Fuzzy estimator for sensorless PMBLDC motor drive under speed reversal

The speed and position estimation from Back EMF has been a problem under speed reversal response due to change of sign of speed. In this paper, an algorithm using fuzzy logic is proposed to estimate the speed and position of BLDC motor from back EMF for sensorless brushless DC (BLDC) motor drives to improve the performance of conventional sensorless drives. Most existing sensorless methods of the BLDC motor have low performance at speed reversal, transients or low speed range and occasionally require additional circuit. For this type of problem, the estimation of speed and position from back-EMF is suitable for high performance because the back-EMF of the BLDC motor has a trapezoidal shape. The proposed algorithm gives robust control for the reversal of the reference speed and continuously calculates position of the rotor at transients as well as steady state. The robustness of the proposed algorithm is proved through the MATLAB simulation.