Uncertainty and disturbance estimator-assisted control of a two-axis active magnetic bearing

In this paper, a robust nonlinear control strategy is developed for a class of second-order nonlinear uncertain systems with uncertainties and disturbances and is applied to two-axis active magnetic bearing position stabilization. The approach is based on a feedback linearization method, robustified by the uncertainty and disturbance estimator, which calculates and robustly cancels system uncertainties and disturbances via appropriate filtering. The controller uses the information regarding the known part of plant dynamics while the terms containing unknown dynamics are treated as additional system uncertainties and disturbances. The algorithm provides excellent performance in stabilizing the active magnetic bearing position and rejecting disturbances both at standstill and under movement. Simulations are given to show the effectiveness of the strategy via an application to an experimentally derived active magnetic bearing model.