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Title: Fault diagnosis of sensor networked complex structures : a virtual beam-like structure approach
Authors: Wang, Hong
Degree: Ph.D.
Issue Date: 2017
Abstract: Fault detection and localization techniques are among the prominent technical processes involved in ensuring reliability. This is particularly true with regard to safety related processes or systems such as trains, power plants, and aircrafts which may also be characterized by limited datasets compiled through real measurements (e.g. pre-launching testing). Sensor-network based fault diagnosis in complex structures with limited prior knowledge is an interesting but difficult topic in structure health monitoring. In this study, a novel method for the fault diagnosis of sensor networked complex structures based on a novel optimized virtual beam-like structure (VBLS) approach is developed to fault diagnosis of the pre-launching systems. The statistical methods together with adaptive threshold technique are presented for fault detection to overcome the challenge of obtaining an appropriate threshold value with only limited experimental data. A complex structure is regarded as a combination of numerous virtual beam-like structures considering the vibration transmission paths from vibration sources to each sensor. The "virtual beam" consisting of a sensor chain automatically represents a candidate vibration transmission path, which can be obtained automatically by an improved optimization algorithm. The dynamic response of the structures in this vibration transmission path can demonstrate obvious fault features if there is a fault (e.g., cracks in connecting rods or around bolts, and bolt-loosening etc.). These fault features can be effectively characterized and efficiently captured and utilized for fault localization using the optimization method based on the virtual beam-like structure concept. This novel virtual beam-like-structure approach is applicable to fault diagnosis of complex structures without too much prior knowledge of the faults, and with only limited prior knowledge of normal operational conditions. Neither does it require stationary response data, nor is it confined to a specific structure design. It is easy to implement within a sensor network attached to the monitored structure. The effectiveness of the proposed virtual beam-like structure approach is well validated in experiments for both single-fault and multi-fault diagnosis including loosening bolts or cracks around bolts of complex structures such as bolted-base hanging structures in satellites. Compared with the classical subtract on negative add on positive (SNAP) localization methods, the proposed virtual beam-like structure (VBLS) approach has proved to be more accurate for fault localization. The computational complexity of the virtual beam-like structure approach has been evaluated, which indicates that the proposed method provides a promising solution to on-line fault diagnosis of the sensor networked complex structures with limited prior knowledge.
Subjects: Hong Kong Polytechnic University -- Dissertations
Fault location (Engineering)
System failures (Engineering)
Pages: xix, 188 pages : color illustrations
Appears in Collections:Thesis

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