Nonlinear control of magnetic bearing in the presence of sinusoidal disturbance

We present a modular control strategy to achieve global asymptotic stability for the regulation problem of a single-axis active magnetic bearing (AMB) in the presence of an unknown sinusoidal disturbance (i.e., the amplitude and the frequency are unknown). Specifically, we design a set of linear, BIBO filters to facilitate the utilization of standard adaptive control techniques to compensate for the effects of the unknown sinusoidal disturbance. In view of the fact that the disturbance frequency might slowly vary with time, we utilize a least squares prediction error-based update law to promote faster convergence of the parameter estimates