A Nonlinear Reduced Order Observer for Rotor Position Estimation of Sensorless Permanent Magnet Brushless DC Motor Drive

This paper presents a nonlinear reduced order observer for rotor position estimation of sensorless permanent magnet brushless DC motor. The PMBLDC motors are widely used as they possess high power density and are simpler to control. However the operation of PMBLDC motor, demands the knowledge of rotor position as a prerequisite. In most of the drive systems, the rotor position sensors and encoders reduce the robustness and also increase the frictional losses. In order to overcome the disadvantages introduced by position sensors, there arises a need for sensorless scheme of the drive. In this paper, a nonlinear reduced order observer based sensorless algorithm is described. As the back EMfs contain the information of rotor position and speed, these two can be extracted with the estimated back EMFs. The back EMFs can be estimated by sensing three input voltages and two currents. The estimated rotor position and speed are close to the actual ones. Simulation results verify the effectiveness of this sensorless scheme