A special application of optical wireless data transfer, namely on-line monitoring and diagnostic of rotors in turbines and engines, has been considered in this thesis. In this application, to maintain line of sight, i.e. data transfer, between a sensor placed on a rotating component inside the turbine and a monitoring point placed in a fixed position outside the turbine, a periodic fast fading channel is generated, which gives the transceivers more flexibility regarding their mounting location. The communication in such a channel is affected by the intermittency and variation of the signal power, which produces a unique channel condition that influences the performance of the optical transceiver. To investigate the channel condition and the error rate of the periodic fast fading channel with signal fluctuation, a model is developed to simulate the optical channel by considering the variation of signal power as a result of the change in the relative position of the photodiode with respect to the Lambertian radiation pattern of the LED, in a simplified linear geometry. The error rate is estimated using the Saddlepoint approximation on a specific threshold strategy. The results show that the channel can afford the sensor data transmission and the performance can be improved by modifying several parameters, such as geometrical distance, transmitter power and load resistor. Compared to a normal channel, a higher load resistor on the photodiode front end has the advantage of decreasing the noise level and increasing the data capacity in the fast fading channel. The analysis of the automatic gain control amplifier indicates that a higher load resistor needs a lower loop gain and from the model of the Transimpedance amplifier (TIA), the bandwidth extension from the amplifier is more significant for a higher resistor. In addition to the theoretical model, an experimental setup is built to emulate the channel in practice. The degree of similarity between the experimental setup and the theoretical model of the channel is estimated from the comparison of the generated communication windows. Since it has been found that differences exist in the duration of the communication window and the variation of the signal power, scaling factors to ensure their compatibility have been derived. Transceiver hardware which implemented the modelled functionality has been developed and a protocol to establish the communication with the required error rate has been proposed. Using the hardware implementation, a detection method for both rising and falling edges of the signal pulses and a threshold strategy have been demonstrated. The device power consumption is also estimated. What is more, the electromagnetic environment of a squirrel cage motor is simulated using the finite element method to investigate the interference and the possibility of providing power to the IR communication devices using power scavenging. In the conclusion, the key findings of the thesis are summarised. A solution is proposed for sensor data transfer using an optical channel for rotor monitoring applications, which involves the design of the IR transceiver, the implementation of the developed protocol and the power consumption estimation.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:560349 |
| Date | January 2012 |
| Creators | Huang, Peng |
| Publisher | University of Warwick |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://wrap.warwick.ac.uk/49665/ |
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