Abstract
A stable position control method of a permanent magnet-type bearingless motor under loaded conditions has been already proposed by the authors. In the proposed control method, the permanent magnet MMF is replaced by the equivalent motor winding current. Information on both a magnitude and a direction of air gap flux is obtained by synthesizing the equivalent current and the q-axis current. A mutual interference between radial force components in two perpendicular axes, caused by an influence of amature reaction, is successfully decoupled.
In this paper, the definition of the equivalent current of permanent magnet is made clear. The equivalent current is dependent on the motor parameters. The influence of the error in the measured equivalent current to the rotor radial position control is discussed. The mutual interference of the radial forces, caused by the measurement error of the equivalent current, is confirmed by experiments. A required accuracy of the measured equivalent current is found. In addition, the influence of the error in the measured leakage reactance to the equivalent current is also presented.
