Optimal Determination of Commutation Position of a Brushless DC Motor by Utilizing the Symmetry of Terminal Voltage

摘要

A brushless DC (BLDC) motor has been used in various applications of electromechanical systems due to its high efficiency and good controllability over a wide range of speed. The position information of a rotor is identified by using the sensors or the sensorless algorithms in order to energize the correct phase of windings. One of the popular sensorless algorithms is to utilize the zero-crossing of the back-emf of non-energized phase. However, it may involve the detection error of rotor position, and it results in the reduction of maximum torque and efficiency of the BLDC motor. Some researchers have proposed an intelligent commutation tuning method by minimizing winding currents[1]. Others presented a new rotor position estimation method based on neutral voltage compensation[2]. Their methods have demerits to monitor both current and terminal voltage. This paper presents a method to determine the exact commutation position of a BLDC motor by utilizing the symmetry of terminal voltage of non-energized phase. It also develops a DSP-based controller to verify the proposed method, and it shows that the proposed method improves the performance of a BLDC motor.