Study On Integrated Control Of Vehicle EPS And LKS System

EPS(Electric Power Steering)compared with the traditional hydraulic power steering,it has the advantages of energy saving,environmental protection and compact structure.EPS has been widely used in vehicles.The lightweight steering and sense of keeping the road feeling become the driver's demand for EPS system.As one of the safety systems of vehicles,LKS(Lane Keeping Assistance System)can remind the driver when the vehicle deviates from the lane and assist the steering,which greatly reduces the traffic accidents caused by the lane deviation of the driver unconsciously.The actuator of the LKS system is the power motor of the EPS system,and the vehicle equipped with EPS and LKS system controls the power motor according to the vehicle deviation when driving.This paper studies the power assist control before lane departure to avoid the lane departure caused by driver's wrong operation due to road adhesion,as well as when the LKS system starts and the passive auxiliary steering system after lane departure.The details are as follows:(1)The dynamics of EPS system is analyzed and the dynamics model is established in Matlab/Simulink.The vehicle model is established based on Carsim software,and the power-assisted characteristic curve suitable for this subject is designed.(2)A method is proposed to estimate the road adhesion coefficient based on vehicle lateral dynamics characteristics.A fuzzy sliding mode variable structure power control method based on road adhesion coefficient is designed and simulated.(3)The joint decision-making method of TLC and DLC is adopted to determine the power-assisted mode or lane keeping mode.A Passive assisted steering control strategy based on improved potential field function is proposed and simulated.(4)The hardware-in-the-loop is built to verify that the fuzzy sliding mode power control strategy based on road adhesion coefficient can better maintain the road sense of the driver under different road adhesion coefficient,and the designed coordinated control strategy can effectively switch between the two systems and timely assist the driver to correct steering.