Rotor speed, position and load torque estimation using back-emf sampling for self-sensing brushless DC machine drives

This paper presents a load torque estimation method for self-sensing brushless DC drives. Torque ripples in brushless DC machines can be reduced using load torque information. This method uses the terminal voltage, the virtual neutral point voltage and the DC-bus current of the machine. The algorithm uses the variation of successive back-emf samples to estimate the rotor speed. The rotor position is estimated by defining an intermediate function of estimated speed and back-emf samples. An estimate of acceleration is used to estimate load torque. The mathematical background is given and discussed and the simulation results prove the performance of the proposed method.