Abstract: Traditional model reference adaptive theory MRAS(Model Reference Adaptive System)of induction motor speed sensorless drive has a shortcoming that the reference model is not accurate. This paper proposes a adaptive speed sensorless control AFO(Adaptive Full-Order Observer) that uses motor itself for the reference model, luenberger full order observer for the adjustable model. The syetem consists of a full order observer that yields the rotor fluxes of motor needs and also estimates the speed using an adaptive law. Based on the Lyapunov stability theory. The adaptive rotor speed is actually derived by using estimated stator currents error and estimated rotor flux. A fast convergent feedback matrix is designed based on the pole assignment method,to ensure the stable operation of the motor in a wide range. In view of the instability of the rotor speed estimation in low speed regenerative braking, by using the Routh stability criterion, a new feedback matrix is designed to guarantee the global stability of the speed estimation. The simulations results show its validity and effectiveness.

Key words: adaptive full order (AFO) observer, indction motor, speed sensorless, the feedback matrix