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The performance of the fuzzy logic controller (FLC) is better under transient conditions, while that of the proportional plus integral (PI) controller is superior near the steady-state condition. The combined advantages of these two controllers can be obtained with hybrid fuzzy-PI speed controller. The computations involved with the FLC are much higher as compared to that of the PI controller. Generally, the FLC output is near the maximum permissible value at the beginning of a transient condition but reducing with the reduction in the speed error. In this paper, instead of the FLC, a fuzzy equivalent proportional (FEP) controller is used along with the PI controller to make it a hybrid PI (HPI) controller which eventually is much faster and less computation intensive. The performance of the vector-controlled permanent magnet synchronous motor drive with this HPI controller is obtained with six switching functions, namely: 1) saturation; 2) hyperbolic tangent; 3) polynomial S function; 4) output of FEP controller only; 5) output of PI controller only; and 6) combination of the outputs of both the PI and FEP controllers. From the results, it is observed that the polynomial S switching function based HPI controller is better in general for most of the performances.
Date of Publication: Oct. 2011