LAUSR

The nonlinear radial forces relationship regarding phase currents and rotor angle demands a nonlinear control structure for bearingless motors. Most state-of-the-art control algorithms of bearingless motors are based on the assumption of linear current to force/torque relationship, and only the nonlinear relationship to the rotor angle is taken into account. However, in some types of bearingless motors, especially in motors with reluctance-type rotor, suspension forces are quadratic functions of the phase currents, which means that, in addition to linear terms, quadratic terms also contribute significantly to force generation. In this article, a novel control structure is presented, which allows controlling a bearingless motor featuring significant nonlinear current to force/torque relationship. Digital signal processor implementable solution was found by a numeric solution followed by the second-order Taylor approximation. To check the functionality, the suggested control structure was implemented with a bearingless flux-switching 12/10 motor.