Study On Key Dynamics Problem Of Urban Low Floor Light Railway Vehicles

In order to alleviate the urban traffic congestion and environmental pollution problems,the requirement for the urban rail transit as the backbone is gradually increasing.Low-floor light rail vehicles are usually used in the urban ground rail transit for the convenience of passengers getting on and off.However,low-floor vehicle bogies are usually matched with the independently rotating wheelsets(IRW).Due to the poor steering performance of the IRWs,leading to the serious wheel flange wear and excessive curve squeal noise,urban light rail low floor trains are facing three major dynamic problems: steering,wear and noise.In this paper,these three major dynamic problems will be studied in depth and the specific research work is as follows:(1)The dynamic model of urban low-floor light rail vehicle system considering the coupling between vehicles,vehicle/track and electromechanical is established.For the fivemodule low-floor light rail train,the force analysis of the IRW,frame and carbody are carried out respectively,especially emphasizing on the coupling effect of joints on the carbody so that the system dynamics model of the train is established.According to the prospective characteristics of the driving mode of the permanent magnet synchronous direct drive wheel motor,a current vector control model of electromechanical coupling is established.Aiming at the characteristics of the embedded track,the rail is considered as the Timoshenko beam with the continuous elastic foundation,and the vehicle/track dynamic coupling model is established.The above three coupling models together constitute the complete urban light rail low-floor train system dynamic model.(2)The guidance problem of light rail vehicles is studied.The steering mechanisms of the traditional wheelset and the IRW are analyzed specifically,and the root causes of the poor steering performance of the IRW are expounded.Based on the dynamic model of light rail train coupling system,the advantages and disadvantages of different steering control methods for IRW are analyzed,and what’s more,a differential control strategy based on the track centerline and the radial line is proposed.Through the simulation analysis,this control method can effectively improve the steering performance of the IRW on various radius curves.(3)The wear problem of light rail vehicles is studied.The wheel-rail multi-point contact wear model for the embedded grooved rail is established.Combined with the above dynamic model of the light rail train coupling system,the modified Contact algorithm and Archard wear model are adopted to calculate the wear of the traditional wheelset and IRW,and analyzed their wear characteristics.Through the simulation analysis,the differential control method of the IRW proposed in this paper can significantly reduce the wheel-rail wear.(4)The squeal noise problem of light rail vehicles is studied.The prediction model of wheel-rail squeal noise is established.Combined with the dynamic model of the light rail train coupling system,the frequency response characteristics of the wheel and the rail are calculated.The internal causes of the squeal noise generated by the traditional wheelset and IRW passing during the curve period are analyzed.Through the simulation analysis,the differential control method of the IRW proposed in this paper can significantly reduce the squeal noise through the curve.