Obstacle Avoidance And Lane Change Trajectory Planning And Tracking For 4WS Vehicle Research

With the continuous development and popularization of intelligent vehicle technology,obstacle avoidance lane change trajectory planning and trajectory tracking control have become the academic hotspots now.Trajectory planning enables intelligent vehicles to achieve safe,efficient and comfortable obstacle avoidance in different traffic scenarios,which is of great value for reducing traffic safety accidents and improving vehicle riding comfort and driving safety.In the field of obstacle avoidance lane change trajectory planning,most algorithms consider factors such as obstacle avoidance and lane change efficiency,safety and comfort,and few people consider lateral stability factors.In the field of obstacle avoidance lane change trajectory tracking,most of the research is focused on front.wheel steering vehicles,and there is a lack of research related to four.wheel steering vehicles.Therefore,in view of the above two problems,this thesis constructs a four.wheel steering vehicle model,based on the quadratic programming algorithm,and adds the lateral stability factor of the vehicle without skidding to the algorithm to optimize the obstacle avoidance lane change trajectory.The four.wheel steering vehicle tracks the optimized obstacle avoidance trajectory to achieve the purpose of obstacle avoidance safety and stable lane change.The main work of this thesis is as follows:1.Four.wheel steering dynamics modelA two.degree.of.freedom four.wheel steering lateral dynamics model was constructed.A four.wheel steering model with proportional steering of the front and rear wheels is established.In the case of angular step,the stability comparison with the front.wheel steering vehicle proves the advantages of the four.wheel steering vehicle.Lay the foundation for follow.up control research.2.Research on obstacle avoidance lane change trajectory planning algorithmThe dynamic programming method is used to solve the safe obstacle avoidance and lane change decision trajectory curve,and expand the discrete convex space through the decision trajectory curve.By analyzing the lateral acceleration threshold of the vehicle without skidding,the maximum curvature threshold is derived.In the constraints of the quadratic programming algorithm,the curvature constraint that prevents the vehicle from skidding is added.In the convex space,the quadratic programming algorithm containing curvature constraint is used to optimize the decision trajectory.In the end,the goal of safety and stability of the planned trajectory was achieved.3.Research on obstacle avoidance and lane change trajectory tracking controlThe trajectory tracking is decoupled,and the longitudinal tracking and lateral tracking of the four.wheel steering vehicle are controlled separately.The LQR algorithm is used to control the lateral movement,and the algorithm controls the longitudinal movement.Build a simple trajectory planner to verify the effectiveness of the tracking controller.Lay the foundation for obstacle avoidance lane change simulation.4.Simulation experiment of obstacle avoidance and lane changing conditionsTwo obstacle avoidance conditions,low.speed static obstacle and high.speed dynamic obstacle,are set to verify the effectiveness of the obstacle avoidance and lane change trajectory planning algorithm.The performance of four.wheel steering vehicles and front.wheel steering vehicles in trajectory tracking was compared and analyzed.Experimental results show that the trajectory optimization algorithm designed in this paper can effectively avoid vehicle sideslip and realize safe obstacle avoidance and lane change.The four.wheel steering tracking controller has good tracking ability at low speeds,and the tracking accuracy decreases at high speeds,but the vehical stability is improved.