Sensor integration and state estimation on magnetically levitated rotors

Magnetically levitation of rotors requires accurate measurement of the shaft location. Commonly used position sensors are mounted externally, which can cause system instability. Therefore, an integrated capacitive measurement system has been developed which allows determination of the rotor position exactly in-plane with the magnetic bearing. Sensor noise is reduced significantly by means of an adaptive linear Kalman filter. Additionally, the filter estimates all state variables, which permits utilization of a state space controller. In this paper, a LQG regulator, which was successfully tested with an experimental setup, is described in detail. A procedure for estimating parameters of the magnetic bearing by means of an extended Kalman filter is proposed in conclusion