Adaptive control of nonlinear zero-bias current magnetic bearing system

The electromagnetic force generated by a magnetic bearing is highly nonlinear and parametric uncertainties in calculation of magnetic force makes the control of magnetic bearings complicated. Zero-bias current magnetic bearings have the potential to reduce power losses because only one electromagnet of the pair is operational at any given time. In this study, an adaptive control is proposed to compute nonlinear control currents of zero-bias magnetic bearing by accepting that the rotor and bearing parameters are unknown. The nonlinear observers are used to provide the estimate of the unmeasured state with an exponentially convergent error decay since the full state of the control system is not available for the feedback. The proposed approach is verified by simulation and experiment.