Research On Steering Safety Of Tractor Semitrailers At Low Speeds

In recent years,there have been increasing numbers of traffic accidents involving tractor semitrailer colliding with crushing road facilities or pedestrians during low-speed turning maneuvers.There are two main factors that contribute to this type of accident: one is the long length of the semitrailer body and the un-adjustable angle of the rearview mirror of the tractor,which leads to a significant blind zone in the driver’s vision;the other is the lateral error between the trajectory of the semitrailer wheels and the front axle wheels of the tractor.In response to the safety issue of low-speed turning for tractor semitrailer,this paper takes a six-axle tractor semitrailer as the research object,studies the adjustable rearview mirror based on the hinge angle between the tractor and the semitrailer,designs an active steering controller for the semitrailer wheels based on PSO-LQR,and explores the effects of semitrailer wheel steering and rearview mirror angle adjustment on the driver’s blind zone in a tractor semitrailer.The main research content and conclusions of the paper are as follows:(1)Study on the corner adjustment system of rearview mirrors for tractor semitrailer.Based on the description of the rearview mirror field of view for tractor semitrailer,the blind zone in the field of view of tractor semitrailer were analyzed.The overall scheme and control logic of the rearview mirror adjustment system were formulated.The relationship between the corner of the left and right rearview mirrors of the tractor semitrailer and the hinge angle between the tractor and the semitrailer was respectively established,and the hinge angle threshold for initiating the rotation of the left and right rearview mirrors was obtained.The impact of rearview mirror corner adjustment on the blind zone of the tractor semitrailer was examined through simulation experiments.The research showed that when the rearview mirror corner follows the hinge angle to turn,the blind zone of the tractor semitrailer can be effectively reduced.(2)Study on semitrailer steering and trajectory deviation of tractor semitrailer.By analyzing the force and kinematics of tractor semitrailer,a dynamic model of tractor semitrailer trailer steering was established.The dynamic model of the tractor semitrailer was verified based on the Truck Sim software.The target path tracking the center of the semitrailer’s rear axle was established,and the lateral error between the trajectory of the tractor’s front axle and the trajectory of the semitrailer’s rear axle was studied.Based on the virtual wheel steering angle of the center of the semitrailer’s rear axle,the allocation relationship of the steering angle of the left and right wheels on the three rear axles of the semitrailer was established.The research showed that the dynamic model of the tractor semitrailer was effective and could be used for the subsequent design and research of low-speed steering trajectory tracking controllers.(3)Study on low-speed steering control of tractor semitrailer.Based on the lateral error between the front axle trajectory of the tractor and the rear axle trajectory of the semitrailer,as well as the heading angle error between the tractor and the semitrailer,a low-speed trajectory tracking controller based on LQR was designed.The weight matrix in the LQR controller was optimized using the particle swarm optimization algorithm PSO.In order to dynamically adjust the weight matrix,the path curvature information was used as a feedforward compensation for the LQR controller,and the "curvature feedforward-PSO-LQR" controller was designed.The performance of the designed controllers was simulated and verified under several typical paths,while also examining the impact of mirror angle adjustment on blind zone in the field of view under semitrailer rear-wheel steering conditions.The study showed that the optimized active steering controller for the semitrailer not only improved the semitrailer’s ability to track the tractor’s trajectory,reduced the hinge angle between the tractor and the semitrailer,but also significantly reduced the lateral forces acting on the semitrailer’s wheels.Active rear-wheel steering can effectively reduce the problem of internal blind zone caused by excessive mirror angle adjustment.The study explores the design of adjustable mirrors for tractor semitrailer,the design of lowspeed steering controllers for semitrailers,and the impact of mirror adjustment and semitrailer wheel steering on blind zone in the field of view for tractor semitrailer drivers.It provides theoretical guidance and technical reference for the study of low-speed steering safety issues for tractor semitrailer.