Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The recent performance improvements of wireless communication systems are presenting possibilites for the use of wireless networks for industrial applications, which typically impose severe restrictions in terms of response time and flexibility. Traditionally most of the industrial protocols employ cable connections, which have limitations in terms of flexibility and development oportunities. The industrial protocol used for this project, is the Modbus protocol. This protocol is developed and implemented on a wireless environment by using data radio modems. The Modbus protocol is a master/slave protocol which provides an industry standard for industrial data transfer. A Modbus driver is designed for radio networks, so that it can function with different PLCs and SCADA packages, supporting Modbus protocol. This enables control and monitoring to be excercised over a long distance, and enables control equipment to be placed as required and not with particular wiring restrictions. / AFRIKAANSE OPSOMMING: Die onlangse verbetering in radiokommunikasiestelsels bied moontlikhede vir die gebruik van radionetwerke vir industriële toepassings, wat gewoonlik streng beperkings plaas in terme van responstyd en buigbaarheid. Tradisioneel is meeste van die industriële protokolle kabelgebaseer, wat redelik onaanpasbaar is. Die Modbus protokol is as basis in hierdie projek gebruik. Dit is 'n meester/slaaf industriestandaard, wat hier aangepas is vir toepassings met radiomodems. Die Modbus drywer is ontwerp om funksioneel te wees met 'n verskeidenheid van PLC's en SCADA pakette, wat die Modbus protokolondersteun. Dit stel beheer- en meetaksies in staat oor lang afstande en laat relatief vrye plasing toe van toerusting sonder bedradingsbeperkings.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Improvements in the area of satellite orientation control in the presence of large actuator gain changes are investigated. Gain changes primarily originate from actuator failures, but may also result from intermittent sensor availability and geomagnetic field effects. The stability and performance of a classic LQR control solution under these conditions is analyzed through simulation, and two adaptive schemes are developed to improve the response. The adaptive schemes mix elements from bang-bang control to increase performance, and banded control to increase robustness. These control schemes are thoroughly tested through simulation and the results are compared with those obtained for the classic solution. Extensive modelling of the system in the MATLAB™ environment is done to support the analysis of the controllers, and hardware sensors are built to provide realistic orientation measurements to the controllers. / AFRIKAANSE OPSOMMING: Verbeterings in die veld van satelliet oriëntasie beheer in die gevalle waar die aktueerders groot veranderinge in aanwins toon, word ondersoek. Aanwins veranderinge word primêr veroorsaak deur aktueerder falings, maar kan ook deur diskontinue sensor metings en magneetveld effekte van die aarde veroorsaak word. Die stabiliteit en gehalte van 'n klassieke LQR beheer strategie onder hierdie omstandighede word ondersoek deur simulasie, en twee aanpasbare beheer strategieë word ontwikkelom die oordrag te verbeter. Die aanpasbare beheer strategieë meng elemente van "bang-bang" beheer om die gehalte te verbeter, en gebande beheer tegnieke om die robuustheid van die stelsel te verbeter. Hierdie beheer strategieë is deeglik in simulasies getoets en die resultate is vergelyk met dié van die klassieke beheerder. Ekstensiewe modelleering van die stelsel is in die MATLAB™ omgewing gedoen om die beheerders te analiseer, en hardeware sensore is gebou om realistiese orientasie metings aan die beheerders te verskaf.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The high pace of technological advancement enables the realisation of ever more advanced mobile communications standards with more functionality than simple voice communications. The hardware that is used to implement the radio sections of these systems generally require long design cycles, much longer than the design cycles of the other components of a communications system. Another problem is that, once new communications standards are introduced, the current hardware platforms used in the terminal equipment becomes obsolete because they can generally not be used with the new standards. This has serious cost implications for both the service provider and the consumer, because both parties have to acquire new equipment to be able to use the new standards. An elegant solution to the above issues is to use software-defined radio sections to replace the hardware radio components. New communications standards can then be supported by simply loading new software onto the equipment, provided the maximum processing capacity of the processor(s) that the software runs on can accommodate the bandwidth requirements of that specific standard. This thesis investigates the ideas behind software defined radio and also describes the design and implementation of a software architecture that can be used to implement software defined radios on general-purpose platforms such as personal computers. / AFRIKAANSE OPSOMMING: Die hoë tempo van tegnologiese vordering maak dit moontlik om baie gevorderde mobiele kommunikasie standaarde te implementeer wat meer funksionaliteit bied as blote spraakkommunikasie. Die hardeware wat gebruik word om die radios van sulke stelsels te implementeer neem gewoonlik langer om te ontwikkel as die ander komponente van die stelsels. Die ander probleem is dat hierdie hardeware gewoonlik nie hergebruik kan word wanneer nuwe kommunikasie standaarde in gebruik geneem word nie omdat die standaarde nie versoenbaar is nie. Dit het tot gevolg dat beide die verbruiker en die diensverskaffer groot bedrae geld moet spandeer om die nuwe tegnologie te kan gebruik. 'n Elegante oplossing vir hierdie probleme is om gebruik te maak van radios waarvan die funksionaliteit in sagteware gedefiniëer word. Nuwe kommunikasie standaarde kan dan gebruik word deur slegs die nodige sagteware op die toerusting te laai, solank die verwerkingskapasiteit van die mikroverwerkers in die stelsel die benodigde bandwydte kan akkommodeer. Hierdie tesis ondersoek die konsepte van sagteware-gedefiniëerde radio en beskryf die ontwerp en implementering van 'n sagteware argitektuur vir die implementering van sagteware-gedefiniëerde radios op veeldoelige platforms soos persoonlike rekenaars.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Common mode currents are a major source of interference in electrical and electronic systems. A universal solution to counteract common mode interference is to introduce an electromagnetic shield with known characteristics. Cable trays are often used to shield cables from unwanted electromagnetic interference (EM!) and its shielding characteristics are defined in terms of its transfer impedance. This thesis pursues the modelling and measurement of the transfer impedance and mutual inductance of non-magnetic cable trays. Theoretical analysis is firstly employed by means of Maxwell's equations after which method of moments (MoM) simulations are performed in order to determine the transfer impedance and mutual inductance within the interior region of a cable tray. The results obtained through simulation are then validated with measurements conducted with an automatic network analyser (ANA). The computational and measured data are in good agreement and the developed model can be used to predict the transfer impedance in the cross-section of non-magnetic cable trays. / AFRIKAANSE OPSOMMING: Gemenernodus strome is 'n bron van interferensie in elektriese en elektroniese stelsels. 'n Universele oplossing om hierdie gemenernodus interferensie teen werk is om 'n elektromagnetiese skerm met bekende eienskappe te implementeer. Geleier leikanale word dikwels gebruik om kabels teen elektromagnetiese interferensie te beskerm en die afskermings eienskappe word in terme van die kanaal se oordragsimpedansie gedefinieer. Hierdie tesis ondersoek die modelering en meting van die wedersydse induktansie en oordragsimpedansie van nie-magnetiese geleier leikanale. 'n Teoretiese analise word eers uitgevoer deur middel van Maxwell se vergelykings waarna metode van momente (MvM) simulasies uitgevoer word om die oordragsimpedansie en wedersydse induktansie in die interne gebied van 'n leikanaal te bepaal. Die resultate verkry deur simulasie word dan bevestig deur meting wat uitgevoer word met behulp van 'n automatiese netwerk analiseerder (ANA). Die numeriese en gemete data stem goed ooreen en die ontwikkelde model kan deurgaans gebruik word om die oordragsimpedansie in die deursnit area van nie-magnetiese geleier leikanale te voorspel.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The development of a radar system is a complex process, requiring a substantial amount of testing. In general, these tests are performed using field trials. Such trials are expensive, and their exact conditions can never be repeated. A radar environment simulator allows for repeatable testing of the majority of a radar's functionality; however, most commercial products are not cost effective. In this thesis we investigate the various approaches to modelling targets and the littoral environment, and then develop a low-cost, largely software defined simulator. This simulator is capable of generating real-time video signals for a monopulse doppler tracking radar. The core simulation routines reside in an extensible software framework which is populated with simple target and clutter models for a prototype simulator. Closed loop tracking tests verify the operation of the prototype simulator. / AFRIKAANSE OPSOMMING: Die ontwikkeling van 'n radarstelsel is a ingewikkelde proses wat verskeie stelseltoetse benodig. Veldtoetse, wat gewoonlik gebruik word, is 'n duur proses, en die toestande is nooit presies dieselfde nie. 'n Radar-omgewingsimulator kan 'n groot deel van 'n radar se funksionaliteit herhaaldelik toets. Daar is egter weinig koste-effektiewe kommersile produkte vir hierdie doel beskikbaar. Hierdie tesis ondersoek verskeie teiken- en omgewingsmodelle, waarna 'n lae-koste, meestal sagteware-gedefinieerde simulator ontwikkel word. Hierdie simulator genereer intydse videoseine vir 'n enkelpuls-dopplervolgingsradar. Die kernfunksionaliteit van die simulator is in sagteware gesetel, en basiese teiken- en omgewingsmodelle is geïmplementeer. Die prototipe-simulator word getoets deur dit aan die radar self te koppel, en dan die teiken-opsporing en -volging te verifieer.

Thesis (MScEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: A unified method is proposed to treat saturation in both Multi-Input-Multi-Output MIMO and Single-Input-Single-Output controllers. This method offers superior performance over existing MIM 0 anti-saturation schemes. The anti-saturation problem is posed as a linear programming problem. A practical and efficient implementation of the algorithm is developed by transforming the problem into its dual linear programming form. The problem, in dual form, is then solved using the dual simplex method rather than the primal simplex method. The nature of the problem when expressed in dual form and the properties of the dual simplex method are harmonised to guarantee an initial basic feasible solution and an optimal bounded final solution in a finite, predictable and minimal number of iterations. The resultant controller never saturates, hence cannot windup. Furthermore the resultant controller always applies the optimal control effort to the plant to minimise the error signal input as follows: • The controller is governed such that while the future free response combined with the present forced response of the controller results in no saturation limits being exceeded, now or at some time in the future, the normal linear response of the controller prevails. • When the future free response combined with the present forced response of the controller will result in a saturation limit being reached, now or at some time in the future, the present time input signal into the controller is optimally governed to prevent the saturation limit from being exceeded at any future time. / AFRIKAANSE OPSOMMING: 'n Metode word voorgestel waarmee versadiging in enkel-inset enkel-uitset en meer-inset meeruitset (MIMU) stelsels beheer kan word. Die metode presteer beter as ander huidige teenversadiging- maatreels vir (MIMU) beheerders. Die teen-versadigings-probleem word as 'n lineere programmeringsprobleem herformuleer. 'n Praktiese en effektiewe implementering van die algoritme word verkry deur die probleem na die duale vorm te transformeer. Die probleem, in duale vorm, word opgelos met die duale simplex metode, in plaas van die direkte metode. Die eienskappe van hierdie formulering is 'n gewaarborgde, aanvanklike, bereikbare oplossing en 'n optimale, begrensde, finale oplossing in 'n eindige, voorspelbare en minimum aantal stappe. Die uiteindelike beheerder versadig nooit nie, en wen gevolglik nie op nie. Die beheerder wend altyd die optimale aanleg-inset aan om die foutsein te minimeer soos volg: • Wanneer die nul-inset gedrag saam met die huidige inset-gedrag geen beperkings nou of in die toekoms saloorskry nie, word geen beperkende aksie geneem nie, en tree die beheerder dus lineer op. • Sodra die toekomstige nul-inset gedrag saam met die huidige inset-gedrag, nou of later versadiging sou veroorsaak, word die huidige inset tot die beheerder optimaal begrens om latere versadiging te voorkom.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: This document describes the breadboard design and practical evaluation of a mobile field station, capable of communicating with the SUNSAT micro satellite. A study of existing satellite communication systems employing LEO satellites, as well as the physical phenomena, influencing the VHF communication link between earth and such satellites was done and used to determine the specifications needed for a functional field station. The design entailed work on different building blocks like a receiver, transmitter and modem unit as well as the writing and testing of the necessary software on a controlling personal computer. The measurements done showed that the field station satisfies most of the specifications, and that it is capable of communicating with a satellite. The document is concluded by suggesting improvements and possible further work before a commercial version of the field station may be build. / AFRIKAANSE OPSOMMING: In hierdie dokument word die ontwerp en praktiese evaluasie van 'n mobiele veldstasie beskryf wat met die SUNSAT mikrosatelliet kan kommunikeer. 'n Ondersoek na bestaande satellietstelsels in lae-aard wentelbane en die fisiese faktore wat die radioskakel tussen die grond en sulke satelliete beïnvloed is gebruik om spesifikasies vir 'n werkende veldstasie daar te stel. Die ontwerpstaak het werk aan 'n ontvanger, sender, modem en beheerproggramatuur ingesluit. Die voltooide veldstasie is gekarakteriseer deur 'n meetproses wat aangetoon het dat dit met 'n satelliet kan kommunikeer. Die dokument word afgesluit met voorgestelde verbeterings en verdere werk aan die veldstasie voordat 'n kommersiële weergawe daarvan voltooi kan word.

Thesis (MScEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: This product is designed as an educational tooL It was developed to make a classroom more organised. Better and easier communication between the teacher and the students can be established, as well as improved communication between different classrooms. The stand alone unit can be used anywhere because there is no wiring between this and the computer. It can be a big addition to the educational system, especially in places where books are not readily available for the students. The system consists of various components. These components are a computer, a stand alone unit and an interconnection for these two. The interconnection was incorporated with the use of radio links. At the computer side of the design, a windows interface was developed to enable the computer user to communicate with the stand alone unit user. The radio link was inserted to make the communication between the computer and the stand alone unit wireless. The stand alone unit consists of a keypad, liquid crystal display, serial port and a floppy drive. The serial port is used as connection between the stand alone unit and the radio links. It is possible to expand the system. The keypad can be replaced by a keyboard to enable the stand alone user to type and save data on the stand alone unit itself, and a hard drive might be added to increase the storage space. The inclusion of the floppy drive makes the system more compact and creates the possibility of transferring data by use of the floppy, which in tum does not limit a person to working only in one place. / AFRIKAANSE OPSOMMING: Hierdieproduk is ontwerp as 'n hulpmiddel vir die onderwys stelsel. Dit is ontwerp om 'n klaskamer meer georganiseerd te maak. Beter en makliker kommunikasie tussen onderwysers en studente word op hierdie manier verseker, asook verbeterde kommunikasie tussen verskillende klaskamers. Die alleenstaande eenheid kan enige plek gebruik word, aangesien daar geen bedrading is tussen die eenheid en die rekenaar nie. Dit kan 'n groot bydrae wees tot die onderwysstelsel, veral in plekke waar boeke nie so alledaags beskikbaar is nie. Die stelsel bestaan uit verskeie komponente. Hierdie komponente is 'n rekenaar, 'n alleenstaande eenheid en 'n verbinding tussen hierdie twee. Die verbinding tussen hierdie twee is met behulp van radio skakels gedoen. By die rekenaar kant van die ontwerp, is 'n rekenaar program geskryf wat die kommunikasie tussen die rekenaar en die alleenstaande eenheid beheer. Die radio skakel is ingesluit in die ontwerp om die kommunikasie tussen die rekenaar en die alleenstaande eenheid draadloos te hou. Die alleenstaande eenheid bestaan uit 'n miniatuur sleutelbord, vloeibare kristal vertoon, 'n serie poort en 'n slapskyf dryf. Die serie poort word gebruik as verbinding tussen die alleenstaande eenheid en die radio skakels. Dit is moontlik om die stelsel te vergroot. Die miniatuur sleutelbord kan vervang word deur 'n standaard sleutelbord om die alleenstaande eenheid gebruiker in staat te stelom data op die eenheid self te tik en te stoor. 'n Hardeskyf kan ook ingevoeg word om die stoor spasie van die stelsel te vergroot. Die insluiting van die slapskyf veroorsaak dat die stelsel meer kompak is en ontwikkel die moontlikheid om die data oor te dra met behulp van die skyf, wat weer 'n persoon in staat stelom op meer as slegs een plek te werk.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The co-existence of electronic devices and their attached transmission cables requires a careful planning regarding the energy leakage across cable shields. This leakage poses potential serious problems and impedes system functioning. This thesis pursues an investigation into the EMC cabling protocols for microsatellite systems. Network analysis techniques are applied in calibrating current probes and to recover the cable transfer impedance, Zr. The calibration approach provides accurate results for frequencies up to 600MHz. The methods used to determine Zr are based on injecting a disturbance current onto the outside of the cable-under-test (CUT) and measuring the corresponding voltage induced on the centre conductor. Useful results are obtained up to 80MHz with the use of a O.5m length of cable. It is thus proposed that Zr is a practical concept for shielding performance evaluation and for the testing of cable philosophy. The results are usable in classifying cables for verification and signal usage. Further research involves a prediction tool called an EMC ITS that simulates the hardware of a microsatellite system to allow studies on design trade-offs, transmission cable criteria and placement of devices. / AFRIKAANSE OPSOMMING: Die gelyktydige bestaan van elektroniese toestelle en hul aangehegte transmissielynkabels benodig deeglike beplanning met betrekking tot die lek van energie deur die kabels se afskerming. Hierdie lekkassie kan ernstige probleme tot gevolg hê en die stelsel se funksionering belemmer. Hierdie tesis loods 'n ondersoek na die EMV bekabelingprotokolle vir mikrosatellietstelsels. Netwerk analise tegnieke word gebruik in die kalibrasie van stroom-probes en die verkryging van die kabel se oordragsimpedansie, Zr. Die benadering wat gevolg is in die kalibrasie verskaf akkurate resultate tot en met frekwensies van 600MHz. Die metode wat gebruik word om Zr te bepaal is gebaseer op die injeksie van 'n versteuringstroom op die buitekant van die toetskabel en die meting van die ooreenstemmende spanning wat opgewek word op die binne-geleier. Bruikbare resultate is tot en met 80MHz verkry met die gebruik van 'n kabel met 'n lengte van O.Sm. Daar word dus voorgestel dat Zr 'n praktiese wyse is om afskermingsprestasie mee te evalueer, asook vir die toetsing van kabel-filosofie. Die resultate is bruikbaar in die klassifikasie van kabels vir verifikasie en seingebruik. Verdere navorsing sluit in 'n voorspellingswyse wat 'n EMV GTS genoem word, wat die hardewaarde van 'n mikrosatellietstelsel simuleer om studie aangaande ontwerpkompromieë, transmissielyn kriteria en die plasing van toestelle binne die gebruiksomgewing moontlik te maak.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In the past few years, a need for consulting on microwave heating has surfaced. Since most specialised microwave components are imported, this adds a hefty price tag in developing the infrastructure for such consultation. This thesis looks at the design oflow cost alternatives for use in the laboratory. A microwave source output with variable output power is often required for consultation. The calculation of product costs may also be simplified if the available microwave power is constant despite load changes. The magnetron as a load was first investigated and a high voltage SMPS was then designed to control the output of the magnetron according to operator / consulting requirements. To ensure adequate feedback of system output and load matching, a dual directional coupler has been designed and implemented. Since the amount of microwave power required has a direct impact on the initial capital expenditure, costs need to be kept low by optimising the system. An impedance matching unit was designed to match the magnetron with the load, saving energy and reducing system costs. Through automation, the system will strive for the optimum load condition without operator intervention. / AFRIKAANSE OPSOMMING: Die afgelope paar jaar het 'n behoefte ontstaan aan konsultasiewerk op die gebied van mikrogolfverhitting. Aangesien gespesialiseerde komponente meestal ingevoer word, bemoeilik die koste daarvan die ontwikkeling van die nodige infrastruktuur vir konsultasie. Hierdie tesis kyk na die ontwerp van goedkoper alternatiewe vir laboratoriumgebruik. 'n Mikrogolf bron met 'n verstelbare kraglewering is dikwels nodig tydens konsultasiewerk. Produk kosteberekinge kan ook vereenvoudig word indien die mikrogolf kraglewering konstant bly, ongeag produk veranderinge. Die magnetron as GS las is eers ondersoek waarna 'n hoogspanning geskakeldekragbron ontwerp is om die uittree van die magnetron te verstel volgens operateur- / konsultasievereistes. 'n Dubbele direksionele koppelaar is ontwerp en by die laboratorium opstelling gevoeg om voldoende terugvoer van die kraglewering en impedansie aanpassing te verseker. Die hoeveelheid mikrogolf drywing wat benodig word, het 'n direkte impak op die aanvanklike kapitale uitgawe vir die stelsel. 'n Optimale stelsel is dus noodsaaklik om kostes te bespaar. 'n Impedansie-aanpassingsnetwerk is ontwerp om die magnetron en las by mekaar aan te pas om sodoende energie en kostes te bespaar. Deur outomatisering streef die stelsel na optimale werkverrigting sonder enige ingryping deur die operateur.