Robust Control of a Voltage-Controlled Three-Pole Active Magnetic Bearing System

The robust stabilization of a voltage-controlled three-pole active magnetic bearing (AMB) system is considered in this paper. The system could suffer both matched and mismatched uncertainties from a variety of sources such as unmodeled magnetic forces due to flux leakage and parametric uncertainties due to manufacturing and assembly errors. The system represents an interesting example that is not in the standard strict feedback form, but allows for the backstepping design. Through a backstepping procedure, two stages of integral sliding-mode control (ISMC) are integrated to form a robust controller. The first stage is a robust controller for the current-controlled three-pole AMB system, which is a nonaffine nonlinear system. It is designed by the feedback linearization approach incorporated with the ISMC. The overall robust stabilizing controller is verified both numerically and experimentally.