Adaptive variable structure control of active magnetic bearings for rigid rotors with uncertain external payloads

In this paper, a contactless magnetic radial shaft bearing adaptive control algorithm has been developed for high speed five degrees of freedom rigid rotors with external asymmetrical loads. The developed control algorithm keeps the rotor on rotating through its geometric axis while keeping on the radial air gap in stator housing to be constant at maximum value in every direction to compensate the mass imbalance due to asymmetrical loading. In this method, the radial air gap lengths along the direct and quadrature axis of bearings are measured and then, from these measurements, the radial position errors and the angular position displacements around the direct and quadrature axes on the radial plane through the stator geometric center are estimated. In this paper we will present the method for high performance active magnetic bearings (AMBs). The method based on robust Variable Structure Control (VSC) with sliding mode in adaptive case. Dynamic Feedback Linearization (DFL) and recent advances in robust control design techniques is to form a new approach for AMB. A robust stabilizing controller forces the system dynamics to the specified desired dynamics, despite gravitational and centrifugal disturbances, modeling uncertainties, and variations in mass, moments of inertia, radii of eccentricities and center of mass of the rotor. The method gives both stability and performance robustness and enable the design for other unstable magnetic levitation systems. The results are very efficient about high speed and wide range of parameter uncertainties.