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, 2005. / This thesis relates to the problem of deterministically tracking an object that moves in a video sequence. A variety image processing and contour fitting algorithms and techniques are discussed. The tracking algorithm fit B-spline templates as is set out in the work done by Blake and Isard. The method builds on the concept that only certain deformations of the moving object's bounding curve is allowed. This is governed by projection into a subspace that allow only the wanted deformations. The deformations are restricted to be mostly linear, but small, nonlinear deformations can also be accomodated.

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))--University of Stellenbosch, 2006. / This project developed a low-cost avionics system for a miniature helicopter to be used for research in the field of autonomous flight (UAVs). Previous work was done on a small, electrically powered helicopter with some success, but the overall conclusion was that the vehicle was underpowered. A new vehicle, the Miniature Aircraft X−Cell, was chosen for its ability to lift a larger payload, and previous work done with it by a number of other institutions. An expandable architecture was designed to allow sensors and actuators to be arbitrarily added to the system, based on the CAN standard. A CAN sensor node was developed that could digitize 12 channels at up to 16 bit resolution and do basic filtering of the data. Onboard computing was provided by a PC/104 based computer running Linux, with additional hardware added to interface with the CAN bus and assist with timing. A simulation environment for the helicopter was evaluated and shown to provide a good test bed for the control of the helicopter. Finally, the avionics was used during piloted test-flights to measure data and judge the performance of both the modified helicopter and the electronics itself.

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. / The successful control of a three-degree-of-freedom gyroscope is presented for the application of steering and stabilising a platform mounted underneath an airship. The end goal is to stabilise a camera for earth observation purposes. The development of the necessary electronics, sensors and actuators along with the hardware and software to interface these components are presented. This include DC drives, torque control systems for the gimbal motors and a speed control system for the gyroscope as well as platform angle and angular rate sensors. A mathematical model for the gyroscope, based on Euler's equations of motion, is presented. Non-linear simulations are performed and compared to measurements of the plant's behaviour to step torque commands to determine the parameters of the gyroscope. Pole placement and LQR optimal control methods are considered in the design of a MIMO controller to steer the platform in the elevation plane, along with a PI controller to steer the platform in the azimuth plane. Ground tests display the success of the steering controllers.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / The basic concepts of wide band mobile ad hoc networking are used in this thesis to extend the functionality of a typical low-speed telemetry system. Although most efforts related to wireless networking are driven by the insatiable demand for high-speed mobile data applications, telemetry applications ensure the continuous wide spread use of lowspeed narrow band data networks. A multi-hop auto-routing telemetry system has the advantages of extended operational range, and portability, for nomadic monitoring, or rapid deployment applications. All stations operate both in their telemetry capacities, providing typical functionality and I/O capabilities, as well as implicit routers, supporting a DSR based protocol to achieve dynamic, multi-hop operation. While the emphasis of work described in the thesis is placed on the optimal design and development of a dynamic, multi-hop telemetry network, a further aspect presented herein is the extension of an existing state transition matrix queuing model to encompass the type of network designed. The model offers a prediction of latency performance of the multi-hop system using half duplex low speed radio links, and corresponds with measured results.

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.