高精度光電編碼器在南極望遠鏡中的應用研究

顧伯忠 徐波 楊世海 杜福嘉 袁祥巖

摘要：南極內陸極低的溫度給天文望遠鏡的設計和研制帶來了很大的挑戰。要實現高精度的跟蹤精度，望遠鏡上只有采用高精度的光電編碼器作為軸角反饋元件，但是南極內陸冬季的溫度范圍從-50度到-80度，在這樣低溫的環境下，直接采用光電編碼器是不可能的。為了實現南極望遠鏡高精度的指向跟蹤運動，特別是優于0.3角秒的跟蹤精度時，必須要選用光電編碼器。本報告首先研究了溫度效應對光電編碼器的影響，提出了一個初步的溫控設計方案，然后基于CFD的模擬優化和低溫環境實驗驗證，提出了實際的溫控方案，并成功應用在第二臺南極巡天望遠鏡的控制系統中。實驗顯示在-80度的環境溫度中，僅需要約6瓦的加熱功率就可以將讀數頭的溫度提高到25度左右，滿足了光電編碼器在南極低溫環境中的使用要求。

關鍵詞：南極望遠鏡；軸角編碼器；熱控；CFD

Research on application of high resolution encoder in Antarctic telescopes

Abstract：The extremely low temperature in Antarctic inland area make a new challenge for telescope design and development. The usage of high accuracy encoder is the only way to improve the telescope tracking accuracy. However， due to the low temperatures ranging from -50 to -80 celsius degree in Antarctic winter time， there is no application of encoders under such a low temperature ever since. To realize the high accuracy of telescope pointing and tracking，especially for the cases of tracking accuracy better than 0.3arcsecond， high resolution encoders must be used. Based on the analysis of temperature influence on encoder， an initial thermal control design is carried out. Secondly， the thermal control method is optimized with CFD simulations and experiments. Finally， the effective thermal control method is used in the second telescope of three Antarctic Survey Telescopes （AST3）. By the comparison of normal temperature experiment and low temperature experiment， the encoder can reach a temperature of about 25 degree when it is under the circumstance of -80 degree after the thermal control design， and the power consumption is less than 6W. The experiment results indicate that the thermal control method can meet the requirement of keeping the temperature of encoder reader above -10 degree in Antarctic winter time by low power consumption .

Keywords：Antarctic telescope；angle encoder；thermal control；CFD

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