Study On Some Nonlinear Dynamics Problems Of Rotor System With Faults And Intelligent Diagnosis Method

Rotating machinery includes large scale of turbine generator, hydraulic motor, nuclear motor, aerospace motor, high-speed compressor, centrifugal engine, centrifugal pump and high accuracy machine that the rotor system is main working body. It is applied in the field of electric power industry, petrochemical industry, metallurgy, machinery, aerospace industry broadly. With the development of science and technology, rotating machinery is having the tendency of large scale, serialization, high-speed, light-duty, centralization, automation, big power and big load. This not only enhances the productivity but also reduces the cost. But once the machinery fault happens, the loss is large. There were disastrous accidents and casualties and the influence are large. So on one hand, the higher need is put forward in speed, content, efficiency, safe side of rotating machinery, on the other hand, it is important to develop advanced state inspect and diagnosis technology. In this paper, the rotor system and engineering structure are studied. The research overview, research goal and research significance of nonlinear rigid, impact and rubbing, foundation looseness, coupling faults, the bifurcation and chaos motion, intelligence fault diagnosis based on the neural networks are discussed and the shortcomings of them are discussed, too. On the basis of them, the bifurcation and chaos motions caused by the nonlinear rigid, impact and rubbing, foundation looseness, coupling faults in rotor system and other corresponding problems are discussed. The problems of sensitive parameter selection in the identification of structure damage fault diagnosis, the improvement measures of diagnosis method and the applications are discussed. The main works in this paper are as follows: 1. The Jeffcott rotor system dynamics equation was constructed which using the linear and cubic to express the strength of center shaft and material physics nonlinear factors. The multiple-scale method was used to research the complex dynamics motions of this kind of rotor system about non-resonance, main-resonance, super-harmonic and sub-harmonic responses. The numerical value analysis method was used to research the complex dynamics motions of the rotor system, and the influence caused by the change of system parameter and chaos motion excitation character was also analyzed. 2. The rigidity of real rotor system usually is nonlinear. In this paper, the rotor system local impact and rubbing dynamics differential equations having the nonlinear rigidity was constructed. The bifurcation and chaos behavior especially the influence on bifurcation and chaos behavior of impact and rubbing fault rotor system caused by the parameters of nonlinear rigidity, rotor rotating speed, eccentric mass was analyzed, using the numerical value analysis method. The bifurcation diagrams, maximum Lyapunov exponent diagrams, Poincar émaps, phase plane portraits, trajectories of journal center, time-history curve, amplitude spectra and power spectrum diagrams of the rotor motion were used. The convert and evolution course of periodical response, quasi-periodical response, double-periodical bifurcation, chaos of the system response was analyzed. 3. The influence on nonlinear dynamics of impact and rubbing fault of rotor system caused by foundation looseness was researched. The local impact and rubbing fault dynamics model and differential equation having the foundation looseness was put forward and constructed. The numerical value simulation of the rotor system was used to analysis the nonlinear dynamic characteristics. The bifurcation and chaos behavior under the different frequency rate and eccentric mass were researched. The influence of system dynamic responses caused by loose mass, impact and rubbing rigidity was analyzed, and the changing characteristics with the nonlinear rigidity of the shaft were researched, too. 4. The rotor system local impact and rubbing dynamics model that considering the stator mass and supporting rigidity and having the foundation looseness fault was put forward. The nonlinear dynamics equation was constructed. Bifurcation and chaos behavior of the rotor system was analyzed. The influence caused by different rotate speed and eccentric mass on the rotor system bifurcation and chaos behavior was researched. 5. The main problems existed in the neural networks, the improvement measures, the advantage and disadvantage and the features were inquired in this paper. The momentum coefficient, learn rate and the number of hidden units were provided utilizing the improvement BP neural networks. A new character parameter in structure damage fault diagnosis neural networks was put forward as an input parameter which overcoming the shortage of using one parameter. In the mean time, a parameter related with damage extent was added. The structure damage problems were analyzed using these parameters. A local minimum differential equation using genetic neural network algorithm was put forward in order to improve the convergence speed and avoid the local minimum. Through the practical fault diagnosis in air-compressor, the validity of it was proved. 6. From the practice, application of integrated neural networks in fault diagnosis were researched and integrated neural networks based on information fusion were established in this paper. The implement measure and principle of sub-neural networks were inquired, and its validity and feasibility were proved through the diagnosis examples.