Considering the influence of time-varying meshing stiffness,tooth backlash,comprehensive transmission error and other excitations on vibration characteristics,a pure torsional nonlinear dynamic model of herringbone planetary gear transmission system was established based on the lumped parameter method.The Runge-Kutta method was used to solve the system dynamics equations numerically,and the steady-state response of the system was obtained.Through phase diagram,the nonlinear response of the system was analyzed by means of Poincaré cross-section technology and spectrum analysis,and the influence of meshing damping on the dynamic characteristics of the system was studied.The results show that the herringbone gear transmission system exhibits rich nonlinear dynamic characteristics under the action of multi-source excitation factors;appropriately increasing the meshing damping,the system will be transformed from chaotic motion to periodic motion,the vibration of the system is weakened,and the stability is improved.