Direction Independent U-function based Sensorless Control of BLDC Motor

In this paper a new function for the sensorless control of brushless DC motor has been introduced. It has the good control characteristics as compared with the real solid state hall sensors. The direction independent U-function is obtained by the direction normalized ratio of square root of squared sum of line to line BEMF to one of the line to line back EMFs. The shape of this signal is like U-letter of alphabet. The simulation studies have been carried out with different speed and load torque references. This function provides the exact replication of the actual solid state Hall sensor positions and provides excellent control over all four quadrants. The proposed method has excellent sustainability in the vibration and load disturbance togetherwith the step load changes. The method is more sensitive at starting and reversals and is stable as real hall signals at other instants.