Synchronous disturbance compensation in active magnetic bearings using bias current excitation

This paper proposes a new approach for simultaneous compensation of two synchronous periodic disturbances in active magnetic bearings; sensor runout and mass unbalance. Using Lyapunov´s method, a novel adaptive algorithm is developed to uniquely determine the harmonic components of both disturbances and guarantee asymptotic stability of the rotor geometric center about the origin. By varying magnetic stiffness through excitation of the bias currents, the system achieves a persistently exciting condition that ensures exponential convergence of estimated parameters to the true values. The algorithm is superior to existing techniques since the identification process can be performed without changing rotor angular speed. Both simulation and experimental results validate the effectiveness of the algorithm