Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: This research focuses on the development of new efficient algorithms for multi-path planning and multi-rigid body constrained attitude control. The work is motivated by current and future applications of these algorithms in: intelligent control of multiple autonomous aircraft and spacecraft systems; control of multiple mobile and industrial robot systems; control of intelligent highway vehicles and traffic; and air and sea traffic control. We shall collectively refer to the class of mobile autonomous systems as “agents”. One of the challenges in developing and applying such algorithms is that of complexity resulting from the nontrivial agent dynamics as agents interact with other agents, and their environment. In this work, some of the current approaches are studied with the intent of exposing the complexity issues associated them, and new algorithms with reduced computational complexity are developed, which can cope with interaction constraints and yet maintain stability and efficiency. To this end, this thesis contributes the following new developments to the field of multipath planning and multi-body constrained attitude control: • The introduction of a new LMI-based approach to collision avoidance in 2D and 3D spaces. • The introduction of a consensus theory of quaternions by applying quaternions directly with the consensus protocol for the first time. • A consensus and optimization based path planning algorithm for multiple autonomous vehicle systems navigating in 2D and 3D spaces. • A proof of the consensus protocol as a dynamic system with a stochastic plant matrix. • A consensus and optimization based algorithm for constrained attitude synchronization of multiple rigid bodies. • A consensus and optimization based algorithm for collective motion on a sphere. / AFRIKAANSE OPSOMMING: Hierdie navorsing fokus op die ontwikkeling van nuwe koste-effektiewe algoritmes, vir multipad-beplanning en veelvuldige starre-liggaam beperkte standbeheer. Die werk is gemotiveer deur huidige en toekomstige toepassing van hierdie algoritmes in: intelligente beheer van veelvuldige outonome vliegtuig- en ruimtevaartuigstelsels; beheer van veelvuldige mobiele en industrile robotstelsels; beheer van intelligente hoofwegvoertuie en verkeer; en in lug- en see-verkeersbeheer. Ons sal hier “agente” gebruik om gesamentlik te verwys na die klas van mobiele outonome stelsels. Een van die uitdagings in die ontwikkeling en toepassing van sulke algoritmes is die kompleksiteit wat spruit uit die nie-triviale agentdinamika as gevolg van die interaksie tussen agente onderling, en tussen agente en hul omgewing. In hierdie werk word sommige huidige benaderings bestudeer met die doel om die kompleksiteitskwessies wat met hulle geassosieer word, bloot te l^e. Verder word nuwe algoritmes met verminderde berekeningskompleksiteit ontwikkel. Hierdie algoritmes kan interaksie-beperkings hanteer, en tog stabiliteit en doeltreffendheid behou. Vir hierdie doel dra die proefskrif die volgende nuwe ontwikkelings by tot die gebied van multipad-beplanning van multi-liggaam beperkte standbeheer: • Die voorstel van ’n nuwe LMI-gebasseerde benadering tot botsingsvermyding in 2D en 3D ruimtes. • Die voorstel van ’n konsensus-teorie van “quaternions” deur “quaternions” vir die eerste keer met die konsensusprotokol toe te pas. • ’n Konsensus- en optimeringsgebaseerde padbeplanningsalgoritme vir veelvoudige outonome voertuigstelsels wat in 2D en 3D ruimtes navigeer. • Die bewys van ’n konsensusprotokol as ’n dinamiese stelsel met ’n stochastiese aanlegmatriks. • ’n Konsensus- en optimeringsgebaseerde algoritme vir beperkte stand sinchronisasie van veelvoudige starre liggame. • ’n Konsensus- en optimeringsgebaseerde algoritme vir kollektiewe beweging op ’n sfeer.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: RoboCup promotes research in robotics and multi-robot systems (MRS). The RoboCup Small Size League (SSL), in particular, offers an entry level opportunity to take part in this field of study. This thesis presents a starting phase for research in robotics and MRS at Stellenbosch University. It includes the full documentation of the mechanical, electronic and software design of an omni-directional soccer robot for RoboCup SSL. The robot is also meant to operate as a hardware and software development platform for research in MRS. The platform was therefore designed with high-level programming language compatibility, a wide range of connectivity, and modularity in mind. The robot uses a single board computer (SBC) running a Linux operating system to accomplish these objectives. Moreover, a driver class library was written in C++ as a software application interface (API) for future development on the robot platform. The robot was also developed with a particular focus on a distributed control architecture. "Player" was implemented as the middleware, which can be used for communication between multiple robots in a distributed environment. Additionally, three tests were performed to demonstrate the functionality of the prototype: a PI speed control test, a direction accuracy test and a static communication test using the middleware. Recommendations for possible future work are also given. / AFRIKAANSE OPSOMMING: RoboCup bevorder navorsing in robotika en multi-robot-stelsels (MRS). Die RoboCup Klein Liga (KL) bied in die besonder die geleentheid om op intreevlak navorsing te doen in hierdie veld. Hierdie tesis verteenwoordig die eerste fase van navorsing in robotika en MRS by Stellenbosch Universiteit. Dit sluit die volledige dokumentasie van die meganiese, elektroniese en sagteware-ontwerp van ’n omnidireksionele sokker-robot vir die KL in. Die robot is ook veronderstel om te dien as ’n hardeware- en sagteware-ontwikkelingsplatform vir navorsing in MRS. Die platform is dus ontwerp met ’n verskeidenheid van uitbreingsmoontlikhede en modulariteit in gedagte asook die moontlikheid om gebruik te maak van ’n hoë-vlak programmeertaal. Om hierdie doelwitte te bereik, maak die robot gebruik van ’n enkel-bord-rekenaar met ’n Linux bedryfstelsel. Verder was ’n sagteware drywer in C++ geskryf om te dien as ’n sagteware-koppelvlak vir toekomstige ontwikkeling op die robot platform. Die robot is ook ontwikkel met die besondere fokus op ’n gedesentraliseerde beheerstels. Player was geïmplementeer as die middelware, wat gebruik kan word vir kommunikasie tussen verskeie robotte in ’n gedesentralliseerde beheerstelsel. Daar is drie toetse uitgevoer om die funksionaliteit van die prototipe te demonstreer, ’n PI spoed beheer toets, ’n rigting akkuraatheidstoets en ’n statiese kommunikasie toets deur van die middelware gebruik te maak. Aanbevelings vir moontlike toekomstige werk word ook verskaf.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Modern-day processors are not getting any faster. Due to the power consumption limit of frequency scaling, parallel processing is increasingly being used to decrease computation time. In this thesis, several parallel paradigms are used to improve the performance of commonly serial SAO programs. Four novelties are discussed: First, replacing double precision solvers with single precision solvers. This is attempted in order to take advantage of the anticipated factor 2 speed increase that single precision computations have over that of double precision computations. However, single precision routines present unpredictable performance characteristics and struggle to converge to required accuracies, which is unfavourable for optimization solvers. Second, QP and dual are statements pitted against one another in a parallel environment. This is done because it is not always easy to see which is best a priori. Therefore both are started in parallel and the competing threads are cancelled as soon as one returns a valid point. Parallel QP vs. dual statements prove to be very attractive, converging within the minimum number of outer iterations. The most appropriate solver is selected as the problem properties change during the iteration steps. Thread cancellation poses problems caused by threads having to wait to arrive at appropriate checkpoints, thus su ering from unnecessarily long wait times because of struggling competing routines. Third, multiple global searches are started in parallel on a shared memory system. Problems see a speed increase of nearly 4x for all problems. Dynamically scheduled threads alleviate the need for set thread amounts, as in message passing implementations. Lastly, the replacement of existing matrix-vector multiplication routines with optimized BLAS routines, especially BLAS routines targeted at GPGPU technologies (graphics processing units), proves to be superior when solving large matrix-vector products in an iterative environment. These problems scale well within the hardware capabilities and speedups of up to 36x are recorded. / AFRIKAANSE OPSOMMING: Hedendaagse verwerkers word nie vinniger nie as gevolg van kragverbruikingslimiet soos die verwerkerfrekwensie op-skaal. Parallelle prosesseering word dus meer dikwels gebruik om berekeningstyd te laat daal. Verskeie parallelle paradigmas word gebruik om die prestasie van algemeen sekwensiële optimeringsprogramme te verbeter. Vier ontwikkelinge word bespreek: Eerste, is die vervanging van dubbel presisie roetines met enkel presisie roetines. Dit poog om voordeel te trek uit die faktor 2 spoed verbetering wat enkele presisie berekeninge het oor dubbel presisie berekeninge. Enkele presisie roetines is onvoorspelbaar en sukkel in meeste gevalle om die korrekte akkuraatheid te vind. Tweedens word QP teen duale algoritmes in ’n parallel omgewing gebruik. Omdat dit nie altyd voor die tyd maklik is om te sien watter een die beste gaan presteer nie, word almal in parallel begin en die mededingers word dan gekanselleer sodra een terugkeer met ’n geldige KKT punt. Parallele QP teen duale algoritmes blyk om baie aantreklik te wees. Konvergensie gebeur in alle gevalle binne die minimum aantal iterasies. Die mees geskikte algoritme word op elke iterasie gebruik soos die probleem eienskappe verander gedurende die iterasie stappe. “Thread” kanseleering hou probleme in en word veroorsaak deur “threads” wat moet wag om die kontrolepunte te bereik, dus ly die beste roetines onnodig as gevolg van meededinger roetines was sukkel. Derdens, verskeie globale optimerings word in parallel op ’n “shared memory” stelsel begin. Probleme bekom ’n spoed verhoging van byna vier maal vir alle probleme. Dinamiese geskeduleerde “threads” verlig die behoefte aan voorafbepaalde “threads” soos gebruik word in die “message passing” implementerings. Laastens is die vervanging van die bestaande matriks-vektor vermenigvuldiging roetines met geoptimeerde BLAS roetines, veral BLAS roetines wat gerig is op GPGPU tegnologië. Die GPU roetines bewys om superieur te wees wanneer die oplossing van groot matrix-vektor produkte in ’n iteratiewe omgewing gebruik word. Hierdie probleme skaal ook goed binne die hardeware se vermoëns, vir die grootste probleme wat getoets word, word ’n versnelling van 36 maal bereik.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The research presented in this thesis serves to provide a tool to autonomously screen for cardiovascular disease in the rural areas of Africa. Vital information thus obtained from patients can be communicated to advanced medical centres by Telemedicine. Cardiovascular disease is then detected in its initial stages, which is essential to its effective treatment. The system developed in this study uses recorded heart sounds and electrocardiogram signals to distinguish between normal and abnormal heart conditions. This system improves on standard diagnostic tools in that it does not require cumbersome and expensive imaging equipment or a highly trained operator. Heart sound- and electrocardiogram signals from 62 volunteers were recorded with the prototype Precordialcardiogram device as part of a clinical study to aid in the development of the autonomous auscultation software and to screen patients for cardiovascular disease. These volunteers consisted of 28 patients of Tygerberg Hospital with cardiovascular disease and, for control purposes, 34 persons with normal heart conditions. The autonomous auscultation system developed during this study, interprets data obtained with the Precordialcardiogram device to autonomously acquire a normal or abnormal diagnosis. The system employs wavelet soft thresholding to denoise the recorded signals, followed by the segmentation of heart sound by identifying peaks in the electrocardiogram. Novel frequency spectral information was extracted as features from the heart sounds, by means of ensemble empirical mode decomposition and auto regressive modelling. These features proved to be particularly significant and played a major role in the screening capability of the system. New time domain based features were identified, established on the specific characteristics of the various cardiovascular diseases encountered during the study. These features were extracted via the energy ratios between different parts of ventricular systole and diastole of each recorded cardiac cycle. The respective features were classified to characterise typical heart diseases as well as healthy hearts with an ensemble artificial neural network. Herein the decisions of all the members were combined to obtain a final diagnosis. The performance of the autonomous auscultation system used in concert with the Precordialcardiogram device prototype, as determined through the leave-one-out crossvalidation method, had a sensitivity rating of 82% and a specificity rating of 88%. These results demonstrate the potential benefit of the Precordialcardiogram device and the developed autonomous auscultation software in a Telemedicine environment. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die navorsing van 'n outonome toetsing en sifting stelsel vir kardiovaskulêre siektes in landelike dele van Afrika, vanwaar mediese inligting per telefoon versend kan word. Die apparaat maak vroeë opsporing van kardiovaskulêre siektes moontlik, wat essensieel is vir effektiewe behandeling daarvan en ook die koste-effek van hierdie siektes verminder. In die huidige ontwikkelde stelsel word normale sowel as abnormale hart-toestande getipeer met opnames van hartklanke sowel as elektrokardiogram-seine. Voordele wat hierdie stelsel bo standaard diagnostiese metodes het, sluit die hanteerbare formaat van die hele apparaat sowel as die nie-noodsaaklikheid van duur beeldskeppende apparaat, of hoogs opgeleide personeel. Hartklank- en elektrokardiogramseine van 62 vrywilligers is met die prototipe "Precordialcardiogram" apparaat opgeneem om by te dra tot die ontwikkeling van die rekenaar sagteware vir die outonome auscultatsie stelsel en om die pasiëntsiftingsvermoë daarvan te toets. Die vrywilligers het 28 pasiënte van Tygerberg hospitaal met abnormale harttoestande ingesluit, sowel as ‘n kontrolegroep van 34 persone met normale harttoestande. Die outonome auskultasie-stelsel wat tot stand gekom het deur hierdie ondersoek maak gebruik van “wavelet” sagte drempeling om geraas uit die opgeneemde seine te verwyder. Daarna word die hartklanke gesegmenteer deur die pieke van die elektrokardiogram te identifiseer. Deur middel van "ensemble empirical mode decomposition" en outoregressiewe modellering, is nuwe inligting aangaande die frekwensie spektra van hartklanke, aanwysend van spesifieke harttoestande, verkry. Die beduidendheid van hierdie eienskappe is bewys en het 'n belangrike rol in die siftingsvermoë van die stelsel gespeel. Hierbenewens is nuwe tyd-gebaseerde eienskappe van die onderskeie kardiovaskulêre siektes wat tydens die ondersoek bestudeer is, geïdentifiseer. Hierdie eienskappe is geëien deur die energie-verhoudings tussen verskillende dele van die ventrikulêre sistolie en diastolie van elke opgeneemde hartsiklus te ontleed. 'n "Ensemble artificial neural network" is gebruik om die geïdentifiseerde eienskappe van hartsiektes sowel as normale harttoestande, te klassifiseer. Hierin is besluite van al die lede van die netwerk gekombineer, ten einde ‘n finale diagnose te maak. Die klassifiseerder se geldigheid is kruis-bevestig deur middel van die laat-een-uit kruisbevestigings-metode. Deur middel van die kruis-bevestigingsmetode is die bedryfsvermoëns van die outonome auskultasie-stelsel, toegerus met die "Precordialcardiogram" apparaat, repektiewelik op 82% vir sensitiwiteit en 88% vir spesifisiteit vasgestel. Hierdie resultate demonstreer die benuttingspotensiaal van die apparaat in 'n Telemedisyne omgewing.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis comprises of the testing and evaluation of a modern diesel engine running on both biodiesel and mineral diesel on the upgraded Bio-fuels Testing Facility (BTF) at Stellenbosch University. The project was motivated by the need to install a modern diesel engine onto the existing BTF test rig for biodiesel testing. In this project, the BTF was re-designed to support a new Volkswagen 1.9L TDI engine. The capabilities of the BTF were then expanded further by the implementation of a low-cost pressure indicating system, utilising an optical pressure transducer. During the testing of biodiesel, it was found that the calorific value of the biodiesel was 14% lower than that of the tested mineral diesel. The ignition quality (cetane index) of the biodiesel was also lower than that of the mineral diesel. Even so, the engine only experienced a maximum power loss of 4.2%. During heat-release analysis, it was determined that there was no significant difference in the combustion process of biodiesel and that of mineral diesel. The conclusion could be made that biodiesel is suitable for use in modern TDI engines. Testing validated the operation of the upgraded test cell, and in trials it was determined that the test results are highly repeatable. The pressure indicating set proved to have some limitations. Only simplified heat-release analyses and reasonable indicated power calculations could be performed with the indicating set. Recommendations were made for improvement in future research. / Centre for Renewable and Sustainable Energy Studies

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The world's astronomy community is working together to build the largest and most sensitive radio telescope in the world namely: the SKA (Square Kilometre Array). It will consist of approximately three thousand dishes which will each require accurate positioning. The Square Kilometer Array has a testbed called the Phased Experimental Demonstrator (PED) in Observatory, Cape Town. A hexapod positioning mechanism is required to position a 3.7 m radio telescope which forms part of an array of seven radio telescopes. This thesis details the design process of the hexapod system. The design consists of the mechanical design of the joints and linear actuators, a kinematic and dynamic model, a controller and a user interface. In order to verify the design for the PED hexapod a scaled prototype was designed, built and tested. The hexapod's repeatability as well as ability to track a path was tested using an inclinometer. The tests confirmed the design feasibility of the PED hexapod and also highlight issues that require care when constructing the full scale hexapod, such as the amount of play in the platform joints. The designed full scale hexapod will have an error angle less than 0.13°, a payload capacity of 45 kg, withstand wind speeds of 110 km/h and cost R160 000. / AFRIKAANSE OPSOMMING: Die wêreld se sterrekundige gemeenskap is besig om saam te werk om die grootste en mees sensitiewe radioteleskoop in die wêreld te bou, naamlik: die SKA (Square Kilometre Array). Dit sal uit ongeveer drie duisend skottels bestaan wat elkeen akkurate posisionering benodig. Die SKA het 'n toetssentrum, genaamd die “Phased Experimental Demonstrator” in Observatory, Kaapstad. 'n Sespoot posisionering meganisme word benodig om die 3.7 m radioteleskoop te posisioneer, wat deel vorm van 'n stelsel van sewe radioteleskope. Hierdie tesis beskryf die proses om die sespoot stelsel te ontwerp. Die ontwerp bestaan uit die meganiese komponent van die koppelings en lineêre aktueerders, 'n kinematiese en dinamiese model, 'n beheerder, asook 'n gebruikersintervlak. 'n Geskaleerde prototipe is ontwerp, gebou en getoets om die ontwerp te verifieer. Die platform se herhaalbaarheid sowel as akkuraatheid om 'n pad te volg was getoets met 'n oriëntasie sensor. Die toetse het probleme uitgelig wat versigtig hanteer moet word gedurende die konstruksie van die volskaalse sespoot, veral die hoeveelheid speling in die koppelings. Die volskaalse sespoot ontwerp het 'n hoek fout van minder as 0.13°, 'n ladingsvermoë van 45 kg en kan 'n windspoed van 110 km/h weerstaan en kos R160 000.

Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The In the Physiotherapy Division of the Faculty of Health Sciences on the Tygerberg Hospital Campus of the University of Stellenbosch, the challenge arose to develop a portable, affordable and yet accurate 3D measurement machine for the assessment of posture in school children in their classroom environment. Currently Division already uses a state-of-the-art VICON commercial medical measuring machine to measure human posture in 3D in their physiotherapy clinic, but the system is not portable and is too expensive to cart around to different places for testing. To respond to this challenge, this Master’s thesis designed and analyzed a machine and its supporting system through both research on stereo-vision methodologies and empirical appraisal in the field. In the development process, the research was required to overcome the limitations posed by small image resolutions and lens distortions that are typical of cheap cameras. The academic challenge lay in the development of an error prediction model through Jacobian derivation and Error Propagation Law, to predict uncertainties of angular measurement calculated by the system. The research culminated in a system that is comparable in accuracy to the VICON within 3mm, and that has 1.5mm absolute accuracy within its own system for a measurement volume radius of 2.5 m. As such, the developed error model is an exact predictor of the angular error to within 0.02° of arc. These results, for both system accuracy and the error model, exceed the expectations on the basis of the initial challenge of the system. The development of the machine was successful in providing a prototype tool that is suitable for commercial development for use by physiotherapists in human posture measurement and assessment. In its current incarnation, the machine will also serve the Engineering Faculty as the most fundamental form of a three-dimensional measuring apparatus using only basic theories and algorithms of stereo-vision, thereby providing a basic experimental platform from which further scientific research on the theory and application of computer vision can be conducted. / AFRIKAANSE OPSOMMING: Die Fisioterapie Afdeling van die Fakulteit Gesondheidswetenskappe op die Tygerberg kampus van die Universiteit van Stellenbosch gebruik ’n allernuutste VICON kommersiële mediese meettoestel om menslike postuur in drie dimensies te meet. Vanuit hierdie Afdeling het die uitdaging ontstaan om ’n draagbare, bekostigbare, maar tog akkurate, drie-dimensionele meetapparaat geskik vir die meet van die postuur van skoolkinders in die klaskamer te ontwikkel. In aanvaarding van hierdie uitdaging, het hierdie Magistertesis ’n toestel en ondersteuningstels ontwerp en ontleed deur beide navorsing in stereo-visie metodiek en terplaatse beoordeling. In die ontwikkelingsproses moes die navorsing die beperkings wat deur klein-beeld resolusie en lens-distorsie (tipies van goedkoop kameras) meegebring word, oorkom. Die akademiese uitdaging lê in die ontwikkeling van ’n voorspellende foutmodel deur van die Jacobianse-afleiding en die Fout Propageringswet gebruik te maak om onsekerheid van hoeksberekening deur die stelsel te voorspel. Die navorsing het gelei tot ’n stelsel wat binne 3mm vergelykbaar is in akkuraatheid met dié van die VICON en ook 1.5mm absolute interne akkuraatheid het in ’n meet-volume radius van 2.5m radius. Die ontwikkelde foutmodel is dus ’n presiese voorspeller van hoekfout tot binne 0.02° van boog. Die resultate met betrekking tot beide die akkuraatheid en die foutmodel het die oorspronklike verwagtinge van die uitdaging oortref. Die ontwikkeling was suksesvol in die skep van ’n prototipe-toestel geskik vir kommersiële ontwikkeling, vir gebruik deur fisioterapeute in die meting en evaluering van menslike postuur. Die stelsel is in sy fundamentele vorm, deur die gebruik van slegs basiese teorieë en algoritmes van stereo-visie, funksioneer as ’n drie-dimensionele meetapparaat. In die fundamentele vorm sal die stelsel die Ingenieursfakulteit dien as ’n basiese eksperimentele platform waarop verdere wetenskaplike navorsing in die teorie en toepassing van rekenaar-visie gedoen kan word.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis documents the research conducted into the control of the feeder subsystem of a Reconfigurable Assembly System (RAS). The research was motivated by a new set of modern manufacturing requirements associated with an aggressive and dynamic global market. The motivation can be more specifically attributed to the need for selective automation, through the installation of reconfigurable systems, in the South African manufacturing industry. The objective of the research was to implement and evaluate Multi-Agent Systems (MASs) and IEC 61499 function block systems as potential control strategies for reconfigurable systems. The control strategies were implemented for the control of the feeder subsystem of an experimental RAS at Stellenbosch University. The subsystem's hardware consisted of a singulation unit with a machine vision camera, part magazines and a six DOF pick-'n-place robot. The structure of the control strategies is based on the ADACOR holonic reference architecture. The mapping of the subsystem holons to the structures of the control strategies is explained. The development and implementation of the control strategies, along with the accompanying lower level software, is described in detail. A system reconfigurability assessment was performed and the results are discussed. The assessment was performed at two levels – the Higher Level Control (HLC) (where the control strategies were implemented) and the low level control and hardware. The assessment was done through four reconfiguration experiments. The evaluation of the HLC was done through both quantitative and qualitative performance measures. The implications of the reconfiguration, involved in each of the respective experiments, on the low level software and hardware are discussed. The experimental results show that agent-based control adds more reconfigurability to the feeder subsystem than IEC 61499 function block control, and that agents have more advantages regarding customizability, convertibility and scalability than IEC 61499 function blocks. Also, the ability of agent-based control to implement reconfiguration changes during subsystem operation makes it more suitable to the case study application. / AFRIKAANSE OPSOMMING: Hierdie tesis dokumenteer die navorsing gedoen in die beheer van die voerder sub-stelsel vir 'n herkonfigureerbare monteringstelsel. Die navorsing was gemotiveer deur „n nuwe stel vereistes vir moderne vervaardiging wat met 'n aggresiewe en dinamiese globale mark geassosieer word. Die motivering kan meer spesifiek toegeskryf word aan die behoefte tot selektiewe outomatisasie, deur middel van die implimentering van herkonfigureerbare stelsels, in the Suid-Afrikaanse vervaardigingsnywerheid. Die doel van die navorsing is om multi-agent stelsels en IEC 61499 funksie-blok stelsels, as potensiële beheerstrategiëe vir herkonfigureerbare stelsels, te implementer en evalueer. Die beheerstrategiëe was geïmplementeer vir die voerder sub-stelsel van „n eksperimentele herkonfigureerbare monteringstelsel by Universiteit Stellenbosch. Die hardeware behels „n skeier-eenheid (singulation unit) met „n masjienvisie kamera, onderdeelmagasyne en „n ses-vryheidsgraad gearktikuleerde optel-en-plaas robot. Die struktuur van die beheerstrategiëe is gebaseer op die ADACOR holoniese verwysingsargitektuur. Die afbeelding van die sub-stelsel holons na die struktuur van die beheerstrategiëe word verduidelik. Die ontwikkeling en implementering van die beheerstrategiëe, asook die gepaardgaande laer-vlak programmatuur, word in detail beskryf. Die stelsel se herkonfigureerbaarheid was geassesseer en die resultate daarvan word bespreek. Die assessering was op twee vlakke gedoen – die hoër-vlak beheer (waar die beheerstrategiëe geimplementeer was) en die lae-vlak beheer en hardeware. Die assessering was gedoen deur middel van vier herkonfigurasie eksperimente. Die hoër-vlak beheer was geëvalueer deur beide kwalitatiewe en kwantitatiewe metings. Die implikasies van die herkonfigurasie, betrokke by die onderskeie eksperimente, op die lae-vlak beheer en hardeware word beskryf. Die eksperimentele resultate wys dat agent-baseerde beheer meer herkonfigureerbaarheid tot die voerder sub-stelsel toevoeg as IEC 61499 funksie-blok beheer. Dit is geïdentifiseer dat agente meer voordele inhou ten opsigte van aanpasbaarheid, skakelbaarheid en skaalbaarheid as IEC funksie-blokke. Agent-baseerde beheer laat ook toe dat herkonfigurasieveranderinge tydens sub-stelsel werking geïmplimenteer kan word – dus is dit meer geskik vir aanwending in die gevallestudie.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis describes the development of a distributed control system for SSL soccer robots. The project continues on work done to develop a robotics research platform at Stellenbosch University. The wireless communication system is implemented using Player middleware. This enables high level programming of the robot drivers and communication clients, resulting in an easily modifiable system. The system is developed to be used as either a centralised or decentralised control system. The software of the robot’s motor controller unit is updated to ensure optimal movement. Slippage of the robot’s wheels restricts the robot’s movement capabilities. Trajectory tracking software is developed to ensure that the robot follows the desired trajectory while operating within its physical limits. The distributed control architecture reduces the robots dependency on the wireless network and the off-field computer. The robots are given some autonomy by integrating the navigation and control on the robot self. Kalman filters are designed to estimate the robots translational and rotational velocities. The Kalman filters fuse vision data from an overhead vision system with inertial measurements of an on-board IMU. This ensures reliable and accurate position, orientation and velocity information on the robot. Test results show an improvement in the controller performance as a result of the proposed system. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van ’n verspreidebeheerstelsel vir SSL sokker robotte. Die projek gaan voort op vorige werk wat gedoen is om ’n robotika navorsingsplatform aan die Universiteit van Stellenbosch te ontwikkel. Die kommunikasiestelsel is geïmplementeer met behulp van Player middelware. Dit stel die robotbeheerders en kommunikasiekliënte in staat om in hoë vlak tale geprogrameer te word. Dit lei tot ’n maklik veranderbare stelsel. Die stelsel is so ontwikkel dat dit gebruik kan word as óf ’n gesentraliseerde of verspreidebeheerstelsel. Die sagteware van die motorbeheer eenheid is opgedateer om optimale robot beweging te verseker. As die robot se wiele gly beperk dit die robot se bewegingsvermoëns. Trajekvolgings sagteware is ontwikkel om te verseker dat die robot die gewenste pad volg, terwyl dit binne sy fisiese operasionele grense bly. Die verspreibeheerargitektuur verminder die robot se afhanklikheid op die kommunikasienetwerk en die sentrale rekenaar. Die robot is ’n mate van outonomie gegee deur die integrasie van die navigasie en beheer op die robot self te doen. Kalman filters is ontwerp om die robot se translasie en rotasie snelhede te beraam. Die Kalman filters kombineer visuele data van ’n oorhoofse visiestelsel met inertia metings van ’n IMU op die robot. Dit verseker betroubare en akkurate posisie, oriëntasie en snelheids inligting. Toetsresultate toon ’n verbetering in die beheervermoë as ’n gevolg van die voorgestelde stelsel.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The knee is the largest, most complicated and incongruent joint in the human body. It sustains very high forces and is susceptible to injury and disease. Osteoarthritis is a common disease prevalent among the elderly and causes softening or degradation of the cartilage and subcondral bone in the joint, which leads to a loss of function and pain. This problem can be alleviated through a surgical intervention commonly termed a “knee replacement”. The aim of a knee replacement procedure is to relieve pain and restore normal function. Ideally, the knee replacement prosthesis should have an articulating geometry similar to that of the patient’s healthy knee, and must allow for normal motion. Unfortunately, this is often problematic since knee prostheses are supplied in standard sizes from a variety of manufacturers and each one has a slightly different design. Furthermore, commercial prostheses are not always able to restore the complex geometry of an individual patient’s original articulating surfaces. This dissertation shows that there is a significant variation between knee geometries, regardless of gender and race. This research aims to resolve the problem in two parts: Firstly by presenting a method for preoperatively selecting the optimal knee prosthesis type and size for a specific patient, and secondly by presenting a design procedure for designing and manufacturing patient-specific unicompartmental knee replacements. The design procedure uses mathematical modelling and an artificial neural network to estimate the original and healthy articulating surfaces of a patient’s knee. The models are combined with medical images from the patient to create a knee prosthesis that is patient-specific. These patient-specific implants are then compared to conventional implants with respect to contact stresses and kinematics. The dissertation concludes that patient-specific implants can have characteristics that are comparable to or better than conventional prostheses. The unique design methodology presented in this dissertation introduces a significant advancement in knee replacement technology, with the potential to dramatically improve clinical outcomes of knee replacement surgery. / AFRIKAANSE OPSOMMING: Die knie is die grootste, mees komplekse en mees ongelyksoortige gewrig in die liggaam. Osteoarthritis is ’n siekte wat algemeen by bejaardes voorkom en die versagting of agteruitgang van die kraakbeen en subchondrale bene in die gewrig tot gevolg het, wat tot ’n verlies van funksionering en pyn lei. Hierdie probleem kan verlig word deur ’n chirurgiese ingryping wat algemeen as ’n “knievervanging” bekend staan. Die doel van ’n knievervangingsprosedure is om pyn te verlig en normale funksionering te herstel. Ideaal gesproke behoort die knievervangingsprostese ’n gewrigsgeometrie te hê wat soortgelyk aan die pasiënt se gesonde knie is, en normale beweging moontlik maak. Ongelukkig is dit dikwels problematies aangesien knieprosteses in standaardgroottes en deur ’n verskeidenheid vervaardigers verskaf word, wat elkeen se ontwerp effens anders maak. Verder kan kommersiële prosteses nie altyd die komplekse geometrie van ’n individuele pasiënt se oorspronklike gewrigsoppervlakke vervang nie. Hierdie proefskrif wys dat daar ’n betekenisvolle variasie tussen knieafmetings is, afgesien van geslag en ras. Hierdie navorsing is daarop gemik om die problem op tweërlei wyse te benader: Eerstens deur ’n metode aan te bied om die optimal knieprostesetipe en -grootte vir ’n spesifieke pasiënt voor die operasie uit te soek, en tweedens om ’n ontwerpprosedure aan te bied vir die ontwerp en vervaardiging van pasiëntspesifieke unikompartementele knievervangings. Die ontwerpprosedure gebruik wiskundige modellering en ’n kunsmatige neurale netwerk om die oorspronklike en gesonde gewrigsoppervlakke van ’n pasiënt se knie te bepaal. Die modelle word met mediese beelde van die pasiënt gekombineer om ’n knieprostese te skep wat pasiëntspesifiek is. Hierdie pasiëntspesifieke inplantings word dan met konvensionele inplantings vergelyk wat kontakstres en kinematika betref. Daar word tot die slotsom gekom dat die pasiëntspesifieke inplantings oor eienskappe kan beskik wat vergelykbaar is met of selfs beter is as dié van konvensionele prosteses. Die unieke ontwerpmetodologie wat in hierdie proefskrif aangebied word, stel beduidende vordering in knievervangingstegnologie bekend, met die potensiaal om die kliniese uitkomste van knievervangingsoperasies dramaties te verbeter.