Algorithm for rapidly predicting the worst surface accuracy of deployable mesh reflectors

Author(s):  
Xiaoshun Wu ◽  
Runhui Cheng ◽  
Tommy H.T. Chan ◽  
Guihai Liu ◽  
Juwei Xia
Keyword(s):  
2015 ◽  
Vol 135 (5) ◽  
pp. 165-170
Author(s):  
Kenta Nakazawa ◽  
Takashi Sasaki ◽  
Kazuhiro Hane

2022 ◽  
Vol 134 (1031) ◽  
pp. 015003
Author(s):  
Yong Zhang ◽  
Guoping Li ◽  
Guohua Zhou ◽  
Qishuai Lu ◽  
Heng Zuo ◽  
...  

Abstract The surface accuracy of a large radio telescope’s primary reflector is easily affected by gravity and temperature change during observations. An active surface system is crucial to ensure the regular operation and high-quality data output of the radio telescope. We propose a real-time closed-loop active surface system including two components. The first component, a new type of photoelectric edge sensor, detects the angle change of the adjacent panels. The second component, the displacement actuator, adjusts the panels’ position and posture to compensate for the angle changes. So, over the entire observation, the closed-loop surface control system with these two components could actively maintain the primary reflector’s accuracy in real time. Using this approach, we constructed an experimental active surface system for the Xinjiang Qitai 110 m Radio Telescope (QTT) to test the maintenance of the surface accuracy. The angle measurement accuracy is better than 0.″2, and the positioning accuracy of the displacement actuator could achieve ±15 μm over the whole 50 mm stroke. The preliminary test results show that the accuracy requirements of the QTT’s primary reflector surface can be met using the active surface system we propose.


Author(s):  
Yi-Fan Lu ◽  
Hong-Hao Yue ◽  
Zong-Quan Deng ◽  
Horn-Sen Tzou

Along with the rapid development of space exploration, communication and earth observation technology, the large space membrane structure gains its widely application. With poor stiffness and large flexibility, the surface accuracy of membrane structures can be easily interfered by the space environment variety, so precise shape control of in-orbit space membrane reflector becomes the focus in space technology area. As an object for this paper, the active control of the membrane reflector deformation under typical thermal disturbance in space is investigated. Considering of Von-Karman geometrical nonlinearity, the equilibrium equations of a circular membrane are firstly presented based on Hamilton’s Principle and Love’s thin shell theory. As a simplification for equilibrium equations, the nonlinear mathematical model for the circular membrane in a symmetrical temperature field is obtained. In the next place, an FE model for a circular membrane under thermal load is developed in Abaqus as an example. By contrasting the FEM deformation analysis with mathematical modeling solutions of circular membrane reflectors under typical thermal load, it is demonstrated that the theoretical model is capable of predicting the amplitude of membrane surface deformation. At last, a boundary actuation strategy for membrane shape control is proposed, which could effectively decrease the membrane wrinkle induced by thermal disturbance via precisely control to the tension of the SMA wire actuators. The simulation result indicates the effectiveness of boundary active control strategy on improving membrane surface accuracy with different temperature distributions. The conclusions of modeling and analysis in this paper will be an essential theoretical foundation for future research on active flatness control for in-orbit large space membrane structure.


2010 ◽  
Vol 126-128 ◽  
pp. 82-87
Author(s):  
Mao Li ◽  
Yong Wei Zhu ◽  
Jun Li ◽  
Jian Feng Ye ◽  
Ji Long Fan

The polishing pad plays a significant role in the Chemical Mechanical Polishing (CMP) process and its wear influences the surface accuracy of the polished wafer. A new polishing pad wear model is introduced and the law of pad wear along the pad radius is discussed, thus a new FAP with optimized pattern is designed and prepared in order. The flatness of the wafer lapped with a uniform pattern pad and that with an optimized pattern was compared. Results show that the PV value of the latter is lower that of the former.


Mechanik ◽  
2018 ◽  
Vol 91 (8-9) ◽  
pp. 737-740 ◽  
Author(s):  
Piotr Zyzak ◽  
Paweł Kobiela ◽  
Arnold Brożek ◽  
Marek Gabryś

In the paper are presented investigation results of an effects of adopted strategy of profile-dividing grinding of a cylindrical gear teeth, performed on the Rapid Höfler 900 grinder, on machining accuracy and surface roughness of the teeth. The strategies have taken into considerations changes in the following parameters determining obtained results of the grinding: number of passes, number of leads, shaping method of the grinding wheel.


2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Jong-Ho Choi ◽  
Min-Hyuk Kim ◽  
Luan Feng ◽  
Chany Lee ◽  
Hyun-Kyo Jung

Various inverse algorithms have been proposed to estimate brain electrical activities with magnetoencephalography (MEG) and electroencephalography (EEG). To validate and compare the performances of inverse algorithms, many researchers have used artificially constructed EEG and MEG datasets. When the artificial sources are reconstructed on the cortical surface, accuracy of the source estimates has been difficult to evaluate. In this paper, we suggest a new measure to evaluate the reconstructed EEG/MEG cortical sources more accurately. To validate the usefulness of the proposed method, comparison between conventional and proposed evaluation metrics was conducted using artificial cortical sources simulated under different noise conditions. The simulation results demonstrated that only the proposed method could reflect the source space geometry regardless of the number of source peaks.


2015 ◽  
Vol 27 (4) ◽  
pp. 42001
Author(s):  
王洪祥 Wang Hongxiang ◽  
朱本温 Zhu Benwen ◽  
陈贤华 Chen Xianhua ◽  
侯晶 Hou Jing ◽  
王景贺 Wang Jinghe

2018 ◽  
Vol 26 (1) ◽  
pp. 219-238 ◽  
Author(s):  
Zhiyong Yang ◽  
Qingnian Liu ◽  
Boming Zhang ◽  
Liang Xu ◽  
Zhanwen Tang ◽  
...  

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