Thesis (MScIng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: This thesis describes the design, modelling and implementation of a prototype request- processing software system, which can be used as the basis for a request processing frame- work for systems with limited request processing resources. Due to design constraints, the request-processor system described here consists of multiple processes. It is problematic to prove that a multiple process design satis es the conditions of a set of prede ned requirements. One way to verify that such a multiple process design works as intended, is to use modelchecking tools. The system was veri ed for correctness and translated into a working prototype soft- ware system. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwerp, modellering en implementering van 'n prototipe versoek- verwerking-sagtewarestelsel. Die stelsel kan gebruik word om 'n versoekverwerkings- raamwerk te ontwerp vir stelsels met beperkte versoekverwerkingshulpbronne. Die ver- soekverwerkingsstelsel bestaan uit veelvoudige prosesse. Die veelvoudige proses-ontwerp was die direkte gevolg van stelselbeperkings. Dit is problematies om te bewys dat 'n multi-proses-ontwerp korrek funksioneer. Mod- elchecking-sagteware kan gebruik word om te veri eer of 'n stelsel korrek funksioneer. Die korrektheid van die stelsel is geveri eer voordat die nale prototipe ge¨implementeer is.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The high performance of present digital phase-locked loops makes it the preferred choice for the generation of stable, low noise, tunable local oscillators in wireless communications applications. Most transmitters use superheterodyn techniques for up-conversion of the modulated signal to the required transmission frequency. Another technique is to inject the modulation signal into a phase-locked loop and consequently generate a frequency modulated signal directly at the transmission frequency. The aim of this study is to obtain a synthesizer configuration for the effective generation of wideband FM, considering both passive and active loop filters. The selection is based on synthesizer output signal quality, settling time and loop response to the modulation signal. / AFRIKAANSE OPSOMMING: Die hoe werksverrigting van fase-sluit lusse maak dit die verkiesde keuse vir die generasie van stabiele, lae ruis, verstelbare ossillators vir draadlose kommunikasie toepassings. Meeste senders gebruik "superheterodyn" tegnieke vir die op-menging van die gemoduleerde sein na die verlangde uitsaai frekwensie. 'n Ander tegniek is om die modulasie sein in 'n fase-sluit Ius te voer en so doende 'n gemoduleerde sein direk by die transmissie frekwensie te genereer. Die doel van hierdie studie is om 'n sintetiseerder konfigurasie te verkry vir die effektiewe opwekking van 'n wyeband FM sein, deur beide passiewe en aktiewe Ius filters in konsiderasie te neem. Die seleksie geskiet gebaseer op sintetiseerder uittree sein kwaliteit, sluit tyd en Ius gedrag as gevolg van die modulasie sein.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Active noise reduction (ANR) is a method of cancelling acoustic noise in a defined enclosure. Two methods exist to implement ANR, they are the analog feedback method and the digital feedforward method. Commercial ANR systems employing feedback methods have been around since the 1980's. Feedforward methods have however only become practically implemental with the age of fast real time digital signal processing. In current systems, feedback ANR is used to attenuate broadband noise whilst feedforward methods are used to attenuate narrow band or tonal noise [2]. This thesis investigates feedforward ANR to cancel broadband acoustic noise in aircraft headsets. Different adaptive filters, optimal configuration of adaptive filters and practical limitations to broadband attenuation for headsets are addressed. Results from this thesis show that at least 10dS noise energy attenuation is attainable over a bandwidth of 2.5kHz. A number of areas for further research are also identified. / AFRIKAANSE OPSOMMING: Aktiewe geraas beheer (AGS) is 'n metode om akoestiese geraas te kanselleer in 'n gedefinieerde omgewing. Twee metodes bestaan om AGS te implementeer. Hulle is die analoog terugvoer en digitale vorentoevoer metode. Kommersiële AGS wat die terugvoer metode gebruik is al in gebruik van die 1980's. Vorentoevoer metodes is egter eers sedert vinnige intydse digitale sein prosessering moontlik. In huidige stelsels word terugvoer AGS gebruik vir die attenuasie van wyeband geraas terwyl vorentoevoer metodes gebruik word om nouband of enkel toon geraas te kanselleer [2]. Die tesis ondersoek vorentoevoer AGS om wyeband akoestiese geraas te kanselleer in vliegtuig kopstukke. Verskillende aanpasbare filters, optimale opstelling van aanpasbare filters en praktiese beperkings tot wyeband attenuasie vir kopstukke word ondersoek. Resultate van die tesis wys dat ten minste 10dS geraas energie attenuasie behaal kan word oor 'n bandwydte van 2.5kHz. 'n Aantal areas vir verder navorsing is ook geïdentifiseer.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis investigates methods to extract the maximum amount of electrical energy from a py panel. The thesis is divided into four parts, focussing on different aspects relating to this topic. The first part will investigate the role that py energy is likely to play in South Africa's future energy scenario, by looking at topics like the greenhouse effect and the economics of energy production. Secondly the thesis will look at how to position py panels optimally for maximum energy generation through the year. A software model of a py panel is developed which can calculate available py energy and energy generation costs for a given location, based on parameters like the positioning of the py panel and historic weather data. Thirdly the optimal design of a maximum power point tracker is investigated. The optimal design, based on a k-sweep voltage ratio maximum power point tracking algorithm, is implemented using a DSP controlled boost converter circuit. Finally, the best methods to store energy generated using py panels are explored. Energy storage technologies are compared for rural, off-grid applications in South Africa, and the design and implementation of a pulse-charging lead-acid battery charging strategy is explained. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek maniere waarop die maksimum hoeveelheid elektriese energie vanuit 'n py paneelonttrek kan word. Die tesis word in vier dele verdeel, wat elkeen fokus op 'n ander aspek van die onderwerp. Die eerste kyk na die rol wat PV energie potensieël kan speel in die toekomstige energie produksie binne Suid Afrika, deur te kyk na onderwerpe soos die kweekhuis effek, en die ekonomiese sy van energie produksie. Tweedens kyk die tesis na metodes om 'n py paneeloptimaal te posisioneer vir maksimum energie deur die jaar. 'n Sagteware model van 'n PV paneel word ontwikkel wat die hoeveelheid beskikbare energie, en die kostes daarvan, kan bereken vir 'n spesifieke plek, gebaseer op PV paneel data en vorige jare se atmosferiese data. Derdens word agtergrond oor maksimum drywingspunt volgers gegee, en die ontwerp en bou van 'n k-variërende, spannings verhouding maksimum kragpunt volger verduidelik, geimplimenteer deur van 'n DSP en 'n opkapper baan gebruik te maak. Laastens word die beste maniere om PV energie te stoor, vir landelike toepassings weg vanaf die Eskom netwerk, ondersoek. Alle beskikbare tegnologieë word eers vergelyk met mekaar, waarna die ontwerp en bou van 'n puls-laai loodsuur batterylaaier verduidelik word.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Flash memory and the errors induced in it by radiation were studied. A test board was then designed and developed as well as a radiation test program. The system was irradiated. This gave successful results, which confirmed aspects of the study and gave valuable insight into flash memory behaviour. To date, the board is still being used to test various flash devices for radiation-harsh environments. A memory protection unit (MPU) was conceptually designed and developed to morntor flash devices, increasing their reliability in radiation-harsh environments. This unit was designed for intended use onboard a micro-satellite. The chosen flash device for this study was the K9F1208XOA model from SAMSUNG. The MPU was designed to detect, maintain, mitigate and report radiation induced errors in this flash device. Most of the design was implemented in field programmable gate arrays and was realised using VHDL. Simulations were performed to verify the functionality of the design subsystems. These simulations showed that the various emulated errors were handled successfully by the MPU. A modular design methodology was followed, therefore allowing the chosen flash device to be replaced with any flash device, following a small reconfiguration. This also allows parts of the system to be duplicated to protect more than one device. / AFRIKAANSE OPSOMMING: 'n Studie is gemaak van" Flash" geheue en die foute daarop wat deur radiasie veroorsaak word. 'n Toetsbord is ontwerp en ontwikkel asook 'n radiasie toetsprogram waarna die stelsel bestraal is. Die resultate was suksesvol en het aspekte van die studie bevestig en belangrike insig gegee ten opsigte van "flash" komponente in radiasie intensiewe omgewmgs. 'n Geheue Beskermings Eenheid (GBE) is konseptueel ontwerp en ontwikkelom die "flash" komponente te monitor. Dit verhoog die betroubaarheid in radiasie intensiewe omgewings. Die eenheid was ontwerp met die oog om dit aan boord 'n mikro-satelliet te gebruik. Die gekose "flash" komponent vir die studie was die K9F1208XOA model van SAMSUNG. Die GBE is ontwerp om foute wat deur radiasie geïnduseer word in die "flash" komponent te identifiseer, herstel en reg te maak. Die grootste deel van die implementasie is gedoen in "field programmable gate arrays" and is gerealiseer deur gebruik te maak van VHDL. Simulasies is gedoen om die funksionaliteit van die ontwikkelde substelsels te verifieer. Hierdie simulasies het getoon dat die verskeie geëmuleerde foute suksesvol deur die GBE hanteer is. 'n Modulre ontwerpsmetodologie is gevolg sodat die gekose "flash" komponent deur enige ander flash komponent vervang kan word na gelang van 'n eenvoudige herkonfigurasie. Dit stelook dele van die sisteem in staat om gedupliseer te word om sodoende meer as een komponent te beskerm.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis investigates and develops some aspects of low speed wireless telemetry applications. The system configuration is one of a single master, controlling and communicating with multiple slave stations over a radio network. The aim of this thesis is to develop a narrow band wireless communications network based on a protocol with slotted time base, utilizing standard, off the shelf hardware. The idea is to investigate different strategies for improvement of data throughput performance under conditions of both low- and high loading, using this basic protocol. Such strategies may, amongst others include collision detection, flow control and pre-scheduling algorithms. This thesis will also show the how the non-adaptive system's data throughput performance can be improved using an adaptive system under low- and high loading. Half-duplex communication mode will be used for data communication. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek en ontwikkel sommige aspekte van laespoed radiotelemetrie toepassings. Die stelselkonfigurasie is een van 'n enkel meesterstasie wat met 'Il aantal buitestasies kommunikeer oor 'n radionetwerk. Die doel van die tesis is om 'n tydgegleufde protokol te ontwikkel vir nouband radiotoepassings, deur gebruik te maak van standaard, maklik beskikbare hardeware. Die doel is om verskillende benaderings te ondersoek vir die verbetering van datadeurset onder toestande van beide hoë- en lae belading. Sulke strategieë mag botsingsdeteksie, vloeibeheer en voor-skedulering insluit. Die tesis salook aandui hoe die data deurset van die nie-aanpasbare metode verbeter kan word, deur gebruik te maak van 'n aanpasbare metode vir beide beladingstipes. Die kommunikasiestelsel is half-dupleks gebaseer.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This thesis documents the research, design, implementation and successful testing of a prototype camera probe to survey the inside of hard rock boreholes. Rock core images are intended to aid mine geologists in recording the borehole rock layers. The system consists of a wide-angle fisheye lens mounted onto a CMOS digital image sensor. The image data is read in and processed by an FPGA, then stored on a removable sn flash memory card. All of the aforementioned components are mounted inside a watertight Perspex tube. Application specific PC software is used to process the data to form strip images of the borehole wall. Using mathematical correlation, these images are stitched together into a virtual core that is a flattened representation of the rock inside the borehole. The probe contains its own power and light source which enables it to be deployed easily with no external wires needed for operation. The storage capacity, image quality, and lighting design can be improved in future design revisions. / AFRIKAANSE OPSOMMING: Die inhoud van hierdie tesis behels die navorsmg, ontwerp, implementering, en suksesvolle toetsing van 'n prototipe kameraprobe wat dit moontlik maak om die binnewand van boorgate in harde rots te besigtig. Beelde van die rotskern vergemaklik die taak van myngeoloë wat die rotslae, waardeur die boorgat strek, moet opteken. Die stelsel behels 'n wyehoek bollens wat op 'n CMOS digitale sensor gemonteer is. Die data gewerf vir die vorming van die beeld word deur 'n FPGA ingelees en verwerk, waarna dit op 'n verwyderbare SD flits geheuekaart gestoor word. Die bogenoemde komponente word alles binne 'n waterdigte Perspexbuis monteer. Gebruikerspesifieke sagteware vir persoonlik rekenaars word gebruik om die data te verwerk en sodoende strookbeelde van die binnewand van die boorgat te vorm. Met gebruik van wiskundige korrelasie word hierdie beelde aan mekaar gelas om 'n virtuele kern te vorm, wat 'n voorstelling is van die rots binne die boorgat. Die probe bevat self krag en ligbronne, wat toelaat dat dit maklik bruikbaar is sonder enige eksterne bedrading. Toekomstige hersienings van die ontwerp sal verbeterde data geheue, beeldgehalte en beligting kan bewerkstellig.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The purpose of this study was to investigate the feasibility of a moon sensor as an alternative or supplemental sensor to supply attitude information to a satellite. The visibility of the moon was evaluated with regards to that of the sun from a satellite (i.e. the feasibility of the moon sensor is compared to that of a sun sensor). An algorithm was developed to calculate the center of the moon, regardless of phase or rotation, to offer increased accuracy of the center of the moon. The accuracy of this algorithm and the possible error margins were evaluated and discussed in both ideal and actual test cases. The sensor was implemented on embedded hardware. The conclusion of the feasibility analysis was that the sensor would function well as a supplemental sensor (e.g. in conjunction with a sun-sensor) rather than as an alternative sensor. The accuracy of the moon center algorithm was satisfactory for attitude deterrnina tion. This sensor could thus be seriously considered for use on a future satellite. / AFRIKAANSE OPSOMMING: Die doel van die studie is om die lewensvatbaarheid van 'n maan-sensor, as alternatiewe of aanvullende sensor, om oriëntasie data aan 'n sateliet te verskaf, te ondersoek. Die sigbaarheid van die maan en die sigbaarheid van die son is met mekaar vergelyk, vanaf 'n sateliet (m.a.w. die uitvoerbaarheid van 'n maan-sensor is vergelyk met dié van 'n son sensor). 'n Algorittne is ontwikkel om die middelpunt van die maan, ongeag van fase of rotasie, te bereken om verhoogde akuraatheid van die maan se middelpunt te bied. Die akuraatheid van die maan-middelpunt algoritme en moontlike foute is evalueer en bespreek in beide ideale sowel as werklike toets gevalle. Die sensor was op hardeware geimplenteer. Die gevolgtrekking van die lewensvatbaarheids analise is dat die sensor effektief sal funksioneer as 'n aanvullende sensor (d.w.s saam met 'n son sensor) eerder as 'n alternatiewe sensor. Die resultate verkry van die evaluasie van die maan-middelpunt algoritme is bevredegind en is voldoende vir oriëntasie bepaling. Die sensor kan dus ernstig oorweeg word vir gebruik op 'n sateliet in die toekoms.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The use of commercial-off-the-shelf components in low earth orbit (LEO) satellite systems has become a very popular design trend. Not only are many of these components sufficiently radiation tolerant, but are also less expensive than their space qualified counterparts. Commercial processors are already used in the on-board computer (OBC) of satellites like SUNSAT 2004, CanX and SNAP-I. With the increasing demand for smaller, less expensive satellites and a shorter time-to-market window, the feasibility of implementing a satellite's OBC as a system-on-a-chip (SoC) is now considered. This thesis describes a single-chip implementation, excluding memory, of a LEO microsatellite's OBC on the commercial grade Altera Excalibur embedded processor. A typical satellite OBC system was developed on the Excalibur device to test the functionality and performance of the device as a single-chip OBC. / AFRIKAANSE OPSOMMING: Die gebruik van kommersiële komponente in lae aardwentelbaan satelliet stelsels het 'n baie gewilde ontwerps neiging geword. Meeste van hierdie komersiële komponente is nie net voldoende bestand teen die radiasie in die ruimte nie, maar boonop goedkoper as soortgelyke komponente wat spesifiek vir de ruimte vervaardig is. Kommersiële verwerkers word alreeds gebruik in die aanboord rekenaar (AR) van satelliete soos SUNSAT 2004, CanX and SNAP-I. Met die aahoudende aanvraag vir kleiner, goedkoper en 'n korter ontwikkelings tydperk, word die implementering van 'n satelliet se AR as 'n stelsel-op-'nskyfie nou oorweeg. Hierdie tesis beskryf 'n enkel-skyfie implementasie, geheue uitgesluit, van 'n lae aardwentelbaan mikrosatelliet se AR op die kommersiële Altera Excalibur geïntregreerde verwerker. 'n Tipiese AR stelsel was ontwikkelop die Excalibur verwerker om die funksionaliteit en werkverrigting van die toestel as 'n enkel-skyfie AR te toets.

Thesis (M.Ing.)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The application of cycloaliphatic epoxide (CE) insulation in the Republic of South Africa is investigated within this thesis. There was a request from industry to evaluate the product and indicate its suitability for application within the various geographic and climatic zones typical of the RSA. An extensive survey was conducted into the historic origins of the material, and the experiences of international utilities applying the insulation medium in respect of polluted conditions. The properties of the Automatic Pressure Gelation (APG) CE insulator manufacturing process are discussed with reference to the manufacture of glass and porcelain insulation, and typical areas for concern are discussed with reference to insulators found to deviate from specification. Typical insulators were obtained from the manufacturers and utilities associated with the product, and were subjected to electrical, material and visual examination tests. The electrical tests included AC wet and dry, lightning impulse, clean fog, salt fog, mould release resiliency and the IEC 1109 voltage test. The material tests included the identification of the epoxide systems in use in the RSA, ultraviolet radiation aging simulation, water hydrolysis and salt deposit density tests. The main findings are: • CE insulation is sensitive to marine pollution and continuous-wetting pollution types. • The use of CE insulation is promoted in respect of inland and medium industrial pollution types. • Class B pin-type CE insulation is prone to partial discharge related failures. • Surface roughening on the insulator surfaces leads to reduced AC wet flashover voltages and increased pollution catch. Additionally: • A comprehensive aging hypothesis was developed detailing three independent aging stages/modes applying to CE insulation. • A hypothesis was developed for a new evaluation method for documenting changes on insulator surfaces due to the action of aging mechanisms: The Surface Area Index. / AFRIKAANSE OPSOMMING: Die aanwending van sikloalifatiese epoksied (SE) isolasie in die Republiek Van Suid Afrika word in hierdie skripsie ondersoek. Hierdie ondersoek is geloods op versoek van die elektrisiteitsbedryf om die toepaslike aanwending van die produk onder die verskeie heersende streeksweersomstandighede binne die RSA te evalueer. Breedvoerige navorsing is gedoen om die geskiedkundige oorsprong van die materiaal vas te stel, sowel as om die prestasie daarvan as insulasiemiddel te boekstaaf. Daar is veral gelet op die prestasie van die materiaal onder besoedelende omstandighede en ondervinding wat opgedoen is deur intemasionale ondememings. Die eienskappe van die automatiese drukjelvormings-vervaardigingsproses (APG) word behandel met verwysing na die maak van glas en porselein insulators. Tipiese probleemareas word bespreek van insulators wat afwyk van spesifikasie af. Verteenwoordigende isolators is vanaf vervaardigers en ondememings verkry wat met die produk bemoei is. Hulle is blootgestel aan elektriese, materiaal en visuele toetse. Die elektriese toetse het die volgende behels: nat en droog wisselstroom, skoon waterdamp, sout waterdamp en die IEe 1109 spanningstoets. Die effek van die verlies van die anti-kleefmiddel (gebruik tydens die gietproses) as gevolg van veroudering is ook in detail behandel. Die materiaaltoetse het ingesluit: die uitkenning van die epoksied stelsels in gebruik in die RSA, gesimuleerde veroudering deur ultravioletligbestraling, water hidroliese en soutlaag digtheids toetse. Die hoofbevindings is: • SE isolasie word bemvloed deur seelug besoedeling sowel as volgehoue benatting. Die gebruik van SE isolasie word voorgestel vir binnelandse gebruik sowel as in gebiede met mediumvlak nywerheidsbesoedeling. • Klas B pen-tipe SE isolasie is geneig tot deelontladings wat dan tot faling lei. • Oppervlakvergroffing lei tot In verminderde wisselstroom orvonksspanning onder nat toestande sowel as verhoogde vangs van besoedeling. Bykomend hiertoe is: • 'n breedvoerige SE verouderingshipotese ontwikkel wat drie onafhanklike stadia en modusse van die verouderingsproses uitgewys het. • 'n hipotese ontwikkel vir In nuwe evaluasiemetode om die verandering in die isolatoroppervlak as gevolg van veroudering te dokumenteer: Oppervlakte- Area Indeks (SAl).