Nonlinear stability analysis of a single mass rotor contacting a rigid backup bearing

This paper investigates the steady-state response of a rigid, single mass rotor with imbalance eccentricity supported by an active magnetic bearing with nonlinear characteristics. The rotor may have intermittent contact with an axially collocated, fixed, rigid and circular backup bearing. A radial offset position of the backup bearing center with respect to the magnetic bearing center is assumed. Parameter studies are carried out, especially for the excitation frequency and the friction conditions at the contact point. For frequencies ranging from the onset of contact up to the critical speed various kinds of periodic, non-periodic and quasi-periodic solutions can be observed. Within the parameter range investigated, a two-periodic orbit with one contact was found to be the dominant stable orbit for low excitation frequencies.