The translational-rotational-coupling dynamic model has been founded of herringbone tooth planetary transmission for analyzing the influence of gear mesh stiffness and bearing stiffness to vibration characteristics of planetary transmission system.In the dynamic model
the proposed model admits three degrees-of-freedom for each component and includes the key factors affecting planetary gears vibration such as component bearing stiffness
time-varying mesh stiffness and so on.The dynamic differential equation is obtained base on system kinematics equation and solve the eigenvalue question of it.The vibration characteristics can be obtained of transmission system.