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This paper presents an improved speed sensorless vector control method for general-purpose induction motors (IMs). The proposed method is based on the d-q axis dynamic model of the induction motor and an improved closed-loop flux observer, which can achieve precise rotor and stator flux estimation over a wide speed range. And then, a rotor-speed-estimation method, based on fuzzy control theory, is discussed and deduced. Simulation results are compared between estimated speed got from fuzzy controller and common PI controller. Finally, a series of experimental research are conducted and the results verify the scheme above is valid and the estimated speed tracks the actual speed well in both rated speed region and field weakening region. The proposed algorithm has simpler control algorithms and little computational burden, both the flux observation and speed estimation can achieve perfect effect in both steady-state operating condition as well as in transient operation.