絕對式光學編碼器之研發

Abstract

工具機產業有「工業之母」之稱號，舉凡汽車、航太等運輸產業或是風力發電太陽能發電等綠能產業，精密工具機設備皆扮演不可或缺的角色。長久以來，我國工具機的產值與出口量皆位於全球排名前五名，因此可說台灣為工具機生產大國，但因內部最重要的位置回饋系統編碼器，須長期仰賴國外進口，成本始終居高不下，導致獲利無法大幅提升。 較常使用的編碼器可分為兩種，一為增量式編碼器，增量式編碼器之優點為易提升其解析度，但缺點在於當斷電再復電時無法判斷目前的位置；而另一種為絕對式編碼器，將每一位置作編碼定義，當斷電再復電時無須參考零點即可判斷目前位置，但因機械結構限制導致精度難以提升。故本研究設計一絕對式編碼器，解決結構上的限制以提升產業競爭力。 本研究所設計之絕對式編碼器，包含內部碼盤或光柵尺之光學架構、編碼理論與數值運算之架構。以往在絕對式編碼器內部碼盤或光柵尺上的光學架構使用全透光或全反射定義絕對位置，而本研究利用不同透光率或反射率的變化呈現出不同的光強度，利用此變化來大幅增加整個絕對位置的編碼數量。 以往使用全透光或全反射的結構，因此可忽略光源衰減之影響。而在本研究中使用不同光強度定義位置，光源強度衰減會影響電壓值判斷，進而影響輸出位置的準確度。因此其中一軌為了校正光源光強度而產生的編碼，利於光源衰退時作數學運算校正電壓值。 在後端數值運算的架構，利用編碼理論與數值計算達到偵錯與容錯之功能，而增強整個編碼的校正能力。最後位置輸出時，每一位置所定義的數值，利用數值計算即能得出75萬個絕對位置，若解析度為400μm時，可製出約300公尺且絕對位置定義不重複之絕對式編碼器。

Machinery is a foundation of industry, covered the transportation and green energy, precision machine equipment is very important in this industry. Both the value of production and export in Taiwan is the world's top five over the years, so we can say that Taiwan is one of the leading country of machine tools. However, the encoders in these equipment are the major import from foreign for a long time. Because of these cost, it can not lead to increase profitability. One of the type is incremental in usual encoder. Its advantage is to easily upgrade the resolution. But when electric power is cut and restored, it can not determine the current position. The other is absolute in usual encoder. Its principle is to define all position. Although it can determine the current position when electric power is cut and restored, precision is difficult to improve due to the mechanical structure. Thus, it can solve the structural limit to enhance the industrial competitiveness in this research designed the absolute encoder. This study developed an absolute encoder, including the grating encoded and computing software. In the past, grating only having total transmittance or total reflectance was used to define absolute position in the absolute encoder. But this study is the use of different reflectance or transmittance for showing different light intensity, to increase the amount of the entire absolute position encoded. Using the structure of total transmission and reflection previously, so it can ignore the problem of light intensity reduction. In this study, using multi-track, and one of the encoded tracks especially solves the problem. When the light is weakening, it is better to arithmetic for correcting voltage value. The frame of back-end software architecture operations, using coding theory and numerical computing enhance the ability of the detection error and correction error. In outputting position, it obtains 750,000 positions by numerical computation and only memorys 15 kinds of voltage range corresponding to values. If the resolution is 400μm in this absolute encoder which is designed by this thesis, the length is about 300 meters and the defined absolute postions is non-repetitive.