Study On The Algorithm Of High-speed Automatic Lane Change For Autonomous Vehicles

As one of the most basic driving behaviors,huge safety hazards may also be caused by the unreasonable lane changing,especially when driving on highways,which may even cause serious traffic accidents to occur,therefore,research on the automatic lane change or auxiliary lane change function of autonomous vehicles is extremely significant for reducing the incidence of traffic accidents.At present,automatic lane changes of autonomous vehicles are mainly divided into free lane change and emergency lane change,expressway becomes its main application scenario,existing research mainly focuses on emergency steering and collision avoidance in expressway scenarios,and relatively little attention has been paid to free lane changes.Therefore,for highway driving scenarios,without considering emergency collision avoidance,a design frame of automatic lane changing algorithms is proposed for autonomous vehicles in this paper.First of all,how to send safe and reliable lane change commands for autonomous vehicles in highway scenes is the technical basis for the realization of autonomous vehicles.Considering that the slow of the vehicle in front is the main reason that induces the vehicle to change lanes,and combined with the main research scene of this paper is the highway scene,an automatic lane change intention generator based on driving dissatisfaction is designed.In terms of lane change feasibility recognition,the existing theory based on the minimum safety distance does not consider the deceleration of the rear vehicle in the target lane,on this basis,a lane change safety recognition model with hierarchical minimum lane change safety distance is proposed,the model considers the impact of lane change on the driver of the rear vehicle,therefore,the lane change process will be smoother and the impact on the rear vehicle of the target lane will be smaller.In terms of target lane selection,the behavior of lane change will interfere with the normal operation of the upstream traffic flow of the target lane,the target lane selector is designed based on the maximum safe average speed of vehicles in the target lane within a certain range.Then,for the problem of lane change path planning and tracking control for high-speed autonomous vehicles,how to plan a smooth and feasible driving path in the dynamic environment is a key link for implementing lane change of autonomous vehicles.A seventh-degree polynomial reference path is adopted based on the analysis and comparison of the fifth-degree polynomial and the seventh-degree polynomial.In terms of high-speed path tracking control,designing an efficient,stable and reliable vehicle motion controller is the ultimate goal for realizing the lane change of autonomous vehicles,feedforward + PID feedback and LQR path tracking controllers are designed respectively in this paper.Aiming at the stability of the vehicles during driving,taking the linear two-degree-of-freedom vehicle model as a reference model,simultaneously considering that the yaw rate and the side-slip angle of the vehicle are constrained by the road friction,the ideal yaw rate and the ideal side-slip angle of the vehicle are computed,and on this basis,a direct yaw-moment stability controller is designed based on PID theory,and the effectiveness of the controller is verified by simulation.Finally,the simulation of the entire lane-changing function is completed by using the Car Sim and Simulink joint simulation platform.