This paper deals with the unbalanced vibration problem of a stabilized active magnetic bearing (AMB) system. First, a model-based integral-type observer is proposed to evaluate the shaft displacement and the unbalancing forces of the rotor of an AMB system controlled by a proportional-integral-derivative (PID) controller. A fuzzy gain tuning mechanism is added to adjust the output of the PID controller in order to overcome the disturbances and suppress the unbalancing vibration. We have shown via simulation that the addition of the integral-type force observer improves the rotating accuracy in the device operating range. The experimental results demonstrate an efficient reduction of the shaft displacement of the rotor. Thus, the proposed scheme allows for a remarkable improvement in the unbalanced vibration of an AMB system over conventional PID controls without fuzzy gain tuning mechanism. (C) 2011 Elsevier Ltd. All rights reserved.