Self-sensing active magnetic bearing using 2-level PWM current ripple demodulation

This paper deals with the implementation of a position estimation method for a small radial active magnetic bearing. Thus, the rotor position is not measured with a sensor but demodulated from the phase current ripple, excited by the 2-level pulse width modulated phase voltages. The mathematical description of the phase currents is given and the demodulation procedure for obtaining the rotor position is outlined. Stable levitation of the rotor is achieved by this method without the need of any physical position sensor. Measurements regarding the estimated sensor signal quality and its dynamic behavior are conducted. Possible future improvements are discussed.