Mechanism of intermittent failures in extreme vibration environment and online diagnosis technology

The intermittent faults induced by environment stress such as extreme vibration have deep impact on the serviceability and reliability of equipment. In this paper, the term of the extreme vibration environment is defined. The finite element simulation model of the component is established, and the mechanism and laws that how the extreme vibration environmental stress induces intermittent faults are analyzed. Based on the elastic-plastic stress theory, a method of calculating component's cumulative damage in extreme vibration environment is proposed. Then a hidden Markov model (HMM) based Tri-State (normal state, intermittent state and fault state) injury correlation model is built. Starting with the relationship analysing between the features in each state of components and the interior cumulative damage, the cumulative damage based HMM model for intermittent fault diagnosis is established. After that, a real-time fault diagnosis method is proposed. Tests are carried out on a helicopter attitude indicator in extreme vibration environment. The test results show that the occurrence probability of intermittent fault becomes large with the increase of the vibration magnitude and time. The proposed fault diagnosis method can detect the intermittent fault efficiently.