① The precise dynamic model considering the friction of tooth surface is established, and the complex time-varying stiffness and the influence of time-varying friction are considered. The dynamic characteristics of the friction excitation of tooth surface are analyzed deeply, and the relationship between the micro characteristics of tooth surface and the dynamic characteristics is obtained;

② Based on the optimization analysis of gear micro modification based on genetic algorithm, a modification scheme with the minimum transmission error as the objective is obtained, and the robustness of the modification scheme is verified by sensitivity analysis under the condition of considering the manufacturing error, which provides an effective method for effectively controlling the overall vibration and noise level of gearbox after mass production;

③ In this paper, the unsymmetrical sideband frequency characteristics formed by the structural parameters of planetary gear transmission are analyzed, and the basic parameters such as the number of teeth, meshing phase and the influence of the order of excitation on the sideband frequency characteristics of planetary gear train are revealed. A general judgment method that can predict the sideband frequency characteristics of planetary gear train according to the known parameters is obtained, and the noise caused by the unsymmetrical sideband frequency is improved by this method.