Our main focus in this thesis is on providing guidelines, methods, and tools for design, configuration, and analysis of configurable and reusable real-time software, developed using a combination of aspect-oriented and component-based software development. Specifically, we define a reconfigurable real-time component model (RTCOM) that describes how a real-time component, supporting aspects and enforcing information hiding, could efficiently be designed and implemented. In this context, we outline design guidelines for development of real-time systems using components and aspects, thereby facilitating static configuration of the system, which is preferred for hard real-time systems. For soft real-time systems with high availability requirements we provide a method for dynamic system reconfiguration that is especially suited for resourceconstrained real-time systems and it ensures that components and aspects can be added, removed, or exchanged in a system at run-time. Satisfaction of real-time constraints is essential in the real-time domain and, for real-time systems built of aspects and components, analysis is ensured by: (i) a method for aspectlevel worst-case execution time analysis; (ii) a method for formal verification of temporal properties of reconfigurable real-time components; and (iii) a method for maintaining quality of service, i.e., the specified level of performance, during normal system operation and after dynamic reconfiguration. We have implemented a tool set with which the designer can efficiently configure a real-time system to meet functional requirements and analyze it to ensure that non-functional requirements in terms of temporal constraints and available memory are satisfied. In this thesis we present a proof-of-concept implementation of a configurable embedded real-time database, called COMET. The implementation illustrates how our methods and tools can be applied, and demonstrates that the proposed solutions have a positive impact in facilitating efficient development of families of realtime systems.

In this thesis, aeroelastic concepts for increased aircraft performance are developed and evaluated. Active aeroelastic concepts are in focus as well as robust analysis concepts aiming at efficient analysis using numerical models with uncertain or varying model parameters. The thesis presents different approaches for exploitation of fluid-structure interaction of active aeroelastic structures. First, a high aspect ratio wing in wind tunnel testing conditions is considered. The wing was developed within the European research project \textit{Active Aeroelastic Aircraft Structures} and used to demonstrate how structural flexibility can be exploited by using multiple control surfaces such that the deformed wing shape gives minimum drag for different flight conditions. Two different drag minimization studies are presented, one aiming at reduced induced drag based on numerical optimization techniques, another one aiming at reduced measured total drag using real-time optimization in the wind tunnel experiment. The same wing is also used for demonstration of an active concept for gust load alleviation using a piezoelectric tab. In all studies on the high aspect ratio wing, it is demonstrated that structural flexibility can be exploited to increase aircraft performance. Other studies in this thesis investigate the applicability of robust control tools for flutter analysis considering model uncertainty and variation. First, different techniques for taking large structural variations into account are evaluated. Next, a high-fidelity numerical model of an aircraft with a variable amount of fuel is considered, and robust analysis is applied to find the worst-case fuel configuration. Finally, a study investigating the influence of uncertain external stores aerodynamics is presented. Overall, the robust approach is shown to be capable of treating large structural variations as well as modeling uncertainties to compute worst-case configurations and flutter boundaries. / QC 20100713

This thesis deals with the reliability analysis of a fuel pump driver circuit (FPDC), which regulates the amount of fuel pumped to a turbojet engine. Reliability analysis in such critical circuits has great importance since unexpected failures may cause serious financial loss and even human death. In this study, two types of reliability analysis are used: &ldquo / Worst Case Circuit Tolerance Analysis&rdquo / (WCCTA) and &ldquo / Failure Modes and Effects Analysis&rdquo / (FMEA). WCCTA involves the analysis of the circuit operation under varying parameters in their tolerance bands. These parameters include the resistances of the resistors, operating temperature and voltage input value. The operation of FPDC is checked and the most critical parameters are determined in the worst case conditions. While performing WCCTA, a method that guarantees the exact worst case conditions is used rather than probabilistic methods like Monte Carlo analysis. The results showed that the parameter variations do not affect the circuit operation unfavorably / operating temperature, voltage input variation and tolerance bands for the resistances are fairly compatible with the circuit operation. FMEA is implemented according to the short circuit and open circuit failures of all the electronic components used in FPDC. The components whose failure has catastrophic effect on the circuit operation have been determined and some preventive actions have been offered for some catastrophic failures.

We design and analyze algorithms for the following two robot navigation problems: 1. TARGET SEARCH. Given a robot located at a point s in the plane, how will a robot navigate to a goal t in the presence of unknown obstacles ? 2. LOCALIZATION. A robot is "lost" in an environment with a map of its surroundings. How will it find its true location by traveling the minimum distance ? Since efficient algorithms for these two problems will make a robot completely autonomous, they have held the interest of both robotics and computer science communities. Previous work has focussed mainly on designing competitive algorithms where the robot's performance is compared to that of an omniscient adversary. For example, a competitive algorithm for target search will compare the distance traveled by the robot with the shortest path from s to t. We analyze these problems from the worst-case perspective, which, in our view, is a more appropriate measure. Our results are : 1. For target search, we analyze an algorithm called Dynamic A*. The robot continuously moves to the goal on the shortest path which it recomputes on the discovery of obstacles. A variant of this algorithm has been employed in Mars Rover prototypes. We show that D* takes O(n log n) time on planar graphs and also show a comparable bound on arbitrary graphs. Thus, our results show that D* combines the optimistic possibility of reaching the goal very soon while competing with depth-first search within a logarithmic factor. 2. For the localization problem, worst-case analysis compares the performance of the robot with the optimal decision tree over the set of possible locations. No approximation algorithm has been known. We give a polylogarithmic approximation algorithm and also show a near-tight lower bound for the grid graphs commonly used in practice. The key idea is to plan travel on a "majority-rule map" which eliminates uncertainty and permits a link to the half-Group Steiner problem. We also extend the problem to polygonal maps by discretizing the domain using novel geometric techniques.

Title: Functional Data Structures and Algorithms Author: Milan Straka Institute: Computer Science Institute of Charles University Supervisor of the doctoral thesis: doc. Mgr. Zdeněk Dvořák, Ph.D, Computer Science Institute of Charles University Abstract: Functional programming is a well established programming paradigm and is becoming increasingly popular, even in industrial and commercial appli- cations. Data structures used in functional languages are principally persistent, that is, they preserve previous versions of themselves when modified. The goal of this work is to broaden the theory of persistent data structures and devise efficient implementations of data structures to be used in functional languages. Arrays are without any question the most frequently used data structure. Despite being conceptually very simple, no persistent array with constant time access operation exists. We describe a simplified implementation of a fully per- sistent array with asymptotically optimal amortized complexity Θ(log log n) and especially a nearly optimal worst-case implementation. Additionally, we show how to effectively perform a garbage collection on a persistent array. The most efficient data structures are not necessarily based on asymptotically best structures. On that account, we also focus on data structure...

SpaceWire est un standard de réseau embarqué promu par l'Agence Spatiale Européenne qui envisage de l'utiliser comme réseau bord unique dans ses futures satellites. SpaceWire utilise un mécanisme de routage Wormhole pour réduire la consommation mémoire des routeurs et les coûts associés. Cependant,le routage Wormhole peut engendrer des blocages en cascade dans les routeurs et, par conséquent,d'importantes variations des délais de livraison des paquets.Comme le réseau doit être partagé par des flux critiques et non-critiques, les concepteurs réseau ont besoin d'un outil leur permettant de vérifier le respect des contraintes temporelles des messages critiques. Pour réaliser cet outil, nous avons choisi comme métrique une borne supérieure sur le délai pire-cas de bout en bout d'un paquet traversant un réseau SpaceWire. Au cours de la thèse, nous avons proposé trois méthodes permettant de calculer cette borne. Les trois méthodes utilisent des hypothèses différentes et ont chacune des avantages et des inconvénients. D'une part, les deux premières méthodes sont très générales et ne nécessitent pas d'hypothèses restrictives sur le trafic en entrée du réseau. D'autre part, la troisième méthode nécessite des hypothèses plus précises sur le trafic en entrée. Elle est donc moins générale mais donne la plupart du temps des bornes plus serrées que les deux autres méthodes. Dans cette thèse, nous avons appliqué ces différentes méthodes à une architecture de référence fournie par Thales Alenia Space afin d'en comparer les résultats. Nous avons également appliqué ces méthodes à des exemples plus simples afin de déterminer l'influence de différents paramètres sur les bornes fournies par nos méthodes. / The SpaceWire network standard is promoted by the ESA and is scheduled to be used as the sole onboard network for future satellites. SpaceWire uses a wormhole routing mechanism to reduce memoryconsumption and the associated costs. However, wormhole routing can lead to packet blocking in routerswhich creates large variations in end-to-end delays. As the network will be shared by real-time and nonreal-time traffic, network designers require a tool to check that temporal constraints are verified for allthe critical messages. The metric we chose for this tool is an upper-bound on the worst-case end-to-enddelay of a packet traversing a SpaceWire network. This metric is simpler to compute than the exact delayof each packet and provide enough guarantee to the network designers. During the thesis, we designed three methods to compute this upper-bound. The three methods use different assumptions and have different advantages and drawbacks. On the one hand, the first two methods are very general and do not require strong assumptions on the input traffic. On the other hand, the third method requires more specific assumptions on the input traffic. Thus, it is less general but usually gives tighter bounds than the two other methods. In the thesis, we apply those methods to a case study provided by Thales Alenia Space and compare the results. We also compare the three methods on several smaller networks to study the impact of various parameters on their results.

Le processus de développement des systèmes avioniques suit des réglementations de sûreté de fonctionnement très strictes, incluant l'analyse du déterminisme et de la prédictibilité temporelle des systèmes. L'approche est basée sur la séparation des étapes de conception et d'implémentation. Une des plus grandes difficultés dans l'approche actuelle se trouve dans la détermination du WCET, qui est nécessaire pour prouver la satisfaction des contraintes de temps-réel dur du système. Dans cette thèse, une méthodologie de relâchement de contraintes temps-réels pour les systèmes de commandes digital est proposé. L'objectif est de réduire le conservatisme des approches traditionnelles basés sur le pire temps d'exécution, tout en préservant la stabilité et les performances de commandes. L'approche a été appliqué au système de commande de tangage d'un avion, ce qui a permi de montrer que le relâchement des contraintes temps réels améliore l'utilisation de la puissance de calcul disponible tout en préservant la stabilité et la qualité de commande du système. / The development process of critical avionics products are done under strict safety regulations. These regulations include determinism and predictability of the systems' timing. The overall approach is based on a separation of concerns between control design and implementation. One of the toughest challenges in the current approach is the determination of the WCET, in order to correctly size the system. In this thesis, a weakened implementation scheme for real-time feedback controllers is proposed to reduce the conservatism due to traditional worst-case considerations, while preserving the stability and control performance. The methodology is tested to the pitch control of an aircraft, showing that weakening the real-time constraints allows for saving computing power while preserving the system's stability and quality of control.

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.

The increasing complexity in the development of a configurable real-time system has emerged new principles of software techniques, such as aspect-oriented software development and component-based software development. These techniques allow encapsulation of the system's crosscutting concerns and increase the modularity of the software. The properties of a component that influences the systems performance or semantics are specified separately in entities called aspects, while basic functionality of the property still remains in the component. When building a real-time system, different sets of configurations of aspects and components can be combined, resulting in different configurations of the system. The temporal behavior of the system changes and a way to ensure the predictability of the system is needed. This thesis presents a tool for aspect-level worst-case execution time analysis, which gives a priori information about the temporal behavior of the system, before the process of composing aspects with components.

Rising complexity in the development of real-time systems has made it crucial to have reusable components and a more flexible way of configuring these components into a coherent system. Aspect-oriented system development (AOSD) is a technique that allows one to put a system’s crosscutting concerns into"modules"that are called aspects. Applying AOSD in real-time and embedded system development one can expect reductions in the complexity of the system design and development. A problem with AOSD in its current form is that it does not support predictability in the time domain. Hence, in order to use AOSD in real-time system development, we need to provide ways of analyzing temporal behavior of aspects, components and resulting system (made from weaving aspects and components). Aspect analyzer is a tool that computes the worst-case execution time (WCET) for a set of components and aspects, thus, enabling support for predictability in the time domain of aspect-oriented real-time software. A limitation of the aspect analyzer, until now, were that no verification had been made whether the aspect analyzer would produce WCET values that were close to the measured or computed (with another WCET analysis technique) WCET of an aspect-oriented real-time system. Therefore, in this thesis we perform a verification of the correctness of the aspect analyzer using a number of different methods for WCET analysis. These investigations of the correctness of the output from the aspect analyzer gave confidence to the automated WCET analysis. In addition, performing this verification led to the identification of the steps necessary to compute the WCETs of a piece of program, when using a third party tool, which gives the ability to write accurate input files for the aspect analyzer.