Comparison Analysis of Two types of Electrical Circuits for Sensorless Brushless DC Motor Control

Abstract

　In this research, the effects of two types of electrical circuits, which detect back Electromotive Force (EMF) signals and output six step square waveform rotor position signals of 3 phase Brushless DC (BLDC) motors, on sensorless control are analyzed by implementing a coupled analysis of a Finite Elements Method (FEM) model of a BLDC motor and the electrical circuit. The 1^st electrical circuit uses a dynamic threshold level which changes automatically according to the back EMF maximum level, and the 2^nd electrical circuit uses a static threshold level which is determined at the start of motor control and is fixed regardless of the back EMF maximum level. Also, the results of the coupled analysis are verified by implementing experimental evaluation using an 8 pole 12 slot BLDC motor and embedded motor controller. Through this research, the advantages of the 1^st electrical circuit is verified.