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

[摘要] ENGLISH ABSTRACT:The Attitude Determination and Control System (ADCS) of the Stellenbosch UniversitySatellite (SUNSAT I) is an integrated system providing some redundancy and the necessarydata management to control the spacecraft. However, the redundancy is not easilyaccessible and there is a lack in flexibility when testing individual modules during integrationor when the system needs to be extended. The objective of this thesis was thusto develop a high reliability, flexible, modular communication system that included sometype of redundancy to manage real-time data and to prevent severe malfunctioning of theentire system.The first step in the project's development methodology was to summarise the requirementsand specifications by studying the current ADCS architecture and data management.An investigation into the Controller Area Network (CAN) protocol showed thatthis technology would fit the requirements very well, leading to the design and implementationof several concept topologies based on CAN. Thereafter, a demonstration modelconsisting of three prototype nodes was composed. The performance of the so calleddual CAN node was analysed and an extrapolation was 'made to determine whether thearchitecture could support the complete ADCS.It was demonstrated that the dual CAN node provides enough room to accommodateall the processors, actuators and sensors of the ADCS. At the same time, it was shownthat reliability and robustness was increased by enhanced redundancy at a node-level aswell as at the greater system-level. A dual CAN bus was provided for redundancy ata node-level. At the system-level, the command and data-gathering modules (ACP orOBC'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 enhancedand the complexity of the communication architecture and related wiring harnesses canbe reduced. This allows easier access to modules and simplifies development.

[发布机构] Stellenbosch University