Local rub-impact fault diagnosis of the rotor systems based on EMD

Aiming at the characteristics of the vibration signal of a rotor system with local rub-impact fault, a local rub-impact fault diagnosis method of rotor system based on EMD (empirical mode decomposition) is proposed in this paper. When the local rub-impact fault occurs in the rotor system, the vibration signals of the rotor system will present amplitude-modulated feature because of the periodic rub-impact between the stator and the rotor. However, it is hard to extract the rub-impact feature for the rub-impact signal is always submerged in the background and noise signals. By using EMD, any complicated signal can be decomposed into a finite and often small number of IMFs (intrinsic mode functions), and each IMF may be amplitude-modulated or frequency-modulated signal. Therefore, the rub-impact signal, background signal and noise signal can be separated efficiently and the fault feature of vibration signal of a rotor system with local rub-impact fault can be extracted after the vibration signal of the rotor system is decomposed by EMD method. The analysis results from the experimental signal show that the intrinsic mode functions of the vibration signal of a rotor system with local rub-impact fault obviously own the amplitude-modulated characteristics, while those under other work conditions own no distinct amplitude-modulated characteristics. Therefore, the EMD method can be applied to the local rub-impact fault diagnosis of the rotor systems efficiently.