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Mathematical Problems in Engineering
Volume 2015, Article ID 967034, 9 pages
http://dx.doi.org/10.1155/2015/967034
Research Article

Subdivision Error Analysis and Compensation for Photoelectric Angle Encoder in a Telescope Control System

1Institute of Optics and Electronics, Chinese Academy of Sciences, No. 1 Guangdian Road, Chengdu 610209, China
2Key Laboratory of Optical Engineering, Chinese Academy of Sciences, Chengdu 610209, China
3University of Chinese Academy of Sciences, Beijing 100049, China
4School of Geosciences and InfoPhysics, Central South University, Changsha 410083, China

Received 19 May 2015; Revised 12 July 2015; Accepted 14 July 2015

Academic Editor: Asier Ibeas

Copyright © 2015 Yanrui Su et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

As the position sensor, photoelectric angle encoder affects the accuracy and stability of telescope control system (TCS). A TCS-based subdivision error compensation method for encoder is proposed. Six types of subdivision error sources are extracted through mathematical expressions of subdivision signals first. Then the period length relationships between subdivision signals and subdivision errors are deduced. And the error compensation algorithm only utilizing the shaft position of TCS is put forward, along with two control models; Model I is that the algorithm applies only to the speed loop of TCS and Model II is applied to both speed loop and position loop. Combined with actual project, elevation jittering phenomenon of the telescope is discussed to decide the necessity of DC-type subdivision error compensation. Low-speed elevation performance before and after error compensation is compared to help decide that Model II is preferred. In contrast to original performance, the maximum position error of the elevation with DC subdivision error compensation is reduced by approximately 47.9% from 1.42 to 0.74. The elevation gets a huge decrease in jitters. This method can compensate the encoder subdivision errors effectively and improve the stability of TCS.