Sensorless Control of Brushless DC Motor Based on Fuzzy Logic

A control strategy of brushless DC (BLDC) motors without position or speed sensor is presented in this paper. The zero crossing of line back-EMFs is proved corresponding to the commutation points. However, if the commutation process is taken into account, the commutation signal generated by the zero crossing of line back-EMFs is slightly lag. So a Kalman filter is employed to estimate the line back-EMFs from the measurements of the stator line voltages and currents, and a fuzzy logic controller is also employed to predict the reference of line back-EMFs to adjust the commutation instant. This control method is simple enough to shorten sample time, provide more wide-speed range, reduce commutation torque ripple, and no neutral voltage, phase shifted or silent phase is required. The performance of the proposed sensorless control scheme is verified by the simulation results