Influence of active magnetic bearing stiffness on Chaotic vibration of flexible rotor

Choosing the appropriate end supports has been great importance in rotating machinery. The mechanical bearings (ball and journal) are more popular types of supports that used in rotating systems. However, the rub-impact between the rotor and bearing is main disadvantage of these types of bearings. Whereby, the active magnetic bearings have been developed recently that removes the rub-impact, but induces new nonlinear factors that affect the dynamical behavior of system. An unbalanced disk is mounted on the shaft. The rotor is modeled as three masses and 8 D.O.F. The governing equations are extracted in form of nonlinear coupled ordinary differential equations. The influence of magnetic bearing stiffness on the chaotic behavior of a flexible rotor supported by active magnetic bearings is investigated. The bifurcation diagrams, phase planes, power spectra, Poincare map and maximum lyapanov exponents are used to analyze the response under different operational conditions. The numerical results shows a rich variety of nonlinear behavior including periodic, sub-periodic, quasi-periodic and chaotic vibration due to active magnetic bearing stiffness. Also the results reveals the significant changes in the chaotic regions in 8 D.O.F model.