Abstract: A new idea of predicting fatigue crack in planetary gear sets is presented, which is based on physical model and gray theory. Aiming at 2K-H planetary gear sets, physics-based models for damaged system with multi-stage severity are established, and simulation data of damaged system is obtained. Feature vector of simulation data selected and computed is used as standard damage mode. Grey correlation analysis is carried out between standard damage mode and the feature vector of signal to be checked. Quantitative detection of cracks is carried out on the basis of the correlation degree. By the aid of simulation data, the grey model is modified so as to have a better performance in predicting fatigue crack. Seeded fault tests are carried out to validate the methodology and a promising result is acquired.

Key words: Fatigue crack, Fault prognostics, Modified gray model, Physical model, Planetary gear sets, Quantitative detection