Research On Emergency Steering Collision Avoidance Control Method For Distributed Four-wheel Independent Drive And Independent Steering Electric Vehicle

Human is the most unstable factor in the road traffic component,so the irregular operation of human is a major factor in traffic accidents.In order to avoid traffic accidents caused by human factors,advanced driver assistance system(ADAS)with emergency collision avoidance technology has gradually become the focus of autonomous driving research.Distributed four wheels independent driving and independent steering electric vehicles because of its simple structure,less than a lot of traditional car transmission mechanism,can make the four wheels independent driving and independent steering characteristics,very suitable for intelligent driving carrier.Due to the characteristics of distributed four wheels independently driving and independently steering electric vehicles and the characteristics of emergency steering collision avoidance,it is necessary to select the steering mode of the vehicle and design the stability controller.Therefore,this paper selects distributed four wheels independently driven and independently steering electric vehicle as the research object,and takes steering mode,stability control and emergency steering collision avoidance strategy as the research content.In this paper,after investigating the steering mode of distributed four wheels independently driven and independently steering electric vehicles and the characteristics of emergency steering to avoid collision,three main steering modes are designed,and the stability controller that can meet all driving modes is designed.Due to the lateral displacement requirements of vehicles in emergency steering to avoid collision,this paper designed three basic steering modes,front wheel steering,proportional steering and wedge steering,based on distributed four wheels independently driven and independently steering electric vehicles.In order to prevent the disturbance to the steering mode,a stability controller based on the optimal control theory of Linear Quadratic regulator(LQR)with additional yaw moment as the control quantity was designed.The additional yaw moment is generated by the driving torque of the left and right rear wheels of the vehicle.After investigating the research status of emergency collision avoidance,this paper designs an emergency collision avoidance strategy based on distributed four wheels independently driven and independently steering electric vehicles,including emergency steering collision avoidance decision planning and path tracking.First by five times polynomial designed a series of alternative paths,and then through the establishment of the weighted values of cost function to evaluate alternative routes to the generation of the path of least value to the desired travel path,finally through the equivalent amount of steering wheel Angle to control,design of model predictive controller to realize the vehicle path tracking function.In order to verify the performance of the emergency steering obstacle avoidance strategy,software co-simulation based on Matlab/Simulink and Car Sim and hardwarein-the-loop testing based on DSP controller,NI real-time controller and other hardware are carried out.Two basic working conditions of emergency steering obstacle avoidance with single obstacle and multiple obstacles are designed,and the three steering modes of vehicles are tested at medium speed and high speed respectively.The results show that the planned path is efficient and reasonable.Three driving modes can achieve emergency collision avoidance,the effect is different;Proportional steering with control is optimal for medium speed and wedge-shaped steering with stability control is optimal for medium and high speed.