Active Magnetic Bearings with Position and Flux Observer

Standard Active Magnetic Bearings are controlled using a current reference and the measured or observed current as state variable in the state space controller. Nevertheless since this approach selects the current as the state expressing the behavior of the magnetic bearing, several disadvantages occur. Indeed it is well known that this method leads to an inherent nonlinear relation between the generated force, the current and the air gap. This paper presents the modeling approach, the control design and the experimental validation of a strategy based on the combined observation of position and flux. The technique is designed and tested on a one-degree of freedom mechanical oscillator actuated by a couple of opposite electromagnets.