Stabilization of a current-controlled three-pole magnetic rotor-bearing system by integral sliding mode control

In this study, a 3-pole active magnetic bearing (AMB) system is stabilized experimentally by an integral sliding mode controller (ISMC). Two cases (i.e., with and without motor) are investigated. It is found that ISMC works for both cases. It is also found that when the rotor speed is zero, the system performance is as good as the system without motor, showing the good robustness of the ISMC controller. When the rotor is spinning, a steady state limit cycle exists. The size of the limit cycle increases with the rotor speed. The effects that cause the limit cycle and suggestions on improving the results are discussed. The results clearly indicate that the 3-pole AMB is indeed feasible. However, delicate calibration and robust nonlinear controller are necessary to yield good performance.