Multi-articulated Road Train Path Tracking With Articulated Disc Variable Damping Control Research

With the accelerating urbanization process and the rapid growth of urban population,as a new urban public transportation,road trains have become the focus of development in recent years by virtue of their high carrying capacity,high transportation efficiency and low operating costs.The coupling effect of multiple carriages and multiple hydraulic articulation devices is likely to cause large turning radius,poor following effect of towing carriages,and decrease in the stability of the whole vehicle,which will lead to major accidents.This paper takes a threearticulated four-car road train as the research object,and improves the vehicle driving stability and road adaptability by improving the trailing carriage following effect and reducing the turning radius,and carries out the following work.1)Vehicle dynamics model building.Firstly,according to the working characteristics of the road train model and the articulated device,the vehicle driving force is described and analyzed by the formula method and the graphical method;secondly,the SAE tire coordinate system and the Pacejka magic formula are used to establish the wheel coordinate system and the tire mathematical model;according to the idealized assumption of the basic maneuvering model of the vehicle motion and the vehicle coordinate system,the single-track linear six degrees of freedom of the road train is established Finally,the vehicle dynamics equations and the articulated moment equations of the road train are derived by means of D’Alembert’s theorem and Newton’s second law.The model is built to reserve the basic theory for the establishment of target path,carriage fuzzy PID controller and variable damping articulation controller later on.2)Vehicle simulation model establishment.Firstly,UM Input software is used to establish a multi-body simulation model of the whole vehicle of the road train;secondly,UM Simulation software is used to establish the vehicle power system,steering system and test environment;finally,the evaluation indexes of the simulation test are selected with reference to the main evaluation methods at home and abroad.This part of work prepares the model for the subsequent control strategy verification.3)The articulated road train path tracking control strategy and articulated disc variable damping control strategy are proposed.The system includes a target path generator based on interpolation method,a trajectory following controller based on fuzzy PID algorithm and a variable damping articulating disc controller based on logic threshold method.Among them,the target path generator introduces three input variables: lateral velocity of the leading point,longitudinal velocity of the carriage center of mass and transverse sway angle value of the carriage,and uses the above variables to establish the target path of each carriage of the road train.The controller introduces two input variables: the longitudinal speed of the vehicle and the speed of the articulated disc to control the damping output value under different conditions.4)Joint simulation and strategy validation.The Simulink control strategy model is compiled and imported into UM Simulation software for joint simulation;the road train path tracking control strategy is verified under transient response test,steady-state circumferential test,single shift line test and snake test road conditions based on GB/T 6323-2014 and GB/T25979-2010.The test results show that: during the driving process of the vehicle in the above road conditions,each carriage basically follows the path of the previous car for stable driving,without obvious rear amplification effect.The relative maximum error of the trajectory between carriages is less than 0.09 m,and the maximum error of the trajectory between the head car and the tail car is less than 0.1m,the RWA value is close to 1,and the turning radius of the vehicle drops from 30 m to 15 m.In summary,compared with the uncontrolled state,the trajectory following ability of each carriage is greatly improved and the turning radius is effectively reduced.When the vehicle driving state is changed,the transverse angular velocity,lateral velocity and articulated disc angle of each carriage can reach the stable state within a short time,and the peak value of each parameter is significantly reduced and the fluctuation problem is solved.