Path Planning And Tracking Under The Condition Of Emergency Collision Avoidance

The rapid development of automobile industry in more than a century has brought great convenience to people's work and life,but also caused serious traffic safety problems.With the increasing emphasis on traffic safety,maj or automobile enterprises and universities all over the world have invested in the research of active vehicle safety technology to improve the driving safety of vehicles.Vehicle collision avoidance system can effectively reduce the occurrence of traffic accidents,so it has quickly become a research hotspot in the field of active safety technology.In view of the fact that the casualty rate of expressway in China is much higher than that of ordinary highways,the study on the emergency collision avoidance condition of expressway is particularly urgent and of more practical significance.In this paper,three existing active collision avoidance methods are studied,and combined with high-speed emergency collision avoidance and other extreme working conditions,the vehicle is determined to avoid obstacles by means of braking and steering combined with collision avoidance.The focus of this paper is to study the path planning and tracking of the emergency collision avoidance system.Considering that road adhesion coefficient has a great influence on collision avoidance path and tracking control effect,this paper estimates road adhesion coefficient online by using Unscented Kalman Filter algorithmFirst,the magic tire model and linear tire model are established.On the basis,a nonlinear vehicle model is established,which is simplified and linearized to obtain a linear vehicle model.The point mass vehicle model is established according to kinematics.Secondly,Unscented Kalman Filter algorithm is studied,and the road adhesion coefficient is estimated by combining with the discrete nonlinear vehicle model.Thirdly,the non-uniform b-spline curve is used to construct the collision avoidance path model.Generate collision avoidance path cluster according to scene information in emergency collision avoidance condition;The obj ective function of passenger comfort index was constructed,and the constraint of anti-sideslip and road adhesion coefficient were added to optimize the collision avoidance path of passenger comfort.Finally,the vehicle longitudinal speed is tracked by PID controller.The linear vehicle model is used to design the model predictive controller,and the front wheel Angle is controlled to track the collision avoidance path.In order to ensure the stability of the vehicle when avoiding collision,the centroid side Angle constraint was added to the model prediction controller,and the road adhesion condition constraint was added according to the road conditionSimulink and Carsim simulation were used to verify the feasibility of the active collision avoidance algorithm.The simulation results show that the path planning algorithm and the path tracking algorithm proposed in this paper can complete the collision avoidance task under the condition of high-speed emergency collision avoidance,and improve the comfort of the passengers and ensure the stability of the vehicle.