Sensorless estimation of rotor position of cylindrical brushless DC motors using eddy current

Abstract

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 by pasting non-magnetic materials where eddy currents can flow on the rotor surface. This process causes a change of amplitude of the phase current according to the rotor position. The experimental results show that the rotor position estimation with maximum error of 26/spl deg/ electrical angle has been realized, which is useful for 120/spl deg/ conduction type cylindrical brushless DC motors.