In order to overcome the shortcomings of the traditional Back Electromotive Force(BEMF) Detection Algorithm

such as filtering delay and error of phase compensation

the morphological filtering is applied to two-dimensional signal to design a digital filter with fixed delay

which makes the filtering delay not to change with the speed and no additional sampling circuit is needed. At the same time

the digital phase-locked loop algorithm is used to improve the delay algorithm of back EMF zero crossing. According to the above methods

a simulation model is built and a controller of brushless DC motor is designed. The simulation and experimental results show that this new BEMF detection algorithm can improve the rotor position detection accuracy of brushless DC motors effectively

and make the control accuracy of speed fluctuations reach the level of one ten thousandth.