A novel back-EMF detection scheme based sensorless control of permanent magnet brushless DC motor drive

The back-EMF (BEMF) zero crossing point (ZCP) based position sensorless control of permanent magnet brushless DC (PM BLDC) motor is a simple and attractive method. But the direct BEMF ZCP methods available in the literature do not take into consideration the discontinuity in motor phase currents during the PWM OFF periods. A detailed analysis has revealed that under this discontinues mode of operation, which happens at lighter loads and smaller duty cycles, there will be problems due to torque pulsations created by the phase advancing and negative torques. In this paper, a novel position sensorless control algorithm with direct BEMF ZCP method, which removes the above problems during the discontinuous modes of operation of the motor, is presented. The developed control algorithm is simulated and the results show that this scheme delivers much better performance.