無感測器直流無刷馬達驅動技術之研究

無刷馬達具有高轉矩、高功率密度等特性，經適當電子轉向，使其具有高效率運轉特性。在工業伺服系統應用上已成為主流，工作在許多場合上。由於一般無刷馬達運轉時，常搭配使用霍爾元件感測器及其對應之邏輯電路驅動馬達。若能夠不需使用感測器來達到相同驅動目的，可更加符合經濟效應。本論文主要為分析以反電動勢為依據之無感測器驅動方法，探討各文獻中無感測器驅動方法之優、缺點，提出一套低成本及易實現的新型無感測器驅動方法。目前文獻所使用的無感測器驅動方法，多為利用反電動勢零交越點，取得馬達的換相訊號，最大的問題點為PWM的導通方式不同因而產生不同的馬達三相端電壓，所以判斷反電動勢零交越點的未導通相端電壓值亦為不同，因此需根據PWM的導通方式而有不同的判斷電壓值。本論文所提出的方法以馬達三相線圈端電壓獲取虛擬中性點電壓(Virtual neutral Voltage)，再將其因PWM造成的諧波與外部施加的直流成分濾除，當此虛擬中性點電壓的波形過零點時，即可代表馬達的反電動勢零交越點(Zero cross point)，但此點提前真實換相點30度，因此利用磁滯比較器搭配電壓型控制電阻(VCR)達到相移的效果，藉由改變磁滯比較器的比較電壓，產生不同的上下觸發點電壓將換相訊號相移30度，得到真實換相點，磁滯比較器尚有一優點為不易受雜訊干擾而產生誤觸發的動作，因此可以避免換相點有誤動作的情形產生，造成馬達誤換相導致轉子鎖死。本論文所提出之估測方法採用中性點獲得反電動勢訊息，所以此法不受限於任何的永磁同步馬達類型與驅動方法，能使用於任何形式的同步馬達與驅動方法，且高速性能亦不受濾波器影響而使整體驅動效率降低。實驗驗證結果顯示，確實可由中性點電壓波形得知反電動勢零交越點，且無感測器估測方法所取得的估測換相訊號與馬達霍爾感知器換相訊號相比皆無誤，可以驗證此方法的實用性與可靠性。

關鍵字

無感測器驅動方法；反電動勢電壓零交越點；虛擬中性點；磁滯比較器；電壓型控制電阻

並列摘要

This thesis presents a low-cost and easily practical method for sensorless brushless dc (BLDC) motor drives. Based on the characteristics of the back electromotive force (back-EMF), the rotor position information would be detected. Hence, the main theme of this thesis is to design a unified approach to back-EMF detection of BLDC drives without using any current and Hall sensors. Pulse-width modulation (PWM) techniques and theoretical analysis of back-EMF are presented, and followed by the proposed unified back-EMF detection method based on virtual neutral voltage of motor. It will be shown that the proposed back-EMF detection method can not be constricted upon any kind of PWM technique and motor with nonideal back-EMF. Since the commutation control is very critical for BLDC motor control, a voltage-controlled phase shifter, composed of hysteresis comparator and voltage-controlled resistor (VCR), is proposed to compensate the phase delay of the back-EMF due to low-pass filter (LPF) under different speeds and also prevent the rapid output oscillations due to noise or high frequency ripples in the neutral voltage. Using the TMS320F2407 chip as a control core, some experiments have been carried out on the prototype, which is the surface-mounted permanent magnet BLDC motor, and the experimental results verify the analysis and demonstrate the practicality and reliability of proposed senosorless-control method.

並列關鍵字

Brushless dc motor ； back electromotive force ； virtual neutral voltage ； hysteresis comparator ； voltage-controlled resistor

參考文獻

[11]陳泊翰，2008，高性能無刷直流馬達無感測器驅動國立成功大學系統及船舶機電工程學系碩士論文。

[2]P. Damodharan and K. Vasudevan, “Indirect Back-EMF Zero Crossing Detection for Sensorless BLDC Motor Operation,” in Proceedings IEEE PEDS Conference, vol. 2, pp. 1107-1111, Nov. 2005.

[3]顏宏諭、陳泊翰、謝旻甫，2008，無刷直流馬達之無感測器驅動技術，馬達電子報，第299期。

[6] J. C. Moreira, “Indirect Sensing for Rotor Flux Position of Permanent Magnet AC Motors Operating in a Wide Speed Range,” IEEE Transactions Industry Applications, vol. 32, no. 6, pp. 1394-1401, Nov./Dec. 1996.

[7]J. X. Shen, Z. Q. Zhu, and D. Howe, “Sensorless Flux-Weakening Control of Permanent Magnet Brushless Machines using Third-Harmonic Back-EMF,” IEEE Transactions Industry Applications, vol. 40, no. 6, pp. 1629-1636, Nov./Dec. 2004.

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無感測器直流無刷馬達驅動技術之研究

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