Research On Vehicle Speed And Obstacle Avoidance Method

As the future development direction of express delivery,the research of unmanned express delivery vehicles has caused wide attention,and under the influence of the epidemic,people have a better understanding of the use of unmanned express delivery.This thesis reviews the current domestic and foreign research status and development trends of unmanned express delivery vehicles and their technologies.In order to solve the problem of how to improve the distribution efficiency in the case of safe driving,the method of vehicle speed obstacle avoidance is researched in this thesis.Research on the process of identifying obstacles and mapping in the driving environment of express delivery vehicles.A 3D lidar with high detection accuracy is selected as the environmental sensing sensor,and an experiment platform for obstacle recognition and mapping is designed.The 3D lidar pitch angle is set to improve the data utilization rate,and the 3D data are filtered and projected to get the obstacle raster map.Finally,the point cloud is matched and processed at the back end.The conversion relationship between the lidar coordinate system corresponding to each frame of the point cloud is obtained,and the whole data is converted to a unified coordinate system to build a complete environmental obstacle grid map.In order to solve the problem of avoiding obstacles at appropriate speed during the driving of express delivery vehicles,an improved dynamic window method for vehicle rollover prevention is proposed in this thesis.Firstly,the kinematics model of the unmanned express delivery vehicle is established.The whole vehicle model is established in the Simulink/Carsim environment,and under the action of the same input signal(vehicle speed,front wheel steering angle),the established vehicle kinematics model is verified.Taking the lateral acceleration as the evaluation index of vehicle lateral stability,the lateral acceleration evaluation factor is added to the objective function of simulated trajectory evaluation,and a certain weight is assigned to it,so as to control the vehicle speed and steering angle.avoid side slip/rollover accidents in the steering process.Finally,the algorithm is simulated and verified by the grid map of environmental obstacles established in this thesis.The experimental results prove that the improved algorithm has the ability to prevent rollover and realizes the vehicle's speedy obstacle avoidance control.In order to solve the problem of planning trajectory tracking in the process of obstacle avoidance,a trajectory tracking controller based on model prediction is designed in this paper.By setting the objective function which takes the trajectory tracking deviation and incremental control quantity as the evaluation index,and in the vehicle kinematics and dynamics constraint conditions,according to the dynamic parameters of the express delivery vehicle,the control amount incremental constraint the limit speed,and the steering angle is constrained.Finally,a Simulink/Carsim joint simulation platform is built for simulation.The experimental results show that the controller designed in this paper has a better tracking ability.