Nonlinear dynamic modeling and analysis of a helicopter planetary gear set for tooth crack diagnosis

Abstract

Planetary gearset is a vital dynamic component in helicopter transmission. In the planetary gearbox, there are many nonlinear dynamic factors, such as time-varying meshing stiffness, bearing support stiffness, comprehensive transmission error and tooth backlash. These nonlinear factors will deeply affect the vibration response characteristics of the gearbox system, and bring new challenges to the crack fault detection and diagnosis. To unveil the nonlinear properties of planetary gear set, a 21 degrees of freedom translational-torsional model of the planetary gear set is established by integrating above-mentioned nonlinear factors. Analysis of the fault influence on natural frequency and statistical indicators of simulation responses, the optimal indicators for fault detection are found. Then, nonlinear dynamic characteristics of gear system under fault state are conducted, and crack fault symptoms are pointed out using time-domain waveform analysis and power spectrum analysis of response signals, which actively illustrates the system fault mechanism and achieves fault isolation. Finally, the effectiveness of the model for planetary gear set with tooth crack is verified by experiments.