Date of submission DDjr4f.1/VVVV· Condition monitoring (CM) based Maintenance is an effective way to ensure a machine's reliability during its useful life,' hence reducing the occurrence of unexpected accidents and bringing economic benefits. Awareness of condition monitoring has grown in recent years and so more attentions have been paid to the subject. Although traditional condition monitoring systems (using vibration, speed measurement, temperature monitoring, .etc) are still very effective in particular fields, they have some deficiencies, such as difficulty in implementation and the inability to provide remote and contactless measurement, which limit the condition monitoring systems' wide application. Acoustic measurements do not have these deficiencies as well as providing information richness. One major drawback limiting the use of acoustic measurements in industry, howev~r,. is that the signal can be seriously influenced by environmental factor§,~.:SUeli.l~s,lreverberation and background noise. Fortunately, developments in h'ardware)t~'chnology and signal processing have shown a potential for reducing these influences by using array technologies. However, large scale acoustic arrays are too expensive to be applied in many situations, and so small scale arrays offer a cost-effective alternative. This thesis concentrates on developing a new condition monitoring system using a small scale acoustic array. This system first localises the acoustic source, which is the object of condition monitoring, in the industrial environment. Then, based upon this localisation, the system uses beam-forming to enhance the signal propagating from the source direction and attenuate signals from other directions. Since reverberation signals often propagate from directions other than the source, this procedure has the potential to reduce the effects of reverberation. Other pre-processing methods, such as band-pass filters and temporal averaging are then used to further enhance the signal to noise ratio. Finally, the processed signals are used to monitor the condition of desired machine and diagnose the potential faults. The thesis is divided into 4 parts. In part 1, the motivation of this project and the reasons why acoustic method and small scale array technologies are used are introduced. In part 2, the technologies relating to ,t~e establishment of this new condition monitoring system are investig,!ted;, .rhe;: cpp.~ents include 1) investigation of the array's configuration, 2) time delay estimation algorithms used in industrial environment and 3) other issues relating to acoustic condition monitoring using the new system. In part 3, the new system is established and used to monitor the condition and diagnose the potential faults of a 4-cylinder diesel engine in industrial environments. The experimental results show that this system is effective in this practical application and has potential to be developed further. In part 4, a summary of this thesis is given.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:504737 |
| Date | January 2008 |
| Creators | Jiang, Jian |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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