Investigation on dynamic characteristics of high-speed EMUs gearboxes under coupling of internal and external excitations

As the structural foundation of gear transmission systems, the dynamic behavior of the gearbox is critical to the operational reliability of high-speed trains. In this study, an electromechanical rigid-flexible coupled multibody dynamic model of a high-speed electric multiple units is developed, incorporating vector-controlled induction motors and accounting for the elastic deformation of the flexible gearbox housing. The dynamic characteristics of the gearbox are analyzed under three types of excitations: gear meshing excitation, wheel-rail excitation (including track irregularities and wheel polygonization), and harmonic torque excitation from the motor. Results indicate that gear meshing excitation mainly contributes to vertical and longitudinal housing vibrations; harmonic torque excitation predominantly occurs at six times the fundamental electrical frequency; track irregularities based on WuGuang spectrum data excite the first-order mode of the housing, inducing resonance; and 10th to 20th order wheel polygonization causes significant vertical vibration of the housing. Further analysis under coupled excitations quantifies the vibration contribution ratios of each source, showing that wheel-rail excitation dominates the housing vibration, while the effects of gear meshing and harmonic torque excitations are relatively minor.