Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The ability of satellites to actively control their attitude has changed the way we live. Navigation
systems, satellite television, and weather forecasting, for example, all rely on satellites which are able
to determine and control their attitude accurately.
This project was aimed at designing and analysing an attitude determination and control system
(ADCS) for a 20 kg Earth observation satellite by means of simulation. A realistic simulation toolset,
which includes the space environment, sensor, and actuator models, was created using MATLAB and
Simulink. An ADCS hardware suite was selected for the satellite based on a given set of pointing and
stability requirements, as well as current trends in the small satellite industry. The hardware suite
consists of among others a star tracker and three reaction wheels.
A variety of estimators and controllers were investigated, after which an application specific ADCS
state machine was defined. The state machine included a Safe Mode for de-tumbling, a Nominal
Mode for normal operation, a Forward Motion Compensation (FMC) Imaging Mode for Earth observation,
and a Target Tracking Mode for ground station tracking. Simulation results indicated that
de-tumbling, coarse and fine sun tracking, FMC factor 4 imaging, and target tracking were successfully
implemented. Lastly, the satellite’s pointing error and stability were determined to be less than 70
arcseconds and 7 arcseconds per second respectively, both values well within the given requirements. / AFRIKAANSE OPSOMMING: Satelliete se vermoë om hul oriëntasie aktief te beheer, het die manier waarop ons lewe, verander.
Navigasiestelsels, satelliettelevisie en weervoorspelling, byvoorbeeld, maak staat op satelliete wat hul
oriëntasie akkuraat kan bepaal en beheer.
Die mikpunt van hierdie projek was die ontwerp en analise van ’n oriëntasiebepaling- en -beheerstelsel
(ADCS) vir ’n 20 kg aardwaarnemingsatelliet deur middel van simulasie. ’n Realistiese simulasieopstelling,
wat modelle van die ruimteomgewing, sensore en aktueerders insluit, was ontwikkel deur
gebruik te maak van MATLAB en Simulink. ’n ADCS hardewarestel was gekies vir die satelliet op
grond van ’n stel rig- en stabiliteitsvereistes, sowel as die huidige tendense in die klein-satellietbedryf.
Die hardewarestel bestaan onder andere uit ’n stervolger en drie reaksiewiele.
Nadat verskeie afskatters en beheerders ondersoek was, was ’n toepassingspesifieke ADCS toestandmasjien
gedefinieer. Die toestandmasjien het ’n Veilige Modus vir onttuimelling, ’n Nominale Modus
vir normale operasie, ’n Vorentoe-bewegingskompensering (FMC) Beeldskandeermodus vir aardwaarneming
en ’n Teikenvolgmodus vir grondstasie volging ingesluit. Simulasieresultate het aangedui dat
onttuimeling, growwe- en fyn sonvolging, FMC faktor 4 beeldskandering en teikenvolging suksesvol
geïmplementeer was. Laastens was die satelliet se rigfout en stabiliteit bepaal as minder as 70 boogsekondes
en 7 boogsekondes per sekonde onderskeidelik, albei waardes gemaklik binne die vereistes.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96979 |
| Date | 03 1900 |
| Creators | Janse van Vuuren, Gerhard Hermann |
| Contributors | Steyn, W. H., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | xiv, 126 pages : illustrations |
| Rights | Stellenbosch University |
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