Research On Lateral Stability Control Of Vehicle Under The Condition Of High-speed Emergency Braking

Vehicle emergency braking at high speed under extreme conditions,such as turning pavement with low adhesion or separated pavement,is prone to lateral stability problems such as yaw and sideslip.With the development of science and technology,electronic products and control technology have been widely used in automobiles,making the vehicle stability control system more and more mature,which greatly improves the lateral stability of vehicle braking process.However,most of the current stability control systems can play a role in the ordinary working conditions,and can not achieve the desired control effect for the limit braking conditions,such as the low-adhesion road steep turning braking conditions and the separation of high-speed emergency braking conditions.In order to improve the lateral stability of vehicle during high speed emergency braking and the deficiency of vehicle stability control system,an integrated controller based on sliding film variable structure AFS(Active Front Steering)control strategy and ESP(Electronic Stability Program)control strategy was designed.Firstly,this paper discusses the causes of vehicle instability,analyses the characteristics of yaw angular velocity and sideslip angle of mass center on vehicle stability,and introduces the methods to improve vehicle stability.The two-degree-of-freedom vehicle model is used as an ideal reference model to calculate the nominal value of control variables,and the lateral stability of vehicles under extreme conditions is analyzed.CarSim software is used to establish the vehicle dynamics model of each subsystem.Based on the control principle of traditional automobile electronic stability controller,the yaw angular velocity and sideslip angle of mass center are selected as control variables,and an automobile ESP controller is established by using adaptive fuzzy PID control method to control the lateral stability of automobile under high-speed emergency braking condition.Meanwhile,the actual yaw angular velocity and principle input to the vehicle are designed by using sliding film variable structure control principle.For the difference of yaw angular velocity,the output is an AFS controller with additional front wheel rotation angle.Secondly,the coordinated control strategy of ESP + AFS based on vehicle condition identification system is adopted to realize the coordinated control of vehicles,so as to achieve the purpose of controlling the lateral stability of vehicles.Finally,two kinds of limit braking conditions are selected,and the effectiveness of the controller is verified by the joint simulation with MATLAB/Simulink and Carsim.