電動輔助自行車中置馬達最佳化設計

Optimal design of a middle motor for a pedal electric cycle

江家銘(Jia-Ming Jiang)

指導教授 ： 陽毅平

國立臺灣大學/工學院/機械工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02140

摘要

本文提出電動輔助自行車薄形中置式永磁馬達的最佳設計。此中置馬達是一個軸向磁通薄型馬達，藉由結合馬達轉子與擺線盤使其在同一平面上，故本研究設計一款動力組，包含一軸向磁通馬達與擺線減速機，達到薄型化的效果，並使空間利用率最大。也因為擺線減速機耐用與堅固之特性，本文動力組相較於其他動力組更為耐用與堅固，適合用於易產生衝擊與碰撞之自行車上。
　　本文先計算電動自行車的動力規格，並決定控制方法及選擇減速機與馬達類型。接著設計擺線減速機之規格參數與效率計算，並依此推算馬達需求規格。然後挑選馬達的類型、繞線方式、槽數與極數，以及繞線規劃，並利用磁路模型求解氣隙磁通密度，進一步求得馬達性能。再以多目標函數的最佳化，得到一組最佳的馬達參數尺寸，利用有限元素分析軟體進行驗證，最後進行製造與測試，實驗數據結果顯示感應電動勢與模擬值雖然只差7%，然而馬達力矩卻因軸承的摩擦力以及霍爾感測器的精度不足下降至原設計規格的一半。

關鍵字

電動自行車 ； 永磁無刷馬達 ； 軸向磁通 ； 擺線減速機 ； 有限元素分析 ； 軟磁複合材料

並列摘要

Pure electric bikes or pedal electric cycles have been welcomed as a kind of new personal transportation. This paper proposes a novel design of a middle motor for pedal electric cycles. This middle motor is an axial-flux permanent magnet brushless dc motor with a stator plate, facing which is a rotor plate as part of a cycloidal reducer next to the stator. The whole set of middle motor and cycloidal reducer is easily installed along the same axle of the crankset of bike.
In the preliminary design, driving requirements are used to make specifications of the middle motor. The numbers of stator slots and magnet poles on rotor are then chosen for a best winding factor and the winding layout is determined accordingly. A one-dimensional magnetic circuit model of the middle motor is built and its shape optimized by using a multifunctional optimization system tool. Finally, the resulting design is verified and refined by the finite element analysis.
A prototype middle motor is fabricated. A new material, soft magnet composite, is used to replace traditional silica steel for stator. The neodymium magnets (NdFeB) are mounted on the rotor surface for its high magnet energy density. Experimental results show that the maximum torque is about 60% of what was designed because of the significant friction exerted from mechanical assemblies. However, the back electromotive force is sinusoidal and the motor is easily and efficiently controlled by sinusoidal current inputs.

並列關鍵字

Electric bike ； brushless permanent magnet motor ； axial flux ； cycloidal speed reducer ； finite element analysis ； Soft magnetic composite

參考文獻

[63] 丁富軒, 直驅式軸向磁通電動輔助自行車馬達最佳設計分析, 碩士論文, 國立台灣大學, 台北, 2013.

[77] 邱卓群, 擺線齒輪減速器之創新設計與分析, 碩士論文, 國立台灣大學, 台北, 2012.

[93] 吳大宇, 電動機車內藏式永磁馬達多目標最佳化設計, 碩士論文, 國立台灣大學, 台北, 2013.

[6] G. Rose, "E-bikes and urban transportation: emerging issues and unresolved questions," Transportation, vol. 39, 2012, pp. 81-96.

[7] W. Chlebosz, G. Ombach, and J. Junak, "Comparison of permanent magnet brushless motor with outer and inner rotor used in e-bike, " in XIX International Conference on Electrical Machines (ICEM), Rome, Italy, 2010, pp. 1- 5.