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A new control strategy of induction motors with stator flux orientation is presented. According to the dynamic model of induction motors, stator flux is controlled effectively but affected by stator resistance. Based on the fuzzy logic control theory the stator resistance estimator is designed to realize stator resistance on-line tuning. The Simulation confirmed the feasibility of the method. Keywords stator flux orientation; fuzzy logic control; stator resistance compensation . INTRODUCTIONVector control and direct torque control (DTC) are most widely used in high dynamic performance AC speed regulation system. Both of them have their own strengths, but also have some weaknesses. In vector control system, rotor flux orientation is used for the dynamic decoupling of the stator current excitation component and torque component, and the PI continuous mode is used for the control of torque and rotor flux ,but its performance depends on the precise of aligning d-coordinate with the direction of rotor flux, called rotor flux orientation .And the observation or calculation of rotor flux is based on the motor mathematical-model, so rotor flux orientation is easily affected by the motor parameters, especially the rotor resistance which varies with temperature in running. In direct torque control system, the PWM drive signals are produced directly according the sectors of the stator flux moved in. And it is not sensitive to the rotor parameters, but the torque ripple is inevitable because of Peng-Peng control. The torque ripple may be reduced by increasing the number of voltage vector, but it cannot be eliminated [1].In this paper, a new control strategy of induction motors with stator flux orientation that combines the advantages of both Vector Control and Direct Torque Control is presented. Stator flux is controlled directly by fully compensating the stator resistance voltage drop. Based on the fuzzy control theory, the strategy of on-line tuning stator resistance is used to avoid the steady-state error of stator flux caused by the variations of stator resistance.The advantage of this strategy is that the flux orientation will not be affected by any motor parameters and also the torque ripple caused by Peng-Peng control is avoided with continuous control. And performance of the system is improved by using this self-adapting strategy [2]. MODEL OF INDUCTION MOTOR BASE ON THE STATOR FLUX ORIENTATION CONTROLIn synchronous speed coordinate (d, q coordinate), when d-axis is aligned the direction of the stator flux s , and q-axis is perpendicular to s , it is called stator flux orientation. According to the magnetic flux equations of synchronous speed coordinates, for induction motor it derives [3]: m s s s r L i L i (1) r m s s s s m r L L i L i L (2) So: m r s s s s m r L L dt di L dt d dt di L dt d ) ( (3) In squirrel-cage motor, we have: 0 r s r r r r j dt d i R u (4) Put (1), (2), (3) into (4),it derives: ) 5 ( ) ( ) ( 0 r m s s s s m s m r s s s s m r m s s s

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