軸向磁通無感測器直流無刷馬達之速度控制

Abstract

直流無刷馬達具有高轉數、高扭力、高功率密度、響應快、輕薄短小及易於控制的特性，但傳統直流無刷馬達是藉由馬達內部的磁場感測器做為換相機制，此方式會使體積與成本增加，且馬達運轉所產生的溫度熱效應會改變電子構件的特性，而造成換相時機不正常等缺點；因此開始採用無感測器的馬達驅動方式。無感測器馬達的換相機制是依據未激磁相的反電動勢訊號做為換相的基礎，即是利用反電動勢位置偵測法得知直流無刷馬達轉子的磁極位置。 一般而言，直流無刷馬達依其定子線圈繞阻方式，可分為徑向磁通與軸向磁通，在相同的體積條件下，軸向磁通馬達比徑向磁通馬達具有更佳的輸出功率與輸出扭矩，且薄型化使重量更輕。故本論文以薄型軸向磁通直流無刷馬達，搭配無感測器驅動的換相方式，應用於清潔機器人，其目的讓使用範圍更加寬廣，容許環境空間所造成的幾何干涉。此外，不同使用條件（地板材質、操作環境、集塵袋髒污程度）會使馬達轉速的飄移而產生吸力太強或減弱之情況發生，而且假若馬達永遠在全速運轉的情形下操作，也會造成馬達壽命減短。所以，本研究進一步設計一系列的速度控制器，包括PID控制器、模糊控制器、以及自調模糊控制器。隨不同操作環境來調整馬達轉速，因應環境特性，調整馬達所相對應的控制參數，避免馬達持續處於高負載與高轉速，以延長馬達的使用壽命，亦達到節能的目的。

關鍵字: 軸向磁通、無感測器、直流無刷馬達、速度控制

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