Simulation of non linear adaptive observer for sensorless induction motor control BENHENICHE Abdelhak (1)-(2) and BENSAKER Bachir (2) benheniche2006@yahoo.fr bensaker_bachir@yahoo.fr (1) Electrotechnical Department; Mouloud Mammeri Tizi-Ouzou University (2) Electronic Department; Badji Mokhtar Annaba University ABSTRACT--This paper presents a model reference adaptive system based sensorless induction motor drive. In this scheme, an adaptive full order flux observer is used. The simulation result show that with the large PI gain for the adaptive scheme, the convergence for the speed estimation is fast and very well, however higher harmonics and noises are included in the estimated speed. Usually noises caused by inverter. Simulation results show that proposed scheme can estimate the motor speed under various adaptive PI gains and estimated speed can replace to measured speed in sensorless induction motor. Keywords: Induction motor; Sensorless control; Pole placement; MRAS speed estimation; Lyapunov function. 1. INTRODUCTION Three phase induction motor is widely used in many industries, mainly due to its rigidness, maintenance free operation, and relatively low cost. In contrast to the commutation dc motor, it can be used in aggressive or volatile environments since there are no risks of corrosion or sparks. However, induction motor constitute a theoretically challenging control problem since the dynamical system is non linear, the electrical rotor variable are not measurable, and the physical parameters are most often imprecisely known. [1]-[2]- [3]-[6]. It is well known from control theory that a state estimator, called also state observer, is a dynamic system that is driven by the input-output of the considered system, estimate asymptotically its unmeasurable state variable. It uses an adaptive mechanism involving as input, the error between the measured and estimated output value of the system. It is a “software sensor”that plays an important role in the estimation of the unmeasurable state variables that are essential not only in the sensorless control techniques. As au result, the drive has a wider adjustable speed range and can be operated at very low speed. This paper presents the simulation results of the proposed scheme which has been implanted on a 0.75KW induction motor driver.The systematic of this paper consist of four sections. Section I describes the overview of the observation and control system structure of induction motor under studies. Section II discusses with the model of adaptive flux observer while section III describes the adaptive scheme for speed estimation. Section V depicts the simulation results of the designed induction motor control. Finally, section VI gives the conclusion of this paper. 2. MATHEMATICAL MODELS FOR INDUCTION MOTOR AND ADAPTIVE FLUX OBSERVER II.1. Dynamic model of induction motor For an induction motor, if the stator current i s and rotor flux ∅  are selected as the state variables equations can be expressed as (1)in the stationary reference frame[2]      ∅  =            ∅  +   0   (1)   =  (2) Where   =       is stator current ∅  = ∅  ∅    is rotor flux