Speed Sensorless Control For BDCMs With Position-Dependent Load Torque

This paper presents the robust sensorless operation for brushless DC motors (BDCMs) loaded by the position-dependent load where the load torque is a function of the rotor angle (not electrical angle). Without any position sensor, the reliable position signals are generated from the motor terminal voltages through sensorless circuits. In order to decrease the speed variations especially in the low speed, an additional gain to adjust output voltage is included in the speed loop to compensate the repetitive position-dependent load. In first, the effects of position-dependent load on the speed variations and the commutation intervals are studied. It shows that we can estimate the position-dependent load from the commutation intervals. Then, we introduce the used sensorless scheme based on sensing terminal voltage. Finally, simulated results have been given to demonstrate the robust performance of the proposed sensorless control for the position-dependent loads.