Novel speed sensorless fuzzy control for induction motors

A novel sensorless system for induction motors based on an adaptive fuzzy system is designed and fully described. The novelty of this new sensor-less structure is obtained by mixing the open-loop estimator response with the steady-state estimator one. A fuzzy adaptive system weights the two estimated speed values according to the motor operating point. The final speed value is obtained averaging the previously weighted speeds. Moreover, the open-loop estimator response is improved by means of using an adaptive fuzzy controlled filter that selects the optimised cut off frequency. The aim of this system is to obtain a moderate performance without a great computational charge. Besides, the final system is more robust against variations of the internal parameters of the motor. The results validate the entire work, not only in transient and steady state but also in the start-up.