Applications of ANFIS and Fuzzy Algorithms for Improvement of the DTC Performance for the Three Phase Saturated Model of Induction Motor

Direct torque control (DTC) of an induction motor fed by a voltage source inverter is a simple scheme that doesn’t need long computation time. The motor terminal voltages and currents are sampled to estimate the motor flux linkage and electromagnetic torque using a flux observer. The main advantage of DTC technique is that it isn’t sensitive to the variation in motor parameters except the stator resistance in its flux observer especially at low speed operation. In this paper, two observers are used for online stator resistance identification for the DTC flux observer, one observer based on fuzzy logic while the other is based on ANFIS algorithm. The saturated p model of the induction motor is used which is more practical than the approximate linear model especially in the large motors. The authors also introduced a speed observer based on Lyapunov design and compared with another observer based on ANFIS design as well as the classical flux observer used with DTC technique. Simulation results show that the observers are validated and give a good performance in the different operating conditions. Also the authors have found that the ANFIS observer gives good performance as well as the Lyapunov and fuzzy observers.