Using Majority Function to Realize Sensorless Brushless DC Motor Control with Back-electromotive Force Filtering

The paper proposed a method of using majority function to realize sensorless brushless DC motor control with back-electromotive force filtering.The method uses DSPIC A/D converter to sample BEMF signal of trapezoidal wave,then it compares the BEMF signal of trapezoidal wave with reconstructed virtual neutral-point of the motor so as to detect crossover point,and uses majority function filter to make filtering procession for the comparative result.When detecting crossover point,the DSPIC30F2010 ADC changes phase for the driving voltage of the motor after one delay time.At last,the method uses control loop to realize(highly efficient) and smooth running of the sensorless brushless DC(motor.) Compared with the mode of using hardware filter or external comparator,the method has the advantages of few hardware,little cost and small PCB size.The actual application showed that the method is simple and practical,which has good performances.