Dynamics Analysis of Nonlinear Pitting Fault of Planetary Gear Transmission System

When the planetary gear transmission system operates under extreme conditions such as poor lubrication, it is prone to tooth surface pitting faults, which seriously affects the transmission accuracy and the service life. In order to ensure reliable operation of the system, it is necessary to deeply explore the dynamic characteristics of the system under pitting failure. In this paper, a nonlinear dynamic model of planetary gear transmission system coupling with multiple excitation factors is established by considering the time-varying meshing stiffness, time-varying friction, transmission error and backlash under pitting fault. The fourth-order Runge-Kutta numerical integration method is used to solve the vibration differential equation of the system, and the vibration characteristics of the system under different rotational speeds and pitting faults are analyzed by means of time domain diagram, phase plane diagram, spectrum diagram, wavelet time-frequency diagram, three-dimension spectrum diagram and bifurcation diagram. The results show that the system exhibits rich nonlinear dynamic behaviors at different rotational speeds, including periodic motion, multi-periodic motion and chaotic motion; that the pitting fault of the gear tooth causes a sudden change in the vibration displacement of the system and reduces the stability of the system by changing the time-varying meshing stiffness; and that, with the increase of rotational speed, the amplitude of system vibration caused by the pitting fault also increases. Finally, the accuracy of the proposed model and calculation method is verified by building a dynamic characteristic test bench of planetary gear transmission system. This paper reveals the intrinsic relationship between pitting fault and system dynamic characteristics, and provides references for the fault diagnosis and condition monitoring of planetary gear transmission system.