Stabilized control strategy under loaded conditions in a bearingless motor based on d-q axis current control

This paper presents a new control strategy to stably support the rotor shaft when a bearingless motor (BELM) based on d-q axis current control is driven under loaded condition. In this type BELM, the magnitude and direction of the suspension force are varied in accordance with the rotor rotation. Unfortunately, it results in the unstable rotor levitation. Thus, the necessity of the compensation for the suspension force command and the validity of that compensation method have been introduced by the authors earlier. However, it is possible that the magnitude and the direction of suspension force are varied with armature reaction under loaded condition. It causes the serious problem in the rotor levitation. Thus, it is obviously found in this paper how the compensation coefficients are conducted to realize the stable rotor levitation even under loaded condition. The effectiveness of the compensation coefficients derived by the proposed method is confirmed in simulation based on a machine model designed by Finite Element Method (FEM) software.