Research On Low-frequency Lateral Sway Of B₀-B₀ Locomotive

With the development of social economy,the proportion of medium and high-speed railway lines above 200km/h in China is increasing rapidly in the railway network,but it is mainly dominated by EMUs.The EMU is more suitable for high-speed railway networks and high-speed intercity traffic.For long-distance passenger transport across existing railway networks and high-speed networks,the mode of power-concentrated EMUs with speeds of160²00km/h is now receiving more and more attention.The power-concentrated EMU adopts the locomotive traction but has certain advantages in the operation mode of the fixed group of the passenger car.In order to realize the interconnection between the existing general speed railway line and the newly built high-speed railway line as soon as possible,a 200km/h B₀-B₀ eight-axle AC drive passenger electric locomotive has been developed in China.The eight-axle electric locomotive reflects the problem of lateral swaying after being put into actual operation.It shows that in the speed range of 130km/h²00km/h,there is always a low-frequency lateral sway of about 1Hz in the carbody,and the front and rear ends of the carbody have phase difference,which seriously affects ride comfort and vehicle safety.In order to solve the problem of low-frequency swaying,this paper establishes the locomotive dynamics model,the transmission relationship of low-frequency vibration of the vehicle is studied,the influence of equivalent conicity on low-frequency swaying is analyzed,the vibration characterisics of the vehicle system are analyzed by root locus method,the causes of low-frequency swaying are clarified,and the influence of key suspension parameters on low-frequency swaying is explored by combining the changes of vibration characteristics,locomotive stability and locomotive lateral vibration spectrum characteristics.Finally,the rectification measures are proposed.The main work and conclusions of this paper are as follows:1)The main characteristic of hunting is that its frequency increases with the increase of speed,and the self-vibration frequency of the carbody has nothing to do with the speed,so that at a certain speed segment,when the bogie hunting frequency is close to the self-vibration of the carbody,resonance will occur,which seriously deteriorates the vehicle's stability.The dynamics calculation also shows that there is a lateral vibration of about 1.3 Hz in wheelset,motor,frame and carbody,which means that the carbody and the bogie are coupled and swaying together when the low-frequency sway occurs.Combined with the modal analysis of the bogie and the carbody,the low-frequency swaying is carbody hunting.2)The influence of high conicity on low-frequency swaying is analyzed by introducing the measured wear tread.The results show that the higher equivalent conicity can significantly suppress low-frequency swaying.The effect of low conicity on low-frequency swaying is analyzed by reducing the rail cants.The results show that the lower equivalent conicity will induce more severe low-freqency swaying,and the calculation results under low conicity are in good agreement with the actual operation of the locomotive.In addition,the calculaitons show that the first wheelset can not effectively attenuate the transverse movement under low conicity,and the vehicle system appears carbody hunting instability.3)The root locus method is used to analyze the vibration characteristics of the vehicle system.The analysis results show that the hunting mode of the bogie and the inherent traverse mode of the carbody are coupled with each other.In the case of low conicity,the real part of the composite characteristic vibration of the“front bogie hunting and vehicle's roll and sawy”is no longer negative when the speed exceeds 150km/h,and the lack of coupling vibration damping is the main reason of low-frequency swaying.4)From the perspective of changing the vibration characteristics,the influence of the main suspension parameters on the“composite vibration”mode and the hunting mode of front bogie under the low conicity is analyzed.The results show that the smaller yaw damper installation angle,the smaller longitudinal positioning stiffness of axle box,the smaller motor damper damping,the smaller yaw damper damping and smaller second horizontal stiffness can increase damping ratio to varying degrees,and the acceleration and lateral stability of the carbody are reduced.The reduction of the installation angle of the yaw damper is most significant for the low-frequency swaying.The locomotive can be effectively rectified from three aspects:reducing the angle of yaw damper,reducing the longitudinal positioning stiffness of axle box and reducing the damping of motor damper,which can effectively suppress the coupling resonance between bogie hunting motion and carbody traverse motion,increasing the hunting motion stability of the front bogie.The results of nonlinear running performance showed that the locomotive dynamic performance can meet the requirements of safe operation after the comprehensive rectification.The results of field tests showed that the locomotive basically eliminates low-frequency lateral sway after the comprehensive rectification.