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Masters Research - Master of Engineering (Research) / This thesis considers a number of related problems in the area of passive and semi-active vibration control of piezoelectric laminates. The thesis consists of three main parts. The first part of the thesis develops a mathematical model of a physical resonant system-piezoelectric laminated simply supported beam. It is essential to have a good understanding of the physical system so that the associated problems with passive and semi-active shunt damping can be addressed. The second part of the thesis is concerned with problems related with current passive shunt damping techniques using a single piezoelectric laminate. One of the current problems with multiple mode techniques is determining the correct resistive damping for each resonant mode. Therefore, a systematic method is presented for determining the optimal resistance elements by minimizing the H2 norm of the damped system. After the design process, shunt circuits are normally implemented using discrete resistors, capacitors and virtual inductors (Riordan Gyrators). The difficulty in constructing the shunt circuits and achieving reasonable performance has been an ongoing problem. A new approach to implementing piezoelectric shunt circuits is presented. A “synthetic impedance”, consisting of a voltage controlled current source and digital signal processor (DSP) system, is used to synthesize the terminal impedance of a required shunt network. The third part of the thesis is concerned with the semi-active vibration control of piezoelectric laminated. This part addresses a number of associated problems with the current passive shunt damping schemes. The foremost being the complexity of the shunt circuits required to dampen multiple modes. They generally act to minimize structural vibration at a specific frequency – which are rarely stationary. Therefore, a new broadband semi-active shunt technique for controlling multiple modes has been developed. The “negative capacitor” controller is proposed theoretically, and then validated experimentally. The negative capacitor is simular in nature to a passive shunt damper as it uses a single piezoelectric transducer to dampen multiple modes of a flexible structure.

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Thesis (MTech (Electrical Engineering))--Peninsula Technikon, 1998. / Word processed copy. Summary in English. Includes bibliographical references (leaves 97-104). Also available online.

Thesis (DTech (Electrical Engineering))--Peninsula Technikon, 2002. / Word processed copy. Summary in English. Includes bibliographical references (leaves 189-199). Also available online.

Thesis (Ph. D.)--University of Sydney, 2000. / Title from title screen (viewed 27 February 2007). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Department of Aeronautical Engineering. Includes bibliographical references. Also issued in print.

Mode of access: Internet via World Wide Web. Available http://hdl.handle.net/1947/9738. / "November 2008" Includes bibliographical references.

Thesis (M.S.)--University of North Texas, Dec., 2009. / Title from title page display. Includes bibliographical references.

Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 1998 / The purpose of this study was to perform an investigation into advances in the field of opto-electronics and to develop a suitable lightwave sensor, for application in smart structures research. Included in the scope of this research was the theoretical development and analysis of an appropriate technology to lead to an implementation of such sensors. This project forms part of an overall plan to gain experience in optoelectronic (photonic) sensor design. In research done previously in smart structure monitoring, piezo-electric techniques with the usual electrical interconnections was used. In a highly distributed sensor system the problems of electromagnetic interference, the tribo-electric effect and noise could be problematic. In this research, opto electronic techniques were thoroughly researched and an improvement on laser based fibre-optic interferometers was made. A non monochromatic lightwave interferometer was developed from theory and a prototype tested. The results suggests that an interferometric sensor can be operated with a non monochromatic source by using a second interferometer to modulate the frequency spectrum of the light before it is detected by a photodetector. Various test and measurement circuits for improved photodetector performance were evaluated, as well as a study of signal processing techniques that would be of use for an upgrade of the project where specific feature detection and analysis using the sensor is envisaged. A specification for a computer based data acquisition system was developed to do initial tests. The project should continue, with the sensor head being improved and all the necessary signal processing routines programmed into a Labview based data acquisition system.

Thesis (DTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 2002 / In the last decade, the South Amcan Electricity Supply Commission would have had their ability to serve an ever demanding public severely tested. With the dilemma of providing electricity supply through hazardous environmental conditions, and with prospects of supplying power even beyond South Afiican borders, the need for a comprehensive damage and power delivery assessment strategy becomes all the more relevant. The rapid growth being made in the evolution of so called "intelligent" structures, with inherent sensor, actuator and control mechanisms built in can have direct influence on a power distribution network. At least in the foreseeable future, the impact ofphotonic sensors with inherent miniaturization, a foremost candidate in Smart System technology, can play a vital role in damage assessment of a potentially large network such as that found in the supply ofelectricity. Smart systems are nonliving systems that integrate the functions of sensing, actuation, logic and control, to respond adaptively to changes in their condition or environment to which they are exposed, in a useful and usually repetitive manner. Sensors are a fundamental part of the evolution of such systems and form the basis for the topic of this dissertation. The use ofoptical fiber sensors is increasing widely mainly due to their (a) miniature size, (b) remote signal processing ability, and (c) multiplexing capabilities. Because of the above features a variety of optical fiber sensing techniques has evolved over the years having potential for a myriad of applications. In this work a systems model and equations was developed for modeling the propagation of light in a optical waveguide, in order to study a Fabry Perrot sensor topology for application as a miniaturised sensor in a new type of smart structure, namely a smart electrical power system.