联轴器不对中导致的车体振动研究
Car Body Vibration Analysis Subject to Coupling Misalignment in Traction System of Metro Vehicle

地铁车辆在牵引和制动阶段车体地板出现异常振动，严重影响了车辆乘坐舒适性，通过理论分析和线路试验，确定引起异常振动的原因并提出解决方案。采用短时傅里叶变换法分析试验数据，得出电机2倍转频为地板振动激扰源。建立了由电机轴、弹性联轴节和小齿轮轴组成的传动系统数学模型，说明了联轴节不对中效应下的电机和小齿轮之间的振动关系，推导出小齿轮轴空间力矩输出表达式，表明不对中效应将激起电机偶数倍转频振动，并以2倍转频振动能量最大，理论上解释了试验结果，指出减小联轴节不对中量可降低振动。减小联轴节不对中量后再次进行试验的结果表明，电机2倍转频振动显著降低，车体振动均方根值和幅值分别降低了41%和53%，车体振动减小到正常车辆水平，理论分析和试验测试结果得到相互验证。
The floor of a car body experiences an abnormal vibration when a metro accelerates and brakes, which significantly deteriorates riding comfort. Theoretical analysis and field experiments are conducted to study this abnormal vibration, with resolution promoted and validation measurements. The short-time Fourier transform (STFT) time-frequency method is applied to tested data. It shows that the excitation of the abnormal floor vibration comes from the twice frequency of motor rotation. A mathematical model consisting of the motor shaft and gear rotor connected by a coupler is built to study the rotary dynamics of the traction system of the railroad vehicle’s powered bogie. Analysis illustrates that the dynamics in the traction system experience a shaft misalignment between the motor shaft and gear rotor. The output torque of the gear rotor is obtained and shows that this misalignment can result in even frequencies oscillation of motor shaft rotation with the twice frequency dominated. The measurement is explained by the analysis, and it is shown that the abnormal vibration can be alleviated by eliminating this misalignment. Validation measurements are conducted after eliminating the misalignment and show that the twice frequency vibration of motor rotation dropp significantly, which reduces the root mean square and amplitude of acceleration of the car body floor by 41% and 53%, respectively. The measurements agree with the theoretical analysis, and a high level of riding comfort is obtained.