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Asymmetrical S-band coupled resonator filtersCoetzee, Nicola 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Due to a more densely packed frequency spectrum, there is an increasing demand for
narrow band filters with asymmetrical transfer function characteristics. The resulting
coupling matrices contain both positive and negative couplings, cross couplings and individual
resonator frequency offsets.
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Development of an active pulsed radar receiver for a mono-static borehole-radar toolWoods, Brian Keith 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2003. / No abstract available
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Wind-electric pump system designLemmer, Edward Charles 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / The aim of this study is to analyse the operation of a wind-electric pumping system (WEPS) as an alternative to conventional mechanical wind pumps for application in stand-alone water-pumping schemes. The steady-state as well as the dynamic operation of such a system is analysed. Through these analyses, practical guidelines are given in the design and sizing of the different system components to ensure efficient and reliable operation. Theoretical analyses are supported by measured results conducted on a small scale wind-electric pump system. The limitations involved in the design and implementation of a large scale wind-electric pump system are presented through a case study. It is firstly concluded that small-scale wind-electric pump systems have the potential of offering superior performance and flexibility to conventional mechanical wind pumps. It is secondly concluded that large-scale wind-electric pump systems are best suited, in terms of economic and practical feasibility, to pumping applications with low pressures and medium to high wind regimes at the turbine installation site.
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Design and implementation of a modular converter with application to a solid state transformerWolf, Marko 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: The purpose of a solid state transformer (SST) is to use power electronic converters to mimic
the operation of the conventional distribution transformer. These power electronic converters
are proposed to overcome the disadvantages of the conventional distribution transformer. The
advantages of a SST include near perfect voltage regulation and harmonic isolation between the
primary and secondary windings of the transformer.
This thesis discusses the design and development of the different converters in a solid state
transformer (SST). A prototype modular back-to-back converter is developed for the input and
isolation stage of the SST. The isolation stage consists of a high voltage DC-DC converter, which
transfers power across the isolation barrier of the SST. This stage is evaluated in the laboratory
with special attention being paid to the efficiency of the converter.
The second aspect that this thesis addresses is the output stage of the SST, namely a three
phase inverter. The discussion of the output stage focuses on the losses occurring in the inverter.
The switching device losses are calculated by means of an adapted numerical method as opposed
to using conventional analytical methods. The presented numerical method is compared to the
existing analytical method and the findings are discussed.
A double loop control strategy is implemented for the output stage inverter. The inner
current loop utilizes a predictive control strategy. The control analysis of the double loop
controller is discussed and evaluated in the laboratory. All the converters that are discussed in
this thesis are evaluated in the laboratory and the relevant measurements are included. / AFRIKAANSE OPSOMMING: Die doel van ’n drywingselektroniese transformator (DET) is om drywingselektroniese omsetters
te gebruik om die werking van die konvensionele distribusietransformator na te boots. Hierdie
drywingselektroniese omsetters word voorgestel ten einde die nadele van die konvensionele distribusietransformator
te bowe te kom. Die voordele van ’n DET sluit in: feitlik perfekte regulering
van spanning en harmoniese isolasie tussen die primˆere en sekondˆere windings van die
transformator.
Hierdie tesis bespreek die ontwerp en ontwikkeling van die verskillende omsetters in ’n drywingselektroniese
transformator (DET). ’n Prototipe modulˆere rug-aan-rug-omsetter word ontwikkel
vir die intree- en isolasiefase van die DET. Die isolasiefase bestaan uit ’n hoogspanning-
GS-GS omsetter, wat drywing oor die isolasiegrens van die DET heen oordra. Hierdie omsetter
word in die laboratorium ge¨evalueer met besondere aandag aan die doeltreffendheid van die
omsetter.
Die tweede aspek waarna in hierdie tesis gekyk word, is die uittreefase van die DET, naamlik
’n driefaseomsetter. Die bespreking van die uittreefase fokus egter op die verliese wat in die omsetter
voorkom. Die verliese van die skakelaars word bereken deur middel van ’n aangepaste numeriese
metode teenoor die gebruik van konvensionele analitiese metodes. Die numeriese metode
wat aangebied word, word vergelyk met die bestaande analitiese metode en die bevindings word
bespreek.
’n Dubbellus-beheerstrategie word vir die uittreefase-omsetter ge¨ımplementeer. Die binneste
stroomlus word ge¨ımplementeer deur van ’n voorspelbare beheerstrategie gebruik te maak. Die
beheeranalise van die dubbellusbeheerder word bespreek en in die laboratorium ge¨evalueer. Al
die omsetters wat in hierdie tesis bespreek word, word in die laboratorium ge¨evalueer en die
relevante metings word ingesluit.
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Single-trial classification of an EEG-based brain computer interface using the wavelet packet decomposition and cepstral analysisLodder, Shaun 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Brain-Computer Interface (BCI) monitors brain activity by using signals
such as EEG, EcOG, and MEG, and attempts to bridge the gap between
thoughts and actions by providing control to physical devices that range from
wheelchairs to computers. A crucial process for a BCI system is feature extraction,
and many studies have been undertaken to find relevant information
from a set of input signals.
This thesis investigated feature extraction from EEG signals using two
different approaches. Wavelet packet decomposition was used to extract information
from the signals in their frequency domain, and cepstral analysis was
used to search for relevant information in the cepstral domain. A BCI was implemented
to evaluate the two approaches, and three classification techniques
contributed to finding the effectiveness of each feature type.
Data containing two-class motor imagery was used for testing, and the BCI
was compared to some of the other systems currently available. Results indicate
that both approaches investigated were effective in producing separable
features, and, with further work, can be used for the classification of trials
based on a paradigm exploiting motor imagery as a means of control. / AFRIKAANSE OPSOMMING: ’n Brein-Rekenaar Koppelvlak (BRK) monitor brein aktiwiteit deur gebruik
te maak van seine soos EEG, EcOG, en MEG. Dit poog om die gaping
tussen gedagtes en fisiese aksies te oorbrug deur beheer aan toestelle soos
rolstoele en rekenaars te verskaf. ’n Noodsaaklike proses vir ’n BRK is die
ontginning van toepaslike inligting uit inset-seine, wat kan help om tussen verskillende
gedagtes te onderskei. Vele studies is al onderneem oor hoe om sulke
inligting te vind.
Hierdie tesis ondersoek die ontginning van kenmerk-vektore in EEG-seine
deur twee verskillende benaderings. Die eerste hiervan is golfies pakkie ontleding,
’n metode wat gebruik word om die sein in die frekwensie gebied voor
te stel. Die tweede benadering gebruik kepstrale analise en soek vir toepaslike
inligting in die kepstrale domein. ’n BRK is geïmplementeer om beide metodes
te evalueer.
Die toetsdata wat gebruik is, het bestaan uit twee-klas motoriese verbeelde
bewegings, en drie klassifikasie-tegnieke was gebruik om die doeltreffendheid
van die twee metodes te evalueer. Die BRK is vergelyk met ander stelsels
wat tans beskikbaar is, en resultate dui daarop dat beide metodes doeltreffend
was. Met verdere navorsing besit hulle dus die potensiaal om gebruik te word
in stelsels wat gebruik maak van motoriese verbeelde bewegings om fisiese
toestelle te beheer.
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An artificial magnetic ground-plane for a log-periodic antennaVisser, Hugo Hendrik 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This paper presents the implementation of an artificial magnetic ground-plane with a low profile
Log-periodic Dipole Array (LPDA) antennas. After the properties of three typical Electromagnetic
Bandgap (EBG) structures are investigated and their bandwidth properties are studied, a
mechanism is presented to improve the band-width over which the EBG surface acts as a perfect
magnetic conductor (PMC). A low profile LPDA is modeled above this surface and the results
indicate an improved band-width region. Compared with a LPDA in free space the frequency
band is shifted higher by the EBG surface and the gain pattern is shifted from a horizontal
orientation to a vertical orientation. / AFRIKAANSE OPSOMMING: Hierdie dokument stel voor die implementering van kunsmatige magnetiese grondvlakke met
Logaritmiese Periodiese Dipool Samestelling (LPDS) antennas. Die eienskappe van drie tipiese
Elektromagnetiese Bandgaping (EBG) strukture word ondersoek en hul bandwydte eienskappe
word bestudeer. ’n Meganisme word voorgestel om die bandwydte te verbeter waar die EBG
oppervlakte soos n perfekte magnetiese geleier optree. ’n Lae profiel LPDS word bo hierdie
oppervlakte geplaas. Die resultate dui aan ’n verbetering in the bandwydte. In vergelyking met
’n LPDS in vrye ruimte skuif die frekwensie band ho¨er as gevolg van die EBG oppervlakte en
die aanwins patroon skuif van ’n horisontale orientasie na ’n vertikale orientasie.
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Advanced take-off and flight control algorithms for fixed wing unmanned aerial vehiclesDe Hart, Ruan Dirk 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis presents the development and implementation of a position based kinematic guidance
system, the derivation and testing of a Dynamic Pursuit Navigation algorithm and a
thorough analysis of an aircraft’s runway interactions, which is used to implement automated
take-off of a fixed wing UAV.
The analysis of the runway is focussed on the aircraft’s lateral modes. Undercarriage and
aerodynamic effects are first analysed individually, after which the combined system is analysed.
The various types of feedback control are investigated and the best solution suggested.
Supporting controllers are designed and combined to successfully implement autonomous
take-off, with acceleration based guidance.
A computationally efficient position based kinematic guidance architecture is designed
and implemented that allows a large percentage of the flight envelope to be utilised. An
airspeed controller that allows for aggressive flight is designed and implemented by applying
Feedback Linearisation techniques.
A Dynamic Pursuit Navigation algorithm is derived that allows following of a moving
ground based object at a constant distance (radius). This algorithm is implemented and verified
through non-linear simulation. / AFRIKAANSE OPSOMMING: Hierdie tesis handel oor die ontwikkeling en toepassing van posisie-afhanklike, kinematiese
leidings-algoritmes, die ontwikkeling van ’n Dinamiese Volgings-navigasie-algoritme en ’n
deeglike analise van die interaksie van ’n lugraam met ’n aanloopbaan sodat outonome opstygprosedure
van ’n vastevlerk vliegtuig bewerkstellig kan word.
Die bogenoemde analise het gefokus op die laterale modus van ’n vastevlerk vliegtuig en
is tweeledig behartig. Die eerste gedeelte het gefokus op die analise van die onderstel, terwyl
die lugraam en die aerodinamiese effekte in die tweede gedeelte ondersoek is. Verskillende
tipes terugvoerbeheer vir die outonome opstygprosedure is ondersoek om die mees geskikte
tegniek te bepaal. Addisionele beheerders, wat deur die versnellingsbeheer gebaseerde opstygprosedure
benodig word, is ontwerp.
’n Posisie gebaseerde kinematiese leidingsbeheerstruktuur om ’n groot persentasie van
die vlugvermoë te benut, is ontwikkel. Terugvoer linearisering is toegepas om ’n lugspoedbeheerder
, wat in staat is tot aggressiewe vlug, te ontwerp.
’n Dinamiese Volgingsnavigasie-algoritme wat in staat is om ’n bewegende grondvoorwerp
te volg, is ontwikkel. Hierdie algoritme is geïmplementeer en bevestig deur nie-lineêre
simulasie.
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Movement control and guidance of an automated underwater vehiclePauck, Simon James 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis presents the design process of the movement control and guidance
systems for an automated underwater vehicle (AUV) constructed by the Institute of
Maritime Technology in Simon’s Town. The full non-linear mathematical model and
simulation environment for the AUV were previously developed in [1]. The design
process in this thesis covers an analysis of existing test data and the performance
of the current systems in place on the AUV, derivation and analysis of the linear
model for the AUV, design of upgraded control and guidance systems, analysis
of the new designs including simulation results, practical implementation of the
new designs and the results thereof. Over the course of this project a number of
flaws were identified in the original control designs and other aspects of the AUV.
Most notably, the capability of the AUV is limited owing to its construction, and
the current control and guidance methods result in poor movement characteristics.
The new control designs are executed through multiple SISO feedback loops, with
the most complicated controllers consisting of proportional and integral control. A
completely new guidance method was designed which grants theAUVthe ability to
track both straight line and circular path segments with no steady state error. These
designs were tested in simulation, with results showing good tracking performance,
even in the presence of output disturbances. The new designs were implemented
on the physical AUV, but testing was limited, with poor results being obtained. The
poor test results were caused primarily by the construction of the AUV. / AFRIKAANSE OPSOMMING: Hierdie tesis stel die ontwerpsproses voor vir die bewegingsbeheer- en navigasiestelsels
vir ’n outonome duikboot wat gebou is deur die Instituut vir Maritieme
Tegnologie in Simonstad. Die volle nie-lineˆere wiskundige model en simulasieomgewing
vir die duikboot is voorheen ontwikkel in [1]. Die ontwerpsproses in
hierdie tesis behels ’n analise van bestaande toetsdata en van die werksverrigting
van die stelsels wat tans op die duikboot ge¨ınstalleer is, die afleiding en analise
van ’n lineˆere model vir die duikboot, die ontwerp van verbeterde beheer- en navigasiestelsels,
die analise van die nuwe ontwerpe, wat simulasieresultate insluit,
die praktiese implementering van die nuwe ontwerpe, en die resultate daarvan.
Deur die loop van die projek is ’n aantal tekortkominge ge¨ıdentifiseer in die oorspronklike
beheerstelselontwerpe en ander aspekte van die duikboot. Die mees
beduidende tekortkominge is dat die vermo¨e van die duikboot beperk word deur
die konstruksie daarvan, en dat die huidige beheer- en navigasietegnieke swak
bewegingseienskappe lewer. Die nuwe beheerstelselontwerpe is uitgevoer deur
’n aantal enkelintree, enkeluittree terugvoerlusse, waar die mees komplekse beheerders
bestaan uit proporsionele en integraalbeheer. ’n Heeltemal nuwe navigasiemetode
is ontwerp, wat die duikboot in staat stel om beide reguit lyne en
sirkulˆere padsegmente te volg sonder ’n stasionˆere volgfout. Hierdie ontwerpe is
getoets in simulasie, waar die resultate goeie volging getoon het, selfs in die teenwoordigheid
van uittreeversteurings. Die nuwe ontwerpe is ge¨ımplementeer op
die fisiese duikboot, maar beperkte toetse is gedoen, en het swak resultate gelewer.
Die swak toetsresultate was hoofsaaklik as gevolg van die konstruksie van die
duikboot.
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Control surfaces in confined spaces : the optimisation of trailing edge tabs to reduce control surface hinge momentsJaquet, Christopher Denis 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: This thesis describes the first project relating to the Control Surfaces in Confined Spaces (CoSICS) project
at Stellenbosch University. The aim of CoSICS project is to reduce the size of control surface actuators,
and this thesis considers the aileron system of commercial aircraft such as the Airbus A320 and A330.
Specifically the project aims to reduce the aileron hinge moment, as this will result in smaller actuators.
Possible methods are discussed where aerodynamic forces are used to reduce the aileron hinge moment
through the use of a wing-aileron-tab configuration. In order to examine the use of the configuration,
first order aerodynamic modelling is performed using two-dimensional thin-aerofoil theory, which is also
extended to a basic three-dimensional approximation.
To determine the maximum reduction in hinge moment several optimisations are performed where only
the tab chord length is varied, both tab and aileron chord lengths are varied, and finally the tab chord
length and aileron span are varied. The optimisation methods used, namely the gradient-based sequential
quadratic programming (SQP) and a real-encoded genetic algorithm (REGA) are discussed in detail and
include general implementations which are then applied to the problem. The optimisations performed are
dual-layered where optimal deflection angles are determined as well as the optimal geometry.
The results of the optimisation are tested using a roll manoeuvre in a specially developed Simulink simulation
environment for this purpose.
The study produces results where new hinge moment values are an order of magnitude smaller than those
of the old configuration, while maintaining suitable lift and rolling moment coefficients. The optimisation
and simulation infrastructure developed in this thesis provides a platform for higher-fidelity models and
components being developed in future work to provide higher fidelity results. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die eerste projek in die Control Surfaces in Confined Spaces-projek1 (CoSICS-projek)
uitgevoer by die Universiteit Stellenbosch. Die doel van die COSICs-projek is om die grootte van beheervlak
aktueerders te minimeer en hierdie tesis handel oor die aileron stelsel van kommersiële vliegtuie
soos die Airbus A320 en A330. Die doel van hierdie tesisis om die skarnier draaimoment van die aileron
te minimeer deur aërodinamiese kragte in te span in ’n vlerk-aileron-hulpvlak konfigurasie. Eerste-orde
aërodinamiese modelle is afgelei met behulp van twee-dimensionele dunvlerkteorie en is gebruik om die
konfigurasie te analiseer. ’n Eerste orde drie-dimensionele benadering is ook ontwikkel.
Om die maksimum vermindering in die skarnier draaimoment te bepaal, is verskeie optimerings uitgevoer
waar eers die hulpvlak se koordlengte gevarieer word, daarna beide die aileron en hulp-vlak se
koordlengtes en laastens die hulp-vlak se koordlengte en wydte. Die twee optimerings metodes wat gebruik
is, nl. ’n sekwensiële kwadratiese programmerings (SKP) tegniek, en ’n reële getal-geënkodeerde
genetiese algoritme (RGGA), word bespreek en ontwikkel voor hulle toegepas word op die probleem.
Twee-vlak optimerings word uitgevoer waar beide die optimale defleksiehoeke en die optimale geometrie
bepaal word.
Die resultate van die optimering word daarna getoets deur middel van ’n rol maneuver wat uitgevoer word
in ’n Simulink simulasie omgewing wat daarvoor geskep is.
Hierdie studie lei tot goeie resultate met skarnier draaimoment waardes ’n ordegrootte kleiner as dié van
die vorige stelsel, terwyl goeie waardes van rol-moment en verheffingskrag koëffisiënte behou word. Die
optimering en simulasie infrastruktuur wat hier ontwikkel word verskaf ’n platform vir meer akkurate
modelle en komponente wat ontwikkel word in toekomstige projekte om meer akkurate resultate te lewer.
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A design environment for the automated optimisation of low cross-polarisation horn antennasVan der Walt, Madele 12 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The aggressive space mapping algorithm is used in this project for the optimisation of electromagnetic
structures. This technique combines the use of fast, less accurate models with more
time-consuming, high precision models in the optimisation of a design.
MATLAB’s technical computing environment possesses powerful tools for optimisation as well
as the graphical representation and mathematical post-processing of data. A software interface,
which uses Visual Basic for Applications, is created between MATLAB and the electromagnetic
solvers, CST Microwave Studio and μWave Wizard, that are used for the fine and coarse model
calculations. The interface enables the direct interchange of data, which allows MATLAB to control
the optimisation for the automation of the design process.
The optimisation of a microwave coaxial resonator with input coupling is used to demonstrate the
design environment. An accurate equivalent circuit model is available to describe the problem.
The space mapping optimisation of this structure works well, with a significant improvement in
the efficiency of the optimisation when compared to standard optimisation techniques.
Multimode horn antennas are of interest for use as feeds in radio-astronomy telescope systems.
The design of a stepped circular horn antenna in the space mapping design environment is presented.
The horn’s radiation pattern is optimised for low cross-polarisation. This structure is much
more complex to model than the resonator example. The generalised scattering matrix representation
is used in the coarse model description. The far-fields are calculated from the aperture fields
by means of the Fast Fourier Transform. Various tests confirm that the optimisation is steered
in the right direction as long as the coarse model response follows the trend of the fine model
response over the optimisation space.
The presented design environment is a powerful tool for the automation of the design of electromagnetic
structures. / AFRIKAANSE OPSOMMING: Die aggressiewe ruimte-afbeelding algoritme word in hierdie projek gebruik vir die optimering van
elektromagnetiese strukture. Hierdie tegniek kombineer die gebruik van vinnige, minder akkurate
modelle tesame met tydrowende hoë presisie modelle tydens die optimering van ’n ontwerp.
MATLAB se tegniese verwerkingsomgewing beskik oor kragtige gereedskap vir optimering sowel
as die grafiese voorstelling en wiskundige verwerking van data. ’n Sagteware koppelvlak, wat
Visual Basic for Applications benut, word geskep tussen MATLAB en die elektromagnetiese
oplossers, CST Microwave Studio en μWave Wizard, wat vir die fyn en growwe model berekeninge
gebruik word. Hierdie koppelvlak maak die direkte uitruiling van data moontlik, wat MATLAB in
staat stel om die optimering te beheer ten einde die ontwerpsproses te outomatiseer.
Die optimering van ’n mikrogolf koaksiale resoneerder met intree koppeling word gebruik om
die ontwerpsomgewing te demonstreer. ’n Akkurate ekwivalente stroombaanmodel is beskikbaar
om die probleem mee te beskryf. Die ruimte-afbeelding optimering van hierdie struktuur werk
goed en toon ’n aansienlike verbetering in die doeltreffendheid van die optimering wanneer dit
met standaard optimeringstegnieke vergelyk word.
Multimodus horingantennes is van belang in radio-astronomie, waar dit as voere vir teleskope gebruik
word. Die ontwerp van ’n trapvormige, sirkelvormige horingantenne in die ruimte-afbeelding
ontwerpsomgewing word aangebied. Die stralingspatroon van die horing word optimeer vir lae
kruispolarisasie. Hierdie struktuur is heelwat meer ingewikkeld om te modelleer as die resoneerder
voorbeeld. Die veralgemeende strooimatriks voorstelling word gebruik in die growwe model
beskrywing. Die ver-velde word bereken vanaf die velde in die bek van die antenne, deur gebruik
te maak van die Vinnige Fourier Transform. Verskeie toetse bevestig dat die optimering in die
regte rigting gestuur word, solank as wat die growwe model se gedrag dié van die fyn model oor
die optimeringsgebied navolg.
Die ontwerpsomgewing wat hier aangebied word, is ’n kragtige stuk gereedskap vir die outomatisering
van die ontwerp van elektromagnetiese strukture.
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