Este trabalho apresenta um estudo sobre sistemas operacionais de tempo real (RTOS) utilizados na implementação da infraestrutura de controle digital para sistemas mecatrônicos, mas serve também como referência para outros sistemas que possuam restrições de tempo. Além de ter um caráter experimental, onde foram medidos e analisados dados como o pior tempo de resposta dos sistemas e a latência para tratamento de interrupções, este trabalho de pesquisa ainda contempla a implementação e uso de RTOS em situações práticas, bem como contempla a construção de uma plataforma geral de pesquisa que servirá de base para futuros trabalhos no laboratório de mecatrônica. Os sistemas analisados neste trabalho foram o VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE e \'mü\'C/OS-II. Outro produto gerado durante este trabalho foi um Live CD para auxiliar na implementação e ensino de conceitos e sistemas de tempo real. / This work presents a study about real time operating systems (RTOS) that are utilized as infrastructure to create digital control systems for mechatronics systems, and also for systems that have critical time constraints. Parameters like worst case response time and interrupt latency were measured for each operating system. This research project also covers the implementation and use of RTOS in practical situations. A general research platform for robotics and real time research was also developed and will be used for future works in the Mechatronics Laboratory. The tested systems were VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE and \'mü\'C/OS-II. Another product released during this work was a Live CD to aid the implementation and teaching of real time systems and concepts.

In critical real-time systems, any faulty behavior may endanger lives. Hence, system verification and validation is essential before their deployment. In fact, safety authorities ask to ensure deterministic guarantees. In this thesis, we are interested in offering temporal guarantees; in particular we need to prove that the end-to-end response time of every flow present in the network is bounded. This subject has been addressed for many years and several approaches have been developed. After a brief comparison between the existing approaches, the Trajectory Approach sounded like a good candidate due to the tightness of its offered bound. This method uses results established by the scheduling theory to derive an upper bound. The reasons leading to a pessimistic upper bound are investigated. Moreover, since the method must be applied on large networks, it is important to be able to give results in an acceptable time frame. Hence, a study of the method's scalability was carried out. Analysis shows that the complexity of the computation is due to a recursive and iterative processes. As the number of flows and switches increase, the total runtime required to compute the upper bound of every flow present in the network understudy grows rapidly. While based on the concept of the Trajectory Approach, we propose to compute an upper bound in a reduced time frame and without significant loss in its precision. It is called the Scalable Trajectory Approach. After applying it to a network, simulation results show that the total runtime was reduced from several days to a dozen seconds.

Este trabalho apresenta um estudo sobre sistemas operacionais de tempo real (RTOS) utilizados na implementação da infraestrutura de controle digital para sistemas mecatrônicos, mas serve também como referência para outros sistemas que possuam restrições de tempo. Além de ter um caráter experimental, onde foram medidos e analisados dados como o pior tempo de resposta dos sistemas e a latência para tratamento de interrupções, este trabalho de pesquisa ainda contempla a implementação e uso de RTOS em situações práticas, bem como contempla a construção de uma plataforma geral de pesquisa que servirá de base para futuros trabalhos no laboratório de mecatrônica. Os sistemas analisados neste trabalho foram o VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE e \'mü\'C/OS-II. Outro produto gerado durante este trabalho foi um Live CD para auxiliar na implementação e ensino de conceitos e sistemas de tempo real. / This work presents a study about real time operating systems (RTOS) that are utilized as infrastructure to create digital control systems for mechatronics systems, and also for systems that have critical time constraints. Parameters like worst case response time and interrupt latency were measured for each operating system. This research project also covers the implementation and use of RTOS in practical situations. A general research platform for robotics and real time research was also developed and will be used for future works in the Mechatronics Laboratory. The tested systems were VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE and \'mü\'C/OS-II. Another product released during this work was a Live CD to aid the implementation and teaching of real time systems and concepts.

Tout comportement défectueux d’un système temps-réel critique, comme celui utilisé dans le réseau avionique ou le secteur nucléaire, peut mettre en danger des vies. Par conséquent, la vérification et validation de ces systèmes est indispensable avant leurs déploiements. En fait, les autorités de sécurité demandent d’assurer des garanties déterministes. Dans cette thèse, nous nous intéressons à obtenir des garanties temporelles, en particulier nous avons besoin de prouver que le temps de réponse de bout-en-bout de chaque flux présent dans le réseau est borné. Ce sujet a été abordé durant de nombreuses années et plusieurs approches ont été développées. Après une brève comparaison entre les différentes approches existantes, une semble être un bon candidat. Elle s’appelle l’approche par trajectoire; cette méthode utilise les résultats établis par la théorie de l'ordonnancement afin de calculer une limite supérieure. En réalité, la surestimation de la borne calculée peut entrainer la rejection de certification du réseau. Ainsi une première partie du travail consiste à détecter les sources de pessimisme de l’approche adoptée. Dans le cadre d’un ordonnancement FIFO, les termes ajoutant du pessimisme à la borne calculée ont été identifiés. Cependant, comme les autres méthodes, l’approche par trajectoire souffre du problème de passage à l’échelle. En fait, l’approche doit être appliquée sur un réseau composé d’une centaine de commutateur et d’un nombre de flux qui dépasse les milliers. Ainsi, il est important qu’elle soit en mesure d'offrir des résultats dans un délai acceptable. La première étape consiste à identifier, dans le cas d’un ordonnancement FIFO, les termes conduisant à un temps de calcul important. L'analyse montre que la complexité du calcul est due à un processus récursif et itératif. Ensuite, en se basant toujours sur l’approche par trajectoire, nous proposons de calculer une limite supérieure dans un intervalle de temps réduit et sans perte significative de précision. C'est ce qu'on appelle l'approche par trajectoire scalable. Un outil a été développé permettant de comparer les résultats obtenus par l’approche par trajectoire et notre proposition. Après application sur un réseau de taille réduite (composé de 10 commutateurs), les résultats de simulations montrent que la durée totale nécessaire pour calculer les bornes des milles flux a été réduite de plusieurs jours à une dizaine de secondes. / In critical real-time systems, any faulty behavior may endanger lives. Hence, system verification and validation is essential before their deployment. In fact, safety authorities ask to ensure deterministic guarantees. In this thesis, we are interested in offering temporal guarantees; in particular we need to prove that the end-to-end response time of every flow present in the network is bounded. This subject has been addressed for many years and several approaches have been developed. After a brief comparison between the existing approaches, the Trajectory Approach sounded like a good candidate due to the tightness of its offered bound. This method uses results established by the scheduling theory to derive an upper bound. The reasons leading to a pessimistic upper bound are investigated. Moreover, since the method must be applied on large networks, it is important to be able to give results in an acceptable time frame. Hence, a study of the method’s scalability was carried out. Analysis shows that the complexity of the computation is due to a recursive and iterative processes. As the number of flows and switches increase, the total runtime required to compute the upper bound of every flow present in the network understudy grows rapidly. While based on the concept of the Trajectory Approach, we propose to compute an upper bound in a reduced time frame and without significant loss in its precision. It is called the Scalable Trajectory Approach. After applying it to a network, simulation results show that the total runtime was reduced from several days to a dozen seconds.