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Proceedings Paper

A method on error analysis for large-aperture optical telescope control system
Author(s): Yanrui Su; Qiang Wang; Fabao Yan; Xiang Liu; Yongmei Huang
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Paper Abstract

For large-aperture optical telescope, compared with the performance of azimuth in the control system, arc second-level jitters exist in elevation under different speeds' working mode, especially low-speed working mode in the process of its acquisition, tracking and pointing. The jitters are closely related to the working speed of the elevation, resulting in the reduction of accuracy and low-speed stability of the telescope. By collecting a large number of measured data to the elevation, we do analysis on jitters in the time domain, frequency domain and space domain respectively. And the relation between jitter points and the leading speed of elevation and the corresponding space angle is concluded that the jitters perform as periodic disturbance in space domain and the period of the corresponding space angle of the jitter points is 79.1″ approximately. Then we did simulation, analysis and comparison to the influence of the disturbance sources, like PWM power level output disturbance, torque (acceleration) disturbance, speed feedback disturbance and position feedback disturbance on the elevation to find that the space periodic disturbance still exist in the elevation performance. It leads us to infer that the problems maybe exist in angle measurement unit. The telescope employs a 24-bit photoelectric encoder and we can calculate the encoder grating angular resolution as 79.1016'', which is as the corresponding angle value in the whole encoder system of one period of the subdivision signal. The value is approximately equal to the space frequency of the jitters. Therefore, the working elevation of the telescope is affected by subdivision errors and the period of the subdivision error is identical to the period of encoder grating angular. Through comprehensive consideration and mathematical analysis, that DC subdivision error of subdivision error sources causes the jitters is determined, which is verified in the practical engineering. The method that analyze error sources from time domain, frequency domain and space domain respectively has a very good role in guiding to find disturbance sources for large-aperture optical telescope.

Paper Details

Date Published: 24 October 2016
PDF: 5 pages
Proc. SPIE 9682, 8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes, 96820C (24 October 2016); doi: 10.1117/12.2241486
Show Author Affiliations
Yanrui Su, Institute of Optics and Electronics (China)
Key Lab. of Optical Engineering (China)
Univ. of Chinese Academy of Sciences (China)
Qiang Wang, Institute of Optics and Electronics (China)
Key Lab. of Optical Engineering (China)
Fabao Yan, Central South Univ. (China)
Xiang Liu, Institute of Optics and Electronics (China)
Key Lab. of Optical Engineering (China)
Yongmei Huang, Institute of Optics and Electronics (China)
Key Lab. of Optical Engineering (China)


Published in SPIE Proceedings Vol. 9682:
8th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Large Mirrors and Telescopes
Myung K. Cho; Bin Fan, Editor(s)

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