Sensorless position and velocity control of cylindrical brushless DC motors at low speed using eddy current

Abstract

In sensorless control methods of the cylindrical brushless DC motors (BLMs), it is impossible to drive motors at low speeds and at standstill because the EMF is used in their methods. This paper proposes to paste nonmagnetic materials on the rotor surface and to use the model including the extended EMF. In the proposed method, the inductance changes depending on the rotor position because of eddy currents, which flow on the nonmagnetic material at high frequency. The rotor position can be estimated at standstill and at low speeds. The simulation results show that the proposed method is very useful.