With the wide use of helical planetary gears in the case of high-speed and heavy loads, the study of dynamic loads characteristics become great significance for reduction vibration and noises. Firstly, correctly describing meshing stiffness and meshing error of planetary gear was the top priority of dynamic analysis, so an approach of loaded tooth contact analysis for planetary gears (PLTCA) combining gear geometry analysis and mechanical analysis of tooth was proposed to calculate meshing stiffness of gears and corner meshing impact, which was prepared for further analysis of planetary gear dynamics. Secondly,considering time-varying meshing stiffness and corner meshing impact excitation, a lumped-parameter planetary gear model was established and forces responses were got by solving the dynamic equations with numerical method.The results showed that the dynamical meshing forces increase remarkably with the speed increase except resonance speed. Besides, installation error, especially the center distance error, is responsible for the difference in value of meshing stiffness, and lead to the more resonance speeds, furthermore. With floating planetary gear , the dynamic forces are reduced at the resonant speeds, and the dynamic meshing force of some gears are obviously reduced with increasing speeds due to the differences in value of meshing stiffness.
