Study Of Adhesion Control Strategy Of Four-axle Electric Locomotive Using Axle Weight Transfer

With China’s western mountainous railroad mileage growing year by year,while driving the economic development of the west,the complex and diverse geological environment that the railroad passes through easily leads to a series of problems affecting the safety of railroad operation such as wheel idling,skidding,wheel-rail scraping and even derailment of rolling stock.In order to make the locomotive vehicles to be used efficiently and adapt to the complex and changing wheel-rail contact rail surface,this paper combines the operation characteristics of electric locomotive,and designs the limit adhesion control method which uses the axle weight transfer formed by the locomotive to control the motor torque output,so as to realize the optimal matching between the wheel-rail adhesion state and the traction motor output torque.Firstly,the creep-slip mechanism,adhesion characteristic curve and factors affecting the adhesion utilization are analyzed according to the wheel-rail adhesion contact theory,and it is concluded that the essence of optimal adhesion utilization is to restrain the most accident-prone wheels near the peak adhesion point.Under the consideration of the influence of the suspension system with nonlinear characteristics and the interaction force between the traction motor and the frame on the axle weight transfer of the locomotive,a dynamics model of a 25 t axle weight four-axle electric locomotive under creep conditions is constructed based on the Polach large longitudinal creep theory using the multi-body dynamics software SIMPACK;the traction transmission and adhesion control system of the locomotive is constructed in MATLAB/Simulink.The system mainly includes equivalent DC power supply,traction converter composed of IGBT components,inverter,adhesion control module and motor vector control speed control module,and the traction drive adhesion control system is combined with the locomotive dynamics model through SIMPACK-MATLAB joint simulation platform to form an electromechanical coupling dynamics model.Secondly,considering the actual operation process,the rolling stock will cause the axle weight transfer under the action of the hook force,thus affecting the effective play of the traction adhesion between the wheels and rails.Based on the electromechanical coupling dynamics model,the axle weight transfer process is analyzed by capturing the adhesion state of each wheel pair,and the axle weight transfer law is summarized to design an ultimate adhesion control method that uses the axle weight transfer of the locomotive to control the motor torque output,and by using the axle weight transfer of the locomotive to distribute the traction torque of the locomotive wheel pairs at different positions,the creep slip rate of the wheels is always kept near the peak adhesion point,which can realize the optimal adhesion utilization of the locomotive when pulling the train.The optimal adhesion utilization is achieved when the locomotive is pulling a train.Finally,the ultimate adhesion control method,which uses the axle weight transfer to control the motor torque,is applied to the joint simulation platform,and the passing capacity and axle weight transfer law of the locomotive under different gradient line conditions are verified;the operation of the locomotive is studied after the ultimate adhesion control method is applied,in which the traction efficiency of the locomotive is improved by 12.9% on the straight dry rail surface and 9.3% on the wet rail surface.As well as under the variable rail surface contact conditions,the locomotive can stably track the wheel-rail adhesion state and timely suppress the occurrence of wheel idling.The feasibility of the ultimate adhesion control method is verified.