Sensorless Rotor-Position Estimation at Standstill of Cylindrical Brushless DC Motors Using Opened Phase Voltage Change Caused by Eddy Currents

Abstract

A rotor position estimation of a cylindrical brushless dc motor at a standstill has been difficult. Therefore, a torque control of a motor has been difficult at starting of the motor, and the realization of the position estimation at a standstill has been desired. This paper proposes a simple processing of a rotor that non-magnetic materials are pasted on a rotor surface. This processing generates an eddy current on non-magnetic materials and causes an opened phase voltage change according to a rotor position. The experimental results used a microcomputer show that it is possible to estimate a rotor position of the cylindrical motor despite of a standstill by using the opened phase voltage change.