Dynamic modeling and analysis of high-speed planetary gear including centrifugal force

The planetary gear in electric vehicles always works at high-speed and variable-speed process. For high speed, the centrifugal force of planets cannot be ignored. Therefore, a dynamic model of the planetary gear for variable-speed process is first proposed which also considers the centrifugal force by deriving the formulae of planet acceleration anew. For the utilization of the model in variable-speed process, the angular displacements are chosen as the generalized coordinates, and the time-variant meshing stiffness and profile error vary with the gear angular displacements directly in this model. Next, the comprehensive influences of profile modification, profile error, and variable-speed process are investigated on the dynamic characteristics of high-speed planetary gear, finding that: the modification can reduce the dynamic meshing forces effectively at low speed, but the reduction disappears at high speed, and profile error excitation is the main reason; profile error excitation is also the main reason of deterioration of the dynamic characteristics of planetary gears at high speed; the dynamic characteristics for variable-speed process are severer than that of steady process at the corresponding same speed.