Research On Lateral Stability Of Semi Trucktrain Based On Differential Braking Andactive Steering Control

Due to its complex structural characteristics and changeable driving environment,semi-trailer train is prone to some traffic accidents,such as tail slashing,folding and roll-over,etc,and these dangerous accidents are mainly caused by the lateral instability of the vehicle.Therefore,the semi-trailer train model with two axles of tractor and three axles of trailer was taken as the research object in this paper.Through the co-simulation of Simulink and Trucksim,the differential braking control and active steering control of trailer were carried out to improve the lateral stability of semi-trailer train.The research work of this paper was mainly carried out from the following aspects:⑴ Set up the model of semi-trailer train.According to the dynamic analysis of the yaw and roll model of the semitrailer train,the five degrees of freedom simplified model and three degrees of freedom simplified model were obtained,and a semi-trailer train model of the same model was built with Trucksim;the parameter identification of the simplified model was completed by data curve fitting and genetic algorithm;the dynamic responses of the simplified model and the Trucksim model were compared under double line shifting conditions.The comparison results show that the established simplified model and the identified parameters are reliable,which can provide a model basis for further research.⑵ Determine the safety level of the vehicle.The change of each state quantity from stable to unstable condition of semi-trailer train was analyzed and the weight of each state quantity was determined;K-means clustering analysis was used to obtain the safety grade and parameter values of semitrailer trains;the online judgment module of safety level of semitrailer train was set up.⑶ Study on Differential Braking of Semi Truck Train.An additional yaw stabilization torque generator was designed based on MPC control theory.Brake torque distribution rules was made and the size of brake torque is calculated;Security level identification control module is built.The simulation was carried out under the condition of double line shift and angular step.The simulation results show that the proposed differential braking controller reduces the peak yaw velocity response of the tractor by 38.5% under the double-line shift condition,and by 61.5% under the first-level safety control condition.Under the angular step condition,the stability of the semitrailer train is effectively improved from roll-instability control to stable running.⑷ Study on Active Steering of Semi Truck Trailer.Based on LQR control theory,the generator of middle axle of trailer was designed.According to the principle of the same tire side force,the rotation Angle of other tires of the trailer was allocated.Particle Swarm Optimization(PSO)algorithm was used to optimize the Q matrix coefficient in LQR control.The simulation was carried out under the condition of double line shifting.The simulation results show that the designed active steering controller can reduce the peak value of side slip angle response of the trailer’s centroid by 66.7%,and the reduction reaches 83.3% after particle swarm optimization,which can effectively improve the lateral stability of the semitrailer train.