Research On Path Planning And Motion Control Algorithm For Unmanned Vehicles On Structured Roads

Path planning and motion control,as the key technologies to realize autonomous driving of unmanned cars,have always been the focus of research in the field of unmanned technology.This paper focuses on the path planning and motion control algorithm of unmanned vehicles on structured road.The main contents of the paper are as follows:(1)In order to meet the requirements of the safety,real-time and smoothness of the obstacle avoidance of the driverless car,a local path planning algorithm based on discrete optimization is proposed.Aiming at the randomness problem of moving obstacles,a safety cost function of moving obstacles based on motion estimation combined with Gaussian convolution is designed to solve the problem of dynamic obstacle avoidance of unmanned vehicles.A new coordinate transformation calculation method is used to transform candidate path from the - coordinate system to geodetic coordinate system,which improves the real-time performance of the algorithm.The joint simulation of PreScan and Matlab/Simulink on different structured road environments and different speeds was carried out,which laid a foundation for the subsequent real vehicle experiment.(2)A hierarchical longitudinal controller is designed,in which the upper cont roller is PID control,while the lower controller uses inverse model analysis to calculate the throttle opening and braking force,and the switching rules of throttle and braking are designed.PreScan and Matlab/Simulink co-simulation were used to verify the velocity following effect of the longitudinal controller.In order to solve the problem that the traditional Pure Pursuit algorithm is difficult to guarantee the robustness and accuracy when tracking the path with variable curvature,an improved adaptiv e presighting Pure tracking control algorithm is proposed.According to the vehicle velocity and the degree of bending of the reference path,the fuzzy control method is used to determine the preview distance according to the driving experience.Then,the front wheel Angle control is calculated by Pure Pursuit algorithm.The joint simulation results of PreScan and Matlab/Simulink show that the proposed control algorithm has better control precision than the traditional Pure Pursuit algorithm.(3)Finally,in order to verify the feasibility and effectiveness of the above proposed algorithm in real vehicle application,the control software of the unmanned vehicle experimental platform was written in the C++ language with Qt Creator under Ubuntu operating system,and the obstacle avoidance path planning experiment and path tracking control experiment of unmanned cars were carried out.The experimental results show that the local path planning algorithm proposed in this paper can guide the unmanned vehicle to complete the avoidance of stationary obstacles and moving obstacles in real time,and the path tracking control algorithm can realize the path tracking control with high accuracy.