System-level Co-simulation of Integrated Avionics Using Polychrony

International audienceThe design of embedded systems from multiple views and heterogeneous models is ubiquitous in avionics as, in partic- ular, different high-level modeling standards are adopted for specifying the structure, hardware and software components of a system. The system-level simulation of such composite models is necessary but difficult task, allowing to validate global design choices as early as possible in the system de- sign flow. This paper presents an approach to the issue of composing, integrating and simulating heterogeneous mod- els in a system co-design flow. First, the functional behavior of an application is modeled with synchronous data-flow and statechart diagrams using Simulink/Gene-Auto. The system architecture is modeled in the AADL standard. These high- level, synchronous and asynchronous, models are then trans- lated into a common model, based on a polychronous model of computation, allowing for a Globally Asynchronous Lo- cally Synchronous (GALS) interpretation of the composed models. This translation is implemented as an automatic model transformation within Polychrony, a toolkit for em- bedded systems design. Simulation, including profiling and value change dump demonstration, has been carried out based on the common model within Polychrony. An avionic case study, consisting of a simplified doors and slides control system, is presented to illustrate our approach

Formal semantics of behavior specifications in the architecture analysis and design language standard

In system design, an architecture specification or model serves, among other purposes, as a repository to share knowledge about the system being designed. Such a repository enables automatic generation of analytical models for different aspects relevant to system design (timing, reliability, security, etc.). The Architecture Analysis and Design Language (AADL) is a standard proposed by SAE to express architecture specifications and share knowledge between the different stakeholders about the system being designed. To support unambiguous reasoning, formal verification, high-fidelity simulation of architecture specifications in a model-based AADL design workflow, we have defined a formal semantics for the behavior specification of the AADL, the presentation of this semantics is the aim of this paper

Modeling and Analysis of Mixed Synchronous/Asynchronous Systems

Practical safety-critical distributed systems must integrate safety critical and non-critical data in a common platform. Safety critical systems almost always consist of isochronous components that have synchronous or asynchronous interface with other components. Many of these systems also support a mix of synchronous and asynchronous interfaces. This report presents a study on the modeling and analysis of asynchronous, synchronous, and mixed synchronous/asynchronous systems. We build on the SAE Architecture Analysis and Design Language (AADL) to capture architectures for analysis. We present preliminary work targeted to capture mixed low- and high-criticality data, as well as real-time properties in a common Model of Computation (MoC). An abstract, but representative, test specimen system was created as the system to be modeled

Élaboration d'une méthodologie de conception des systèmes embarqués basée sur la transformation du modèle fonctionnel de haut niveau vers le prototype virtuel

La croissance rapide des progrès technologiques combinée aux demandes exigeantes de l’industrie entraîne une augmentation de la complexité des systèmes embarqués. Cette complexité impose plusieurs contraintes et critères à respecter pour produire des systèmes compétitifs et robustes. Aussi, les méthodologies de conception ont grandement évolué au cours des dernières années pour encadrer le développement de ces systèmes complexes et assurer leur conformité aux requis initiaux. C’est ainsi que de nouvelles approches basées sur des modèles sont apparues, pour pallier à ces difficultés et maîtriser le niveau de complexité. Mais souvent ces approches basées sur des modèles traitent les aspects fonctionnels et logiciels du système sans prendre en considération les aspects d’exécution sur de réelles plateformes matérielles. Les travaux développés dans le cadre de ce projet de recherche visent à mettre en oeuvre une nouvelle méthodologie de conception des systèmes embarqués. Cette méthodologie permet d’établir un lien entre le niveau fonctionnel des modèles et la plateforme d’exécution matérielle de l’application en question. L’approche développée est basée sur l’utilisation du langage de modélisation AADL pour décrire le comportement logiciel du système embarqué à un haut niveau d’abstraction. Ensuite, une chaîne de transformation automatique convertit le modèle AADL vers un modèle SystemC. Finalement, l’environnement Space Studio est utilisé pour construire un prototype virtuel de la plateforme. Cet environnement permet l’exécution des aspects fonctionnels du système sur des ressources matérielles. Les performances du système peuvent ainsi être validées et raffinées en se basant sur une exploration architecturale de la plateforme matérielle. Une application d’imagerie a été exploitée en tant qu’étude de cas pour expérimenter ce flot. Il s’agit d’une application de décodage vidéo MJPEG (Motion JPEG). Durant l’expérimentation, un modèle AADL de l’application MJPEG a été développé décrivant son comportement fonctionnel. Ensuite, la chaîne de transformation utilisée traduit automatiquement le modèle AADL en un modèle SystemC. Le modèle SystemC a servi comme élément de base représentant l’aspect logiciel dans l’environnement de prototypage virtuel et de conception conjointe Space Studio. L’outil Space Studio s’est montré utile en permettant la création rapide d’un prototype de plateforme matérielle d’exécution, le partitionnement des fonctions logicielles sur des ressources matérielles et la validation et raffinement des performances du système. Les résultats d’expérimentation obtenus furent concluants. La vitesse d’exécution a été visiblement augmentée et le temps pris pour achever la simulation du système a été réduit de 81.86%. En ce qui concerne le taux d’occupation du processeur quant à lui a considérablement diminué, ce qui pourra ainsi diminuer le taux de puissance consommée par les ressources matérielles. Ainsi le traitement de données par unité de temps s’est amélioré 12 fois de plus après le raffinement porté sur l’assignement des fonctions logicielles sur la plateforme matérielle. Dans le cadre de ce projet, un article scientifique a été publié (Benyoussef et al., Février 2014) à la conférence ERTS 2014 (Embedded Real Time Software and Systems). Ce travail présente le contexte et la problématique liée aux méthodologies basées sur des modèles, la nouvelle approche de modélisation développée ainsi qu’une preuve de concept avec une application de décodage MJPEG

Transformação assistida de modelos: mecanismo de suporte para o desenvolvimento de cyber-physical systems

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia de Automação e Sistemas, Florianópolis, 2014O termo Cyber-Physical System representa um dispositivo eletrome-mecânico controlado por um sistema baseado em computador, exemplos deste tipo de sistema incluem robôs, aviões, redes inteligentes, entre outros. Devido a natureza multidisciplinar dos Cyber-Physical Systems, eles normalmente são projetados utilizando diferentes modelos. A perspectiva "cibernética" deste tipo de sistema pressupõe a existência de: (i) um modelo matemático que representa a dinâmica do sistema físico, (ii) algoritmos de controle, e (iii) um projeto do sistema computacional embarcado. Dentro deste contexto, esta tese de doutorado investiga uma forma de abordar adequadamente o projeto do sistema computacional embarcado de um Cyber-Physical System baseada na modelagem funcional do mesmo. Buscando evitar desta forma a criação de modelos funcionais e arquitetônicos dissociados, e além disso, promover uma abordagem de projeto dirigido por modelos, proporcionando benefícios como a independência de plataforma, níveis de abstração mais altos, e a reutilização de informações. Como resultado da pesquisa realizada, e apresentada uma solução que ajuda a realizar a transição do modelo funcional para o modelo de arquitetura de software durante o processo de desenvolvimento de um Cyber-Physical System. Para isso, é sugerido como relacionar elementos de um modelo funcional com elementos de um modelo de arquitetura. A solução proposta, chamada de "Transformação Assistida de Modelos (AST)", fornece suporte para a transformação de modelos Simulink utilizados para a modelagem funcional em modelos arquitetônicos expressos em AADL, e aumenta a confiabilidade de que os modelos funcional e arquitetural são consistentes entre si, uma vez que diminui ocorrência de erros de inconsistência de interface (portas, tipos de dados e conexões) entre os mesmos. A AST contribui portanto, com a implantação/integração de aplicativos vericados em arquiteturas validadas tornando o processode desenvolvimento de Cyber-Physical Systems mais robusto. Durante os experimentos, realizados na forma de estudos de caso, os modelos gerados pela AST mostraram-se passíveis de análises sintáticas, verificações comportamentais, e análises de escalonabilidade e de la-tência de fluxos, o que serviu para reforçar a escolha pelo de o uso de modelos AADL durante o processo de desenvolvimento de CPS. Também foi implementado no escopo desta pesquisa, o protótipo de uma ferramenta computacional que automatiza a aplicação da solução proposta. O protótipo foi implementado utilizando a linguagem de programação Java, e empacotado como um plugin para ser usado dentro do ambiente OSATE (Open Source Architectural Environment Tool ), que é um processador de modelos AADL que roda dentro do Eclipse. O plugin em questão, chamado de AS2T, também pode ser considerado uma alternativa para estender a cadeia de transformação de modelos do ambiente TOPCASED, que é um ambiente OpenSource para desenvolvimento de sistemas embarcados críticos que também faz uso do OSATE.Abstract: Cyber-Physical System (CPS) is a denomination used to represent an electro-mechanical device controlled by a computerized system. Examples of CPS include robots, airplanes, smart grids, among others. Due to the multidisciplinary nature of CPSs, they are normally de-signed using different models. The "cybernetic" perspective assumes the existence of: (i) a mathematical model that represents the dynamics of the physical system, (ii) some control algorithms, and (iii) a design of the embedded computing system. In this context, this thesis investigates a way to adequately address the design of the architecture embedded computing system of a CPS based on apreliminary functional model. Looking forward to avoid the creation of decoupled functional and architectural models and aiming to promote a model-based design approach for CPS, the proposed approach targets using higher levels of abstraction and model-information reuse. The solution presented in this thesis is named "Assisted Transformation of Models" (AST), it focuses on discussing how to related elements of a functional model with the elements of an architectural model. AST provides support for the transformation of the Simulink models used for the functional modeling into architectural models expressed in AADL. As benets of using the proposed solution, one can see that it increases the reliability that the functional and architectonical models are consistent between themselves, especially when considering the connection interfaces between components (ports and connections data types). Experiments were conducted to validate the proposed transformation process. The generated models were analyzed in respect to the syntax correctness and also regarding additional model analyses, such as behavioral verication and schedulability analysis. The work provides a prototype tool that automates the proposed transformation process. Such tool can be used as plugin from OSATE (Open Source Architectural Environment Tool), which is an AADL processor that runs within Eclipse. The AS2T plugin can be considered an alternative to extend the chain of transformation of models of the TOPCASED environment, which is an OpenSource development environment of critical embedded systems that makes use of OSATE

Applying patterns in embedded systems design for managing quality attributes and their trade-offs

Embedded systems comprise one of the most important types of software-intensive systems, as they are pervasive and used in daily life more than any other type, e.g., in cars or in electrical appliances. When these systems operate under hard constraints, the violation of which can lead to catastrophic events, the system is classified as a critical embedded system (CES). The quality attributes related to these hard constraints are named critical quality attributes (CQAs). For example, the performance of the software for cruise-control or self-driving in a car are critical as they can potentially relate to harming human lives. Despite the growing body of knowledge on engineering CESs, there is still a lack of approaches that can support its design, while managing CQAs and their trade-offs with noncritical ones (e.g., maintainability and reusability). To address this gap, the state-of-research and practice on designing CES and managing quality trade-offs were explored, approaches to improve its design identified, and the merit of these approaches empirically investigated. When designing software, one common approach is to organize its components according to well-known structures, named design patterns. However, these patterns may be avoided in some classes of systems such as CES, as they are sometimes associated with the detriment of CQAs. In short, the findings reported in the thesis suggest that, when applicable, design patterns can promote CQAs while supporting the management of trade-offs. The thesis also reports on a phenomena, namely pattern grime, and factors that can influence the extent of the observed benefits