Active tilt compensation methods for bearingless disc motors

Disturbance and resonance effects may cause tilt vibrations in bearingless disc motors. Typically, these vibrations are only very poorly dampened by passive stabilization torques. In this paper, two strategies to actively suppress tilt vibrations are proposed: additional tilt damping by flux modulation and by radial rotor position deflection. Tilt oscillations can be reduced by modulating the magnetic air-gap flux with a d-axis current as a function of the tilt angle and its first derivative. Another option is to move the rotor towards a position offering increased tilt stiffness, depending on the tilt oscillation amplitude and speed. In order to analyse the effect, mathematical models of the two methods considering parameters of a bearingless flux-switching disc motor prototype are set up and analyzed numerically.