Torque Ripple Minimization of BLDC Motor by Kalman Filter

In classical control of brushless dc motors, flux distribution is assumed trapezoidal and fed current is controlled rectangular to obtain a desired constant torque. However, in reality this assumption may not be correct due to nonuniformity of magnetic materials and design trade-offs. These factors together with current controller limitation, can lead to an undesirable torqueripple. Hence torque ripple has been the main issue of the servo derive systems, in which the speed fluctuation, vibration and acoustic noise should be minimized. This torque ripple also deteriorates the precision of the parameters of brushless dc motors.To minimizing of torque ripples we are using an adaptive filter technique i.e., kalmanfilter(KF) is using minimizing the torque ripples. KF design framework for general nonlinear systems, the key of which includes the single-domain nonlinear filtering and segmentation over domain of interest (DOI). The estimation error system is firstly transformed into a polytopic system through a global linearization procedure, such that theKalmanFilter(KF) is formulated by linear matrix inequalities (LMIs).the torque ripple minimization in BLDCmotor by using kalman filter. Torque ripples are minimized by using so many methods like by using improved dc-dc converters, by using micro controllers, by using implementation of zero crossing detectors , by using extended kalman filter etc. . These all cannot be accurately minimize the ripples. they all can be minimize the ripples up to 60% . Kalman filter is used based on the estimation of the previous instants ..It can be resolved b step by step process we can get ripples up to 40% . The reduction variable have to select basedin the trial and error method.so that we cannot achieve 100% torque ripple minimization. The simulation results validate the effectiveness of the proposed scheme. Keywords-BLDC Motor, Kalman Filter, Torque ripple reduction 1.Introduction:1.1 Brushless DC Motors:The brushless DC motor drive system incorporating motors with permanent magnet excitations are being used in a rapidly expanding range of applications, including computer peripherals, automotive and machine tool industries applications such as robot, electric bicycle, wheelchairs and home appliances due to the high power density and efficiency with an excellent maintenance characteristic. Furthermore, small BLDC motor are much interested in the un-manned aero vehicles such as a drone. The usage of high power , high speed BLDC motor s are dramatically increased in these markets. Although BLDC motors have an excellent torque characteristics, the output torque has ripple due to the non-linear back-EMF of the motor and the commutation current ripple. As well known, the back-EMF of the motor is effected by the characteristics of the permanent magnet and stator, and has high order harmonics due to the slot effect and magnetization direction of the magnet with concentrated phase windings. These harmonics make torque ripple with a constant phase current in the conduction region. Furthermore the current ripple in the commutation region where the conducting phase changing region, makes additional torque ripple. The shaft position sensors, such as Optical or Hall-effect sensors are usually used to detect exact rotor position. The brushless DC motor has trapezoidal Electro Motive Force (EMF) and quasi-rectangular