Fuzzy logic direct torque control for permanent magnet synchronous motors

An outstanding feature of the conventional direct torque control (DTC) for permanent magnet synchronous motors (PMSM) is its fast dynamic response. However, large torque and flux linkage ripples are generated because of the use of the hysteresis controllers and the crude position signals based on six 60° angular regions for selecting the space voltage vectors. This paper proposes a fuzzy logic based PMSM DTC system, in which the torque error, stator flux linkage error and the stator flux vector angular position are all properly fuzzified into several fuzzy subsets, so that a more suitable space voltage vector can be selected to minimize the torque and flux linkage ripples. Both the simulation and the experimental results show that the modified DTC system has a much better steady state performance while retaining the good dynamic performance.