Copyright © 2001 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Partially filled centrifuges exhibit unstable behavior over particular rotational speed ranges. To remove this unstable behavior, three different control approaches are presented which are experimentally implemented using a magnetic bearing. First, by means of a PD-controller the system stiffness is changed leading to a shift of the instability region. Second, the instability region is removed by a cross coupled feed back of the rotor vibration velocities. This cross coupling directly counteracts the fluid excitation mechanism. Third, a disturbance observer is presented which allows to estimate and compensate the not exactly known fluid force.