| Tractor semi-trailer is an important vehicle in the field of transportation.Compared with other modes of transportation,it has the unique advantages of fast,flexible and so on.However,due to its large load capacity,large size,high centroid when fully loaded,special structure and other characteristics,it is easy to cause traffic accidents when driving on low adhesion road under the limit conditions,resulting in huge personal and property losses,and the lateral instability is the main cause of the accident.Therefore,the research on the lateral stability of tractor semi-trailer is of great significance to ensure the safety of transportation and people’s life and property,and can provide a good theoretical basis for the research and development and improvement of safety technology of tractor semitrailer.Based on the summary and analysis of the research and application of the lateral stability control and active yaw moment of the tractor semi-trailer at home and abroad,this paper studies a method of using the active yaw moment of the semi-trailer to improve the lateral stability of the full vehicle under the limit condition of low adhesion road.In this paper,a coordinated control strategy of hub motor electronic differential and mechanical braking is proposed.Hub motors are added to the wheels on both sides of the semi-trailer,and the active yaw moment generated by differential drive and differential braking is used to improve the lateral stability of the tractor semi-trailer.The effectiveness of the proposed method is verified by the co-simulation of Truck Sim and MATLAB/Simulink.The results show that the proposed cooperative control strategy achieves good control effect under the limit condition of low adhesion road,and the control effect is further improved compared with the traditional differential braking.This paper mainly focuses on the following aspects:(1)The research status of tractor semi-trailer lateral stability control and active yaw moment at home and abroad is summarized,and the research enlightenment is obtained,and the advantages and feasibility of the proposed control method are analyzed.(2)This paper analyzes the configuration of the tractor semi-trailer and the advantages of differential braking and hub motor drive.Based on the vehicle dynamics simulation software Truck Sim,the whole vehicle model of nonlinear tractor semi-trailer is established,and the actual running state of the vehicle is output.The linear four degree of freedom monorail reference model is established by Matlab/Simulink,and the ideal value of vehicle operation is output.The hub motor is selected and modeled.(3)In this paper,the method of controlling the lateral stability of semitrailer train and generating active yaw moment is studied.The yaw rate of tractor and trailer is taken as control variable.The upper controller adopts fuzzy PID control,takes the yaw rate deviation and deviation change rate of tractor and semi-trailer as input,and outputs the required active yaw moment of tractor and semi-trailer;The lower controller is the torque distributor.Two torque distribution methods of differential braking and cooperative control are studied.According to the target wheel drive/brake rules and torque distribution rules,the drive/brake torque of each wheel is output;The tractor generates active yaw moment by differential braking,and hub motors are installed on both sides of semi-trailer wheels,the driving/braking torque of the hub motor and the differential braking of the mechanical braking system are coordinated to generate the active yaw moment.In order to prevent the wheels from locking,the slip ratio of each wheel is controlled in the optimal range.(4)The Truck Sim/Simulink co-simulation platform was built.Under the condition of low adhesion road and full load of semi-trailer,the co-simulation was carried out under three typical working conditions of double lane shifting,fishhook and steering wheel angle step.The simulation results show that the proposed control strategy can effectively reduce the values of lateral stability parameters such as yaw rate,sideslip angle,articulation angle,roll angle and lateral acceleration when the tractor semi-trailer is running on the low adhesion road.It can not only effectively restrain the occurrence of lateral instability such as sideslip and folding,but also improve the roll stability to a certain extent.The results show that the control effect of the cooperative control is better than that of the traditional differential braking control,and it can improve the lateral stability of the tractor semi-trailer on the low adhesion road more effectively. |
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