Research On Braking Stability Control Of Tractor-semitrailer Based On Exhaust Brake

The increase of highway mileage has promoted the development of road transport.Compared with transportation modes of the truck,the tractor-semitrailer,with characteristics of drop and pull transport,zone transport and roll-on roll-off transport,has become the most important means of road transport,the braking stability of which has attracted people's attention.In order to make the tractor-semitrailer have a good braking performance,continuous braking devices should be installed on the vehicle to share the braking load.But continuous braking devices only apply to driving wheels of the tractor,and change the original braking force distribution,which are likely to make braking stability worse and especially result in spins,folds,rollovers and other dangerous situations during turning braking.Based on the exhaust brake condition,the tractor-semitrailer dynamic model is established in this paper and the braking stability of the model is studied by simulation.The main research contents are as follows:Firstly,through a research of various continuous braking technology theory and a comparative analysis of performance,the exhaust brake technology is selected as a continuous braking system for the vehicle.According to the needs of the study,a reasonable vehicle coordinate system and freedom degree are selected,and a 10-DOF dynamic model of the tractor-semitrailer is established considering air pressure hysteresis characteristics of the service brake,which lays a theoretical foundation for the establishment of the simulation model.Secondly,the dynamic model of the tractor-semitrailer is built with MATLAB/Simulink simulation software,including the vehicle movement model,the slip angle model,the wheel movement model,the slip rate model,the main brake model and the exhaust brake model.Based on the dynamic model,the service brake alone simulation and the service brake and the exhaust brake joint simulation are carried out;the brake speed,the yaw rate and lateral acceleration of the tractor,the yaw rate and lateral acceleration of the semi-trailer,the folding angle and so on are exported;a comparison of the braking stability under two different operating conditions is made.Finally,according to braking instability conditions,a control strategy of the differential brake is designed,with which the longitudinal force of the vehicle is changed to provide additional yaw moment,so the vehicle movement attitude is changed and the lane tracking ability and the braking stability are improved.A slip rate fuzzy control strategy is used to make the vehicle maximize the use of the ground attachment condition to ensure the optimal yaw moment control.The effect of the control strategy is verified by turning braking simulation under high and low adhesion coefficient road surface conditions,and the main braking instability forms of the tractor-semitrailer under different adhesion coefficient road surface conditions are contrastively analyzed.This paper is of great significance to the study on braking stability of the united braking system on the tractor-semitrailer,and it provides favorable support for the development of the vehicle stability control system.