FAST望远镜舱索系统位置、振动频率的动态检测是实现闭环控制的基础。针对传统测量方法用于FAST望远镜舱索系统缩比模型振动频率检测时操作复杂、干扰性大和不易实现的缺点，根据被测物体连续振动变化的特点，提出双目视觉高速动态测频方法。该方法通过计算被测物点位三维坐标，利用快速傅立叶变换对离散的实时点位信息进行频谱变换，分析确定被测物的振动频率。实验显示，双目视觉高速动态测频方法在频率分辨率为0.04 Hz的情况下，重复测量、分时段测量的误差分别小于0.08 Hz和0.04 Hz，表明对于舱索系统之类的低频振动物体，该方法能有效满足振动频率的动态测量要求。
It is the foundation to realize closed loop control that the FAST telescope feed cabin-cable's location and vibration frequency are dynamically measured. Due to the fact that traditional measurement methods for FAST telescope cabin-cable scaled model's vibration frequency measuring are of complicated operation, large disturbance, and difficult to realize, a high-speed dynamic frequency-measuring method based on binocular camera is put forward to cope with the characteristics of continuous changes in the vibrating object to be measured, It calculates object's three-dimensional coordinates, and uses fast Fourier transform to obtain the spectrum of real-time discrete point locations. Then the vibration frequency is analyzed. Experiments show that in the case of frequency's resolution being 0.04 Hz, the repeated measurement and time-segmented measuring errors of binocular camera high-speed dynamic frequency measuring are not greater than 0.08 Hz and 0.04 Hz, respectively, indicating that for low frequency vibrating objects like the feed cabin cable, this method can effectively satisfy the requirement of dynamic frequency measuring.
[1] Nan Rendong, Di Li, Cheng Jinjin, et al. The five-hundred-meter aperature spherical radio telescope (FAST) project[C]//Proceedings of the International Topical Meeting on Microwave Photonics. New York:IEEE,2015:331-346.
[2] 孙京海, 朱文白, 南仁东. FAST馈源支撑系统中质量阻尼器的初步设计[J]. 天文研究与技术, 2009, 6(1):36-42. Sun Jinghai, Zhu Wenbai, Nan Rendong. Design of the mass damper preliminary in fast feed supporting system[J]. Astronomical research and technology, 2009, 6(1):36-42.
[3] 骆亚波. 测量机器人在FAST馈源动态跟踪测量中的应用[D]. 郑州:中国人民解放军信息工程大学, 2003. Luo Yabo. The application of measuring robot in the fast feed dynamic tracking measurement[D]. Zhengzhou:Information and Engineering University of the Chinese PLA, 2003.
[4] 任红飞. GPS动态测量技术的检测及其在FAST工程中的应用研究[D]. 郑州:中国人民解放军信息工程大学, 2008. Ren Hongfei. Detection of GPS dynamic measurement technology and its application in FAST engineering[D]. Zhengzhou:Information Engineering University of the Chinese PLA, 2008.
[5] 胡金文, 朱丽春. FAST项目中激光惯性融合测量技术的研究[J]. 科学技术与工程, 2009(11):2884-2889. Hu Jinwen, Zhu Lichun. Research on measurement technology of laser inertial fusion in the project of FAST[J]. Scientific Technology and Engineering, 2009(11):2884-2889.
[6] 张玉贵. 烟气轮机叶片振动的非接触式在线监测关键技术研究[D]. 天津:天津大学, 2008. Zhang Yugui. Study on key technology of non-contact online monitoring of vibration of flue gas turbine blade[D]. Tianjin:Tianjin University,2008.
[7] Waxman A M, Sinha S S. Dynamic stereo:passive ranging to moving objects from relative image flows[J]. IEEE Transactions on Pattern Analysis and Machine Intelligence, 1986(4):406-412.
[8] 范生宏. 工业数字摄影测量中人工标志的研究与应用[D]. 郑州:中国解放军信息工程大学, 2006. Fan shenghong. Research and application of artificial mark in industrial digital photogrammetry[D]. Zhengzhou:Information Engineering University of the Chinese PLA, 2006.
[9] 黄桂平. 数字近景工业摄影测量关键技术研究与应用[D]. 天津:天津大学, 2005. Huang Guiping. Research and applications for key techniques of digital close range industrial photogrammetry[D]. Tianjin:Tianjin University, 2005.
[10] 于英. 双目立体工业摄影测量关键技术研究与应用[D]. 郑州:中国解放军信息工程大学, 2010. Yu Ying. Key technology research and application of binocular stereo industrial photogrammetry[D]. Zhengzhou:Information Engineering University of the Chinese PLA, 2010.
[11] Akay M. Nonlinear biomedical signal processing vol. Ⅱ:Dynamic analysis and modeling[M]. Wiley:Wiley-IEEE Press, 2000.
[12] Smith C C, Dahl J F, Thornhill R J. The duality of leakage and aliasing and improved digital spectral analysis techniques[J]. Journal of Dynamic Systems, Measurement, and Control, 1996, 118(3):741-747.
[13] Antoniou A. Digital signal processing[M]. Toronto, Canada:McGraw-Hill Book Companies, 2006..
[14] Shannon C E. Communication in the presence of noise, Proc[J]. Institute of Radio Engineers, 1949, 37(1):10-21.
[15] Nyquist H. Certain topics in telegraph transmission theory[J]. Proceedings of the IEEE, 2002, 90(2):280-305.
[16] 滕军, 幸厚冰. 索参数对斜拉结构固有频率的影响分析[J]. 工程抗震与加固改造, 2010, 32(6):25-30. Teng Jun, Xing Houbing. The effect analysis on the natural frequency of the suspension structure by cable parameters[J]. Journal of Engineering and Seismic Strengthening, 2010, 32(6):25-30.
