This thesis introduces a novel online set-point modulation (SPM) technique that employs fuzzy logic to adjust the timing and magnitude of control system set-points. After first applying fuzzy logic-enabled SPM to underdamped second order systems for testing purposes, the new scheme is then applied to an electromagnetic transient simulation model of Manitoba Hydro’s existing Ponton SVC system, and the results are then compared to the original SVC system that uses traditional control approaches. Conclusions show that fuzzy logic-based SPM improves the controlled voltage’s transient overshoot response to changes in the voltage set-point.

This thesis introduces a novel online set-point modulation (SPM) technique that employs fuzzy logic to adjust the timing and magnitude of control system set-points. After first applying fuzzy logic-enabled SPM to underdamped second order systems for testing purposes, the new scheme is then applied to an electromagnetic transient simulation model of Manitoba Hydro’s existing Ponton SVC system, and the results are then compared to the original SVC system that uses traditional control approaches. Conclusions show that fuzzy logic-based SPM improves the controlled voltage’s transient overshoot response to changes in the voltage set-point.

Entsprechend der sogenannten Set-point-Theorie besitzt jeder Mensch eine individuell festgelegte Körpermasse, die über große Zeiträume konstant gehalten und gegen Abweichungen verteidigt wird. Es wird angenommen, dass der Körper auf noch unbekannte Weise Änderungen in der Körpermasse per se wahrnimmt und daraufhin Mechanismen aktiviert, die zur Regenerierung der ursprünglichen Masse führen. In dieser Arbeit wurde die Hypothese getestet, dass eine künstliche Erhöhung der Körpermasse zu einer kompensatorischen Reduktion in der Körpermasse führt, um das Ausgangsgewicht wieder zu regenerieren. Die Körpermasse von männlichen und weiblichen Mäusen wurde akut durch die Implantation von Gewichten mit einer Masse von 10% der aktuellen Körpermasse in die Bauchhöhle erhöht. Bei Gültigkeit der Set-point-Theorie sollte die Körpermassereduktion der Masse des zusätzlichen Gewichtsimplantats entsprechen. Die Mäuse reagierten auf die künstlich erhöhte Körpermasse geschlechtsspezifisch. Männchen zeigten eine partielle Reduktion in der Körpermasse. Weibchen zeigten langfristig jedoch keine Änderungen in der Körpermasse. Die Reduktion der Körpermasse erfolgte bei den Männchen durch eine Abnahme in der Fettmasse. Die fettfreie Masse war in beiden Geschlechtern nicht verändert. Änderungen in der Körpermasse wurden vor allem durch Änderungen in der Energieaufnahme hervorgerufen. Ein Einfluss des Energieumsatzes auf Änderungen in der Körpermasse konnte nicht nachgewiesen werden. Die Regulation der Körpermasse entsprechend eines massespezifischen Set-points konnte partiell für die Männchen gezeigt werden. Bei den Männchen könnte daher die Wahrnehmung der Körpermasse in die Regulation der Körpermasse teilweise integriert sein. Weibchen verminderten ihre Körpermasse dagegen trotz der künstlichen Körpermasseerhöhung nicht. Das führte zur Bewahrung der Energiereserven und spricht eher für die Regulation der Körpermasse entsprechend des notwendigen Energiebedarfs im Vergleich zu Änderungen in der Körpermasse per se. Diese Ergebnisse zeigen, dass die Regulation der Körpermasse geschlechtsspezifischen Mechanismen unterliegt. Dementsprechend sind auch geschlechtsspezifische Ansätze zur Therapie von Übergewicht und Adipositas notwendig. / The set-point theory of body mass assumes that humans possess an individually determined body mass which is maintained over long periods and which is defended against deviations. It is supposed that the body can perceive changes in body mass per se, this process leading to activation of mechanisms aiming at regeneration of initial body mass. Here the following hypothesis was tested: An artificial increase in body weight leads to a compensatory reduction in body mass in order to regenerate initial body weight. Body mass of male and female mice was acutely increased by implanting weight loads into the abdominal cavity. Additional weights corresponded to 10% of initial body mass. According to the set-point theory we expected the mice to decrease body mass to the extend of the additional weight. A gender-specific response was observed. Males showed a partially reduced body mass. In contrast, females did not show body mass changes in the long-term. Males reduced their body mass at the expense of fat mass. Fat free mass was unchanged in both genders. Changes in body mass were mainly caused by changes in energy intake. An impact of energy expenditure on body mass changes could not be demonstrated. Body mass regulation according to a mass-specific set-point could be partially shown for males. Therefore, in males perception of body mass could be partially integrated in the regulation of body weight. Females did not decrease their body mass despite artificially increased body mass pointing to preservation of their energy depots. This argues for regulation of body mass according to needed energy requirements rather than according to changes in body mass per se. These results show that body mass regulation underlies gender-specific mechanisms. Accordingly, gender-specific approaches are needed for treating overweight and obesity.

The generation of compressed air comprises 20% of the total electricity usage in the mining industry, although compressed air is often seen as a free source of energy. There are however significant costs associated with generating compressed air and maintaining a compressed air system. There are several methods to optimise the electricity used to generate compressed air. The focus of this study is on one of these methods – the implementation of a dynamic air compressor selector. A Dynamic Compressor Selector (DCS) system was developed to fulfil this purpose. DCS is a system that combines demand- and supply-side management of a compressed air network. DCS calculates a pressure set point for compressors and schedules the compressors according to the demand from the end-users. End-users include shafts, plants, workshops and smelters. DCS takes all of the compressors and end-users into consideration while doing the calculations. This dissertation focuses on the DCS implementation process and on the problems encountered by previous authors while implementing the DCS technology. Additional problems were encountered while the DCS technology was implemented. DCS was however still successfully implemented. This study will expand the implementation procedure to ensure that the technology can be implemented successfully in the future. DCS was implemented at a platinum mine in South Africa where it was able to calculate pressure set points for the compressors. DCS was able to accurately match the supply of, and demand for compressed air closely, resulting in lower overall compressed air usage. DCS improved compressor scheduling and control, limiting compressor cycling. Improved compressor scheduling and control resulted in significant decreases in the electricity used to generate compressed air at the mine. A target average evening peak clip of 2.197 MW was simulated, set and achieved. Evening peak clip power savings in excess of an average of 3 MW were achieved. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

The generation of compressed air comprises 20% of the total electricity usage in the mining industry, although compressed air is often seen as a free source of energy. There are however significant costs associated with generating compressed air and maintaining a compressed air system. There are several methods to optimise the electricity used to generate compressed air. The focus of this study is on one of these methods – the implementation of a dynamic air compressor selector. A Dynamic Compressor Selector (DCS) system was developed to fulfil this purpose. DCS is a system that combines demand- and supply-side management of a compressed air network. DCS calculates a pressure set point for compressors and schedules the compressors according to the demand from the end-users. End-users include shafts, plants, workshops and smelters. DCS takes all of the compressors and end-users into consideration while doing the calculations. This dissertation focuses on the DCS implementation process and on the problems encountered by previous authors while implementing the DCS technology. Additional problems were encountered while the DCS technology was implemented. DCS was however still successfully implemented. This study will expand the implementation procedure to ensure that the technology can be implemented successfully in the future. DCS was implemented at a platinum mine in South Africa where it was able to calculate pressure set points for the compressors. DCS was able to accurately match the supply of, and demand for compressed air closely, resulting in lower overall compressed air usage. DCS improved compressor scheduling and control, limiting compressor cycling. Improved compressor scheduling and control resulted in significant decreases in the electricity used to generate compressed air at the mine. A target average evening peak clip of 2.197 MW was simulated, set and achieved. Evening peak clip power savings in excess of an average of 3 MW were achieved. / MIng (Mechanical Engineering), North-West University, Potchefstroom Campus, 2015

Hybrid renewable energy systems (HRESs) have become increasingly popular, especially for isolated regions. This thesis describes the design of a HRES for the isolated Ha'apai Island group in Tonga following a devastating cyclone which happened in 2014. Several renewable power generation and storage possibilities were investigated; solar, wind and battery were found to be feasible for Ha'apai. The conceptual design of a new energy storage system, the Subterranean Ocean Energy Storage System (SOESS), is also discussed as a possible alternative to batteries and a more viable substitute for an ocean renewable energy storage (ORES) system. For the proposed Ha'apai system, the optimum system configuration (solar 450 kW, wind 550 kW, battery 1,216 kAh/4,864 kW) with 90% renewable penetration was obtained using the HOMER software. Based on the optimum system configuration, load flow simulations of both the previous system and the proposed HRES were performed in DIgSILENT PowerFactory. The results of the load flow analysis show that all the transformers and transmission lines in both systems operate safely in both peak and nominal load conditions, and that the voltage levels of all LV buses are within the acceptable range of ±5%. The detailed system topology of the proposed HRES is discussed from the system implementation point of view. A unique set point control algorithm for the start-up/shut-down of the diesel generators was developed. The system dynamic performance was simulated according to the control logic during the three main switching events in DIgSILENT PowerFactory. The dynamic simulation results indicate that the proposed system would operate safely with acceptable voltage and frequency oscillations. This thesis could be used as a template for the design of other isolated HRESs with high renewable penetrations.

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This dissertation investigates the application of Genetic Algorithms (GA) and Simulated Annealing (SA) based search techniques to the problem of deriving an auto-pilot that can emulate a human operator or other controller flying a Small unmanned Helicopter (SH). A Helicopter is a type of Vertical Take Off and Landing Vehicle (VTOL). The maneuvers are none aggressive, mild maneuvers, that include u-turns, ascending spirals and other none extreme flight paths. The pilot of the helicopter is a Fuzzy logic Controller (FC) pilot; it is assumed that the pilot executes the maneuvers with skill and precision. The FC pilot is given set- points (points in space) that represent a path/flight maneuver and is expected to follow them as closely as possible. Input/Output data is then collected from the FC pilot executing maneuvers in real time. The collected data include control signals from the FC pilot to the SH and the resulting output signals from the SH that include time, x, y, z coordinates and yaw (the angle of the SH relative to the x, y axis). The Genetic Algorithm/Simulated Annealing based search algorithm attempts to generate a set of mathematical formulas that best map the collected data. The search algorithm presented in this dissertation was implemented in Java and has a JSP (Java Server Pages) graphical user interface. The results obtained show that the search technique developed; termed Genetic Algorithm / Simulated Annealing controller or (GA/SA) controller allows for the derivation of accurate SH control equations. The results include performance quantification of the algorithm in the derivation phase and the testing phase. Graphs are included; they demonstrate the accuracy and path data of the GA/SA controller as compared to the FC pilot and other controllers. The final results showing the formulas found are also included. A technique was also developed during this dissertation to encode the genetic strings that represent the candidate formulas during the search. This technique allowed the combination of strings to yield new formulas that are valid. The results can be used by other investigators to expand the complexity of the formulas generated during the search. The technique has advantages such as the ability to operate in open-loop conditions and is able to fly the SH without the need for set-point data and without the need for GPS or some other location determination technology. The technique may be used as a backup controller that can take over control of a helicopter in case the main controller is unable to function due to a GPS malfunction or another situation where accurate positioning data cannot be obtained.

This dissertation is primarily concerned with dynamic HIV/AIDS parameter estimation, set against the background of engineering, biology and medical science. The marriage of these seemingly divergent fields creates a dynamic research environment that is the source of many novel results and practical applications for people living with HIV/AIDS. A method is presented to extract model parameters for the three-dimensional HIV/AIDS model in situations where an orthodox LSQ method would fail. This method allows information from outside the dataset to be added to the cost functional so that parameters can be estimated even from sparse data. Estimates in literature were for at most two parameters per dataset, whereas the procedures described herein can estimate all six parameters. A standard table for data acquisition in hospitals and clinics is analyzed to show that the table would contain enough information to extract a suitable parameter estimate for the model. Comparison with a published experiment validates the method, and shows that it becomes increasingly hard to coordinate assumptions and implicit information when analyzing real data. Parameter variations during the course of HIV/AIDS are not well understood. The results show that parameters vary over time. The analysis of parameter variation is augmented with a novel two-stage approach of model identification for the six-dimensional model. In this context, the higher-dimensional models allow an explanation for the onset of AIDS from HIV without any variation in the model parameters. The developed estimation procedure was successfully used to analyze the data from forty four patients of Southern Africa in the HIVNET 28 vaccine readiness trial. The results are important to form a benchmark for the study of vaccination. The results show that after approximately 17 months from seroconversion, oscillations in viremia flattened to a log10 based median set point of 4:08, appearing no different from reported studies in subtype B HIV-1 infected male cohorts. Together with these main outcomes, an analysis of confidence intervals for set point, days to set point and the individual parameters is presented. When estimates for the HIVNET 28 cohort are combined, the data allows a meaningful first estimate of parameters of the three-dimensional HIV/AIDS model for patients from southern Africa. The theoretical basis is used to develop an application that allows medical practitioners to estimate the three-dimensional model parameters for HIV/AIDS patients. The program demands little background knowledge from the user, but for practitioners with experience in mathematical modeling, there is ample opportunity to fine-tune the procedures for special needs. / Dissertation (MEng)--University of Pretoria, 2006. / Electrical, Electronic and Computer Engineering / Unrestricted

In wastewater treatment plants, the amount of ammonium is one example of a measure to determine the quality of the effluent wastewater. Ammonium is regarded as a hazardous chemical for aqueous ecosystems and can cause eutrophication due to its high nitrogen content. The ammonium content in the treated wastewater is controlled by aeration of the biological treatment stage, in which ammonium is converted to nitrate. The aeration process often accounts for the largest energy consumption of the wastewater treatment plant, which motivates automatic control solutions that can both aid in reducing the discharge of ammonium in the effluent and improve the energy efficiency of the aeration process. One such control technique currently used by several large municipal wastewater treatment plants in Sweden is ammonium-based aeration control. In this technique, the aeration process is controlled based on measurements of the effluent ammonium concentration. The purpose of the thesis was to study an extension of ammonium-based aeration control that could better adapt to daily, and often large, fluctuations in the influent load. The proposed method is to use an iterative algorithm to tune the set-point of the ammonium feedback controller. The objective is to, over a given time interval, achieve a flow-proportional mean of the effluent ammonium concentration close to a desired value for a wide range of influent loads. The method was tested by extensive simulations, and the results indicate that the iterative set-point tuning algorithm has the potential to offer a superior ability to achieve a desired flow-proportional mean at the end of a given evaluation period and, in some instances, energy savings compared to standard ammonium feedback control.