| The tractor-trailer consists is a combination of a tractor and a multi-section non-driving trailer through a rigid connection.With its large load,high efficiency and low cost,it plays an important role in China’s freight logistics industry.The tractor-trailer consists has problems such as simple connection mode and long body length,which leads to problems such as large turning radius and irregular track when the train goes straight.At the same time,due to unstable factors such as load and trailer parameters,the whole train is turned.Dangerous situations such as folding,appendix,and snake-shaped swing may occur in the middle,which may affect its safe use.Therefore,it is necessary to optimize the trajectory of the tractor-trailer consists to maintain the stability of the trailer train during steering.This paper combines the evaluation criteria of various types of steering stability,and selects various evaluation indicators that can accurately reflect the yaw stability and lateral motion characteristics of the steering train.Through the virtual modeling method,the multi-rigid body dynamics model of the tractor-trailer consists is established,and the vehicle test and virtual simulation are carried out to verify the accuracy of the model.Through the steady-state rotation test and the corner step test of the trailer system with different steering modes,the effects of the two modes of the trailer axle steering and the steering wheel steering on the steering stability of the vehicle are compared.Development and optimization strategy for wheel steering mode with better controllability and steering.The paper analyzes the influence of the structural parameters of the whole train on the steering stability of the tractor during the steering.Using the experimental optimization design theory,the ADAMS/Insight design test is used to perform two-level sensitivity analysis on multiple primary variables.The six parameters with large impact factors were selected as design variables,and a comprehensive model of trailer train steering stability score was established.The response surface test design was designed and the response surface model was fitted.The model is optimized by genetic algorithm to find the optimal matching of the hard point coordinates of the structural parameters.It is found that the parameters are optimized by this method,the distance between the connection point and the front axle of the tractor is appropriately reduced,the distance between the front axle of the trailer and the rear axle of the tractor is reduced.The results show that the offset distance is reduced by 22.8% after optimizing the structural parameters.The lateral acceleration and yaw rate of the tractor were reduced by 42.7% and 13.8%,respectively,and the trailers were 36.9% and 19.1%.Steering characteristics changed from oversteer to neutral.The control stability is improved to a certain extent,but it is difficult to eliminate the yaw action of trailer carriage during steering,and the stability of yaw and track are difficult to be guaranteed.Therefore,the control of the track of tractor-trailer consists is selected to ensure the stability.Based on the mathematical analysis of the multi-degree-of-freedom vehicle steering model and the description of the vehicle steering characteristics by mathematical expression,the formula for controlling the steering Angle of the trailer and the difference of steering angular velocity of the front axle of the tractor is derived.Based on joint simulation of ADAMS&Simulink,a Proportion Integration and Differentiation(PID)fuzzy control closed-loop feedback control system with the ratio of rear axle’s Angle to front axle was established.Based on the proportional control algorithm,the wheel Angle of the trailer steering shaft is controlled in real time.The results show that the migration distance can be reduced by up to 92.7% after the control strategy is added through the control track tracking method.The peak values,such as lateral acceleration and inclination Angle of the carriage,were reduced under various working conditions without significant fluctuations,and the lateral stability of the whole vehicle was significantly improved. |
