Research On Ttrajectory Planning And Stability Control Of Vehicle Active Collision Avoidance System

Active collision avoidance system can effectively reduce the driver's labor intensity and driving complexity,and improve the safety,comfort and traffic efficiency of high-speed driving.Based on the active steering system,this paper focuses on the trajectory planning and stability tracking control of active collision avoidance vehicles.The main contents of this paper are as follows:Firstly,the vehicle dynamics model,vehicle kinematics model,driver model,tire model andactive front wheel steering system model,which mainly includes steering wheel and steering axle coupling model,double-row planetary gear system model,steering motor model and gear rack model,are built.It lays the foundation for trajectory planning and stability control of active collision avoidance system.Secondly,the minimum safe distance model,critical steering distance model and lateral safe distance model are built.The strategy,which is to plan the trajectory in segments,is used and the lane-change trajectory cluster is planned with the help of five-degree polynomial.By analyzing the critical collision conditions for potentially dangerous points when vehicles change lanes,critical conditions for comfortable operation of vehicles and physical limits of vehicles,and discussing the dynamic constraints,kinematics constraints and dynamic optimization objectives of the trajectory planning system,the optimal collision avoidance trajectory can be obtained.Finally,the stability control strategy of the active collision avoidance system is designed.Aiming at the problems of excessive control output and contradictory stability and tracking performance of H_?hybrid sensitivity control method under some conditions,the extension control idea is introduced into H_?hybrid sensitivity control.The H_?/extension control method,combining the advantages of H_?hybrid sensitivity control and extension control is proposed and the stability tracking control strategy of collision avoidance system based on H_?/extension control method is designed.The validity of the designed control strategy is verified under various conditions.The simulation results show that the proposed strategy of planning trajectory can effectively avoid the obstacles,which are conventional driving or have a sudden change in lateral position.The stability control strategy based on H_?/extension control can achieve the desired effect with the smallest control output on the premise of guaranteeing stability.The research results of this paper can provide a theoretical basis for the design and development of active collision avoidance system of vehicle.