| All kinds of mechanical devices and structure tend to become large-scale and high efficient with the industry developing and progress of science and technology. The mechanical devices and structure become very complex to meet the need of industry. The structure or devices are damaged is couldn't avoided during working under complex load and working for a long time. The loss caused by crash, fatigue, eroding and wear is about 6%- 8% of GDP of U.S.A. and Japan. In our country, accident number of structural damage is 10 times as many as that in € intense industrialization country in eighties of last century. In 1986, the loss is 12 hundred million $ caused by the space shuttle named "challenger" of U.S.A. crashed. In 1985, the accident cause of joint of electromotor set of Datong power plane crashed, In 1988, the accident cause of main beam of electromotor set of Qinling power plane crashed, those accident cause of loss near 1 hundred million RMB. In our country, 6 serious accidents ware been caused by rotor of over 50Mw electromotor set damaged badly during 1984 to 1991. Therefore, the study the theory and technique about large scale and complex mechanicaldevices and structure online inspect and early fault diagnosis is urgent task. Especially, how to detect the fault of structure as early as possible is engineers most want to do. But it is very difficult that faint signal produced by early fault is recognized.The research reports of our country and overseas show that at present the study of structure damage inspect by vibration characteristics carry out most on the simple and symmetry structure just as beam and frame etc. and result is given based on finite element numeric calculation. But the structure and join of practical device is quite complex, it is impossible modeling the practical device reliably by FE. So that realizing complex industrial device inspect online and early fault diagnosis by using vibrate testing technique is a problem that want to be solved urgently.Fault diagnosis technique is intercross subject. Especially, the base in theory of fault diagnosis of complex system is provided based on modern control theory, signal processing, pattern recognition, optimum method, decision-making and manual intelligent are developed rapidly.Structure damage detection is a research project that has wide background of industrial application. But realizing large-scale and complex structure damage inspect online is depend on techniques such as development of accurate testing technique and signal processing method, based on getting to the best advantage mix model of structure damage detection, the sensors are placed on structure reasonably and optimallyetc.The large-scale vibrating device as a researched object, the method of structure damage detection is studied. In general NDT technique such as ultrasonic test, ray test, magnetism test and pervade test etc. are applied in offline mostly. The project scheme is multi-testing points modeling to large-scale vibrating structure, getting detail vibrateproperties and structure damage characteristics from plenitudinous offline tests and analysis to structure as impotent information of online automatic fault diagnosis database. Then the method of few-testing points modeling to getting structure damage information has been researched. Placing sensors reasonably and realizing large-scale and complex structure damage inspect online are targets of this project.The large-scale vibrating screen has been applied widely in coal industry and other industrial areas as a kind of important device. As vibration mechanical device, it works very hardly and works in very wretched environment so that the beam of screen is damaged easily. Therefore, it is very important how to detect the fault of beam as early as possible to make the repair schedule reasonably and economically and to avoid the body hurt and device damage.In this thesis, how can locate a damaged beam of screen is studied serially. The regulation of beam vibration characteristics change depend on damage de...
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