A Time-Triggered Constraint-Based Calculus for Avionic Systems

The Integrated Modular Avionics (IMA) architec- ture and the Time-Triggered Ethernet (TTEthernet) network have emerged as the key components of a typical architecture model for recent civil aircrafts. We propose a real-time constraint-based calculus targeted at the analysis of such concepts of avionic embedded systems. We show our framework at work on the modelisation of both the (IMA) architecture and the TTEthernet network, illustrating their behavior by the well-known Flight Management System (FMS)

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

Model-Driven Approach to the Optimal Configuration of Time-Triggered Flows in a TTEthernet Network

International audienceThe SAE standard Time-triggered Ethernet defines a strong networking infrastructure, which supports the engineering of avionic systems. Avionic functions are often designed independently and integrated to form the avionic system. The iterative integration approach helps in controlling the design complexity of evolving avionic systems and aims at minimizing the cost associate with the reconfiguration of scheduling parameters of already integrated parts. On the other hand, the iterative approach requires to specify and manage a huge set of constraints, which are then solved to compute the optimal scheduling parameters. In this paper, we focus on this issue of manual specification of these constraints by the system engineer. We propose a model-driven approach, which provides the required abstractions and automation to support the system engineer in using effectively the iterative integration approach. The abstractions consist in a metamodel, which describes the system at a given integration step and a metamodel for the constraints. The automation consists in a model transformation which enables generating automatically the relevant constraints at integration step

Oral sensitivity to oleic acid and food behaviors in athletes

International audienceThe purpose of this study was to test the hypothesis that fat oral-intensity perception may be associated with level of physical activity, food preferences and consumption of fat-rich foods. METHODS: 52 top athletes from different discipline (weightlifting, kayaking, athletics…) of both sexes (27 male, 25 female) underwent anthropometric measurement, assessment of body composition, and completed a 4-day diet record and physical activity diary. In addition, they were screened for oral sensitivity to oleic acid (0.375 mM, 0.75mM, 1.5mM, 3mM, 6mM, 12mM) using triplicate sensory evaluations for each concentration. According to the threshold of fat perception, subjects were allocated to three groups G1 (0.375mM-3mM), G2 (6mM-12mM), G3> (12mM). Further, food habits and behaviors (food habits and behaviors questionnaire) were also established. RESULTS: Male athletes; BMI, 25,3±4,4kg/m², age, 18,88±1,53 years, BF%, 12,52±9,2, TEE, 3763,1±460 kcal . Female athletes; BMI, 24,17±4,54 kg/m², age, 16,11±1,93 years, BF% 21,70±7,4, TEE, 3106±310,05 cal. 85%. (n = 44) of subjects were classified as hyposensitive and nonsensitive (G2, G3). These subjects differed from those who were classified as hypersensitive (G1). Hyposensitive and nonsensitive subjects have a higher training volume, and total energy expenditure. They consumed significantly more energy, fat, saturated fat, fatty foods, , compared to hypersensitive subjects (all P < 0.05). CONCLUSION: An inability to perceive low concentrations of fatty acids in foods was associated with higher training volume and greater consumption of fatty foods. Our results suggest the probability of criminalization of physical activity in the regulation of orosensory fat taste perception and therefore fat intake