Robust magnetic bearing control using stabilizing dynamical compensators

This paper considers the robust control of an active radial magnetic bearin g system, having a homopolar, external rotor topology, which is used to sup port an annular fiber composite flywheel rim, A first-order dynamical compe nsator, which uses only position feedback information, is used for control, its design being based on a linearized one-dimensional second-order model which is treated as an interval system in order to cope with parameter unce rtainties, Through robust stability analysis, a parameterization of all fir st-order robustly stabilizing dynamical compensators for the interval syste m is initially obtained. Then, by appropriate selection of the free paramet ers in the robust controller, the H-2 norm of the disturbance-output transf er function is made arbitrarily small over the system parameter intervals, and the H-infinity norm of the input-output transfer function is made arbit rarily close to a lower bound. Simulation and experimental results demonstr ate both stability and performance robustness of the developed controller.