Nonlinear dynamics of a horizontal rotor with asymmetric magnetic supports

In this paper, a horizontal rotor with passive anisotropic asymmetric magnetic bearings nonlinear model is developed. The model is based on the experimental evidence of an educational demonstrator, a powerful benchmark which highlights features of rotordynamics systems. An experimental setup is developed using laser sensors to track the displacements of the rotor and tachometer to record the rotor angular speed. Several test campaigns are performed with different initial conditions to characterise the educational demonstrator. The first test campaign is oriented to identify the system structural properties, while the second one is focused on the nonlinearity identification. The rotor modelling is divided into three stages with progressive increase in complexity, starting from the overall linear structural behaviour to the nonlinear subharmonic resonance phenomenon. The model is developed with a generalised approach suitable for a wide range of operating conditions and rotor configurations. Progressively, the developed rotor models are compared to highlight their limitations and advantages. Finally, rotor trajectory analysis and time–frequency analysis are used in the numerical-to-experimental comparison.