Simulation and experimental evaluation of a flexible time triggered ethernet architecture applied in satellite nano/micro launchers

The success of small satellites has led to the study of new technologies for the realization of Nano and Micro Launch Vehicle (NMLV) in order to make competitive launch costs. The paper has the objective to define and experimentally investigate the performance of a communication system for NMLV interconnecting the End Systems as On-Board Computer (OBC), telemetry apparatus, Navigation Unit...we propose a low cost Ethernet-based solution able to provide the devices with high interconnection bandwidth. To guarantee hard delays to the Guide, Navigation and Control applications we propose some architectural changes of the traditional Ethernet network with the introduction of a layer implemented in the End Systems and allow for the lack of any contention on the network links. We show how the proposed solution has comparable performance to the one of TTEthernet standard that is a very expensive solution. An experimental test-bed equipped with Ethernet switches and Hercules boards by Texas Instruments is also provided to prove the feasibility of the proposed solution

Intégration itérative des systèmes avioniques communicants en mode synchrone et asynchrone

Les systèmes avioniques modernes sont des systèmes distribués complexes et évolutifs. Ces systèmes sont conçus d’une manière itérative en intégrant à chaque itération une ou plusieurs fonctionnalités. L’ajout de nouvelles fonctionnalités impose des coûts supplémentaires de reconfiguration de telle sorte que l’ensemble du système soit conforme aux exigences temps-réel. Ces systèmes reposent également sur l’adoption d’un protocole de communication déterministe tel que le protocole AFDX. Ce dernier est utilisé dans les avions modernes tels que l’A380 de Airbus et le B787 de Boeing. Il repose sur une communication asynchrone avec limitation de la bande passante. Ce mécanisme permet d’assurer des délais finis de communication. La recherche de plus de déterminisme a poussé la communauté scientifique à chercher d’autres alternatives à AFDX. Le standard Time-triggered Ethernet constitue une bonne alternative. En plus de la communication asynchrone à bande passante limitée, il définit également une communication synchrone. Suivant le type de communication, les approches de vérification des exigences temps-réel diffèrent. Pour analyser les flux asynchrones, on utilise principalement des approches analytiques. Elles assurent un bon compromis entre performance et pessimisme. Pour les flux synchrones, on s’appuie plutôt sur le formalisme de contraintes pour synthétiser un ordonnancement faisable. La combinaison des deux flux constitue un défi en termes de vérification. De plus, les approches de vérification définies ne modélisent ni l’aspect évolutif ni la notion coût.----------ABSTRACT: Modern avionics systems are complex and evolving distributed ones. They are designed iteratively by integrating at each iteration one or more functionalities. Adding new functionality may impose additional reconfiguration costs so that the whole system complies with the realtime requirements. These systems also rely on the adoption of a deterministic communication protocol such as AFDX. The latter is used in modern aircrafts such as the Airbus A380 and the Boeing B787. It relies on asynchronous communication with bandwidth limitations. This mechanism ensures finite communication delays. The search for more determinism encourage the scientific community to look for other alternatives to AFDX. The Time-triggered Ethernet standard is a good alternative. In addition to asynchronous communication with limited bandwidth, it also defines synchronous ones. Depending on the type of communication, verification approaches of real-time requirements differ. To analyze asynchronous flows, we mainly use analytical approaches. They ensure a good compromise between performance and pessimism. For synchronous flows, we rely instead on constraint formalism to synthesize a feasible scheduling. The combination of the two flows is a challenge in terms of verification. In addition, defined verification approaches do not model neither the evolving aspect nor the cost concept