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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/54640 |
| Date | 12 1900 |
| Creators | Steyn, Willem Hermanus |
| Contributors | Schoonwinkel, A., 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 | 1 v. : ill. |
| Rights | Stellenbosch University |
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