A sensorless estimation of rotor position of cylindrical brushless DC motors using eddy current

A rotor position estimation of a cylindrical brushless DC motor at a standstill has been difficult, and the realization has been desired. This paper proposes a simple processing of a rotor such that nonmagnetic materials are pasted on a rotor surface which allows eddy currents to flow. This processing causes a change of a voltage of an opened phase according to a rotor position. The experimental results show that the rotor position estimation of which maximum error was 19/spl deg/ at an electrical angle was realized.