Motion control strategy and operational behaviour of a high speed bearingless disc drive

In the last decade, bearingless drives have found their way into applications such as pumps for delicate media like blood [1] or sensitive chemicals [9] as well as drives for bioreactors [13] and chemical process chambers [3]. With all these applications running at relatively low speeds below 15.000rpm, the suitability of bearingless drives for high speed operation remained unclear. This paper will give a brief description of a high speed bearingless disc drive, designed to reach speeds beyond 100.000rpm. Aside from special requirements such as rotor material strength and low stator loss characteristics, the control system also faces new tasks arising from the combined motor - bearing unit. Eventually, the operational behaviour of the constructed prototype on the basis of phase current amplitude and resulting rotor orbit is presented.