Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This thesis presents the development of an adaptive longitudinal control system for an unmanned aerial vehicle (UAV). The project forms part of a research effort at Stellenbosch University into different fault-tolerant control techniques for UAVs. In order to demonstrate the usefulness of fault-tolerant adaptive control, the control system was designed to handle damage-induced longitudinal shifts in the centre of gravity (CG) of the aircraft, which are known to have a dramatic effect on the stability of a fixed-wing aircraft. Using a simplified force and moment model, equations were derived which model the effect of longitudinal CG shifts on the behaviour of the aircraft. A linear analysis of the longitudinal dynamics using these equations showed that the short period mode can become unstable for backward CG shifts. An adaptive pitch rate controller with the model reference adaptive control structure was designed to re-stabilise the short period mode when the CG shifts backwards. The adaptive law was designed using Lyapunov stability theory. Airspeed, climb rate and altitude controllers were designed around the pitch rate controller to allow full autonomous control of the longitudinal dynamics of the UAV. These outer loops were designed with constant parameters, since they would be unaffected by CG shifts if the adaptive pitch rate controller performed as desired. Pure software simulations as well as hardware-in-the-loop simulations showed that the adaptive control system is able to handle instantaneous shifts in the centre of gravity which would destabilise a fixed-gain control system. These simulation results were validated in flight tests, where the aircraft was destabilised using positive feedback and re-stabilised by the adaptive control system. Thus the simulation and flight test results showed that an adaptive control can re-stabilise an unstable aircraft without explicit knowledge of the change in the aircraft dynamics, and therefore could be effective as part of an integrated fault-tolerant control system. / AFRIKAANSE OPSOMMING: Hierdie tesis bied die ontwikkeling aan van ’n aanpassende longitudinale beheerstelsel vir ’n onbemande vliegtuig. Die projek is deel van navorsing by die Universiteit van Stellenbosch oor verskillende fout-tolerante beheertegnieke vir onbemande vliegtuie. Om die doeltreffendheid van aanpassende beheer te demonstreer, is die beheerstelsel ontwerp om situasies te kan hanteer waar die vliegtuig só beskadig word dat sy massamiddelpunt agtertoe skuif, wat ’n groot invloed op die stabiliteit van ’n vastevlerk-vliegtuig kan hê. ’n Vereenvoudigde model van die kragte en momente wat op die vliegtuig inwerk is gebruik om vergelykings af te lei wat beskryf hoe die gedrag van die vliegtuig verander as die massamiddelpunt agtertoe verskuif. Hierdie vergelykings is gebruik in ’n lineêre analise van die longitudinale dinamika van die vliegtuig, wat getoon het dat die kortperiode-modus onstabiel kan raak as die massamiddelpunt agtertoe verskuif. ’n Aanpassende heitempobeheerder met die modelverwysings-aanpassende beheerstruktuur is ontwerp om die kortperiode-modus weer te stabiliseer wanneer die massamiddelpunt agtertoe verskuif. Die aanpassingswet is ontwerp deur die gebruik van Lyapunov se stabiliteitsteorie. Lugspoed-, klimtempo- en hoogtebeheerders is rondom die aanpassende heitempobeheerder ontwerp sodat die longitudinale dinamika van die vliegtuig heeltemal outonoom beheer kan word. Hierdie buitelusse is ontwerp met vaste parameters, aangesien hulle nie geraak sal word deur verskuiwings in die massamiddelpunt as die aanpassende heitempobeheerder na wense werk nie. Suiwer sagteware-simulasies, sowel as hardeware-in-die-lus-simulasies, het getoon dat die aanpassende beheerstelsel oombliklike verskuiwings in die massamiddelpunt goed kan hanteer, waar sulke verskuiwings ’n beheerstelsel met vaste parameters onstabiel sou maak. Hierdie simulasie-resultate is bevestig deur vlugtoetse te doen, waar die vliegtuig onstabiel gemaak is deur positiewe terugvoer, en weer deur die aanpassende beheerstelsel stabiel gemaak is. Die simulasie- en vlugtoetsresultate wys dus dat aanpassende beheer ’n onstabiele vliegtuig weer kan stabiliseer sonder eksplisiete kennis van die veranderinge in die dinamika van die vliegtuig. Aanpassende beheer kan dus doeltreffend wees as deel van ’n geïntegreerde fout-tolerante beheerstelsel.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This thesis presents the study, analysis and design of electronically tunable filters, that can be tuned over a wide frequency range (20-500MHz), for use in a direct sampling receiver. The final design does not have to be a single filter, but may be comprised of a filter bank which enables switching between the filters. The band of interest is too low to use normal transmission lines and lumped elements have to be used. Different topologies that can implement Coupled Resonator filters with lumped elements are investigated. Devices that can be used for tuning are also investigated and varactor diodes are found to be the most suitable tuning devices currently available. Two filters, one at the high-end and one at the low-end of the band, were designed and built, both using varactor diodes. These filters perform well in terms of tuning range, but achieving low losses with current technologies in this band remains difficult. / AFRIKAANSE OPSOMMING: Hierdie tesis meld die studie, analise en ontwerp van elektronies verstelbare filters, wat verstelbaar is oor ’n wye band (20-500MHz), vir gebruik in ’n direk-monster-ontvanger. Die finale ontwerp hoef nie ’n enkele filter te wees nie, maar kan bestaan uit ’n filterbank wat skakeling tussen die filters toelaat. Die betrokke band is te laag vir die gebruik van normale transmissielyne en diskrete komponente moet gebruik word. Verskillende topologieë wat gekoppelde resoneerder filters implementeer met diskrete komponente is ondersoek. Verstelbare komponente word ook ondersoek en varaktor diodes blyk die mees geskikte verstelbare komponent wat huidig beskikbaar is in hierdie band. Twee filters, een aan die hoë kant en een aan die lae kant van die band, is ontwerp en gebou, beide met varaktor diodes. Hierdie filters het wye verstelbare bereik, maar dit is steeds moeilik om verliese te beperk met die huidige tegnologie.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / In order to rapidly detect, monitor and predict changes in milk as it ferments, sensors would need to be designed specifically for milk. To this end, invasive surgical stainless steel probes were investigated and the probe impedances were characterised according to measurements made in various saline concentrations. Based on these findings, specific probes were designed that were robust and easy to use in milk. To measure multiple probe sensors continuously and accurately, an automatic measurement device was designed and manufactured. The device was self-sustaining, portable and calculated and stored all probe impedance data internally, allowing experimental runs to take place in controlled laboratory environments. The probes designed in this thesis were consequently tested in various milk fermentation experiments and it was found that surgical stainless steel probes were effective at detecting and monitoring fermentation changes. The probe impedance changes also lead the pH changes in milk, giving it a predictive element. The probe sensor studies provided enough data so that studies could be done into potential non-invasive sensors. Therefore, capacitive sensors were investigated and a fringe field capacitor was presented as a potential non-invasive milk fermentation sensor.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Through the Karoo Array Telescope, and its extension MeerKAT, South Africa is demonstrating its capabilities to host the most powerful radio telescope ever, the Square Kilometre Array (SKA). This new interferometer is intended to assist radio astronomers in unlocking the mysteries concealed in the far regions of the universe. A thorough investigation of Radio Frequency Interference (RFI) sources at each stage of the design becomes relevant for the success of the project. The electromagnetic coupling through coaxial cables is the main focus of this thesis since 90% of the Electromagnetic Compatibility (EMC) problems come from inadequate system layout and grounding, where cabling plays the major role. Interest revolves around better noise immunity, low radiation and cost. Transfer impedance (ZT ) and shielding e ectiveness (SE) are used as the cable selection criteria. Several measurements of coaxial cables identi ed on KAT-7 have been performed for ZT characterisation from 300 kHz up to 1.3 GHz. A current injection method is used to identify the ZT for the low frequency region. We derived the high frequency part of ZT , with a reverberation chamber technique (RC) measuring shielding e ectiveness. At rst, we calibrated the RC according to the relevant IEC 61000-4-21 standard and evaluated the result with an Open Area Test Site (OATS) E- eld estimation. The accuracy of the E- eld within the chamber is also addressed, based on statistical analysis of the chamber's independent samples. The OATS E- eld equivalent determination showed a good correlation with the OATS E- eld data of a standard radiator. A coaxial air-line ZT veri ed the theoretical ZT model within 7 dB and showed the expected 20 dB/decade slope variation. Furthermore, the braiding porpoising e ect has been noticed with some cable samples. Here, a variation less than 20 dB/decade occurs at lower frequency. Then, the slope changes to 20 dB/decade at high frequency. This study illustrates a practical comparison of cable performance and constitutes a rst approach to RFI mitigation of the MeerKAT cabling system. / AFRIKAANSE OPSOMMING: Deur middel van die Karoo Reeks Teleskoop, asook sy uitbreiding MeerKAT, demonstreer Suid-Afrika sy vermo om die mees kragtige radioteleskoop ooit, die Vierkante Kilometer Reeks (SKA), te vestig. Hierdie nuwe interferometer is bedoel om radiosterrekundiges te help in die ontsluiting van die geheimenisse wat versteek is in die verre reike van die heelal. 'n Deeglike ondersoek van Radio Frekwensie Steurings (RFS) bronne by elke stadium van die ontwerp is belangrik vir die sukses van die projek. Die elektromagnetiese koppeling deur koaksiale kabels is die hoo okus van hierdie tesis, aangesien 90% van die elektromagnetiese versoenbaarheid (EMV) probleme ontstaan as gevolg van onvoldoende stelsel-uitleg en beaarding, waar kabels die hoofrol speel. Beter ruis-immuniteit, lae straling en koste vorm die areas van belang. Oordragimpedansie (ZT ) en afskermingsdoeltre endheid (SE) word gebruik as die kabelkeuringskriteria. Verskeie metings van koaksiale kabels wat op KAT-7 gedenti seer is, is uitgevoer vir ZT karakterisering van 300 kHz tot 1,3 GHz. 'n Stroom-induseringsmetode is gebruik om die ZT vir die lae-frekwensiebereik te identi seer. Ons het die ho-frekwensie deel van ZT afgelei met 'n weerkaatsingskamer tegniek (RC) wat afskermingsdoeltre endheid meet. Eerstens het ons die RC gekalibreer volgens die relevante IEC 61000-4-21 standaard en die resultaat met 'n Ope Area Toetsterrein (OAT) E-veld benadering gevalueer. Die akkuraatheid van die E-veld in die kamer is ook aangespreek, gebaseer op 'n statistiese analise van die kamer se onafhanklike monsters. Die OAT E-veld ekwivalente benadering het goed met die OAT E-veld data van 'n standaard uistraler gekorreleer. 'n Koaksiale lugmedium-transmissielyn ZT bevestig die teoretiese ZT model binne 7 dB en het ook die verwagte 20 dB/dekade variasie in helling getoon. Verder is die golwende e ek oor die kabelomvlegting opgemerk met sekere kabels. Hier is 'n variasie van minder as 20 dB/dekade gevind by die laer frekwensie. Dan verander die helling na 20 dB/dekade teen ho frekwensie. Hierdie studie toon 'n praktiese vergelyking van die verrigting van die kabel en 'n eerste benadering tot RFS tempering van die MeerKAT kabelstelsel.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The purpose of this project is to develop a number of coaxial resonator lters. Firstly, the theoretical model of the lter is discussed, with a Tchebyscheff LC-ladder prototype lter used to derive a generalised bandpass lter. From this, generalised Combline- and Interdigital lters are derived. Following this, various options and limitations in the mechanics of microwave lters are discussed. Results are shown for an in-depth study considering the unloaded quality factor for thirteen di erent resonators. Each resonator is unique in the method of manufacturing, polishing, as well as plating. Utilizing the information obtained from the unloaded quality factor measurements, three coupled coaxial resonator lters, are designed for use in a radar system, namely a sixth order 2125 MHz Combline lter, a sixth order 9250 MHz Interdigital lter and a third order 9250 MHz Interdigital lter. Optimal results were obtained when both resonators and coupled transmission line lters were constructed from aluminium that was wire-cut and then silver electroplated. / AFRIKAANSE OPSOMMING: Die omvang van hierdie projek behels die ontwerp en bou van ko-aksiale resoneerder filters. Eerstens word die teoretiese modellering van die lters bespreek. 'n Tchebyscheff LC-leer prototipe filter word gebruik as basis vir 'n generiese banddeurlaat filter. Die banddeurlaat lter word gebruik om die afgeleide Kamlyn- en Interdigitale filter te de finieer. Hierna volg 'n bespreking aangaande die verskillende moontlikhede in die meganiese vervaardiging van mikrogolf filters. 'n Gedetailleerde studie word gedoen om die onbelaste kwaliteitsfaktore van 13 verskillende resoneerders te bepaal. Elkeen van hierdie resoneerders is uniek in die metode van vervaardiging, polering, asook die platering daarvan. Deur gebruik te maak van die resultate van die onbelaste kwaliteitsfaktore, word drie gekoppelde ko-aksiale resoneerder filters ontwikkel vir die gebruik in 'n radarstelsel, naamlik 'n sesde-orde 2125 MHz Kamlyn lter, 'n sesde orde 9250 MHz Interdigitale filter, asook 'n derde orde 9250 MHz Interdigitale filter. Die beste resultate was gevind toe beide resoneerders en gekoppelde ko-aksiale resoneerder filters vervaardig is uit aluminium wat gedraadsny en silwer geplateer is.

Thesis (MscEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The Cape Peninsula University of Technology, in collaboration with Stellenbosch University, is developing a 3-unit CubeSat for a low earth polar orbit. The two main payloads are a camera and a radio frequency beacon. This beacon will be used to calibrate the radar antenna patterns of an antenna of the Hermanus Magnetic Observatory at their base in Antarctica. This thesis describes the development of an aerodynamic attitude determination and control system needed to achieve three-axis stabilisation of the satellite and to perform accurate pointing of the camera. The satellite structure is designed to utilise aerodynamic means of control. It includes four feather antennae for passive pitch-yaw stabilisation and two active aerodynamic roll control paddles. The sensors used are a three-axis magnetometer, ne sun sensor and nadir sensor. Three attitude determination methods are investigated, namely the Triad, Rate Kalman Filter and Extended Kalman Filter algorithm. Apart from the aerodynamic control elements of the satellite, three magnetic torque rods and three nano-reaction wheels are also included in the design. Three control modes for the satellite are identi ed and various control methods are investigated for these control modes. The various attitude determination and control methods are evaluated through simulations and the results are compared to determine the nal methods to be used by the satellite. The magnetic Rate Kalman Filter is chosen as attitude determination method to be used when the satellite is tumbling and a combination of the sun Rate Kalman Filter and the Triad algorithm is to be used when the satellite experiences low angular rates. The B-dot and Y-spin controller is chosen for the detumbling control mode, the aerodynamic and cross-product control method for the three-axis stabilisation control mode and the quaternion feedback control method for the pointing control mode of the satellite. The combination of magnetic and aerodynamic control proved to be su cient for the initial stabilisation of the satellite, but the three nano-reaction wheels are required for the pointing control of the imaging process. / AFRIKAANSE OPSOMMING: Die Kaapse Skiereiland Universiteit van Tegnologie, in samewerking met die Universiteit van Stellenbosch, is tans besig met die ontwikkeling van 'n 3-eenheid CubeSat vir 'n pol^ere, lae aard-wentelbaan. Die twee loonvragte van die satelliet bestaan uit 'n kamera en 'n radiofrekwensie-baken. Die radiofrekwensie-baken sal gebruik word om 'n antenna van die Hermanus Magnetiese Observatorium, by hul basis in Antarktika, se radar antenna patrone te kalibreer. Hierdie tesis beskryf die ontwikkeling van 'n aerodinamiese ori entasiebepaling en -beheerstelsel wat benodig word om die satelliet in drie asse te stabiliseer en om die kamera noukeurig te rig. Die satelliet se struktuur word ontwerp vir aerodinamiese beheer. Dit sluit vier veerantennas in vir passiewe duik-gier beheer, asook twee aerodynamiese rolbeheer appies vir aktiewe beheer. Die sensors wat gebruik word sluit 'n drie-as magnetometer, fyn sonsensor en nadirsensor in. Drie ori entasiebepalingsmetodes word ondersoek, naamlik die Drietal, Tempo Kalman lter en die Uitgebreide Kalman lter algoritmes. Buiten die aerodinamiese beheerelemente van die satelliet, word daar ook drie magneetstange en drie nano-reaksiewiele ingesluit in die ontwerp. Daar word onderskeid getref tussen drie beheermodusse en verskeie beheermetodes word ondersoek vir hierdie beheermodusse. Die verskeie ori entasiebepalings- en ori entasiebeheermetodes word ge evalueer deur middel van simulasies en die resultate word vergelyk om die beste metodes vir die satelliet se gebruik te bepaal. Die magnetiese Tempo Kalman lter word gekies as ori entasiebepalingsmetode vir 'n tuimelende satelliet en die kombinasie van die son Tempo Kalman lter en Drietal algoritme word gebruik vir 'n satelliet met lae hoektempos. Die B-dot en Y-spin beheerder word gekies vir die tuimelbeheermodus, die aerodinamiese en kruisproduk beheermetode vir die drie-as-stabilisasie-beheermodus en die kwaternioon terugvoer beheermetode vir die rigbeheermodus van die satelliet. Daar word bepaal dat die samespanning van magnetiese en aerodinamiese beheer voldoende is vir die aanvanklike stabilisering van die satelliet, maar dat die drie nano-reaksiewiele benodig word om die kamera te rig tydens die beeldvormingproses.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The successful design, implementation and testing of a feedback control system for tab-deflection control of a shape memory alloy (SMA) based control surface actuator is presented. The research is performed as part of the Control Surfaces in Confined Spaces (CoSICS) research project conducted at Stellenbosch University. The research group investigates ways to provide control surface actuation in size-restricted spaces in commercial aircraft such as the Airbus A320 and A330. This is achieved by investigating the concept of trailing edge tabs to reduce the required torque load, resulting in reduced actuator requirements enabling the use of smaller actuators. This thesis contributes to the project by investigating the possibility of using SMA-based actuators in reduced hinge moment requirement applications. An SMA-based tab actuator demonstrator design is presented. Mathematical models are derived for the SMA material, thermodynamics and actuator geometry. The models are combined to formulate an SMA-based control surface actuator model. The model is utilised in four tracking feedback controller designs; two based on linear and two based on non-linear control techniques. The manufactured prototype is presented along with the incorporated hardware for controller implementation. System identification follows and validates the three mathematical models. Practical verification of the model and two of the controllers is conducted. The unimplemented controllers are implemented through a validated model simulation. Controller evaluation, based on the dynamic controller performance, is conducted. The results validate the concept of using an SMA actuator for tab-deflection control and indicate important limitations for the intended application. / AFRIKAANSE OPSOMMING: Die tesis behels die ontwerp, implementering en toetsing van ’n terugvoer beheerstelsel vir hulpvlak defleksie beheer van ’n vorm-geheue allooi (SMA) gebaseerde aktueerder. Die navorsing vorm deel van die Beheervlakke in Begrensde Ruimtes (CoSICS) navorsingsprojek by Stellenbosch Universiteit. Die CoSICS navorsing behels ’n ondersoek na beheervlak aktueering in beknopte spasies in kommersiële vliegtuie soos die Airbus A320 en A330. Die probleem word aangespreek deur ’n ondersoek na aerodinamiese hulpvlakke wat ’n vermindering in skarnier moment tot gevolg het en sodoende die aktueerder vereistes verminder. Hierdie tesis dra by tot die projek deur die moontlikheid van die gebruik van SMAgebaseerde aktueerders in verminderde skarnier moment vereiste toepassings te ondersoek. ‘n SMA gebaseerde hulpvlak demonstrasie aktueerder ontwerp word voorgelê. Wiskundige modelle vir die SMA materiaal, termodinamika en prototipe geometrie is geformuleer en gekombineer om ‘n SMA gebaseerde beheervlak aktueerder model te ontwikkel. Die model word in vier beheerder ontwerpe toegepas. Twee ontwerpe is op liniëre en twee op nie-liniëre beheer tegnieke gebaseer. Die prototipe en nodige hardeware vir beheerder implementasie is voorgedra. Stelsel identifikasie is toegepas en verifieer die drie wiskundige modelle. Praktiese verifikasie van die model en twee beheerders is gedoen. Die ongeïmplementeerde beheerders is deur die geverifieerde aktueerder model gesimuleer. ‘n Beheerder evaluasie gebaseer op die dinamiese beheerder gedrag word toegepas. Die evaluasie beklemtoon kritiese aspekte en beperkinge in verband met SMA aktueering. Die resultate regverdig die gebruik van ‘n SMA aktueerder vir hulpvlak defleksie beheer en beklemtoon belangrike beperkinge ten opsigte van die voorgestelde toepassing.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A methodology is developed to manage the large number of RFI Culprits on a new Radio Telescope location such as the South African site being developed in the Karoo, both during construction and ongoing operations. The requirement for RFI control is presented, with brief reference to the more traditional methods used by other Radio Telescope observatories. The new approach is then presented, based on methods used in the engineering field of Logistic Engineering. Three case studies are used to illustrate how the approach can be applied. Finally, recommendations are made on how the approach can be implemented for new Radio Telescope projects. / AFRIKAANSE OPSOMMING: ‘n Metodolgie word ontwikkel vir die beheer van die groot aantal Radiofrekwensiesteurings oortreders by ‘n nuwe Radio Teleskoop terrein, soos die Suid Afrikaanse terrein wat huidiglik in die Karoo ontwikkel word. Die metodolgie geld beide gedurende konstruksie en gedurende bedryf. Die behoefte vir RFS beheer word aangebied, met kortlikse melding van die meer tradisionele metodes wat ander Radio Teleskoop Sterrewagte gebruik. ‘n Nuwe aanslag, gebaseer op die metodolgieë van Logistieke Ingenieurswese, word dan aangebied. Drie gevallestudies wys hoe hierdie nuwe aanslag toegepas kan word. Laastens word aanbevelings gemaak om hierdie nuwe aanslag met nuwe Radio Teleskoop projekte te implimenteer.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Augmented reality is a fairly young research field, still in an infancy stage at Stellenbosch University. Since this is one of the first augmented reality projects, one goal is to present a theoretical study of augmented reality. This study is given in the literature study, along with a review of the available development solutions. While there are various tools available with which one can create markerbased augmented reality applications, these tools are not meant for testing new techniques and algorithms in an augmented or mixed reality. The remaining goals of this project is to create a platform for the rapid design of augmented reality applications, and to expand the capabilities of this platform beyond marker-based augmented reality. In this project we present the design and implementation of a pragmatic mixed-reality framework capable of a wider variety of applications. A design is shown where marker tracking can be used alongside other computer vision techniques to design new applications. The framework utilises stereo cameras to find the position of real world objects, and a 3D display to make the mixed reality environment as immersive as possible. Proof of concept test applications built with the framework are presented. Colour based techniques are used to find a user’s hand and create a virtual representation of it. This allows the user to interact with a virtual object in an augmented reality scene by ‘touching’ it with her hand. / AFRIKAANSE OPSOMMING: Toegevoegde realiteit is ’n jong navorsingsveld by Universiteit Stellenbosch. Aangesien hierdie een van die eerste projekte is wat fokus op toegevoegde realiteit, is ’n teoretiese studie van toegevoegde realiteit as ’n doel gestel. Dit word verskaf in die literatuurstudie, tesame met ’n oorsig oor bestaande oplossings vir die ontwikkeling van toegevoegde realiteit sagteware. Bestaande oplossings is gefokus op die ontwikkeling van merker-gebaseerde toegevoegde realiteit, maar los min ruimte vir die toets van nuwe tegnieke toepasbaar op die veld. Dit lei tot die oorblywende doelwitte van die projek: om ’n platform te ontwerp vir die ontwikkeling van merker-gebaseerde toegevoegde realiteit programme, asook om die platform uit te brei. Ons lewer ’n pragmatiese ontwikkelingsraamwerk wat dit moontlik maak om ’n verskeidenheid nuwe toegevoegde realiteit programme te ontwikkel. Die raamwerk is ontwerp sodat die ontwikkelaar merkers saam met ander rekenaarvisie tegnieke kan gebruik om sagteware te skep. Stereo kameras word gebruik om die posisie van werklike voorwerpe te vind. Die raamwerk maak ook gebruik van ’n 3D skerm om virtuele objekte te vertoon. Toetsprogramme gebou as ’n bewys van die konsep, word vertoon en bespreek. ’n Kleur-gebaseerde tegniek word gebruik om ’n gebruiker se hand te vind, en ’n virtuele voorstelling van die hand word geskep. Die gebruiker kan virtuele voorwerpe laat reageer deur dit met haar hand aan te raak.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Radar Cross Section (RCS) is an important parameter in radar engineering. Often, electrically large structures are of interest in RCS analysis due to the high operating frequencies of radar systems. Simulation of these problems can be more e cient than measurement due to the cost associated with measurement. The Method of Moments/Physical Optics (MoM/PO) hybrid method combines the advantages of the MoM and PO, making it suited to solving electrically large problems that may contain some small complex detail. The requirement for high meshing resolution when analysing some electromagnetic problems, however, signi cantly increases memory requirements. As a result, the hybrid MoM/PO becomes computationally expensive for electrically large problems. In this work, a linear phase term is introduced into the RWG basis function formulation of the MoM/PO hybrid. The addition of the linear phase term allows the use of large triangular mesh elements in the PO region, resulting in the analysis of electrically large problems. The bene t of this formulation is that it allows a reduction in computational cost whilst maintaining the accuracy of the hybrid MoM/PO. This improved hybrid is tested on various planar test cases and results show that it attains the same level of accuracy as the original MoM/PO hybrid. / AFRIKAANSE OPSOMMING: Radardeursnit is 'n belangrike parameter in radaringenieurswese. As gevolg van die hoë frekwensies wat deur baie radarstelsels gebruik word, is elektriesgroot probleme dikwels van belang in die berekening van die radardeursnit van teikens. Die modellering en berekening van die radardeursnit van teikens kan meer kostedoeltre end as metings wees, as gevolg van die beduidende koste van radardeursnitmetings. Die hibriede Moment-Metode/Fisiese-Optika tegniek kombineer die voordele van die twee tegnieke, wat dit geskik maak vir elektries-groot probleme met klein, komplekse detail. Indien die gewone benadering egter gevolg word om 'n hoë resolusie faset-model te gebruik, bly dit berekeningsintensief met groot rekenaar geheuevereistes vir elektries-groot probleme. In hierdie studie word 'n lineêre fase term ingesluit in die formulering van die Rao-Wilton-Glisson (RWG) basisfunksies vorm van die hibriede Moment-Metode/Fisiese-Optika tegniek. Die toevoeging van die lineêre fase term maak dit moontlik om groot driehoekfasette in die Fisiese-Optika gebied te gebruik, wat beteken dat elektries-groot probleme makliker opgelos kan word. Die voordeel van hierdie nuwe formulering is dat die berekeningslas en -tyd verminder word terwyl die akkuraatheid van die oorspronklike hibriede Moment-Metode/Fisiese-Optika tegniek behou word. Hierdie verbeterde hibriede tegniek word getoets aan die hand van verskeie platvlak toetsgevalle en die resultate dui daarop dat die akkuraatheid vergelykbaar is met die van die oorspronklike hibriede Moment-Metode/Fisiese-Optika tegniek.