Sensorless control of a PM synchronous motor for direct drive washer without rotor position sensors

Sensorless control of a PM synchronous motor for direct drive washers with parameter variation is presented. The rotor position is estimated by using the d-axis and q-axis current errors between the real system and the model of the position estimator. The stator resistance is measured near zero speed when the motor changes its rotating direction. The variation of the stator resistance and back EMF constant due to the temperature variation is compensated for in the model of the position estimator. The gains in the position estimator are also adapted according to motor speed. The increase in the DC link voltage caused by the regenerated power at braking is reduced by adding the extra (gamma)-axis current in the DC link capacitor voltage controller.