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Jiang P.,CAS National Astronomical Observatories | Jiang P.,Key Laboratory of Radio Astronomy
2014 31th URSI General Assembly and Scientific Symposium, URSI GASS 2014 | Year: 2014

The reflector of Five-hundred-meter Aperture Spherical radio Telescope (FAST) is supported by cable-net structure, so that to enable its reflector surface to form a paraboloid from a sphere in real time through active control. However, such form-changing operation would lead to about 500MPa stress range for the cable-net structure. Such stress range is nearly twice as much of that defined by the relative standard. So the cable-net structure is the most critical and expendable part of FAST reflector system. The service life of FAST would directly depend on the residual fatigue life of its cable-net structure. Then, the present paper would make an effort to find a more appropriate deformation strategy to decrease the stress amplitude of the cable during form-changing operation. © 2014 IEEE. Source


Hu K.,Key Laboratory of Radio Astronomy | Yusup A.,Key Laboratory of Radio Astronomy
ICEIEC 2013 - Proceedings of 2013 IEEE 4th International Conference on Electronics Information and Emergency Communication | Year: 2013

The pointing of an antenna always exists deviation due to track deformation, gravity and thermal influence. Through long time observation, we find that sunlight also has some influence on antenna structure. In order to get the antenna pointing deviation in the effects of the sunlight of 25m antenna in Urumqi, we use the frame-typed level and thermometer to make a week's measurement about the temperature around the antenna and the antenna tilt. The measured data was analyzed and combined with the track deformation data, and the pointing error fixed model as well as the thermal load deformation model were built. The measured data was fitted by the two models, and the result shows that the model can well reflect the pointing error and thermal load error, thus can give a better understanding of the antenna deformation, and also can give some good reference to antenna pointing calibration and the antenna's reconstruction. © 2013 IEEE. Source


Kong X.,CAS National Astronomical Observatories | Kong X.,Key Laboratory of Radio Astronomy | Kong X.,University of Chinese Academy of Sciences | Jiang P.,CAS National Astronomical Observatories | And 3 more authors.
Gongcheng Lixue/Engineering Mechanics | Year: 2013

A five-hundred-meter Aperture Spherical radio Telescope (FAST) is supported by a cable-net structure, which enables its surface to form a paraboloid in real time under active control. However, such form-changing operation would lead to about 500MPa of a fatigue stress range for the cable-net structure. This stress range is more than twice as that defined by the relative standard. Therefore, the cable-net structure is the most critical part of a FAST reflector system. Obviously, the fatigue stress will have a significant impact on the reliability of FAST during its service life. The dimensional analysis is used for studying main factor which affects the stress range of structure. Based on the finite element software ANSYS, the form-changing of cable-net structure is simulated. At last, optimal form-changing strategy is proposed for releasing the fatigue stress of cable-net structure, which would be in favor of improving the reliability of a cable-net structure. Source


Hu K.,Key Laboratory of Radio Astronomy | Yusup A.,Key Laboratory of Radio Astronomy | Chang W.,Key Laboratory of Radio Astronomy
ICEIEC 2013 - Proceedings of 2013 IEEE 4th International Conference on Electronics Information and Emergency Communication | Year: 2013

This paper is the article which researches the control algorithm applied to servo system of antenna sub-reflector, the main control algorithm is fuzzy sliding mode control algorithm. This paper first introduces the idea of fuzzy-sliding mode algorithm, then describes the background knowledge about applying to the antenna sub-reflector. The main content of this paper is simulation and comparative analysis, firstly introduces the details of the theoretical model of fuzzy sliding mode controller including sliding mode controller and fuzzy controller, secondly combines these two controller by using a simply way, new controller is fuzzy-sliding model controller. Then this paper gets out some figures of response curves by Simulink. According to the comparison with the response curves of PID algorithm, conclusion can be obtained that: Compared with the PID controller, fuzzy-sliding mode controller has better superiority. It can satisfy the higher requirements of sub-reflector to the speed of response and control accuracy. © 2013 IEEE. Source


Zhou K.,CAS National Astronomical Observatories | Zhou K.,Key Laboratory of Radio Astronomy | Zhou K.,University of Chinese Academy of Sciences | Zhou K.,Paris Observatory | And 9 more authors.
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2016

Terahertz electromagnetic radiation (from 0.1THz to 10THz) that lies in the boundary region between light and radio waves has attracted much attention in recent years due to its certain extraordinary properties. This paper presents the design and simulation investigation of a 0.66THz low-loss subharmonical mixer based on GaAs Schottky barrier diodes. The antiparallel diodes pair is fabricated from China Electronics Technology Group Coporation-13 Institute, flip-chip mounted on a 25um-thick gallium-arsenide substrate. The simulation results exhibits that the conversion loss of the mixer is below 10 dB in the band from 0.6THz to 0.7THz. © IEEE. Source

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