OUTPUT-FEEDBACK CONTROL OF CURRENT-FED INDUCTION-MOTORS WITH UNKNOWN ROTOR RESISTANCE

On the basis of a third-order reduced model of an induction motor (cur rent-fed) we design an output feedback control (from rotor speed measu rements) which guarantees global exponential tracking of speed and rot or flux modulus reference signals. An adaptive version is designed whe n load torque is constant and unknown, The rotor resistance, which is a crucial parameter for the control, is updated by a seventh-order dyn amic estimator designed on the basis of speed, current, and voltage si gnals. The estimator provides exponentially convergent estimates In ph ysical operating conditions, A good performance of the adaptive contro l algorithm using a sampling time of 0.5 ms is documented by experimen tal tests, Experiments show that the main advantage of the proposed co ntrol with respect to the classical field oriented control algorithm i s the decoupling of speed and flux tracking; in addition, efficiency i s improved in presence of rotor resistance variations.