Design of a Polarization-Analyzer Control System for the Lijiang 2.4m Telescope

Xin Yuxin; Qu Zhongquan; Fan Yufeng; Zhang Ruilong; He Shousheng

Astronomical Research and Technology > 2012 > 9(1): 78-85.

Xin Yuxin, Qu Zhongquan, Fan Yufeng, Zhang Ruilong, He Shousheng. Design of a Polarization-Analyzer Control System for the Lijiang 2.4m Telescope[J]. Astronomical Research and Technology, 2012, 9(1): 78-85.

Citation:

PDF (1645 KB)

Design of a Polarization-Analyzer Control System for the Lijiang 2.4m Telescope

1.
Yunnan Observatory, Chinese Academy of Sciences, Kunming 650011, China
2.
Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
3.
Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650011, China

More Information

Received Date: January 07, 2011
Revised Date: January 19, 2011
Published Date: January 14, 2012

Graphical Abstract

Abstract

Abstract

Polarimetry is one of the four major types of astronomical measurements (spectroscopy, photometry, polarimetry, and imaging). A polarization analyzer is an effective tool in polarimetry. We have realized a closed-loop polarization-analyzer control system, which consists of a step motor and an absolute encoder. The step motor is controlled through the TCP/IP protocol, and the encoder is controlled through the RS485 serial communication. The system has a polarization-angle measurement error of 0.42°, a stepping angle of 22.5°, and a slew range of 0~360°. These sufficiently meet the requirements for polarimetry. A traditional polarization-analyzer control system is of open loop and contains a step motor and a Hall device. Through the Hall-effect switch the initial position of the polarizer can be determined, and then commands are sent to the step motor for designated angles, such as 45°, 90°, 135°, and 180°. It is easy to be operated to realize its basic function but it has large errors because of lost steps of the motor, the number of which is hardly known. In case when the system is restarted after unexpected power out, the current position of the motor cannot be specified and the entire system (including the step motor) has to be initiated again. We use an absolute encoder to replace the Hall device in our closed-loop polarization-analyzer control system. We can inquire the absolute encoder to retrieve the information about the current position of the polarizer. The systematic error can be controlled by the encoder also, and the positioning accuracy depends on the resolution power of the encoder. There is no need to worry about any power off for the system because the position is displayed in real time. Overall, our polarization-analyzer control system has very good positioning accuracy and robust performance. It is convenient for polarimetric applications.
- Polarimetry,
- Closed-loop control,
- Step motor,
- Absolute encoder

FullText(HTML)

References (8)

References

[1]	谭徽松. 天体物理方法[M]. 昆明:云南天文台南方基地, 2008:114.
[2]	程福臻. 实测天体物理[M]. 合肥:中国科学技术大学, 2005:95-102.
[3]	Z Q Qu, X Y Zh, X K Chen, et al. A Solar Stokes Spectrum Telecope[J]. Solar Physics, 2001, 201(2):241-251.
[4]	S Bagnulo, M Sterzik. Measuring Stellar Magnetic Fields with FORS1 at the ESO VLT[C]//Svetlana V Berdyugina, K N Nagendra, Renzo Ramelli. Proceedings of the Conference Held 17-21 September. San Francisco:Astronomical Society of the Pacific, 2009:511.
[5]	Gisler Daniel, Schmid Hans Martin, Thalmann Christian, et al. CHEOPS/ZIMPOL:a VLT Instrument Study for the Polarimetric Search of Scattered Light from Extrasolar Planets[C]//Alan F M Moorwood, Iye Masanori. Ground-based Instrumentation for Astronomy. Proceedings of the SPIE, 2004, 5492:463-474.
[6]	C Packham, M Escuti, J Ginn, et al. Polarization Gratings:A Novel Polarimetric Component for Astronomical Instruments[J]. Publications of the Astronomical Society of the Pacific, 2010, 122:1471-1482.
[7]	Stanley B Lippamn. C++ Primer[M]. 李师贤, 译. 北京:人民邮电出版社, 2009.
[8]	梁伟. Visual C++网络编程经典案例详解[M]. 北京:清华大学出版社, 2010.

Articles Related

[1]	Hou Xiaozheng, Xu Qian, Liang Juan, Yi Letian, Xue Fei, Wang Hui. Research on Fast Calibration of Rotary Encoder Based on Particle Swarm Optimization [J]. Astronomical Research and Technology, 2022, 19(5): 487-492. DOI: 10.14005/j.cnki.issn1672-7673.20211213.002
[2]	Wang Gang, Lin Jiaben, Guo Jingjing, Zhang Xinwei, Tong Liyue, Bai Yang, Chen Chuiyu. Multi-axis Stepper Motor Control System Based on FPGA [J]. Astronomical Research and Technology, 2020, 17(2): 185-190.
[3]	Zhang Zongmeng, Wang Zhenglan, Yang Dehua, Wu Changcheng, Jin Zhenyu. Development and Test of a Stepper Motor Driven Displacement Actuator [J]. Astronomical Research and Technology, 2019, 16(3): 329-334.
[4]	ZHANG Li, WANG Jia-ning, ZHU Yong-tian, WU Li-yan. The SOPC-technology Based Design and Implementation of an IP Controller Core of the Low-Resolution Multi-Object Spectrograph for the LAMOST [J]. Astronomical Research and Technology, 2010, 7(1): 40-46.
[5]	HE Jun-bo, YAN Yi-hua, LIU Fei, CHANG Huan. The Design of a Closed-loop Control System for a Antenna Array [J]. Astronomical Research and Technology, 2008, 5(4): 373-379.
[6]	MAO Yao, BAO Qi-liang, MA Wen-li, YIN Yi-lin. Driving System Design for 1.2 m Alt-Az Telescope and Synchronized Control for Multi-motor [J]. Astronomical Research and Technology, 2006, 3(3): 289-294.
[7]	TIAN Li-li, WANG Jin-hu, CHEN Ying-wei, XIAN Shu-hua, LI Feng-yun, WANG Hong-qi. The Application of the Tape Encoder and Ring Encoder on the 2.16m Telescope [J]. Astronomical Research and Technology, 2005, 2(3): 170-176.
[8]	ZHENG Xiang-Ming, WANG Wu, FENG He-Sheng. Pointing Model Study of the 1.2m Telescope-Establishment of Small Period Model of Measuring Angle Coder [J]. Astronomical Research and Technology, 2004, 1(1): 64-68.
[9]	Wu Zhenyu, Wang jiaji. The Absolute Proper Motion of M3 and Its Galactic Orbit [J]. Publications of the Yunnan Observatory, 1999, 0(S1): 327-331.
[10]	Xiong Guanzhu, Chen Peisheng. The Absolute K Magnitude and the Distance of OH/IR Stars [J]. Publications of the Yunnan Observatory, 1995, 0(3): 1-8.