Thesis (Ph.D.) - Carleton University, 2007. / Includes bibliographical references (p. 173-177). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2007. / Includes bibliographical references (p. 80-92). Also available in electronic format on the Internet.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves [143]-147).

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 110-116). Also available on the Internet.

No description available.

M.Ing. / Please refer to full text to view abstract

M.Ing. / This thesis demonstrates the measurement of temperature distribution across a metal plate and the non-contact measurement of torsion in a rotating shaft. After a thorough theoretical study of the origin of fibre Bragg gratings, methods of fabrication and erasing of gratings, methods of demodulating the signals from gratings, and methods of discriminating between strain and temperature variations in gratings, simulations and experiments were done to prove the feasibility of both temperature distribution measurement and non-contact torsion measurement. For the measurement of temperature distribution, a 450 x 450 x 1.6 mm type 304 stainless steel plate was used. Two 4,7Ω 25W resistors were used as heat sources, and five fibre Bragg gratings measured the temperature at strategic points on the plate. The measured values were interpolated appropriately and a three-dimensional representation of the temperature distribution was shown on a personal computer monitor. The measurement of torsion was first done on a non-rotating 25 mm diameter solid shaft with torque applied. Both resistive strain gauges and fibre Bragg gratings were attached to the shaft and the measurement results compared well. Up to 90 Nm of torque was applied to the shaft. The non-contact measurement of torsion on a rotating shaft was done with fibre Bragg gratings and involved the use of graded index (GRIN) lenses for transmitting optical information between the light source, the gratings, and back to the spectrum analyser through free space. A special Böhler steel with high yield strength was used, and the set-up was mounted on a lathe. The one end of the shaft was clamped in the lathe chuck, and the other was fixed to an automobile drum brake system, allowing the application of torque on the rotating shaft. Up to 97 Nm of torque was applied to the shaft rotating at 190 rpm, and the results are within 10% of the expected values. As far as we are aware, this is the first time that torsion is measured by fibre Bragg gratings without the need to have physical contact with the shaft, i.e. slip rings, to transmit the information to and from the sensors. The experimental results of this thesis confirm that fibre Bragg grating sensors can be applied usefully in temperature distribution measurement, as well as in the measurement of torsional stress in rotating shafts.

M.Ing. (Electrical and Electronic Engineering) / An experimental study of a multi-point optic fibre sensor for monitoring temperature changes is presented. The multi-point optic fibre sensor is made of a serial array of weak-reflectivity identical gratings. The weak-reflectivity identical gratings form the interferometric cavities UV printed on the single mode fibre. The ability to measure temperatures changes at different cavities along the serial array is particularly interesting for the monitoring of power transformers, high temperature furnaces and jet engines. Changes in temperature in each respective cavity is measured based on the spectral shift in the phase of the light from each respective cavity. The performance of the multi-point fibre sensor system is evaluated. Further, a theoretical and experimental investigation of a serial array composed of two cavities of different lengths is conducted. This investigation is aimed at measuring the impact of the overlap of the two distinct cavities in their respective frequency domain and determining the accuracy of the measurement. The result found shows that the sensor phase response is no more linear to temperature changes. It is also found that the nonlinear response of the sensor to temperature changes increases with the magnitude of the overlap.

M.Ing. / The aim of this project is to research the feasibility of an all-fibre laser distance measurement device that utilises a figure-eight fibre laser (F8L), in the nonlinear amplifying loop mirror (NALM) configuration, as a light source and implements pulse compression to improve the accuracy and signal-to-noise ratio of the system. A figure-eight fibre laser in the NALM configuration for use in a laser distance measurement device is described. The theory of fibre lasers is discussed, including mode-locking and Qswitching, and the characteristics of a NALM loop are analysed. By varying the length of the NALM loop from 500 m to 2000 m or inserting highly nonlinear dispersion shifted fibre, a variety of pulses in the picosecond to nanosecond range can be produced. The lengths of the pulses depend on the length of the NALM loop, the pump power and the setting of the polarisation controllers. The figure-eight fibre laser is pumped with a 980 nm laser diode up to 550 mA, which corresponds to 320 mW. Distance measurements are done with short unmodulated and long modulated pulses. Distance measurement with short unmodulated pulses is discussed only briefly and tested with a simple experiment. The focus of this project is distance measurement with long modulated pulses. A low autocorrelated binary sequence is modulated onto one of the long pulses produced by the figure-eight fibre laser by an electro-optic amplitude modulator. The long pulse gives the proposed system a good signal-to-noise ratio (SNR), while the modulation improves the accuracy. A Barker code of length 13 is proposed as modulation code because of its good autocorrelation properties. The Barker code will improve the accuracy 13-fold, with a corresponding increase in SNR. An electro-optic amplitude modulator is used to implement the modulation. The modulated long pulse is then sent to a target. After reflection, the signal is detected and cross-correlated to obtain the time-of-flight for the pulse. The code generation and cross-correlation are implemented with an FPGA via VHDL programming. The distance to a target can be calculated by knowing the time-of-flight and the speed of light in the propagation medium. In this project the resolution, single-shot precision, accuracy, linearity, repeatability and maximum unambiguous distance of the proposed all-fibre laser distance measurement device are examined.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial ful lment of the requirements for the degree of Master of Science in Engineering. Johannesburg, 2015 / Control of systems are important in most industrial sectors, they nd applications in electronics, machine design and navigation. These control systems often use sensors to work e ectively. One such sensor is an accelerometer, which is used to measure acceleration with one or more degrees of freedom. This research report investigates the modelling, system identi cation and controller design for an accelerometer, a Fibre Optic Accelerometer (FOA). Such a device may be applied in many applications such as anti-skid control, structural failure in buildings and bridges, as well as strategic missile guidance. This report presents a model of a FOA demonstrator which crudely models an industrially developed accelerometer, the demonstrator is made of a jig consisting of a guitar string and electromagnets. Such a model needs to account for a distributed parameter beam combined with a permanent magnet and four electromagnets. The guitar string is modelled using three beam models, namely a spring/damper model, an Assumed Modes Model (ASM) and a Transfer Function Model (TFM). The parameters for these beam models are identi ed using the Nelder-Mead simplex algorithm and the least squares method. The electromagnets within the jig, are modelled using a mathematical model obtained through curve tting of experimental data. The overall FOA sensor is optimised using a lead-lag controller. Five cost functions where investigated, these cost functions are H1, Integral Square Error (ISE), Integral Absolute Error (IAE), Integral Time Square Error (ITSE) and Integral Absolute Time Error (IATE). It was found that the guitar string may be modelled using a single degree of freedom beam model. This is based on a number of reasons, such as the aperture size - through which the tip Light Emitting Diode (LED) projects, the tip mass (permanent magnet) - acting as a natural damper and the fact that Position Sensing Device (PSD) only measures the tip position. It was found that a single degree of freedom model in two orthogonal axes, with a single link beam spring/damper model was the most suitable representation of the guitar string. And the IAE lead-lag controller was found to be the most e ective in controlling a guitar string, this e ectiveness was due to least settling time. / MT2017