The application of Duffing oscillator in characteristic signal detection of early fault

This paper presents a study of application of Duffing oscillator for extracting the features of early mechanical failure signal. By analysis of global solutions and bifurcation set of Duffing equation, we conclude that the bifurcation threshold, which corresponds to the maximum orbit outside the homoclinic orbit of Duffing equation, can be used to detect weak signal, such as the characteristic signal of early machinery fault. Therefore, the Duffing oscillator is suitable to be a model for weak signal detection, although some relative aspects for practical uses should be considered carefully. In this paper, the strategies for testing whether the weak signal is exists and how to estimate its amplitude are discussed in detail. Moreover, an example is presented here to demonstrate the utility of this method by analyzing the early rub-impact signal appearing in a rotor. The results show that the method is effective for early detection of fault described by specific periodic-motion components such as rub-impact fault of rotor in aeroengine. (C) 2003 Elsevier Science Ltd. All rights reserved.