Effect of state feedback controller on dynamic behavior of a rotor supported by active magnetic bearings

Dynamic behavior of a horizontally supported Jeffcott-rotor system vial four electromagnetics poles is investigated. The magnetic force has a highly nonlinear relation to the control current and the air gap in the active magnetic bearing. The nonlinearities due to the centrifugal force, electromagnetic force, and the rotor weight are considered in the rotor model. The lateral oscillation of the rotor is controlled using a state feedback control system. The vibration of the rotor is modeled by a second order nonlinear ordinary differential equations with quadratic and cubic nonlinearities. The oscillatory characteristics of the considered system is investigated using the multiple time scales perturbation method assuming weak nonlinearity and soft excitation. Numerical simulations are carried out to validate the accuracy of the analytical results. The results show high efficiency of the applied controller velocity gain in forcing the considered nonlinear system to respond as a linear one with a single periodic attractor.