A research programme is described to develop an optical method to measure the instantaneous angular speed (lAS) of machinery in condition monitoring. In this research, special consideration is given to the development ofa non-contact method of measuring IAS using a laser mouse. Further development of its application to the detection ofparallel misalignment fault in condition monitoring is described. This research requires multidisciplinary design, involving the knowledge from measurement, electrical instruments, optics, mechanical engineering, majntenance engineering, modelling and programming. The research presented is a novel approach to non-contact measurement of lAS through the use of a laser mouse. Initial investigation of the characteristics of this device shows its potential for the measurement of lAS. The software application is developed to adapt the laser mouse to the Microsoft Windows operating system. Tests are carried out which show that the pixel variation acquired by the laser mouse has a linear relationship with its physical movement relative to the movement of the rotating shafts. Calibration tests show good correlation with the results of conventional, contact IAS measurement using a shaft encoder. It is concluded that using a laser mouse to measure the IAS is reliable method. An application of the IAS technique to the detection of the parallel shaft misalignment faults on a geared induction motor is described. Firstly, a mathematical model of IAS is developed for parallel misalignment. Secondly, a geared induction motor test rig is used to validate the model and to demonstrate the practical efficacy of IAS measurement by a laser mouse as a condition monitoring tool for detecting and identifying such faults. Finally, in agreement with the lAS model, the motor test rig is applied to show that parallel misalignment can be identified from the features extracted from the lAS data produced by the laser mouse. Specially, in the time domain, the amplitude of IAS waveform and the standard deviation of the IAS variation have a great increase when the parallel misalignment is occurred. The increase of the magnitude of parallel misalignment can make the amplitude of IAS waveform and the standard deviation of the IAS variation larger. In the frequency domain, the amplitude of the first component of rotational frequency appears much higher than those of the 2nd and 3rd components and has more increases, when the parallel misalignment is occurred. As the fault severity increased, the key characteristic of IAS spectra is a rise in the level of the first component of rotation frequency. The sensitivity of IAS to variations in power supply frequency and torque is also investigated using the motor test rig. It is found that variation in power supply frequency can increase in the value of the amplitude of IAS waveform and the standard deviation of IAS variation in the time domain, and can also increase in the amplitude of first component of rotational frequency in IAS spectra in the frequency domain. However, there is found to be little change in IAS with variation in torque. In conclusion, the laser mouse approach to non-contact measurement of lAS presented in this thesis can be used as an alternative to existing contact and non-contact methods, and the IAS technique can be used to identify the parallel misalignment faults in condition monitoring.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:491490 |
| Date | January 2008 |
| Creators | Zhi, Shengke |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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