Rotor unbalance compensation without angular position sensor for Active Magnetic Bearing

Active Magnetic Bearing (AMB) levitates a rotor without any physical contact so that the drag loss of rotating machine can be significantly reduced. Rotor unbalance causes vibration because the rotating unbalance mass tends to pull the rotor out of the center position. Also, the vibration force increases as the rotor speed increases. As a result, the magnetic bearing should supply the increased force in order to place the rotor in position. This paper proposes a rotor unbalance compensation method in order to reduce both vibration and bearing force without any angular position sensor.