Hybrid dynamic modeling and analysis of the electric vehicle planetary gear system

In this study, a hybrid model is proposed for the flexible helical planetary gear by coupling the lumped-parameter dynamic models for the sun and planets, and reduced FEMs (finite element models) for the ring and carrier. To consider the planet centrifugal forces, the formula for planet acceleration is newly derived. Moreover, a method is also proposed to include centrifugal, inertia, and Coriolis forces in the reduced FEM of the carrier which possesses rigid rotating motion, so that the model is applicable to high-speed operations. The meshing points vary in the circumference direction in the condensed ring model. The translational and angular displacements (including the rigid and vibration displacements) are chosen as the generalized coordinates. The time-variant meshing stiffness and profile error excitation directly vary with the gear angular displacements. Thus, the proposed model can also be used for the variable-speed process. Considering the structure details, the FEM of the electric motor is also constructed to obtain the motor torque. Electromechanical dynamic analysis is conducted for the planetary gear of electric vehicles during stable and variable speed processes, and some improvement methods are proposed, investigated and evaluated.