ABSTRACT: Sensorless controls of induction motor drives are widely used in industry due to their high performance. Of the various Sensorless control technique Model Reference adaptive system (MRAS) is the most widely used, in which PI controllers are conventionally used in the adaptation mechanism. The performance of many of the previously developed sensorless schemes for control of induction motor in low speed region is not found to be satisfactory. To improve the performance in the low speed region a novel method is proposed in this paper in which the conventionally used PI controller is replaced by an integrated fuzzy logic controller (IFLC) which is nothing but the combination of PI and fuzzy logic controller. Simulations are performed in Matlab/Simulink to verify the effectiveness of the proposed method. Simulation results are presented, analysed and compared for both PI and IFLC based MRAS speed observer and it is observed that the performance of motor during low speed region is improved with IFLC when compared to PI controller. Keywords: Sensorless control, MRAS, PI controller, IFLC I. INTRODUCTION Induction motors are widely used in high performance ac drives due to their low cost, ruggedness and reliable operation when compared to DC motors. Although induction motors have many advantages, they posses time-varying dynamic interactions and hence it is very difficult to design a high performance induction motor drive system using PI controller. Also when we are using speed sensors for speed measurement the reliability of the system decreases and hence the need for sensorless control of induction motor arises. With the use of sensorless control the cost and size of the drive are reduced there by increasing the reliability and robustness of the system with considerable reduction in maintenance requirement. Of the various sensorless techniques discussed in literature, it is observed that these techniques have been applied successfully for high and medium speed operation [1, 2] but very low speed and zero speed operation still pose a problem. Amongst the different sensorless technique in literature MRAS is one of the most attractive techniques used due to their simplicity of design Majority of adaptation schemes used PI controller in the adaptation mechanism to generate the estimated motor speed. Conventionally used PI controller in the adaptation mechanism was replaced by a fuzzy logic controller i
