Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2005. / The successful development of a conventional flight autopilot for a model aircraft is presented. All aspects of the autopilot design are considered, from modeling to flight tests. A mathematical aircraft model, as a function of the aircraft’s physical parameters alone, is presented. A controller architecture capable of regulating the motion variables required for conventional flight using only low cost, off-the-shelf sensors is developed. The controller design complements the aircraft model development technique used, by reducing the sensitivity of the controller performance to the model accuracy. The avionics and ground station design is presented. The avionics includes a generic Inertial Measurement Unit (IMU). The total avionics cost is only R5000. Results from three days of flight tests demonstrate the autopilot’s success. Its rapid success can largely be attributed to the extensive simulations of the entire autopilot in the two non-linear simulators developed.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / In this study the focus is on the implementation of a coreless axial ux permanent magnet (AFPM) generator for use in a wind generator application with direct battery charging. The wind generator power system is analysed and discussed. The common concerns with AFPM wind generators in recti er-fed direct battery charging applications, such as maximum power point matching and acoustic noise emission, are discussed. In this study the AFPM wind generator is theoretically analysed and the different winding topologies for this type of machine are evaluated. This evaluation is based on a theoretical analysis and con rmed by nite element analysis and practical measurements. It is shown that an AFPM machine equipped with nonoverlapping windings can give a similar performance to that of normal overlapping windings, while using less copper. It is shown in this thesis that the coreless AFPM generator has a relatively low internal phase synchronous inductance resulting in severe problems with regard to maximum power matching and noise. A method is proposed and in detail analysed in this thesis whereby better power point matching is achieved and near-sinusoidal current is obtained using AFPM generators in direct battery charging wind energy systems. The wind generator system's performance is verified with a SimplorerTM simulation package and practical measurements. The calculations from theoretically derived equations are in good agreement with finite element and measured results.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / This thesis relates to the successful development of a flight control system to perform a range of aerobatic manoeuvres autonomously. The project is the first to try to extend the flight control capabilities of the Computer and Control group at the University of Stellenbosch. A simplified mathematical aircraft model is developed which encapsulates the important dy- namic characteristics of the airframe. It is demonstrated how computational fluid dynamics software can be used to calculate the stability and control derivatives of a conventional air- frame. A vehicle independent kinematic state estimator is presented and used to obtain the complete aircraft state vector. The estimator makes use of extended Kalman filter theory to combine a series of low quality sensor measurements in an optimal manner. A model predictive control strategy is then used to regulate the aircraft about arbitrary, time variant trajectories. The controller’s architecture is not in any way specific to the aerobatic manoeuvres demonstrated in this project. The avionics and ground station used for the implementation of the estimator and control algorithms are presented. The development of a hardware in the loop simulator is discussed and used to verify the correct implementation of the respective algorithms. Finally, practical results from two days of flight tests are presented.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This thesis relates to the design of a camera system for a nanosatellite based on a CMOS image sensor. The design specifications and constraints are considered followed by the proposal of a versatile design with all the required functions imple- mented on a single FPGA. These functions include bad block management, data routing, an EDAC, a soft-core processor, glue logic to external devices, and com- munication busses. The Altera Nios II soft-core processor is implemented in this design, which en- ables simple changes to be made in software. A good mixture of intellectual prop- erty soft-cores, open-source cores, and user created logic are utilised in this broad base design, containing a combination of hardware, digital logic, and software. Low power and compact devices are selected for this design to minimize the power usage and the physical size of the camera system. The system's peak power consumption is 952mW which is below the required maximum consumption of 1W. This design's performance is therefore ideal for a subsystem onboard a nanosatel- lite.

Thesis (MScEng (Electrical and Electronic Engineering))--Stellenbosch University, 2008. / The continued advancement and improvement of software-defined radio technology has been a key factor in furthering research into the implementation of most signal processing algorithms at baseband. Traditionally, these algorithms have been carried out at RF, but with the coming of SDR, there has been a need to shift the processing down to baseband frequencies which are more compatible with the fast developing software radio technology. The study looks at selected demodulation algorithms and investigates the possibility and benefits of carrying them out at QBB. The study ventures into the area of beamforming, multipath compensation, Doppler shift compensation and matched filter detection. The analysis is carried out using Matlab simulations at RF and QBB. The results obtained are compared, not only to evaluate the possibility but also the benefits in terms of the processing load. The results of the study showed that indeed, carrying out the selected demodulation algorithms at QBB was not only possible, but also resulted in an improvement in the processing speed brought about by the reduction in the processing load.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / Next-generation nanosatellites are becoming a very cost effective solution to gain access to space. Modern manufacturing technology together with low power low cost devices makes the development of nanosatellites, using standard industrial components, very attractive. A typical nanosatellite will have only one microprocessor, capable of performing all the computing tasks onboard the satellite - housekeeping, AODC (Attitude and Orbit Control) and instructing the different payloads aboard the satellite. One of the major requirements was to choose a processor from a dominant manufacturer in the market that will still be available for future satellite missions. Just as the 8051 dominated the 8-bit market, the ARM7 processor is fast becoming a market leader in the segment for 16-bit applications. ARM processors has also been used much in handheld devices in recent years - which emphasize the low power requirements and stability of these processors in embedded applications. This thesis investigates the different processors that are currently available. A complete system design is done, taking into account all the different modules needed onboard a very small Low Earth Orbit (LEO) satellite. Finally, some test results are given showing how this system can be reliably used onboard a nanosatellite in future.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This thesis documents the design and implementation of an S-band receiver for phasecomparison monopulse radar. The design and evaluation of the various sub-systems involved in realizing the receiver are discussed in detail. The designed sub-systems are connected via low loss coaxial cables to form the complete phase-comparison monopulse radar receiver. The performance of the receiver is evaluated and compared with the theoretical results, in terms of frequency response, gain and noise figure. The designed receiver is finally connected to an existing antenna system, and a preliminary test of the complete radar is performed. The initial results show that the design is successful, but the boresight-axis of the radar has shifted in angle and requires pre-comparator phase shifting in order to obtain accurate tracking. ii

The properties of an elliptical microwave applicator are investigated. The investigation includes the analytical solution of the cutoff frequencies and electromagnetic field patterns in elliptical waveguides. This requires the solution of Mathieu Functions and becoming familiar with an orthogonal elliptical coordinate system. The study forms part of a wider investigation into the microwave heating of minerals and a cavity is designed in such a way that modes are produced at 896MHz. Extensive use is made of simulation packages. These software packages require that the user knows the dielectric properties of materials that are part of simulations. Therefore, the determination of these properties through measurement and the use of genetic algorithms is considered. A method to improve an S-band waveguide measurement system by implementing time domain gating and an offline calibration code previously written forms an integral part of this section of the project. It is found that, within limits, elliptical waveguides tend to produce a greater number of modes within a certain frequency range when compared to rectangular waveguides.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / The aim of this thesis is to implement a Digital Audio Broadcasting (DAB) system in a Software Defined Radio (SDR). The physical modulation part of the DAB transmitter for one of the transmission modes as well as its receiver is to be implemented and tested in the SDR. DAB transmission mode II is implemented.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2007. / With the rapid advancement of communication technologies and broadband communication, an era is starting to emerge where everything and everyone is always connected, regardless of geography. No other technology has made this more possible than over-the-air data communications technologies such as Wi-Fi, WiMAX and cellular technologies. With the possibility of connecting more devices to a common communications network, more and more applications become available and necessary. One such application is a concept designed to manage a different type of network; the traffic networks of large metropolitan areas. These networks carry more traffic with each passing year and the need to manage them fficiently has become essential. A system to manage traffic networks is an intelligent transport system (ITS), which integrates all methods of transportation into a single manageable resource. Information about the current status of the traffic network can be relayed to road users, allowing them to make informed decisions about alternative routes, or to emergency personnel to inform them of accidents that occurred on the traffic networks. In order to implement an ITS, a communication network is required. This thesis investigates different communication technologies, discussing their merits and shortcomings in an ITS implementation. A suitable technology is selected and a communications system is conceptualised. The communications system is an ad hoc wireless network and a routing protocol used to manage the network, is designed and tested through simulation. The TH(O)RP routing protocol was developed with a focus on scalability, stability and low latency in an ad hoc network. TH(O)RP was designed to operate in an ITS environment, where traffic intersection controllers (TIC) are monitored from a central entity, with optimal routes between the central entity and the TICs, that can be automatically configured and repaired.