本研究目標為探討影響高精度磁性編碼器(Magnetic encoder)準確度(Accuracy)的磁性尺充磁製程條件。當磁性尺材料的磁化強度(Magnetization)與均勻度達到需求規格後，充磁製程條件將會影響磁場強度(Magnetic field strength)一致性與磁極距(Pole pitch)準確度，而這兩個指標將是決定編碼器準確度與解析度(Resolution)的重要參數。
磁性編碼器之主要零件包括磁性尺、讀頭及訊號處理IC；其牽涉之關鍵技術涵蓋磁性尺的材料與製程技術、充磁製程技術、讀頭之材料與製程及校正技術、讀頭封(安)裝與磁性尺組合技術、訊號讀取與解析技術、以及系統整合與評估校正技術等。其中充磁製程條件包括充磁機脈衝電流大小及其穩定性、充磁頭尺寸與線圈匝數設計、充磁頭治具及其運動平台的定位解析度、重複精度及準確度、平台真直度(Straightness)與Pitch, Yaw及Roll的誤差、以及環境控制等。由於製程條件的種類相當多，本文將從理論模擬與實驗來找出各種充磁條件對磁性編碼器位置準確度的影響程度，最後精進製程方法。
針對本文目標，研究方法分為充磁實驗與電腦模擬兩部分。實驗方面使用三種不同導磁率材料當作充磁底座，並在底座挖六種寬度之槽孔，量測充磁後剩磁磁場強度，觀察波峰與磁極距之變化趨勢，爾後使用磁阻感測器解析磁性編碼器位置，並與光學編碼器或雷射干涉儀位置作比較計算磁性編碼器絕對(Absolute)與增量(Incremental)位置精度。模擬方面使用ANSYS Maxwell電磁分析軟體，重複上述實驗之不同背鐵模型輸入脈衝電流作電磁計算，與實驗結果相比得知理論誤差值，進一步推測誤差發生之原因並且嘗試改善。經由上述研究方法，自製磁性編碼器已能達±10 μm/m以內之位置精度。

The purpose of this study is to investigate the effect of magnetizing process conditions to the accuracy of a magnetic encoder. When the strength and uniformity of magnetization satisfy the specification, magnetizing process conditions will impact on magnetic field strength and pole pitch. These two parameters are key factors to decide accuracy and resolution.
The main components of a magnetic encoder include scale, read head and signal processor IC. The critical technologies of magnetic encoder involve material processing, magnetizing, read head packaging, assembling, signal resolving, system integration and calibration. Among which, magnetizing part includes current stability, head geometry, winding, fixture, environmental control and linear stage. As for linear stage, accuracy, repeatability, resolution, roll, pitch, yaw and straightness are important. This research discovered how various process conditions influence the accuracy by simulation and experiment.
Experiments were planned to detect peak value and pole pitch of magnetic scales which were magnetized on the 3 magnetic permeability base with each 6 groove width. The AMR sensor measuring results were compared by optical encoder and laser interferometer. Simulations were also set up to build the same model through Maxwell CAE and were contrasted to experimental results. Magnetic encoder which fabricated by research team can reach accuracy ±10 μm/m after completing this study.

[1] Gardner research, “2016 World Machine Tools Survey,” Gardner Business Media, 2016, pp.3-10.
[2] 經濟部經濟部工業局2015-2017工具機暨零組件產業專業人才需求調查，取自：http://hrd.college.itri.org.tw/ITSD/download_paget.aspx
[3] K. Miyashita, T. Takahashi, and M. Yamanaka, “Features of a magnetic rotary encoder,” IEEE Trans. Magn., Vol. 23, (1987)2182 -2184.
[4] J. Lopez, M. Artes, and I. Alejandre, “Vibration Behavior Analysis of Optical Linear Encoders Based on Different Scanning Methods,” SEM Annual Conference, June 1-4, 2009.
[5] 東洋磁氣工業株式會社，取自：http://www.magnix.com/
[6] Y. J. Luo, E. T. Hwang, and S. M. Huang, “Multi-pole magnetization of high resolution magnetic encoder,” Proceedings of EEIC/ICWA Exposition, Chicago, USA, Oct. 4-7, (1993)237 -242.
[7] Y. Kikuchi, T. Yoneda, Y. Kataoka, K. Shiotani, H. Wakiwaka, and H. Yamada, “Considerations of output voltage waveform on magnetic linear encoder for artificial heart using linear pulse motor,” Sens. Actuator A-Phys. 81, (2000)309-312.
[8] 歐陽遠聲, 2014, “高解析度磁儲媒介設計與製作,” 碩士論文, 國立清華大學/動力機械工程研究所
[9] 陳家妤, 2015, “磁性量測系統之磁化與精度分析,” 碩士論文, 國立清華大學/動力機械工程研究所
[10] 徐志豪, 2015, “多種極距磁性尺研發,” 博士論文, 國立清華大學/動力機械工程研究所
[11] N. Takahashi, “3D analysis of magnetization distribution magnetized by capacitor-discharge impulse magnetizer,” Journal of Materials Processing Technology, 108, pp. 241-245, 2001.
[12] N. C. Cheung, “An innovative method to increase the resolution of optical encoders in motion servo systems,” in IEEE Int. Conf. on Power Electronics and Driver Systems.（PEDS）, 1999, pp. 797-802.
[13] 金重勳, 2002, “磁性技術手冊,” 中華民國磁性技術協會
[14] 清華大學生醫工程與環境科學系彭旭霞教授醫用磁振造影實驗室，取自：http://oz.nthu.edu.tw/~u9762127/hhpeng/c_pmri_syllabus_2016.html
[15] Magnetic domain. Retrieved from：https://en.wikipedia.org/wiki/Magnetic_domain
[16] 安培定律. Retrieved from：http://www.twwiki.com/category-view-3037-9.html
[17] Hard and soft magnet. Retrieved from：https://en.wikibooks.org/wiki/Introduction_-to_Inorganic_Chemistry/Metals_and_Alloys:_Structure,_Bonding,_Electronic_and_Magnetic_Properties
[18] Electronics Tutorials. Retrieved from： http://www.electronicstutorials.ws/electro-magnetism/hall-effect.html
[19] Sensitec. Retrieved from： http://sensitec.com/
[20] Renishaw XL-80 laser system. Retrieved from：http://www.renishaw.com.tw/
[21] 曾天陽, 2018, “磁性編碼器系統準確度提升之研究,” 碩士論文, 國立清華大學/動力機械工程研究所
[22] Alexander H. Slocum, 1992, “Precision Machine Design,” pp. 61-64, New Jersey: Prentice Hall.
[23] 蔡信威, 2015, “磁性尺系統整合,” 碩士論文, 國立清華大學/動力機械工程研究所