無感測器直流無刷馬達驅動與誤差補償

Abstract

本論文針對無感測器的直流無刷馬達提出了一種十二步驅動方法來取代霍爾元件。此驅動方法藉由干擾觀測器來偵測兩種反電動勢差；反電動勢差及二次反電動勢差可以各提供六個換相點，形成一個擁有三十度解析度的偵測方法。同時，本論文引入 PWM_ON_PWM 切換方式來消除馬達非導通相續流的影響。實驗結果與常用的線電壓差驅動方法做比較，證實本論文的方法擁有更好的性能。 然而，實務上驅動馬達時存在著各種誤差來源：低通濾波器的換相延遲、感測器雜訊、轉子的永久磁鐵結構、功率元件及二極體的壓降等等。這些誤差來源造成不準確的換相點，進而導致電流漣波。本論文將此現象做深入的研究，並同時考慮實務上馬達反電動勢的波形，提出一個以電流為指標的補償方法。此方法不只能夠量化這些誤差的總和並補償之，還能夠推導出等效的反電動勢波形。並針對此方法提出三個演算法來提高此方法的可行性及適用性。

This thesis presents a new twelve-step sensorless drive for brushless DC motor (BLDC) based on back-electromotive force (back-EMF) differences, which are estimated from the disturbance observer (DOB) structure. Availability of rotor position information with a resolution of 30 degrees and commutation without phase shift are the advantages of using the back-EMF differences. By designing a proper low pass filter in the DOB structure, the proposed sensorless drive has better performance by comparing with the back-EMF detection method based on line voltage differences. However, there are a variety of error sources during commutation; these errors are being analyzed in depth. The overall effect of these errors reflects on the commutation instants; commutation error leads to pulsating current. The unideal back-EMF waveform, on the other hand, results in crown-shape current waveform instead of rectangular. Considering the commutation error and the unideal back-EMF into the study of the current waveform, this thesis introduces a Current Index approach that can be applied to derive the overall commutation error and the equivalent flat width of the back-EMF waveform. Furthermore, three algorithms are presented to increase the feasibility of the proposed method.