Comparative study of alternative fuzzy logic control strategies of permanent magnet brushless AC drive

Application of fuzzy logic control to a vector-controlled permanent magnet brushless AC motor drive shows that it exhibits better speed control performance than the PI control, but it introduces significant current harmonics. Nonlinear distribution of fuzzy sets in the membership function of the output variable is employed to reduce the current harmonics, albeit with the deterioration of the speed control performance. A simple adaptive fuzzy logic control algorithm with self-tuned threshold speed error is proposed. It offers excellent speed control performance and robustness to parameter variations, whilst current harmonics are significantly reduced. The control performance under alternative control strategies is compared experimentally.