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Feasibility of the PowerPc 603ETM for a LEO satellite on-board computerVos, Jacu 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: For space designs, just as for terrestrial applications, the appetite for more computing
power is virtually insatiable. Further, like portable applications, space use implies severe
power constraints. Among currently available commercial processors, the PowerPC family
ranks high in Million Instructions Per Second (MIPS) per watt, but its suitability for space
applications outside low-earth orbits (LEOs) may be limited by the radiation environment,
particularly single ev nt effects (SEE).
This thesis covers the feasibility of using the PowerPC 603e™ processor for LEO satellite
applications. The PowerPC architecture is well established with an excellent roadmap,
which makes for a baseline microprocessor with long-term availability and excellent software
support. The evaluation board design leverages Commercial Off-The-Shelf (COTS)
technologies, allowing early integration and test. It provides a clear path to upgrades and
provides a high performance platform to suit multiple missions. / AFRIKAANSE OPSOMMING: Die soeke na rekenaars met hoer werkverrigting sal nooit ophou rue. Dit geld vir beide
rekenaars op aarde as satelliet aanboord rekenaars. Rekenaars vir ruimte gebruik word ook
streng drywingsbeperkings opgele. Die PowerPC familie vergelyk baie goed met ander
verwerkers, maar hul bruikbaarheid vir ruimte toepassings kan dalk beperk word tot lae
wentelbane waar die ruimte radiasie omgewing meer toeganklik is.
Die skrywe behandel die bruikbaarheid van die PowerPC 603e verwerker vir lae wentelbaan
satelliet gebruik. Die welgestelde argitektuur, bekombaarheid en uitstekende sagte- _
ware ondersteuning verseker 'n standvastige fondasie. Kornmersiele komponente het
voorkeur geniet in die hardeware ontwerp wat spoedige ontwikkeling sowel as aanpasbaarheid
verseker. Die ontwerp bied 'n hoe werkverrigting en maklik opgradeerbare oplossing
vir 'n groot verskeidenheid gebruike.
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The evaluation of an ARM-based on-board computer for a low earth orbit satelliteDreijer, Gregor (Gregor Steve) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The use of commercial-off-the-shelf (COTS) components and emerging technologies in
satellite systems has become increasingly popular over the past few years. This is mainly due
to advances in radiation shielding and system-level reliability improving techniques. The use
of a new generation commercial processor in the design of a satellite's on-board computer
(OBC) is now considered a feasible option.
The aim of this thesis was to evaluate the use of a commercial grade ARM processor in a low
earth orbit (LEO) microsatellite on-board computer. The process began with the selection of
the most suitable ARM processor for an aBC design. A typical aBC system was developed
for the chosen processor, in order to test its functionality and performance in anOBC design. / AFRIKAANSE OPSOMMING: Die afgelope paar jaar het die gebruik van gewone kommersiële komponente en die nuutste
tegnologie in satelliet stelsels heelwat toegeneem. Dit kan grootliks toeskryf word aan die
vordering in bestralings afskerming en stelselvlak betroubaarheid tegnieke. Die gebruik van
'n nuwe generasie kommersiële verwerker in die ontwerp van 'n satellite aanboord rekenaar
(AR) is nou prakties uitvoerbaar.
Die doel van hierdie tesis was om die gebruik van 'n ARM verwerker in 'n lae
aardwentelbaan mikrosatelliet aanboord rekenaar te evalueer. Eerstens moes die mees
geskikte kommersiële ARM verwerker vir 'n AR ontwerp gevind word. Daarna is 'n tipiese
AR stelselontwikkel om die verwerker se funksionaliteit en werkverrigting te toets.
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Investigation of a high-speed serial bus between satellite subsystemsRetief, Francois 04 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The aim of this thesis is to investigate the implementation of a high-speed serial bus based
on the IEEE Std 1394-1995 specification for use in a microsatellite.
Earth observation microsatellites carry imagers (or cameras) that take photographs of
the earth. Each photograph generates a large volume of digital data that has to be
transferred to either a storage device, a RF transmission unit or a video processing device.
Traditionally, the connection between such systems were dedicated serial bus systems that
were custom designed for just that purpose.
This thesis will investigate the the implementation of a generic alternative to such a
custom serial bus. The IEEE 1394 serial bus will allow many devices and subsystems to
be connected to the serial bus and will allow these different subsystems to exchange data
between each other.
As an example implementation, a real-time video link between two points using the IEEE
1394 serial bus will be developed. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om ondersoek in te stel na die bou van 'n hoëspoed seriebus
vir gebruik in 'n mikrosatelliet gebaseer is op die IEEE Std 1394-1995 spesifikasie.
Aardobservasie-mikrosatelliete bevat kameras wat fotos van die aarde neem. Elke foto
genereer groot volumes digitale data wat na óf 'n massastoor, óf 'n RF-sender, óf 'n
video-verwerkingseenheid gestuur word. Tradisioneel is elkeen van hierdie verbindings
met 'n toegewyde seriebus gedoen wat spesiaal vir daardie doel gemaak is.
Hierdie tesis het dit ten doelom ondersoek in te stel na 'n generiese alternatief vir hierdie
toegewyde seriële busse. Die IEEE 1394 seriebus sal toelaat dat verskeie eenhede en
substelsels aan mekaar gekoppel kan word en dat hulle data tussen mekaar kan uitruil.
Ter demonstrasie sal 'n intydse videoskakel ontwerp word wat die IEEE 1394 seriebus
gebruik om data tussen twee punte oor te dra.
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Java implementation of AX.25 link-layer protocol for future micro-satellitesRamonyalioa, Thethe Tshepo 04 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This thesis investigates the viability of implementing the AX.25 protocol in Java, for
satellite applications. The AX.25 protocol forms part of the Communications subsystem
of a micro-satellite. It describes the implementation of a standard packet-radio link-layer
communication protocol in Java, for future use on satellite on-board computers, allowing
amongst other things, a reliable communications platform.
An investigation into factors that make AX.25 preferable over other communication
protocols, as well as advantages of Java as a language used in the implementation, is
made. The design of the implementation is described. Finally, efficiency of the Java
implementation is evaluated and optimizations identified and recommended. / AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die lewensvatbaarheid van 'n Java implementering van die AX.25
protokol vir satelliet toepassings. AX.25 is deel van die kommunikasie stelsel van 'n
mikro-satelliet. Dit beskryf die implementering van 'n standaard radio data kommunikasie
intervlak in Java vir die toekomstige gebruik op die aanboord-rekenaarstelsels van
satelliete. Hierdie intervlak bied, insluitende ander eienskappe, 'n betroubare
kommunikasie platform.
In Deeglike ondersoek na die faktore wat AX.25 meer aanloklik maak vir satellite
toepassings is gemaak, asook hoe 'n Java implementering vergelyk met ander beskikbare
tegnologie. Die geskiktheid van Java vir die implementering word ook bespeek in die lig
van evaluerings wat gedoen is op die finale protokol.
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Towards a distributed real-time system for future satellite applicationsRozendaal, A. (Abraham) 12 1900 (has links)
Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The Linux operating system and shared Ethernet are alternative technologies with the potential to
reduce both the development time and costs of satellites as well as the supporting infrastructure.
Modular satellites, ground stations and rapid proto typing testbeds also have a common
requirement for distributed real-time computation. The identified technologies were investigated
to determine whether this requirement could also be met.
Various real-time extensions and modifications are currently available for the Linux operating
system. A suitable open source real-time extension called Real-Time Application Interface
(RTAI) was selected for the implementation of an experimental distributed real-time system.
Experimental results showed that the RTAI operating system could deliver deterministic realtime
performance, but only in the absence of non-real-time load.
Shared Ethernet is currently the most popular and widely used commercial networking
technology. However, Ethernet wasn't developed to provide real-time performance. Several
methods have been proposed in literature to modify Ethernet for real-time communications. A
token passing protocol was found to be an effective and least intrusive solution. The Real-Time
Token (RTToken) protocol was designed to guarantee predictable network access to
communicating real-time tasks. The protocol passes a token between nodes in a predetermined
order and nodes are assigned fixed token holding times. Experimental results proved that the
protocol offered predictable network access with bounded jitter.
An experimental distributed real-time system was implemented, which included the extension of
the RTAI operating system with the RTToken protocol, as a loadable kernel module. Real-time
tasks communicated using connectionless Internet protocols. The Real-Time networking (RTnet)
subsystem of RTAI supported these protocols. Under collision-free conditions consistent
transmission delays with bounded jitter was measured. The integrated RTToken protocol
provided guaranteed and bounded network access to communicating real-time tasks, with limit
overheads. Tests exhibited errors in some of the RTAI functionality. Overall the investigated
technologies showed promise in being able to meet the distributed real-time requirements of
various applications, including those found in the satellite environment. / AFRIKAANSE OPSOMMING: Die Linux bedryfstelsel en gedeelde Ethernet is geïdentifiseer as potensiële tegnologieë vir
satelliet bedryf wat besparings in koste en vinniger ontwikkeling te weeg kan bring. Modulêr
ontwerpte satelliete, grondstasies en ontwikkeling platforms het 'n gemeenskaplike behoefte vir
verspreide intydse verwerking. Verskillende tegnologieë is ondersoek om te bepaal of aan die
vereiste ook voldoen kan word.
Verskeie intydse uitbreidings en modifikasies is huidiglik beskikbaar vir die Linux bedryfstelsel.
Die "Real-Time Application Interface" (RTAI) bedryfstelsel is geïdentifiseer as 'n geskikte
intydse uitbreiding vir die implementering van 'n eksperimentele verspreide intydse stelsel.
Eksperimentele resultate het getoon dat die RTAI bedryfstelsel deterministies en intyds kan
opereer, maar dan moet dit geskied in die afwesigheid van 'n nie-intydse verwerkingslas.
Gedeelde Ethernet is 'n kommersiële network tegnologie wat tans algemeen beskikbaar is. Die
tegnologie is egter nie ontwerp vir intydse uitvoering nie. Verskeie metodes is in die literatuur
voorgestelom Ethernet te modifiseer vir intydse kommunikasie. Hierdie ondersoek het getoon
dat 'n teken-aangee protokol die mees effektiewe oplossing is en waarvan die implementering
min inbreuk maak. Die "Real-Time Token" (RTToken) protokol is ontwerp om voorspelbare
netwerk toegang tot kommunikerende intydse take te verseker. Die protokol stuur 'n teken tussen
nodusse in 'n voorafbepaalde volgorde. Nodusse word ook vaste teken hou-tye geallokeer.
Eksperimentele resultate het aangedui dat die protokol deterministiese netwerk toegang kan
verseker met begrensde variasies.
'n Eksperimentele verspreide intydse stelsel is geïmplementeer. Dit het ingesluit die uitbreiding
van die RTAI bedryfstelsel met die RTToken protokol; verpak as 'n laaibare bedryfstelsel
module. Intydse take kan kommunikeer met verbindinglose protokolle wat deur die "Real-Time
networking" (RTnet) substelsel van RTAI ondersteun word. Onder ideale toestande is konstante
transmissie vertragings met begrensde variasies gemeet. Die integrasie van die RTToken
protokol het botsinglose netwerk toegang aan kommunikerende take verseker, met beperkte
oorhoofse koste as teenprestasie. Eksperimente het enkele foute in die funksionaliteit van RTAI
uitgewys. In die algemeen het die voorgestelde tegnologieë getoon dat dit potensiaal het vir
verskeie verspreide intydse toepassings in toekomstige satelliet en ook ander omgewings.
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An attitude control system for the deployment and stabilisation of a tethered dual CubeSat missionKearney, Mike-Alec 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The use of electrodynamic tethers on-board satellites is an exciting scientific prospect. These conductive tethers provide the means for satellites to generate power and to do propulsion by electrodynamic interaction with the geomagnetic field. Although well researched in theory, the concept has not enjoyed much success in practice. This study aims to utilise low-cost CubeSats as experimental tool to verify many of the theoretical principles that govern the behaviour of conductive tethers in orbit. The study provides a theoretical background of the concept by evaluating past tether missions and analysing existing theory. A feasible application of an electrodynamic tether within the size and weight limitations of a Nano-satellite is formulated. Existing theoretical work is adapted to model the dynamics and electrodynamics of specifically Nano-satellites. Using these mathematical models, control and estimation algorithms are designed which would provide stable deployment of a tethered CubeSat pair and stable control of the orientation of the tethered system. To be able to implement these algorithms on a satellite mission, a prototype of a sensor capable of measuring the angle of the tether using a CMOS camera is designed and built. A hardware platform is built to test the deployment of the tether using an electric motor. Electronics are designed to control the operation of the camera, to do motor control, and to run control and estimation algorithms. Using the results obtained from the practical tests done on the hardware, and using the theoretical models and control algorithms designed, a full orbital simulation of the deployment was done. This simulation includes the performance of the deployment system, the electrodynamic performance of the tether in earth‟s plasmasphere, and the estimation and control algorithms to control the system. Different deployment strategies are analysed and their performance are compared. / AFRIKAANSE OPSOMMING: Die gebruik van elektrodinamiese toue aanboord satelliete is 'n opwindende wetenskaplike vooruitsig. Hierdie geleidende toue verleen aan die satelliete die vermoë om krag op te kan wek en propulsie deur elektriese interaksie met die geomagnetiese veld te kan doen. Alhoewel dit goed nagevors is in teorie, het die konsep nog nie veel sukses in die praktyk geniet nie. Hierdie studie het dit ten doel om lae-koste CubeSats aan te wend as 'n eksperimentele instrument om baie van die teoretiese beginsels wat geld vir die gedrag van geleidende toue in wentelbane te verifieer. Die studie bied 'n teoretiese agtergrond van die konsep deur die evaluering van vorige tou-missies sowel as die analise van bestaande teorie. 'n Uitvoerbare toepassing van 'n elektrodinamiese tou binne die grootte- en gewigsbeperkinge van 'n Nano-satelliet is geformuleer. Bestaande teoretiese werk is aangepas om die dinamika en elektrodinamika spesifiek van toepassing op Nano-satelliete, te modelleer. Deur hierdie wiskundige modelle te gebruik, is beheer- en afskattingsalgoritmes ontwerp wat stabiele ontplooiing van 'n verbinde CubeSat-paar en stabiele beheer van die oriëntasie van die verbinde stelsel sal verseker. Om hierdie algoritmes te implementeer op 'n satelliet-sending, is 'n prototipe van 'n sensor wat in staat is om die hoek van die tou met behulp van 'n CMOS kamera te meet, ontwerp en gebou. 'n Hardeware platform is gebou om die ontplooiing van die tou met behulp van 'n elektriese motor te toets. Elektronika is ontwerp om die kamera te beheer, motor beheer te doen asook om beheer- en afskattingsalgoritmes uit te voer. Deur gebruik te maak van die resultate wat verkry is tydens die praktiese toetse wat gedoen is op die hardeware, en deur gebruik te maak van die teoretiese modelle en beheeralgoritmes wat ontwerp is, is 'n volle wentelbaan-simulasie van die ontplooiing gedoen. Hierdie simulasie sluit die gedrag van die ontplooiingstelsel, die elektriese gedrag van die geleidende tou in die aarde se plasmasfeer, en die afskatting- en beheeralgoritmes om die stelsel te beheer in. Verskillende ontplooiingstrategieë word ontleed en hul gedrag word vergelyk.
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Design and implementation of generic flight software for a CubeSatHeunis, Andre Emile 12 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The main on-board computer in a satellite is responsible for ensuring the correct
operation of the entire system. It performs this task using flight software. In order to
reduce future development costs, it is desirable to develop generic software that can
be re-used on subsequent missions. This thesis details the design and implementation
of a generic flight software application for CubeSats.
A generic, modular framework is used in order to increase the re-usability of the flight
software architecture. In order to simplify the management of the various on-board
processes, the software is built upon the FreeRTOS real-time operating system.
The Consultative Committee for Space Data Systems’ telemetry and telecommand
packet definitions are used to interface with ground stations. In addition, a number
of services defined in the European Cooperation for Space Standardisation’s Packet
Utilisation Standard are used to perform the functions required from the flight
software.
The final application contains all the command and data handling functionality
required in a standard CubeSat mission. Mechanisms for the collection, storage and
transmission of housekeeping data are included as well as the implementation of
basic fault tolerance techniques. Through testing it is shown that the FreeRTOS
scheduler can be used to ensure the software meets hard-real time requirements. / AFRIKAANSE OPSOMMING: Die hoof aanboordrekenaar in ’n satelliet verseker die korrekte werking van die hele
stelsel. Die rekenaar voer hierdie taak uit deur van vlugsagteware gebruik te maak.
Om toekomstige ontwikkelingskostes te verminder, is dit noodsaaklik om generiese
sagteware te ontwikkel wat hergebruik kan word op daaropvolgende missies. Hierdie
tesis handel oor die besonderhede van die ontwerp en implementering van generiese
vlugsagteware vir ’n CubeSat.
’n Generiese, modulêre raamwerk word gebruik om die hergebruik van die sagteware
te verbeter. Ten einde die beheer van die verskillende aanboordprosesse te
vereenvoudig, word die sagteware gebou op die FreeRTOS reëletyd bedryfstelsel.
Die telemetrie- en telebevelpakket definisies van die “Consultative Committee for
Space Data Systems” word gebruik om met grondstasies te kommunikeer. Daarby
is ’n aantal dienste omskryf in die “Packet Utilisation Standard” van die “European
Cooperation for Space Standardisation” gebruik om die vereiste funksies van die
vlugsagteware uit te voer.
Die finale sagteware bevat al die bevel en data-hantering funksies soos wat vereis
word van ’n standaard CubeSat missie. Meganismes vir die versameling, bewaring en
oordrag van huishoudelike data is ingesluit sowel as die implementering van basiese
fouttolerante tegnieke. Toetse het gewys dat die FreeRTOS skeduleerder gebruik
kan word om te verseker dat die sagteware aan harde reëletyd vereistes voldoen.
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Development of an onboard computer (OBC) for a CubeSatLumbwe, Lwabanji Tony January 2013 (has links)
Over the past decade, the satellite industry has witnessed the birth and evolution of the
CubeSat standard, not only as a technology demonstrator tool but also as a human capacity
development platform in universities. The use of commercial off the shelf (COTS) hardware
components makes the CubeSat a cost effective and ideal solution to gain access to space in
terms of budget and integration time for experimental science payloads.
Satellite operations are autonomous and are essentially based on the interaction of
interconnected electronic subsystems exchanging data according to the mission requirements
and objectives. The onboard computer (OBC) subsystem is developed around a microcontroller
and plays an essential role in this exchange process as it performs all the computing tasks and
organises the collection of onboard housekeeping and payload data before downlink during an
overpass above the ground station.
The thesis here presented describes the process involved in the development, design and
implementation of a prototype OBC for a CubeSat. An investigation covering previously
developed CubeSat OBCs is conducted with emphasis on the characteristics and features of
the microcontroller to be used in the design and implementation phases. A set of hardware
requirements are defined and according to the current evolution on the microcontroller market,
preference is given to the 32-bit core architecture over both its 8-bit and 16-bit counterparts.
Following a well defined selection process, Atmel’s AT91SAM3U4E microcontroller which
implements a 32-bit Cortex-M3 core is chosen and an OBC architecture is developed around it.
Further, the proposed architecture is implemented as a prototype on a printed circuit board
(PCB), presenting a set of peripherals necessary for the operation of the OBC. Finally, a series
of tests successfully conducted on some of the peripherals are used to evaluate the proposed
architecture.
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A multi-mode attitude determination and control system for small satellitesSteyn, Willem Hermanus 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 1995. / ENGLISH ABSTRACT: New advanced control techniques for attitude determination and control of small (micro)
satellites are presented. The attitude sensors and actuators on small satellites are limited in
accuracy and performance due to physical limitations, e.g. volume, mass and power. To
enhance the application of sophisticated payloads such as high resolution imagers within these
confinements, a multi-mode control approach is proposed, whereby various optimized
controller functions are utilized during the orbital life of the satellite.
To keep the satellite's imager and antennas earth pointing with the minimum amount of control
effort, a passive gravity gradient boom, active magnetic torquers and a magnetometer are
used. A "cross-product" detumbling controller and a robust Kalman filter angular rate
estimator are presented for the preboom deployment phase. A fuzzy controller and
magnetometer full state extended Kalman filter are presented for libration damping and Z-spin
rate control during inactive imager periods.
During imaging, when high performance is required, additional fine resolution earth horizon,
sun and star sensors plus 3-axis reaction wheels are employed. Full state attitude, rate and
disturbance estimation is obtained from a horizon/sun extended Kalman filter. A quaternion
feedback reaction wheel controller is presented to point or track a reference attitude during
imaging. A near-minimum time, eigenaxis rotational reaction wheel controller for large
angular maneuvers.
Optimal linear quadratic and minimum energy algorithms to do momentum dumping using
magnetic torquers, are presented. A new recursive magnetometer calibration method is
designed to enhance the magnetic in-flight measurements. Finally, a software structure is
proposed for the future onboard implementation of the multi-mode attitude control system. / AFRIKAANSE OPSOMMING: Nuwe gevorderde beheertegnieke vir die oriëntasiebepaling en -beheer van klein (mikro-)
satelliete word behandel. Die oriëntasiesensors en -aktueerders op klein satelliete het 'n
beperkte akkuraatheid en werkverrigting as gevolg van fisiese volume, massa en kragleweringbeperkings.
Om gesofistikeerde loonvragte soos hoë resolusie kameras binne hierdie
tekortkominge te kan hanteer, word 'n multimode beheerbenadering voorgestel. Hiermee kan
'n verskeidenheid van optimale beheerfunksies gedurende die wentelleeftyd van die satelliet
gebruik word.
Om die satellietkamera en -antennas aardwysend te rig met 'n minimale beheerpoging, word 'n
passiewe graviteitsgradiëntstang, aktiewe magneetspoele en 'n magnetometer gebruik. 'n
"Kruisproduk" onttuimellings beheerder en 'n robuuste hoektempo Kalmanfilter afskatter is
ontwikkel vir die periode voordat die graviteitsgradiëntstang ontplooi word. 'n Wasige
beheerder en 'n volledige toestand, uitgebreide Kalmanfilter afskatter is ontwikkel om librasiedemping
en Z-rotasietempo beheer te doen gedurende tydperke wanneer die kamera onaktief
is.
Gedurende kamera-opnames word hoë werkverrigting verlang. Fyn resolusie aardhorison, son
en stersensors met 3-as reaksiewiele kan dan gebruik word. 'n Volledige oriëntasie, hoektempo
en steurdraaimoment Kalmanfilter afskatter wat inligting van bogenoemde sensors
gebruik, is ontwikkel. 'n “Quaternion” reaksiewiel terugvoerbeheerder waarmee die satelliet
na verwysings oriëntasiehoeke gerig kan word of waarmee oriëntasiehoektempos gevolg kan
word, word behandel. 'n Naby minimumtyd, "eigen"-as reaksiewielbeheerder vir groothoek
rotasies is ontwikkel.
Optimale algoritmes om momentumontlading van reaksiewiele met lineêre kwadratiese en
minimumenergie metodes te doen, word afgelei en aangebied. 'n Nuwe rekursiewe kalibrasietegniek
waarmee 'n magnetometer outomaties gedurende vlug ingestel kan word, is ontwikkel.
Ten slotte, word 'n programstruktuur voorgestel vir aanboord implementering van die nuwe
multimode beheerstelsel.
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The design and development of an ADCS OBC for a CubeSatBotma, Pieter Johannes 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The Electronic Systems Laboratory at Stellenbosch University is currently developing a fully 3-axis controlled Attitude Determination and Control Subsystem (ADCS) for CubeSats. This thesis describes the design and development of an Onboard Computer (OBC) suitable for ADCS application. A separate dedicated OBC for ADCS purposes allows the main CubeSat OBC to focus only on command and data handling, communication and payload management.
This thesis describes, in detail the development process of the OBC. Multiple Microcontroller Unit (MCU) architectures were considered before selecting an ARM Cortex-M3 processor due to its performance, power efficiency and functionality. The hardware was designed to be as robust as possible, because radiation tolerant and redundant components could not be included, due to their high cost and the technical constraints of a CubeSat.
The software was developed to improve recovery from lockouts or component failures and to enable the operational modes to be configured in real-time or uploaded from the ground station. Ground tests indicated that the OBC can handle radiation-related problems such as latchups and bit-flips. The peak power consumption is around 500 mW and the orbital average is substantially lower. The proposed OBC is therefore not only sufficient in its intended application as an ADCS OBC, but could also stand in as a backup for the main OBC in case of an emergency. / AFRIKAANSE OPSOMMING: Die Elektroniese Stelsels Laboratorium by die Universiteit van Stellenbosch is tans besig om ’n volkome 3-as gestabiliseerde oriëntasiebepaling en -beheerstelsel (Engels: ADCS) vir ’n CubeSat te ontwikkel. Hierdie tesis beskryf die ontwerp en ontwikkeling van ’n aanboordrekenaar (Engels: OBC) wat gebruik kan word in ’n ADCS. ’n Afsonderlike OBC wat aan die ADCS toegewy is, stel die hoof-OBC in staat om te fokus op beheer- en datahantering, kommunikasie en loonvragbestuur.
Hierdie tesis beskryf breedvoerig die werkswyse waarvolgens die OBC ontwikkel is. Verskeie mikroverwerkers is as moontlike kandidate ondersoek voor daar op ’n ARM Cortex-M3-gebaseerde mikroverwerker besluit is. Hierdie mikroverwerker is gekies vanweë sy spoed, effektiewe kragverbruik en funksionaliteit. Die hardeware is ontwikkel om so robuust moontlik te wees, omdat stralingbestande en oortollige komponente weens kostebeperkings, asook tegniese beperkings van ’n CubeSat, nie ingesluit kon word nie.
Die programmatuur is ontwikkel om van ’n uitsluiting en ’n komponentfout te kan herstel. Verder kan programme wat tydens vlug in werking is, verstel word en vanaf ’n grondstasie gelaai word. Grondtoetse het aangedui dat die OBC stralingverwante probleme, soos ’n vergrendeling (latchup) of bis-omkering (bit-flip), kan hanteer. Die maksimum kragverbruik is ongeveer 500 mW en die gemiddelde wentelbaankragverbruik is beduidend kleiner. Die voorgestelde OBC is dus voldoende as ADCS OBC asook hoof-OBC in geval van nood.
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