Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2000. / South Africa has an immensely rich reserve of minerals which still has to be exploited. The problem with these reserves is that they exist in reefs where the mining environment is extremely hazardous, and where mining is very expensive. These are only two of the reasons why borehole radar has recently become a very important field of research in the South African mining industry. These radars have to operate in rock, which has a number of electromagnetically problematic characteristics, which greatly complicate modelling and design of suitable radars. The goal of this project is to demonstrate how the Finite Difference Time Domain (FDTD) method may be used to electromagnetically model and simulate borehole radars and subterranean environments.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / The Automatic Position Reporting System (APRS) is a well-established packet communication protocol that offers users a graphical position display system and a peer-to-peer textual message service. APRS is used in temporary and mobile networks where rapid deployment of infrastructure is required and limited a priori knowledge of the network topology is available. The APRS protocol can be used for emergencies and public service applications. ARPS, functioning as an access network, was originally designed to require low complexity and support high flexibility of a network. These design directives have limited APRS’s performance by resulting in low throughput and poor reliability. In order for APRS to be used in time-critical applications, these limitations would need to be improved. The thesis considers the limitations of ARPS by proposing an improved protocol stack with a substitution of the media access control (MAC) layer. The new protocol is modelled in order to develop a largely platform-independent implementation, which could be efficiently retargeted for different platforms. Lastly, a protocol performance evaluation is done in order to determine the resulting improvements on APRS and the overall viability of the proposal.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In the wool trade the mean diameter of wool is a primary indicator of wool quality. It is currently standard practice for a wool grower to send samples to a laboratory for classification before and after shearing. The devices used to make measurements on samples are often big and bulky and sensitive to the environment, thus they are not ideally suited for on site testing. A brief discussion of the industry is given with background information on existing devices as well as information about organic fibres in general. We test an experimental device which has the potential to be robust and compact based on the Fourier optical principle. Two initial designs are considered and the transmission design is further developed into a working system. The working system is evaluated in a sample measurement experiment. In our sample measurement experimentwe determine the mean diameter of a set of samples which has been analysed by an external testing body such that the measurements could be compared. / AFRIKAANSE OPSOMMING: In diewol bedryfword die gemiddelde diameter vanwol as ’n primêre kwaliteitindeks gebruik. Dit is tans gebruiklik om wol monsters na ’n laboratorium te stuur vir klassifikasie voor en na die skape geskeer word. Die toestel wat gebruik word om die wol monsters te klassifiseer is geneig om groot, lomp en sensitief vir die omgewing te wees en is sodoende nie ideaal vir veld gebruik nie. ’n Kort uitleg van die industrie word gegee tesame met agtergrond inligting van bestaande toestelle asook agtergrond oor organiese vesels in die algemeen. Ons toets ’n eksperimentele toestel wat potensieel kompak en aanpasbaar kan wees en gebaseer is op die Fourier optiese prinsiep. Twee aanvanklike ontwerpe word oorweeg en eindelik word die transmissie ontwerp verder ontwikkel tot ’n werkende sisteem. Die sisteem word geëvalueer in ’n monster meting eksperiment. In die monster meting eksperiment bepaal ons die gemiddelde diameter van ’n stel monsters waarvan die gemiddelde diameter deur ’n eksterne liggaam bepaal is om sodoende die metings te kan vergelyk.

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 (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 (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).

Thesis (MScEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Recent research has shown that standard substation capacitive voltage transformers (CVTs) and current transformers (CTs) can be used for the measurement of wideband high voltage phenomena by employing these apparatus in a transconductance topology. With this topology the voltage waveform can be obtained by integration of the ground return current in the earth straps of the CVT and the CT. This technique does, however, impose unique requirements on the amplification and integration instrumentation due to large dynamic range requirements and the strict offset specifications required for accurate integration. This thesis describes a programmable, wideband signal conditioning system for high voltage (HV) measurements using the transconductance topology. A suitable system topology, optimised to reduce the problems usually associated with grounding and electromagnetic interference (EMI) in HV environments, is proposed. This system consists of an analog signal conditioning subsystem, a digital signal conditioning subsystem and a high speed serial fibre-optic link. The analog signal conditioning subsystem conditions the signals from a sensor to levels suitable for the digitiser of the digital signal conditioning subsystem. The high bandwidth specification of the application made it necessary to consider both discrete and integrated implementation of the analog signal conditioning subsystem. Based on the simulated and laboratory test results of both implementations, the optimum design was chosen for the developed system. The digital signal conditioning subsystem, which performs the integration, as well as the serial optic-fibre link control logic was implemented using programmable logic array (PLA) technology. The digital data is transmitted across the fibre-optic link. This data is then converted back to an analog signal. Keywords: High voltage measurements, Transconductance topology. / AFRIKAANSE OPSOMMING: Onlangse navorsing het aangetoon dat standaard substasie kapasitiewe spanningstransformators en stroomtransformators gebruik kan word om wyeband hoogspanningsverskynsels te meet deur hierdie apparatuur in 'n transkonduktansie topologie aan te wend. Met hierdie topologie kan die spanningsgolfvorm verkry word deur die integrasie van die aardstrome in die aardverbindings van die kapasitiewe spanningstransformators en stroomtransformators. Hierdie tegniek stel egter unieke vereistes vir die versterkings- en integrasieinstrumentasie te wyte aan groot dinamiese bereik vereistes en die streng afset spesifikasies wat benodig word vir akkurate integrasie. Hierdie tesis beskryf 'n programmeerbare, wyeband seinkondisioneringstelsel vir hoogspanningsmetings deur van die transkonduktansie topologie gebruik te maak. 'n Geskikte stelseltopologie, wat geoptimiseer is om probleme, wat gewoonlik met aarding en elektromagnetiese interferensie in hoogspanningsomgewings geassosieer word, te verminder, is voorgestel. Die stelsel bestaan uit 'n analoog seinkondisioneringsubstelsel, 'n digitale seinkondisioneringsubstelsel en 'n hoëspoed seriële optiese vesel koppelvlak. Die analoog seinkondisioneringsubstelsel kondisioneer die seine vanaf 'n sensor na geskikte vlakke vir die versyferaar van die digitale seinkondisioneringsubstelsel. Die hoë bandwydte spesifikasie van die toepassing vereis die inagneming van beide diskrete en geïntegreerde implementerings van die analoog seinkondisioneringsubstelsel. Gebaseer op gesimuleerde en laboratorium toetsresultate van beide implementerings is die optimale ontwerp vir die ontwikkelde stelsel gekies. Die digitale seinkondisioneringsubstelsel wat die integrasie uitvoer, asook die seriële optiese vesel koppelvlak beheerlogika is geïmplementeer met behulp van programmeerbare logika skikking tegnologie. Die digitale data word gestuur oor die optiese vesel koppelvlak. Hierdie data word dan terug geskakel na 'n analoog sein. Sleutelwoorde: Hoogspanningsmetings, Transkonduktansie topologie.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The need for a locally manufactured, cost-effective, fuel management system led to the design and development of a functional prototype. This thesis presents the design, development and full implementation of two functional prototypes. While field tests performed on the first prototype assisted in identifying necessary modifications, a need for greater complexity in support hardware was also identified. In order to comply with the cost-effective nature of the project, it was realized that this complexity could only be achieved via the implementation of a CPLD based system. Using Altera's Maxplus II design software, the CPLD code was synthesized according to the required specifications then simulated and analyzed On completion of the new CPLD based system, the second prototype, one of Altera's megacore functions is implemented and used as a substitute to an external hardware. All necessary modifications were successfully completed and the system was installed. / AFRIKAANSE OPSOMMING: Die benodiging van 'n lokale vervaardigde, koste effektiewe brandstofbeheerstelsel het gelei tot die ontwerp en ontwikkeling van 'n funksionele prototipe. Hierdie tesis dek die ontwerp, ontwikkeling en volle implementasie van twee funksionele prototipes. Terwyl toetse op die eerste prototipe gebruik is om die nodige aanpassings te identifiseer, is daar ook besef dat daar meer komplekse hardeware onderstuening benodig word. Om die koste effektiewe aard van die projek te handhaaf, is daar gesien dat die nodige kompleksieteit alleenlik deur middel van die implementering van 'n 'CPLD' gebaseerde sisteem bereik kan word. Deur gebruik te maak van Altera se Maxplus II ontwerp sagteware, is die 'CPLD' kode met die nodige spesifiekasies gesintiseer, gesimuleer en geanaliseer. Na voltooing van die tweede prototiepe, die 'CPLD' gebaseerde sisteem, is een van Altera se megacore funksies geimplementeer en gebruik as 'n plaasvervanger vir eksteme hardware. AIle nodige aanpassings is suksesvol voltooi en die sisteem is geinstalleer.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Handwritten signature verification (HSV) is the process through which handwritten signatures are analysed in an attempt to determine whether the person who made the signature is who he claims to be. Banks and other financial institutions lose billions of rands annually to cheque fraud and other crimes that are preventable with the aid of good signature verification techniques. Unfortunately, the volume of cheques that are processed precludes a thorough HSV process done in the traditional manner by human operators. It is the aim of this research to investigate new methods to compare signatures automatically, to eventually speed up the HSV process and improve on the accuracy of existing systems. The new technology that is investigated is the use of the so-called hidden Markov models (HMMs). It is only quite recently that the computing power has become commonly available to make the real-time use of HMMs in pattern recognition a possibility. Two demonstration programs, SigGrab and Securitlheque, have been developed that make use of this technology, and show excellent improvements over other techniques and competing products. HSV accuracies in excess of99% can be attained. / AFRIKAANSE OPSOMMING: Handgeskrewe handtekening verifikasie (HHV) is die proses waardeur handgeskrewe handtekeninge ondersoek word in 'n poging om te bevestig of die persoon wat die handtekening gemaak het werklik is wie hy voorgee om te wees. Banke en ander finansiele instansies verloor jaarliks biljoene rande aan tjekbedrog en ander misdrywe wat voorkom sou kon word indien goeie metodes van handtekening verifikasie daargestel kon word. Ongelukkig is die volume van tjeks wat hanteer word so groot, dat tradisionele HHV deur menslike operateurs 'n onbegonne taak is. Dit is die doel van hierdie navorsmg om nuwe metodes te ondersoek om handtekeninge outomaties te kan vergelyk en so die HHV proses te bespoedig en ook te verbeter op die akkuraatheid van bestaande stelsels. Die nuwe tegnologie wat ondersoek is is die gebruik van die sogenaamde verskuilde Markov modelle (VMMs). Dit is eers redelik onlangs dat die rekenaar verwerkingskrag algemeen beskikbaar geraak het om die intydse gebruik van VMMs in patroonherkenning prakties moontlik te maak. Twee demonstrasieprogramme, SigGrab en SecuriCheque, is ontwikkel wat gebruik maak van hierdie tegnologie en toon uitstekende verbeterings teenoor ander tegnieke en kompeterende produkte. 'n Akkuraatheid van 99% of hoer word tipies verkry.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of the thesis is the design of an economical do - it - yourself ground station for school pupils to communicate with SUNSAT 1. The ground station should also be more economical than a hand - held transceiver radio. The do - it - yourself requirement is there to arouse an interest in electronics, radio frequency electronics and satellite communications in school pupils. A system-level design was done for a ground station consisting of modules which may be bought individually as do - it - yourself kits to eventually produce a full set. The modules are a VHF receiver, a VHF transmitter, a UHF down converter and a modem. Each module has functions which aid in the process of communications (data as well as voice) between the satellite and the ground station. A VHF receiver was designed and implemented to be capable of receiving RF signals from SUNSAT 1. A crystal controlled oscillator was designed that oscillates with a frequency tolerance of less than or equal to ± 0.003 % when aligned without the necessary IlF equipment. An economical Broadband Signal Generator was implemented with a 74ACT14 logic IC, which may be used to align the receiver. The higher harmonics of a square wave with a fundamental frequency of 4 kHz are used as a RF source. A sound card was utilised as a modem to receive 1200 baud AFSK (AX.25 protocol) data and the software was also used to display the data on PC. The data was transmitted from another ground station / AFRIKAANSE OPSOMMING: Die doel van die tesis is die ontwerp van 'n ekonomiese doen - dit - self - grondstasie vir skoolkinders om met SUNSAT I te kan komunikeer. Die grondstasie moet ook meer ekonomies wees as 'n handstelradio. Die doel van die doen - dit - self - beginsel is om die belangstelling in elektronika, RF elektronika and satelliete by skoolkinders aan te moedig. 'n Stelsel ontwerp van 'n grondstasie is gedoen wat bestaan uit modules wat afsonderlik as doen - dit - self - modules aangeskaf kan word om so tot 'n totale grondstasie op te bou. Die modules is die "VHF" - ontvanger, "VHF" - sender, UHF - afmenger en 'n modem. Elke module verskaf funksies wat bydra om met SUNSAT I te kan kornmunikeer. 'n VHF - ontvanger wat in staat is om RF - seine vanaf SUNSAT I te ontvang is ontwerp en gebou. 'n Kristal b heerde ossillator is ontwerp met 'n frekwensie toleransie van kleiner en gelyk aan ± 0.003 % wanneer dit ingestem word sender die nodige RF toerusting. 'n Ekonomiese wyeband - seingenerator is gemplementeer met 'n 74ACT14 logiese vlokkie om as 'n RF - bron gebruik te word om die ontvanger in te stel. Die boonste (hoer) harmoniek van die 4 kHz vierkantsgolf word as 'n "RF bron" gebruik. 'n Klankkaart is suksesvol gebruik as 'n modem om 1200 baud AFSK data (AX.25 protokol) te ontvang en die data met die nodige sagteware op 'n skerm te vertoon. Data is uitgcstuur vanaf 'n ander grondstasie.