane line respectively.If the lane line is straight,the “deviation judgment line method” is used.If the lane line is curved,the "time to lane crossing method" is used to make early warning decision for lane departure.(2)In order to solve the problem that lane keeping effect decline when the quality of lane line is not good,two different algorithms are used to deal with the detected lane lines with different quality.When the detected lane line is in good condition,the trajectory offset is calculated by the “preview trajectory planning method”.When the detected lane line is not good,the offset of the trajectory is calculated by the "offset superposition method".(3)In order to solve the problem of many disturbances and the poor real time performance during vehicle driving,a LKA controller based on nonsmooth finite time(No S-FT)control is designed.This controller has stronger convergence and anti-interference performance.The control effect of lane keeping is more timely and effective.(4)In order to solve the problem of vehicle’s instability due to the active corrective action by lane keeping actuator,a vehicle stabilization No S-FT controller is designed.The controller output the direct yaw moment(DYM)and the active front wheel steering(AFS)acting on the vehicle body to maintain the driving stability.Then the optimal distribution of the DYM between four wheels is carried out.(5)The simulation verification is carried out for the designed algorithm.First,the validity of the LKA algorithm and stability control is verified separately in the Simulink environment.Then the Prescan/Carsim/Simulink co-simulation platform is built,and the simulation is carried out to verify the comprehensive effect of the algorithm in a more realistic environment.The simulation results show that the designed algorithm can keep the car in the roadway safely,and the control effect is timely and accurate.When the actuator is corrected for direction,the car is still stable and has good anti-interference performance.