Sensorless Control of Brushless Drives Using Back emf Mapping

A simple inexpensive technique is presented in this paper for sensorless control of brushless DC motors (BLDCMs) based on the back emf (BEMF) measurement. Through the presented algorithm, the point at which the power is switched on or off to the phases, is calculated with accuracy in simple mathematical equations by capturing samples of the BEMF which are mapped back to reference values. The sampling utilizes the analog to digital converter (ADC) implemented in microcontrollers which eliminates using filters, comparators, and the delays called through look up tables after the detection of the zero crossing point (ZCP). Experimental results are also given to verify the proposed algorithm.