Direct Torque Control of Permanent Magnet Synchronous Motor Based on Fuzzy Logic

In the conventional direct torque control (DTC) of a permanent magnet synchronous motor (PMSM), hysteresis controllers are employed to select the proper voltage vector resulting in large torque ripples, and the inverse voltage vector, used in this system instead of the zero voltage vectors used in an induction motor, can accelerate the torque response but enlarges the torque ripples at the same time. To improve the steady state performance of the PMSM DTC system a fuzzy logic scheme is introduced in this paper. In the PMSM fuzzy DTC system, the stator flux linkage error, the torque error and the stator flux angle are all properly fuzzified into several fuzzy subsets to accurately select the voltage vector, and the real stator flux angle is mapped onto a sextant region in order to minimize the number of fuzzy rules and shorten the computation time. Experimental results show that both the steady state and dynamic performances are improved by the application of the fuzzy logic scheme.