Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: A different approach of employing attitude sensors with incomplete measurements
in an attitude determination system is investigated. The amount of available attitude
sensors on small satellites are limited, and the failure of sensors can be fatal
when accurate attitude determination is necessary. The problem with sensors
with incomplete measurements is that they must be used in combination with
other sensors to obtain three dimensional attitude information. The aim is to
enhance the possible number of sensor combinations that can be employed, in an
attempt to improve the ability of the attitude determination system to tolerate
sensor failures.
An alternative sensor structure consisting of a magnetometer and two horizon
sensors is presented. A method to obtain vector observations of the attitude
from a combination between magnetometer and horizon sensor measurements is
derived and tested. A full state Extended Kalman Filter is used to determine
the satellite's attitude, attitude rate and disturbance torque from these vector
observations.
A second Extended Kalman Filter structure, using only magnetometer measurements,
is implemented. The magnetometer Extended Kalman Filter and the
horizon/magnetometer Extended Kalman Filter are integrated to obtain a single
Extended Kalman Filter structure to determine the satellite's full attitude state.
Integration is done by switching between the different pairs of vector information.
A systematic analysis of the integrated filter's dynamic behaviour during
the switching stages is done by means of a series of case studies. / AFRIKAANSE OPSOMMING: Die gebruik van oriëntasiesensore met onvolledige metingsdata in oriëntasiebepalingsstelsels
is ondersoek. Slegs 'n beperkte aantal oriëntasiesensore is beskikbaar
op mikro satelliete. 'n Foutiewe sensor kan dus noodlottig wees wanneer akkurate
oriëntasiebepaling nodig is. Die probleem met sensore met onvolledige metingsdata
is dat dit in sensor kombinasies gebruik moet word om drie dimensionele
oriëntasieinligting te verkry. Die doel is dus om die moontlike aantal sensor kombinasies
sodanig te vermeerder dat die oriëntasiebepalingsstelsel beter bestand
sal wees teen moontlike sensor falings.
'n Alternatiewe sensor struktuur, bestaande uit 'n magnetometer en twee horison
sensore, is ondersoek. 'n Metode vir die verkryging van 3-as oriëntasie inligting
vanaf 'n kombinasie van magnetometer en horison sensor metingsdata is afgelei
en getoets. 'n Vol toestand uitgebreide Kalmanfilter is gebruik om the satelliet
se oriëntasie, oriëntasie snelheid en versteurings draairnoment vanaf die vektor
observasies af te lei.
'n Tweede uitgebreide Kalmanfilter struktuur, wat slegs magnetometer metingsdata
gebruik, is geïmplementeer. Die magnetometer filter en die horison/magnetometer
filter is geïntegreer sodat een uitgebreide Kalmanfilter struktuur volle
oriëntasie inligting kan aflei vanaf verskillende pare vektors met oriëntasie inligting.
Integrasie is gedoen deur te skakel tussen die verskillende vektorpare. 'n
Sistematiese analise van die geïntegreerde filter se dinamiese gedrag gedurende
die oorskakelingstye is gedoen deur middel van 'n reeks gevallestudies.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53469 |
| Date | 12 1900 |
| Creators | Maass, E. (Eanette) |
| Contributors | Treurnicht, J., 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 | 106 p. : ill. |
| Rights | Stellenbosch University |
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