Research on speed sensorless direct torque fuzzy control of induction motors

In order to solve the large torque ripples which exist in induction motors based on conventional direct torque control(DTC), especially at a low speed, fuzzy control theory is applied to DTC system. The speed of induction motor is estimated by Mras(Model Reference Adaptive System) method. Based on Mras and fuzzy control of speed sensorless induction direct torque control model is constructed. The stator current and stator voltage of induction motor are used to develop speed sensorless is based on Mras. In the fuzzy model strategy, the structure of the three-input single-output are adopted, the stator flux angle, the stator flux, the stator flux error, and the torque error are as fuzzy variables which are fuzzed into several fuzzy subsets to optimize select of the voltage vector. The control system is simulated on the platform of Matlab/Simulink. Compared to the conventional direct control system, the results of the simulation prove that the method of the fuzzy DTC controller can effectively improve the low-speed performance of the induction motor, reduce the torque ripple, and have a good dynamic response performance.