| Summary: | 碩士 === 國立交通大學 === 工學院精密與自動化工程學程 === 100 === The characteristics of brushless direct current (BLDC) motors include high speed, high torque, high power density, rapidly transient response, and ease of control. With many advantages, BLDC motors have become more and more popular in our life and are applied to a wide variety of applications like DVD player, hard disk, i-Robot, electrical vehicles, compressor, etc. Conventional BLDC motors use internal magnetic sensors, e.g. Hall effect sensors to feedback signals and obtain rotor position. However, due to cost and size subject to mechanical or environment constraints, and reliability of thermal effect that may cause commutation error. Sensorless control methods without Hall-effect sensors have been widely used in recent years. According to stator winding patterns, BLDC can be radial or axial windings. Axial-flux BLDC motors outperform radial field in aspects of torque, power, efficiency, and compact geometry shape [Krishnan and Beutler, 1985]. Hence this thesis focuses on analyzes and then realizes a sensorless drive for the axial-flux BLDC motor with a position estimation method to control the motor from standstill state to desired speed based on back-EMFs zero-crossing of floating phase; i.e. not excited phase of BLDC motor estimated method and arrange in pairs with open-loop start-up algorithm to implement velocity control of BLDC motors. Finally, simulation and experimental results will demonstrate effectiveness of the proposed sensorless control method.
Keywords: Axial-Flux, Sensorless, BLDC, Velocity control
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