A Study of Sensorless Commutation Methods for Brushless DC Motors

Abstract

Due to advantages including high efficiency, linear speed torque characteristics and better superior speed performance, Brushless DC (BLDC) motors have been applied in many industrial areas, including automotives, aerospace, HVAC, refrigeration, medicine and industrial automation. BLDC motors are controlled in either sensor or sensorless condition, and many control methods have been proposed to improve their performance. This thesis investigates two sensorless control methods based on line voltage differences and the disturbance observer respectively. Each of these two sensorless control methods is first verified through Simulink simulation results, and then implemented in an experimental environment based on the DRV8312 Digital Motor Control Kit from Texas Instruments. To ensure the correct commutation of the BLDC motor, different phase delay compensation algorithms are applied to compensate the time delay from the low pass filters for these two sensorless control methods, respectively. Finally, a comparison is made between these two sensorless drives, and the robustness of the sensorless drives during loading transient is demonstrated by simulation results.