Estimation of initial rotor position for slotless PM motor

The initial rotor position estimation is one of some serious problems about sensorless control of permanent magnet synchronous motors. This paper describes an estimation method of the initial rotor position for a slotless permanent magnet motor. The method is based on the variation of the current response when the voltage vector is applied to the motor. To estimate the polarity of the rotor magnetic pole, the rotor is slightly moved. As a result, the average of the estimation error is 3.42 electrical degrees.