Suspension Force Ripple Reduction Control of a Magnetically Levitated Axial Gap Bearingless Motor

An axial-flux type magnetically levitated bearingless motor was developed with three degrees-of-freedom (DOF) active positioning control. The permanent magnetic coupling and motor stator are located at the top and bottom of the rotor, respectively. The axial and tilt positions of the rotor and the rotor speed are actively controlled. The permanent magnetic coupling passively stabilizes the radial motion of the rotor. This study investigates the active control for reducing the tilting suspension force ripple of the axial flux bearingless motor. The proposed current regulation, which is based on the pseudo-inverse matrix of the current-force constants, has significantly reduced the suspension force ripple of the bearingless motor.