高精度光电编码器在南极望远镜中的应用研究

摘要

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 .%南极内陆极低的温度给天文望远镜的设计和研制带来了很大的挑战。要实现高精度的跟踪精度，望远镜上只有采用高精度的光电编码器作为轴角反馈元件，但是南极内陆冬季的温度范围从-50℃～80℃，在这样低温的环境下，直接采用光电编码器是不可能的。为了实现南极望远镜高精度的指向跟踪运动，特别是优于0.3角秒的跟踪精度时，必须要选用光电编码器。该报告首先研究了温度效应对光电编码器的影响，提出了一个初步的温控设计方案，然后基于CFD的模拟优化和低温环境实验验证，提出了实际的温控方案，并成功应用在第二台南极巡天望远镜的控制系统中。实验显示在-80℃的环境温度中，仅需要约6 W的加热功率就可以将读数头的温度提高到25℃左右，满足了光电编码器在南极低温环境中的使用要求。