NONLINEAR DYNAMICS OF A MAGNETICALLY SUPPORTED ROTOR ON SAFETY AUXILIARY BEARINGS

This study concerns the dynamic response of a rotor landed on auxiliar y (catcher) bearings in an Active Magnetic Bearing (AMB) supported rot or, following postulated loss of power or overload of the AMB. An anal ytical model involving a disk, a shaft and auxiliary bearings on dampe d flexible supports is constructed and appropriate equations of the no nlinear dynamic system are developed. The equations include a switch f unction to indicate contact/non-contact events and determine the exist ence of contact normal forces and tangential friction forces between t he shaft and the hearings. Steady state solutions are obtained An anal ytical method was formulated and used to yield solutions for cases wit h well balanced rotors, in absence of any side forces. The Fixed Point Algorithm (FPA) is used to obtain steady state periodic solutions of the unbalanced rotor for various parameters. The FPA is used to determ ine the stability of the periodic solutions and the the of bifurcation involved. Multiple periodic solutions, quasi-periodic and chaotic res ponses are detected and discussed. A set of preliminary guidelines for selection of the parameters of rite catcher bearings is given.