Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 204-215).

Thesis (M.S.)--Ohio University, August, 2002. / Title from PDF t.p.

Thesis (M.S.)--Ohio University, August, 2004. / Title from PDF t.p. Includes bibliographical references (p. 69-71)

Thesis (MScIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 152-162). Available also in a digital version from Dissertation Abstracts.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Improvements in the area of satellite orientation control in the presence of large actuator gain changes are investigated. Gain changes primarily originate from actuator failures, but may also result from intermittent sensor availability and geomagnetic field effects. The stability and performance of a classic LQR control solution under these conditions is analyzed through simulation, and two adaptive schemes are developed to improve the response. The adaptive schemes mix elements from bang-bang control to increase performance, and banded control to increase robustness. These control schemes are thoroughly tested through simulation and the results are compared with those obtained for the classic solution. Extensive modelling of the system in the MATLAB™ environment is done to support the analysis of the controllers, and hardware sensors are built to provide realistic orientation measurements to the controllers. / AFRIKAANSE OPSOMMING: Verbeterings in die veld van satelliet oriëntasie beheer in die gevalle waar die aktueerders groot veranderinge in aanwins toon, word ondersoek. Aanwins veranderinge word primêr veroorsaak deur aktueerder falings, maar kan ook deur diskontinue sensor metings en magneetveld effekte van die aarde veroorsaak word. Die stabiliteit en gehalte van 'n klassieke LQR beheer strategie onder hierdie omstandighede word ondersoek deur simulasie, en twee aanpasbare beheer strategieë word ontwikkelom die oordrag te verbeter. Die aanpasbare beheer strategieë meng elemente van "bang-bang" beheer om die gehalte te verbeter, en gebande beheer tegnieke om die robuustheid van die stelsel te verbeter. Hierdie beheer strategieë is deeglik in simulasies getoets en die resultate is vergelyk met dié van die klassieke beheerder. Ekstensiewe modelleering van die stelsel is in die MATLAB™ omgewing gedoen om die beheerders te analiseer, en hardeware sensore is gebou om realistiese orientasie metings aan die beheerders te verskaf.

Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The SUNSAT RAMDISK was studied, and tests performed to assess its flight readiness. Errors were detected, and modifications had to be made to ensure proper operation. SUNSAT was subsequently launched, and to date the RAMDISK is still functioning correctly. The flight readiness testing of the RAMDISK was considered a pre-study to designing a second generation RAMDISK. A conceptual mass memory storage device support structure was designed. This second generation RAMDISK, or memory drive is intended to be used on a second generation SUNSAT, or SUNSAT 2. The design is targeted for implementation in fields programmable gate arrays (FPGA's) and was realised using VHDL. This hardware description language is an accepted standard, and can be implemented in a number of different programmable logic devices; both SRAM and fuse-link based. Simulations were performed to verity the functionality of the design, and to determine whether the data transfer specifications could be met using programmable logic devices. A modular design methodology was followed. The memory drive was designed so that any type and amount of memory can be added to the drive without a major design change. The simulations indicated that a data capturing speed of 130 Mbits/s could be maintained. / AFRIKAANSE OPSOMMING: Die SUNSAT massa geheue module is bestudeer, en toetse is daarop uigevoer om die vlug gereedheid te bepaal. Foute is gevind, en veranderinge moes aangebring word om korrekte werking te verseker. SUNSAT is gelanseer en die geheue module werk tot op datum nog korrek. Die geheue module se vlug gereedheid toetse is beskou as In voor studie vir die ontwerp van In tweede generasie geheue module. In Konseptueie massa stoor toestel struktuur is ontwerp. Hierdie tweede generasie geheue module, of geheue skyf is bedoel om op In tweede generasie SUNSAT, of SUNSAT 2 gebruik te word. FPGA's is die teiken tegnologie vir hierdie ontwerp en VHDL is gebruik om die ontwerp te realiseer. Hierdie hardeware beskrywingstaal word as In standaard aanvaar en kan in verskillende herprogrammeerbare tegnologieë gebruik word. Sirnulasies is gedoen om die funksionaliteit van die ontwerp te verifieer, en om te bepaal of die nodige data oordragstempo gehandhaaf kan word met herprogrammeerbare tegnologie. In Modulêre ontwerpsfilosofie is gevolg. Die geheue skyf is ontwerp sodat dit enige tipe en hoeveelheid geheue kan ondersteun sonder om groot veranderinge aan die ontwerp te doen. Die sirnulasies toon dat In data oordragstempo van 130 Mbits/s gehandhaafkan word.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: This document describes the breadboard design and practical evaluation of a mobile field station, capable of communicating with the SUNSAT micro satellite. A study of existing satellite communication systems employing LEO satellites, as well as the physical phenomena, influencing the VHF communication link between earth and such satellites was done and used to determine the specifications needed for a functional field station. The design entailed work on different building blocks like a receiver, transmitter and modem unit as well as the writing and testing of the necessary software on a controlling personal computer. The measurements done showed that the field station satisfies most of the specifications, and that it is capable of communicating with a satellite. The document is concluded by suggesting improvements and possible further work before a commercial version of the field station may be build. / AFRIKAANSE OPSOMMING: In hierdie dokument word die ontwerp en praktiese evaluasie van 'n mobiele veldstasie beskryf wat met die SUNSAT mikrosatelliet kan kommunikeer. 'n Ondersoek na bestaande satellietstelsels in lae-aard wentelbane en die fisiese faktore wat die radioskakel tussen die grond en sulke satelliete beïnvloed is gebruik om spesifikasies vir 'n werkende veldstasie daar te stel. Die ontwerpstaak het werk aan 'n ontvanger, sender, modem en beheerproggramatuur ingesluit. Die voltooide veldstasie is gekarakteriseer deur 'n meetproses wat aangetoon het dat dit met 'n satelliet kan kommunikeer. Die dokument word afgesluit met voorgestelde verbeterings en verdere werk aan die veldstasie voordat 'n kommersiële weergawe daarvan voltooi kan word.

Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The purpose of this thesis is the description of the development of a QPSK demodulator for the Sunsat 1 groundstation. A general overview of the functioning and requirements of a typical QPSK demodulator system is given. Several methods or algorithms for clock and carrier recovery are discussed. Specific attention is given to the QPSK demodulator chipset from Philips used for the implementation of the demodulator. The digital decoding logic used to serialize the parallel I and Q datastream is explained. Finally measurement techniques for performance evaluation of QPSK systems are investigated. As part of this the implementation loss of the developed QPSK demodulator is measured. / AFRIKAANSE OPSOMMING: Die doelwit van hierdie tesis is om die ontwikkeling van 'n QPSK demodulator vir die Sunsat 1 grondstasie te beskryf. 'n Algemene oorsig oor die funksionering en vereistes van 'n tipiese QPSK demodulator stelsel word gegee. Verskeie algoritmes en tegnieke vir klok en draersein herwinning word ondersoek en bespreek. Spesifieke verwysing word telkens gemaak na die QPSK demodulasie vlokkie paar van Philips gebruik vir die implementering van die demodulator. Die digitale dekodering logika benodig vir die datastroom verpakking word ondersoek en beskryf. Laastens word daar gekyk na meettegnieke en evaluasie van QPSK demodulasie stelsels se prestasie. As deel hiervan word die implementasie verlies van die ontwikkelde QPSK demodulator stelsel gemeet.