Bibliography: leaf 54. / Beginning with the developed version of a shaded pole motor a contour of the area concerned is defined which follows the boundary between rotor iron and rotor conducting medium, the pole gap, figure 1. In this case the analysis is restricted to a region which is given in y-direction as the distance between rotor –and stator iron over half a pole pitch in x-direction. Due to the shading ring it is not possible to define boundary conditions for the contour parts along the pole –and the pole-gap axis

Bibliography: leaves 99-101. / Automatic ore sorting machines are in common use in the mining industry. These machines generally separate valuable mineral-bearing rocks from waste rocks. At the Premier Diamond Mine in South Africa kimberlite, a diamond-bearing rock is separated from gabbro which is a waste rock. Work had been conducted previously in the Department of Electrical Engineering at the University of Cape Town to find a viable method for discriminating between gabbro and kimberlite. A technique using microwave irradiation attenuation was successful when using parallel-sided smooth-surfaced rocks. This technique used linearly polarized square antennas at 35GHz. Problems were experienced, however, with irregu1arly shaped rock s. The aim of the present study was therefore to deve1op a technique which will sort irregularly shaped rocks and eliminate the problems associated with them.

Includes bibliography. / The objective of this thesis is to determine whether Adaptive Noise Cancelling can be used successfully in determining the state of machine elements. In addition, this thesis was used to gain experience in real-time computing. This was done by designing and building a real-time machine monitoring package using an IBM PC and a TMS 320C25 digital signal-processing chip manufactured by Texas Instruments. To determine which adaptive algorithm should be used in the package, experiments were carried out on a computer with different types of adaptive noise cancelling algorithms, the two main ones being the Least-Mean-Squares (LMS) and Recursive-Least-Squares (RLS) algorithms.

Bibliography: leaves 58-62. / Registration of two or more images of the same scene is an important step in image processing that seeks to extract information not obtainable from one of the images in question. This process is required in many Engineering, Scientific and Medical applications. The accuracy of this step is crucial to the reliability of subsequent image processing and or decisions made on its basis. The huge size of the date to be processed, the speed at which the processing is required and the accuracy requirements necessitates a quick, efficient, robust and in some respects automatic program which efficiently harnesses available computing resources. This is the object of this project - the design of an image registration algorithm with a bias for SAR/InSAR applications but also applicable for other registration purposes, implemented on a parallel cluster of computing nodes.

Includes bibliographical references. / A market has been identified for 23 GHz, short-haul, low-capacity, digital radio. The dissertation presents the development of the varactor controlled Gunn oscillators that constitute the crystal locked microwave sources of the radio. An accurate description of a design procedure for Gunn oscillators at 23 GHz is presented. With reference to advanced modulation methods which require constant modulation indices, a method of linearising the voltage/frequency characteristic of the varactor controlled Gunn oscillator is described, which allows direct modulation of the source at 23 GHz. Due to the wide operating temperature of the radio a technique to temperature compensate the oscillator is presented. The dissertation ends with an investigation how the semiconductor device's spread affects the oscillator characteristics and an evaluation of the noise performance of the Gunn oscillator.

Bibliography:leaves 203-205. / Decentralised control schemes are becoming more common in industry as the advantages of decentralised control become more apparent. These advantages include fewer tuning parameters than centralised controllers, the simplification and cost reduction of hardware requirements and greater reliability. In addition the application of decentralised controller design to large scale systems allows established CAD methods to be implemented easily and efficiently. When the control engineer designs a distributed controller the system is divided up into a number of subsystems and a controller designed for each subsystem. The controllers are designed independently for each subsystem ignoring any interaction that may occur between the different subsystems. In terms of the input-output representation of the system this means that the matrix representing the controller will be in a block diagonal form. In general the interactions between the different subsystems will not be negligible. In some cases the interactions will be such that stabilising the individual subsystems will not be sufficient to stabilise the system as a whole. Stability theorems are required to enable the designer to check if the decentralised controller that he has designed will in fact stabilise the system as a whole. Such stability theorems have been devised although at present they are too conservative. However even with such theorems available the designer must still select the subsystems to be controlled in such a way as to satisfy the conditions laid down for stability. The stability theories usually are based on a particular matrix structure. If the matrix representing the system possesses a structure detailed by the stability theorem in question then, subject to various conditions, the system as a whole will be stable under decentralised control. In this thesis a number of different matrix structures are considered that give information as to the stability of the closed loop system. Methods are developed that allow the designer to rearrange the matrix in such a way as to obtain a particular structure, if this is possible.

Bibliography: p. 102-103. / It was the objective of this project to design and build a transmitter/receiver unit that indicates when the ore level in a vertical ore chute falls below the level of the signal path. The design was commissioned by De Beers Consolidated Mines to be implemented in South Africa's largest diamond producing mine, the Finsch Mine at Limeacres in the north-western Cape. The system requirements laid out'by de Beers stressed that the unit is to be used as a backup system, and thus its absolute reliability was of highest importance.

Bibliography: leaves 78-79. / Partial response signaling ( PRS) has been used successfully to improve the spectral properties of Pulse Amplitude Modulated (PAM) digital transmission systems. This thesis investigation studied the effect of PRS on frequency- and phase-modulated carrier systems, in particular on their spectral performance and their maintenance of constant envelope.

Includes bibliographical references. / This project arose as a result of inefficiencies in the diamond recovery process at Premier Mine. A considerable amount of barren waste rock, gabbro, is mined along with the diamond bearing kimberlite. No automated method exists for separating the kimberlite from the waste rock and a device was required to effect ore sorting on a rock by rock basis. Experimentation with a microwave oven indicated that samples of kimberlite were more attenuative than samples of gabbro. The possibility of using microwave heating for rock differentiation was investigated but was impractical to implement. A study of low power microwave attenuation and reflection measurements was undertaken. Reflection measurements were found to be impractical due to the similar amounts of reflected signal from the different rock types. Microwave signal attenuation through rock samples was studied over a broad frequency spectrum. A detectable difference in signal attenuation was found through the gabbro and kimberlite. The difference in signal attenuation increased with increasing frequency. Different techniques to implement signal attenuation measurements through rock samples were investigated. The passing of rock samples through waveguide structures was found to be impractical in this application. Microwave signal attenuation measurements were successful when rock samples were placed between a transmitting and a receiving antenna. Equipment was designed and constructed with an operating frequency of 35GHz chosen due to the small antenna aperture area and the large attenuation difference at this frequency. Static measurements with this equipment revealed the problems with signal scattering and reflection from some irregularly shaped samples of low loss gabbro. The importance of these phenomenon could only be gauged from dynamic measurements. Dynamic measurements were performed using a laboratory test system with a conveyor belt capable of moving at speeds of up to 5 m/s. It was found that 93% of the kimberlite could be correctly detected whilst rejecting 67% of the gabbro. The system functioned satisfactorily and led to the filing of several patents.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This research project investigates the design, modelling and application of an open-air capacitive voltage sensor assembly for the measurement of wideband High Voltage signals on three-phase transmission lines. The advantages and disadvantages of conventional methods used to measure these voltages are reviewed and the advantages of the open-air capacitive sensor are established. The main research objective of this project involves extending the application of previously developed single-phase capacitive sensor topologies to three-phase applications. A three-phase set of mobile, compact and relatively inexpensive capacitive voltage sensors for open-air application under overhead transmission lines are designed and constructed, including a data acquisition triggering system for the measurement of transient waveforms. Equivalent circuit models, using a Thévenin equivalent approach, are developed for the three-phase sensor topology and the associated three-phase transmission line configuration. A number of different methods for simplifying the associated Thévenin equivalent impedance and voltage equations are evaluated. The decoupling of the voltage waveforms measured by the individual sensors for a three-phase transmission line configuration is subsequently examined with the view to derive mathematical relationships for determining the phase conductor voltages from the measured sensor voltages. The performance of the sensor assembly is experimentally evaluated under laboratory conditions as well as field conditions. An outdoor HV test facility, representing a scaled three-phase flat transmission line structure, is developed for evaluation of the three-phase sensor topology in a controlled environment. The methodology for decoupling the phase voltages and reconstructing the phase conductor voltages from the voltages induced on the sensors is evaluated using measured data obtained with this HV test facility. It is shown that the three-phase capacitive voltage sensor topology as applied in the test facility delivers good results for the measurement of three-phase transient voltage waveforms.