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Title: Design and implementation of gearboxes vibration based condition monitoring system
Author: Ibrahim, Ghalib Rzayyig
ISNI:       0000 0004 2712 6084
Awarding Body: The Manchester Metropolitan University
Current Institution: Manchester Metropolitan University
Date of Award: 2011
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The use of gearboxes for power transfer is widespread throughout industry. However, machines today are operating at higher speeds than ever before and gear wear and fatigue failures are serious and legitimate concerns. Incipient fault detection in gears has thus become the subject of intensive investigation and at this stage of development there are many competing condition monitoring methods based on vibration signal analysis. Vibration signals obtained from a gearbox were complex multi-component signals, generated by tooth meshing, gear shaft rotation, gearbox resonance vibration signatures and a substantial amount of noise. This thesis summarizes the research steps taken after a review of (i) current maintenance strategies, (ii) gearbox condition monitoring techniques, (iii) gear vibration fundamentals and (iv) common gearbox failure modes. A mathematical model of the gearbox was used to predict the effects of load and tooth breakage effects on induced vibrations. A test rig was built around an 11 kW two stage helical gearbox, designed and fabricated for experimental data collection. Simulation and experimental work was carried out for a healthy pair of gears under different loads for different drive speeds and a pair suffering from degrees of tooth breakage. Conventional methods using the time-domain of the vibration signal (RMS, kurtosis, skewness and the zero figure of merit) were used for detecting and diagnose the seeded faults. The total energy method was applied to the gear meshing frequency and its sidebands, as obtained from the FFT, to detect the presence of the faults, and the results compared with those obtained by the conventional techniques. The proposed method appears much more effective at detecting and diagnosing tooth breakage than statistical features extracted from the time-domain. Joint time-frequency domain techniques were then used to determine their effectiveness for diagnosing the seeded faults in the gearbox system when the gearbox operates under output loads and at different speeds. A comparison was made between empirical mode decomposition and smoothed pseudo Wigner-Ville distribution methods based on vibration signature. From the results obtained it appears that the empirical mode decompose technique offers a more effective and faster way to detect faults. To improve signal-to-noise ratio, a novel scheme based on adaptive noise cancellation technique with a least squares algorithms was used on the gearbox experimental vibration signals. It is concluded that this method offers the most effective way of all those tested to detect faults.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available