Study On Nonlinear Dynamic Characteristics And Application For Rotor System Based On Local Wave Method

Rotor system is the heart of rotating machinery, whose dynamics has been being paid much attention to. ft is nonlinear in essence for most of rotor dynamics. With the development ol' science and technology, research on nonlinear dynamics characteristics of roi.or system are urgent. In this paper, studies have been done on fault diagnosis and modal analysis Cor rotor systems and can be summed up into the following:1. Local-wave method is studied and applied to nonlinear rotor system and non-stationary signal. By comparing with several time-frequency analysis , the method can be proved to more effective than others. The result shows that nonlinear system can be represented by timc-frequency analysis of system's signal, and Local-wave method can clearly explain time梖requency characteristics of nonlinear system.2. Local-wave method is successfully applied to fault diagnosis of rotating machinery, and some innovative fault diagnosis method are developed.Local-wave method supplies an effective tool to purify the orbit of rotor, it can present, adaptive decomposition of vibration signal, and reconstruct the signal according to known information of fault features of rotor. The purified orbit can clearly show the fault feature of rotor system.Local-wave method is applied to analyze the experimental data of .two kinds of early faults such as rotor and stator rub and misalignment. The results by ordinary frequency analysis arc also given. It is shown that the method can express clearly the time-frequency characteristies of vibration signal, and used as the feature extraction of the early faults.Local-wave method is applied to analyze the coupled vibration of a crack and rub-impact rotor system, the result shows that it can express clearly the time-frequency characteristics of vibration response and represent all components and their instantaneous frequency, and supply the effective information for the early faults diagnosis.3. An innovative method based on IMF and chaos is developed for the fault diagnosis of rotor system. The characteristics of the Duffing equation' s solutions are studied, the Tract ional dimension is applied to identify the chaos and bifurcated parameters, and can accurately design the chaotic oscillators. The early misalignment faults can be diagnosed and identi fied through distinguishing the oscillator phase transform, and supply the effective information for the early faults diagnosis of rotor.'I. Based on study of Local-wave method and fractal dynamics, fractal dimensions of IMF are developed as condition parameters for the fault diagnosis of rotor system. By analyzing the sensitivity of fractal dimensions of IMF on different faults, the method can fully reflect the feature embodied in vibration signal. Examples verify the validity.5, Local-wave method is applied to parameter identification of nonlinear system, and an innovative method has been developed for modal parameter identification of the nonlinear system. Examples show that the method has high precision of parameter identification. For the identification of dynamic intrinsic frequency and damping. The instantaneous modalI!parameters can be obtained by measuring the vibration response in non-stationary running condition and using the identification method.