The Rub Faults Study Of Rotor Systems Based On Chaotic And Fractal Theory

Rotor system is the most important part of rotating machinery, its faults will bring enormous economy loss. Because of influence of nonlinear factors(nonlinear oil-film force, nonlinear internal resistance, rub impact , crack and so on), rotor system appears nonlinear dynamic characteristic. Presently, researches for couple rub-impact fault of nonlinear factor are not already mature, its dynamic behavior is complicate, and sometimes presents chaotic character, so theory research for its behavior can supply vigorous evidence for fault diagnosis. Meanwhile, fractal fault feature extraction method of phase space reconstruction based on chaotic time series appears in the field of equipment fault diagnosis, and offers a new measure for underst- anding profoundly fault behavior of complicated nonlinear dynamic system from a new viewpoint, supplies foundation for recovering nature of fault from chaotic phenomena as well, so research of chaos and fractal feature for rotor system's vibration signal has important significance.The couple rub-impact fault of rotor system's nonlinear factor is researched. Actually several onlinear factors of rotor system couple at he same time, and different excited factors exist mutual influence, which make rotor rub-impact fault more complicated, nonlinear dynamic characteristic more abundance. So, as for nonlinear coupled rub impact fault, the paper establishes Jeffcott rotor system dynamic model with nonlinear rub-impact and oil-film force coupled.Numerical analysis for nonlinear dynamic differential equation of rotor system is made. Four-order Runge-kutta for rub-impact fault's dynamic differential equation with nonlinear factor coupled to solve is adopted, chaotic feature is researched when radial displacement is 0.3, Poincare maps,phase diagram and axis orbit are analyzed, and presents effectively periodic,qusi-periodic and chaotic motions. For different radial displacements and speed influence factors, the paper is devoted on dynamic of rotor rub-impact with change of frequency ratio, extract feature parameter of chaos and fractal , and find inherent law of chaos evolvement, which supplies theory basis further for researching nonlinear dynamic of rotor system..The paper is devoted to extract chaos and fractal feature of rotor system's typical fault at the viewpoint of phase space reconstruction. Phase space reconstruction for chaotic attractor is made and important para- meter m andτare researched. Experimental data of normal,unbalance,rub-impact and whirling of oil-film measured on bently rotor's experimental platform are analyzed.The largest Lyapunov exponent of vibration is calculated to judge whether it is belong to chaos or not , then correlation dimension feature is extracted adopting G-P algorithm to calculate correlation dimension. Correlation dimension is important factor desc- ribing fractal complexity, and can depict degree of singularity of chaotic attractor. Through amount of calc- ulation, the paper extracts feature exponent of chaos and fractal of rotor system with different states, recov- ers feature of chaos and fractal with different states, supplies effective method for diagnosing typical faults of rotor system..