Experimental Electromechanical Characterization of Slotted and Slotless Miniature Bearingless Drives

Proposal of angle detection method for concentrated winding bearingless motors with less magnetic interference due to current

“…Angle errors in the detected rotor angle can cause deviation in the direction of suspension forces. 1,4 Reference [1] clarifies that angle errors not only lead to interference between with suspension control in the X and Y directions but also reduce phase margin, and cause levitation to be vibratory. Therefore, identifying and improving factors causing angle errors are crucial from both motor control and suspension control perspectives.…”

“…In addition to physical displacements mentioned above, magnetic flux caused by current (hereinafter referred to as current flux) is also a cause of angle errors. Surrounding magnetic fields are influenced not only by rotor magnet flux but also by the effects of current flux, 4,[6][7][8] and this makes it difficult to accurately detect the rotor angle using Hall sensors. Reference [8] indicates that during angle feedback control, sensor disturbance caused by the motor windings and current control based on the detection angle interfere with each other, and angle/velocity oscillation phenomena is observed.…”

“…Furthermore, in bearingless motors excluding consequent pole or homopolar types, the rotor angle is also utilized for suspension control. Angle errors in the detected rotor angle can cause deviation in the direction of suspension forces 1,4 . Reference [1] clarifies that angle errors not only lead to interference between with suspension control in the X and Y directions but also reduce phase margin, and cause levitation to be vibratory.…”