International Journal of Engineering Research and Development e-ISSN: 2278-067X, p-ISSN: 2278-800X, www.ijerd.com Volume 9, Issue 4 (December 2013), PP. 51-56 51 A Modified Iterative Learning Controller for Reducing Torque Pulsations in Field Oriented Control Driven Permanent Magnet Synchronous Motor K.Jeyaprakash 1 , B.Adhavan 2 , C.S.Ravichandran 3 PG scholar, EEE Dept, Sri Ramakrishna engineering college, Coimbatore 1 Associate professor, EEE Dept, Sri Ramakrishna engineering college, Coimbatore 2 Abstract:- Permanent magnet synchronous motors are mostly used in low and high power and variable speed applications. Major disadvantage of PMSM is that the motor exhibits torque pulsations due to many factors from motor and drive. This paper proposes a modified iterative learning controller to reduce the pulsations in torque of permanent magnet synchronous motors (PMSM). Modified ILC has memory to store previous control actions and previous error. Proposed ILC scheme consists of previous and current loop gain in order to minimize the torque oscillations. Previous control actions are stored and used to reduce the steady state periodic torque pulsations. Space vector pulse width modulation is used to reduce the harmonic noise in motor current which in turn improves performance of drive. Torque error is calculated and the i qs ref current gets altered accordingly to minimize torque variations. The simulation of the PMSM drive with field oriented control and proposed controller is done using MATLAB 2009b. The results obtained shows better reduction of torque pulsation and improved performance over conventional methods. Keywords - PMSM, Torque Pulsation, Modified Iterative Learning Control (ILC), Space Vector Pulse Width Modulation (SVPWM), Field oriented control (FOC). I. INTRODUCTION PMSM motors plays major role in high performance servo applications, robotics and adjustable speed drives (ASDs) where torque pulsations can adversely affect the drive system performance. DC and AC induction motors are getting replaced by PMSM in the industries due to compactness, efficiency, robustness, reliability and shape adoption to the working environment power density and torque-to-inertia ratio. It is necessary to reduce these torque pulsations to increase efficiency and lifetime of drive system and to improve the production in industries. The causes of torque pulsations includes  Non-sinusoidal distribution of flux linkage,  Self and mutual inductances with harmonics,  Variable magnetic reluctance at stator slots. An active filter (AF) with an IGBT and two RLC high-pass EMI noise filters are used to reduce the torque ripple. The filter uses the hysteresis voltage control method is used in filter and the hysteresis current control method is used in motor main circuit. In this way, it makes sure that almost sinusoidal voltage is applied to the motor termin als[2]. An extended Kalman filter with state variables stator current and PM flux to estimate the flux variations due to the non-sinusoidal flux distribution is designed. A current compensation is done to reduce the negative influence caused by demagnetization[9]. A modified periodic current reference is tracked to obtain smooth torque.In order to improve current tracking in the presence of periodic reference signals and disturbances in field oriented control driven PMSM, the repetitive current control techniques is applied. The q-axis current reference has been modified to achieve constant torque [4]. Nonlinearity of PMSM and existence of inverter makes the drive nonlinear and time- variant. The system is changed to linear time-invariant system by linearization of model around average values, which can be used to optimize vector control [6]. Space Vector PWM (SVPWM) refers to a special switching sequence of the upper three power transistors of a three-phase power inverter. It has been shown to engender less harmonic distortion in the output voltages and(or) currents applied to the phases of an AC motor and to provide more efficient use of supply voltage compared with sinusoidal modulation technique [3,5].