Research On Active Obstacle Avoidance Control Of Vehicle

With the continuous increase in the number of automobiles in China,the number of automobile accidents is also increasing.In order to reduce the occurrence of accidents and improve driving safety,automobile active obstacle avoidance control system has become a hot topic of research.In this thesis,active obstacle avoidance based on longitudinal braking and steering lane-changing is studied,which has certain theoretical value and practical significance.First,the overall plan of the vehicle’s active obstacle avoidance control system was designed,the function and structure of each component were determined,and the decisionmaking mechanism for different obstacle avoidance methods of the control system was designed.In the research of the longitudinal braking obstacle avoidance control system,firstly,vehicle longitudinal dynamic system was established by CarSim—the dynamic simulation software,and the vehicle longitudinal inverse engine model and inverse braking system model were established in Matlab/Simulink.Based on the analysis of the braking process,factors such as the road adhesion coefficient,self-vehicle speed,the acceleration of the preceding vehicle were comprehensively considered.The safety distance model was proposed,and three typical motion conditions of the front vehicle were analyzed,such as typical static condition,uniform motion condition and emergency braking condition.Finally,in the controller design,a twolayer control method was adopted.The LQR control strategy was used by the upper layer to determine the desired acceleration,and PID control was used by the lower layer.The strategy tracked the expected acceleration determined by the upper layer to achieve the expected deceleration and to maintain the distance between vehicles.In the research of the steering lane-changing obstacle avoidance control system,a threedegree-of-freedom vehicle dynamics model and a tire magic formula model were designed,and the fifth-degree polynomial lane-changing trajectory was designed and combined with the minimum longitudinal lane-changing distance,a steering lane-changing safety distance model was proposed.In this model,the safety of lane change was judged according to the given lane change trajectory and the distance between the two vehicles.The model predictive control was selected to avoid obstacles in the steering lane change,and the basic vehicle dynamics model was approximated and linearized to improve the real-time performance of the algorithm.Various constraints under the vehicle steering lane change were designed to ensure the stability of the vehicle steering lane change.Finally,based on the CarSim and Matlab/Simulink simulation platform,joint simulation verification was conducted in this thesis.In the longitudinal braking and obstacle avoidance,three typical motion conditions of the vehicle ahead were set up,including typical static conditions,constant speed motion conditions and emergency braking conditions.The results all showed that the vehicle could successfully avoid obstacles under different road adhesion coefficients and driving conditions,and the effect was better than the comparison algorithm,which proved the effectiveness of the longitudinal braking obstacle avoidance control system.In steering lane-changing obstacle avoidance,the vehicle could realize steering lane-changing obstacle avoidance in a smaller distance,and could follow the interfering vehicles with relatively low speed in the target lane,which proved the effectiveness of the steering lanechanging obstacle avoidance control system.