Sensorless Control of BLDC Motors at Low Speed Based on Differential BEMF Measurement

BLDC drives are widely employed in industry due to their intrinsic robustness and high torque-to-weight ratio. The availability of cheap embedded processing power in recent years paved the way for the widespread use of sensorless control techniques; the removal of speed and position sensors leads to substantial increase of robustness and cost savings. Nevertheless, traditional sensorless BLDC control techniques suffer from low efficiency at low speed due to degraded signal to noise ratio on feedback signals and low dynamic response. This paper describes a novel sensorless control algorithm based on a differential measurement, which allows higher dynamic performance and lower minimum operating speed with respect to traditional techniques without requiring dedicated hardware solutions or complex calculations.