Active suppression of structural force harmonics in PM bearingless motors

In permanent magnet (PM) bearingless motors some design characteristics can create ripples on force during the rotation depending on the levitation current and the rotational speed. This paper proposes a method to eliminate these ripples by the injection of additional current harmonics. This current is injected by a special structure of control taking into account the interaction highlighted by the theatrical analysis of the force ripples. This control method is validated by experimental results.