Eccentricity Compensation for Bearingless Motor Based on the Tracking of the Minimum Antieccentric Levitation Current

The error of the radial displacement sensor causes a deviation between the rotor levitation position of the bearingless motor (BM) and the geometric center of the stator. As a theoretical basis, force analysis of the rotor is performed first to analyze the effects caused by the aforementioned deviation. A radial levitation force modeling scheme for BM is proposed in this article, whose derivation is directly on the rotor coordinate system. The proposed modeling scheme has a simpler form of expression and a more straightforward physical concept than the traditional scheme. To completely compensate for the aforementioned deviation, a levitation position eccentricity compensation scheme for BM based on the tracking of the minimum antieccentric levitation current is proposed in this article. The proposed scheme takes the amplitude of the antieccentric levitation current vector as the index, which characterizes the degree of eccentricity of the rotor and dynamically adjusts the rotor levitation position in two dimensions and, finally, makes the rotor stably levitated at the optimal point, where the amplitude of the antieccentric levitation current vector is minimum. The absence of parameter dependence, ease of implementation, and generality makes the proposed scheme attractive. Meanwhile, the design of the displacement regulator can also be simplified. Sufficient simulation and experiments verify the effectiveness of the proposed scheme.