Development of a fault-tolerant bus system suitable for a high-performance, embedded, real-time application on SUNSAT's ADCS

Farr, Xandri C. (2000-12)

Thesis (MEng)--University of Stellenbosch, 2000.

Thesis

ENGLISH ABSTRACT: The Attitude Determination and Control System (ADCS) of the Stellenbosch University Satellite (SUNSAT I) is an integrated system providing some redundancy and the necessary data management to control the spacecraft. However, the redundancy is not easily accessible and there is a lack in flexibility when testing individual modules during integration or when the system needs to be extended. The objective of this thesis was thus to develop a high reliability, flexible, modular communication system that included some type of redundancy to manage real-time data and to prevent severe malfunctioning of the entire system. The first step in the project's development methodology was to summarise the requirements and specifications by studying the current ADCS architecture and data management. An investigation into the Controller Area Network (CAN) protocol showed that this technology would fit the requirements very well, leading to the design and implementation of several concept topologies based on CAN. Thereafter, a demonstration model consisting of three prototype nodes was composed. The performance of the so called dual CAN node was analysed and an extrapolation was 'made to determine whether the architecture could support the complete ADCS. It was demonstrated that the dual CAN node provides enough room to accommodate all the processors, actuators and sensors of the ADCS. At the same time, it was shown that reliability and robustness was increased by enhanced redundancy at a node-level as well as at the greater system-level. A dual CAN bus was provided for redundancy at a node-level. At the system-level, the command and data-gathering modules (ACP or OBC's) can now effectively be multiplexed on the network of actuators and sensors. Furthermore, it was shown that error detection capabilities and diagnostics can be enhanced and the complexity of the communication architecture and related wiring harnesses can be reduced. This allows easier access to modules and simplifies development.

AFRIKAANSE OPSOMMING: Die Attitude Determination and Control System (ADCS) van Stellenbosch University Satellite (SUNSAT I) is 'n geïntegreerde stelsel wat voorsiening maak vir 'n mate van oortolligheid en 'n vermoeë om stelseldata te bestuur vir goeie satellietbeheer. Nietemin, hierdie oortolligheid is nie baie toeganklik nie en daar is 'n gebrek aan aanpasbaarheid tydens die toets en integrasie van individuele modules of moontlike stelseluitbreidings. Die doelwit van hierdie tesis was dus die ontwikkeling van 'n betroubare, aanpasbare, modulêre kommunikasie stelsel wat 'n tipe oortolligheid insluit sodat intydse data bestuur kan word en algehele stelselondergang vermy kan word. Die eerste stap in die projek se ontwikkelings metodiek was om 'n opsomming te verkry van die vereistes en spesifikasies deur die huidige ADCS se argitektuur en databestuur te ondersoek. 'n Ondersoek na die Controller Area Network (CAN) protokol het getoon dat hierdie tegnologie aan baie van die vereistes voldoen. Dit het aanleiding gegee tot die ontwerp en implementering van 'n paar konsep ontwerpe gebaseer op CAN. Daarna is 'n demonstrasie model bestaande uit drie prototipe nodusse gebou. Die werksverrigting van die sogenoemde dual CAN node, is ondersoek en 'n ekstrapolasie was gemaak om vas te stelof die argitektuur die volkome ADCS kan huisves. Deur demonstrasie was daar getoon dat die dual CAN node wel genoeg ruimte verskaf om al die verwerkers, aktueerders en sensors van die ADCS te akkommodeer. Daar was terselfdertyd getoon dat betroubaarheid en robuustheid verhoog is deur die verbeterde oortolligheid op 'n node-vlak sowel as op die groter stelsel-vlak. 'n Dubbele CAN bus is gebruik vir oortolligheid op 'n node-vlak. Op 'n stelsel-vlak kan die bevel-en-dataversamelings modules (ACP en aBC's) effektief gemultipleks word op die netwerk van aktueerders en sensors. Daar was verder getoon dat die foutopspoorings vermoeë en diagnostiese vermoeë verbeter kan word en die kompleksiteit van die kommunikasie argitektuur en ooreenkomstige kabelharnasse vereenvoudig kan word. Die gevolg is vereenvoudigde toegang tot modules en vergemaklikde opgradering.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/51686
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