Research on Torsional Vibration in Traction Drive System of High-speed Train

In high-speed train, since parts of driving medium are not fully rigid, it is common to have fluctuation of rotating speed in different sizes and phase leading to shaft torsional vibration in driving devices for kinds of reasons. Slight vibration can change the torsional stress on axis, which aggravate axial fatigue damage and decrease the service life, severe vibration may result in shaft damage, which have effect on operation security of the train. This paper firstly established two-mass model of drive system and got the transfer function, introduced the mechanism of torsional vibration through theoretical analysis, which proved that torsional vibration is a system stability problem. Then the author established the Simulink model of traction drive system, which proved unstable factor like speed step and load disturbance can result in shaft torsional vibration phenomenon. Finally analyzes influence parameters of vibration frequency and amplitude by simulation. Introduction Safety, comfort and quickness are usually the most concern issues for passenger in high-speed train. Traction motor drives load through driving device like gearbox, coupling and so on, for the rigidity of those devices are limited, elastic deformation will result in torsional vibration along the direction of rotation. When the excitation frequency is given or load disturbance is happened, device will storm energy and cause oppositely phased angular deflection. So the angular deflection between motor and load will be enlarged, which will cause shaft torsional vibration in drive system [1]. Torsional vibration originated from application of rolling mill, low-damping mechanical oscillator consists of the long axis and large inertia load, vibration caused by step-input and load disturbance will menace the integrity of system and lower the quality of each component [2, 3]. Torsional vibration may trigger other form of vibration, which will cover itself. Torsional vibration will be observed only when shaft failure because of fatigue accumulation. This paper mainly analyzes the mechanism and influence factors of torsional vibration of two-mass system through theoretical analysis and simulation. Mechanism Analysis of Torsional Vibration Actual system model can be equivalent to a two-mass system because it is not a rigid connection between traction motor and load, and elastic damping elements can be neglected for their rotational inertia are all small compared with full inertial load [4, 5]. So driving system can be simplified into a two-mass torsional vibration model as Fig. 1 based on following assumptions [6, 7]: (1) without concern the own vibration state of bearing and motor; (2) Without regard to efficiency of powerdriven transmission and gap of drive system; (3) Without regard to the elasticity of train axle, gear, gear shaft and so on; (4) Drive, driving elements are seen as lumped mass. 6th International Conference on Mechatronics, Materials, Biotechnology and Environment (ICMMBE 2016) © 2016. The authors Published by Atlantis Press 159