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Development of a satellite network simulator tool and simulation of AX.25, FX.25 and a hybrid protocol for nano-satellite communicationsLe Roux, Jan-Hielke 12 1900 (has links)
Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Nano-satellites are mostly used in lower earth orbit applications, where communication
intervals are limited, often to a combined total of less than one hour per day. With these type
of inherent limitations of lower earth orbits, there are also the physical size and equipment
restriction of nano-satellites to consider, especially those of the CubeSat specification. It is
of critical importance to use the limited time and communication resources as effectively as
possible.
The network protocol has a huge influence on reliability and throughput of a satellite network.
An important requisite for designing, comparing and improving network protocols is
a network protocol simulator, that is able to envisage the design results. Simulation can
facilitate rapid development and unforeseen discoveries. Very little information is currently
available regarding communication protocols used in nano-satellites. This thesis aims to
explore and improve the current status of nano-satellite network simulation, as well as to
demonstrate the development of an improved communication protocol strategy.
It was found that there is a lack of proper simulation tools for satellite networks, which led
to the development of SatSim. SatSim is a discrete event network simulation tool, developed
in Python, which can be used to develop and analyse network protocols. SatSim was verified
by comparing simulation results with other published results, which made use of different
software tools and theoretical throughput calculations.
AX.25 is one of the most commonly used network protocols in the nano-satellite industry.
It was implemented in SatSim and verified with theoretical throughput calculations, as
no other simulation data on AX.25 was available. AX.25 was used as a baseline protocol
to improve upon. FX.25 was developed by the Stensat Group in an attempt to improve
AX.25. FX.25 adds forward error correction to AX.25, by wrapping additional data around
the AX.25 frames. This method maintains backward compatibility with AX.25. FX.25 was
implemented in SatSim and the simulation results proved that FX.25 was a more reliable
protocol than AX.25, as it can communicate at lower elevations and over noisier communication
channels. However, the drawback of the additional forward error correction is the
increased overhead, which reduces the overall payload data throughput.
A modular AX/FX.25 protocol was then implemented in SatSim, to exploit the strengths of
both protocols. This hybrid protocol yielded significant improvements to data throughput
and can enable future software defined radio or hardware developments. / AFRIKAANSE OPSOMMING: Nano-satelliete word hoofsaaklik gebruik in lae-aard wentelbaan toepassings waar kommunikasietyd
beperk is, soms tot minder as een uur per dag. Gepaardgaande met hierdie inherente
beperking van lae-aard wentelbane, is daar ook die verminderde omvang en kapasiteit
van nano-satelliete, veral ten opsigte van die CubeSat spesifikasie. Effektiewe aanwending
van die beperkte tyd en kommunikasie-hulpbronne is dus noodsaaklik.
Die keuse van netwerk protokol het ’n beduidende invloed op die betroubaarheid en data
deurset van ’n satelliet netwerk. ’n Belangrike voorvereiste vir die ontwerp, vergelyking
en verbetering van netwerk-protokolle, is ’n netwerk simulator. Beperkte inligting is tans
beskikbaar oor kommunikasie protokolle in nano-satelliet toepassings. Hierdie tesis fokus
op die verbetering van nano-satelliet netwerk-simulasie, asook die ontwikkelling van ’n verbeterde
netwerk-protokol strategie vir nano-satelliet toepassings.
Dit het na vore gekom dat daar ’n leemte is in die beskikbaarheid van simulasie sagteware
wat gerig is op die ondersoek van satelliet netwerke. Hierdie waarneming het die ontwikkeling
van SatSim genoop. SatSim is ’n diskrete-gebeurtenis netwerk-simulasie sagtewarepakket
wat in die Python programmeertaal ontwikkel is om netwerk protokolle te ontwikkel en te
analiseer. SatSim was geverifieer deur simulasies te vergelyk met die resultate van ander
navorsingspublikasies, wat van verskillende sagtewarepakkette gebruik gemaak het, sowel as
teoretiese deursetberekeninge.
AX.25 is een van die netwerk protokolle wat mees algemeen in die nano-satelliet bedryf
voorkom. AX.25 was geïmplementeer in SatSim en geverifieer met teoretiese deursetberekeninge.
AX.25 was gebruik as ’n grondslag om op te verbeter. FX.25 was ontwikkel
deur die Stensat Group in ’n poging om op AX.25 te verbeter. FX.25 voeg vorentoefoutkorreksie
by tot AX.25, deur addisionele data tot die AX.25 netwerk pakkies te voeg.
Hierdie benadering bewerkstellig agteruit-verenigbaarheid met AX.25. FX.25 was geïmplementeer
in SatSim en simulasieresultate dui daarop dat FX.25 ’n meer betroubare protokol
is as AX.25, omdat dit teen laer elevasiehoeke en oor swakker kommunikasiekanale kan
kommunikeer. Die verbeterde betroubaarheid is ten koste van datadeurset, as gevolg van
die toevoeging van die vorentoe-foutkorreksiedata.
’n Modulêre AX/FX.25 protokol was geïmplemeteer om te kapitaliseer op die sterk eienskappe
van beide protokolle. Hierdie hibriede protokol het ’n beduidende verbetering gelewer
ten opsigte van data deurset en kan toekomstige sagteware-gedefinieerde radio en hardewaretoepassings
stimuleer.
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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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A CAN based distributed telemetry and telecommand network for a nanosatelliteKhumalo, Simphiwe 03 1900 (has links)
Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2008. / A communications protocol is designed for real time control and data handling for a
Nanosatellite application. The communication protocol is based on the Controller Area
Network (CAN) technology. The protocol handles different message types such as time
synchronization, telecommand messages, telemetry acquisition, unsolicited telemetry
messages, large file transfers and debug messages.
The design of the protocol entails finding a suitable target microcontroller in which the
protocol implementation is demonstrated. This requires consideration of a number of
development factors such as cost, complexity, availability, reliability and operational
environment (space). The AVR AT90CAN128 microcontroller was chosen as a target
microcontroller as it gave most of the required factors mentioned above.
The protocol implementation involves developing low level software drivers, the middleware
and the application programs to demonstrate handling of each supported message. In the
implementation the media access scheme and low layer communication is provided by the
CAN low level kernel (physical and data link layers).
The protocol performance was evaluated by measuring the software response latencies, the
bus throughputs and the software efficiencies. Power consumption due to CAN
communication was also measured.
System reliability was tested by loading the CAN bus with extreme communication traffic
and letting the system run for a long time. The observation was that messages were handled
consistently.
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Attitude determination and control system for EyasSAT for Hardware In the Loop applicationGroenewald, Christoffel Johannes 04 1900 (has links)
Thesis (MEng) Stellenbosch University, 2014 / ENGLISH ABSTRACT: An Attitude Determination and Control System (ADCS) demonstrator and testing platform
was required for satellite engineering students. The ADCS demonstrator and testing
platform will allow students to develop insight into the concepts and challenges of ADCS
design and implementation. The existing model nano-satellite EyasSAT was used as a
design platform for a new ADCS demonstrator. A new ADCS module (ADCS_V2) was
developed to replace the existing EyasSAT ADCS module. The new module allows for
three-axis ADCS and the demonstration of the ADCS on an air bearing platform. The air
bearing allows full freedom of movement for yaw rotations with limited pitch and roll rotations.
The actuators and sensors required for the ADCS were developed and integrated
into EyasSAT. In addition a new PCB was designed to form the ADCS_V2 module. Attitude
determination algorithms and attitude control algorithms were implemented and
tested using MATLAB Simulink simulations. These algorithms were then implemented
on the ADCS_V2 module. The ADCS was tested using Hardware In the Loop (HIL)
techniques and an air bearing. The yaw attitude of EyasSAT could be controlled within
0.4 degrees accuracy with all the sensors active. In order to stabilize the air bearing
platform, the pitch and roll angles were rate controlled. The pitch and roll rates were
damped to within 6 mrad/s. / AFRIKAANSE OPSOMMING: ’n Oriëntasiebepaling en Beheerstelsel (OBBS) demonstrasie en toets platform was benodig
vir satellietingenieurswese studente. Die nuwe OBBS sal studente toelaat om insig te
ontwikkel met betreking tot die idees en uitdagings wat verband hou met die ontwikkeling
en implementering van ’n OBBS. Die huidige nano-sateliet model EyasSAT was gebruik
as ’n ontwerpsbasis vir die nuwe OBBS. Die nuwe OBBS was ontwikkel om die huidige
module van EyasSAT te vervang. Die nuwe OBBS laat oriëntasiebepaling en -beheer in
drie asse toe. Die nuwe OBBS en EyasSAT kan die werking van ’n OBBS demonstreer
op ’n luglaerplatform. Die luglaer laat vrye rotasie om die gierhoek toe terwyl die rol- en
stygings-as beperk word. Die aktueerders en sensors wat benodig word vir die OBBS is
ontwikkel en geïntegreer in EyasSAT saam met ’n nuwe gedrukte stroombaanbord om die
nuwe OBBS te vorm. Orientasiebepaling en orientasiebeheer algoritmes is geïmplementeer
en getoets met die hulp van MATLAB Simulink simulasies. Die algoritmes was op
die OBBS module geïmplementeer en getoets deur gebruik te maak van HIL tegnieke en
praktiese toetse op die luglaer. Die rotasie hoek van EyasSAT kan met ’n akkuraatheid
van 0.4 grade beheer word indien al die sensors gebruik word. Die rol en stygingshoeksnelheid
was gekanselleer om die luglaer stabiel te hou. Die hoeksnelheid van die twee
asse kon tot kleiner as 6 mrad/s beheer word.
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A superconducting quantum interference device (SQUID) magnetometer for nanosatellite space weather missionsOgunyanda, Kehinde January 2012 (has links)
Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology, 2012 / In order to effectively determine the occurrences of space weather anomalies in near Earth orbit, a highly sensitive space-grade magnetometer system is needed for measuring changes in the Earth’s magnetic field, which is the aftermath of space weather storms. This research is a foundational work, aimed at evaluating a commercial-off-the-shelf (COTS) high temperature DC SQUID (superconducting quantum interference device) magnetometer, and
establishing the possibility of using it for space weather applications. A SQUID
magnetometer is a magnetic field measuring in
strument that produces an electrical signal
relative to the sensed external magnetic field intensity.
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