Rotational motion stabilization for a vertical shaft magnetic bearing with a sliding mode controller and observer

In this paper we present a sliding mode controller and observer for stabilization and rotor positioning of a rotating vertical shaft magnetic bearing. Rotor imbalance causes vibrations, mathematically modeled as sinusoidal disturbances. This necessitates robustness inherent in sliding mode observers and controllers. The sliding mode control design includes (i) the definition of an equilibrium manifold upon which the magnetic bearing has the desired stability and tracking properties and (ii) the controller selection for driving the system to this manifold and maintaining it there. A sliding mode observer strategy is proposed to estimate derivatives of measured signals in the presence of unmatched disturbances by filtering discontinuous approximations of the derivatives. Simulation results demonstrate the utility and robustness of a sliding mode controller and observer for stabilizing the rotational dynamics of a magnetic bearing