Electromagnetic torque observation of brushless DC motor based on hall position signals

This paper proposed a novel electromagnetic torque observation method for brushless DC motor (BLDCM), based on analysis of the relationship between back electromotive force (back EMF) waveform function and hall position signals. This method solves the problem of observation of torque's amplitude and sign without continuous rotor position information. Compared with traditional methods, the proposed method doesn't need continuous rotor position information and the back EMF waveform, but only the discrete hall position signals. The experimental results show that, the amplitude and sign of the torque can be calculated effectively, both in steady state and the forward/reverse running switching process. the proposed method can be used in direct torque control (DTC) of BLDCM.