La mise en oeuvre de systèmes autonomes nécessite le développement et l'utilisation d'architectures logicielles multi-couches qui soient adaptées. Typiquement, une couche fonctionnelle renferme des modules en charge de commander les éléments matériels du système et de fournir des services élémentaires. Pour être robuste, la couche fonctionnelle doit être dotée de mécanismes de protection vis-à-vis de requêtes erronées ou inopportunes issues de la couche supérieure. Nous présentons une méthodologie pour tester la robustesse de ces mécanismes. Nous définissons un cadre général pour évaluer la robustesse d'une couche fonctionnelle par la caractérisation de son comportement vis-à-vis de requêtes inopportunes. Nous proposons également un environnement de validation basé sur l'injection de fautes dans le logiciel de commande d'un robot simulé. Un grand nombre de cas de tests est généré automatiquement par la mutation d'une séquence de requêtes valides. Les statistiques descriptives des comportements en présence de requêtes inopportunes sont analysées afin d'évaluer la robustesse du système sous test. / The implementation of autonomous systems requires the development and the using of multi-layer software architecture. Typically, a functional layer contains several modules that control the material of the system and provide elementary services. To be robust, the functional layer must be implemented with protection mechanisms with respect to erroneous or inopportune requests sent from the superior layer. We present a methodology for robustness testing these mechanisms. We define a general framework to evaluate the robustness of a functional layer by characterizing its behavior with respect to inappropriate requests. We also propose an validation environment based on fault injection in the control software of a simulated robot. A great number of test cases is generated automatically by the mutation of a sequence of valid requests. The descriptive statistics of the behaviors in the presence of inappropriate requests are analyzed in order to evaluate the robustness of the system under test.

In die Infrastruktur unserer Gesellschaft sind komplexe IT-Systeme fest eingebettet. Die Verbreitung und Verstetigung von IT-Systemen betrifft zentrale Bereiche unserer Gesellschaft beispielsweise Verkehrs-, Finanz- oder Gesundheitssystem. Lange Zeit standen funktionale Aspekte bei der Entwicklung informationstechnischer Systeme im Vordergrund. In den letzten Jahren haben sich jedoch nichtfunktionale Eigenschaften von IT-Systemen wie Robustheit zu unverzichtbaren Schlüsseleigenschaften in einer Vielzahl von Anwendungsfeldern entwickelt. Systeme während der Betriebsphase sind Veränderungen der gegebenen Einsatz- und Betriebsbedingungen durch Störungen der Umgebung oder auch Verschleißerscheinungen ausgesetzt. Ziel der Forschungsarbeit ist es ein Konzept für die Systemeigenschaft Robustheit zu entwickeln. Für ein gegebenes System mit einem definierten Funktionsziel ist zu analysieren, inwieweit es robust hinsichtlich Störungen der Einsatzbedingungen, verursacht durch Ereignisse der Umgebung, ist und folglich trotzdem das Funktionsziel erfüllt. Das vorgestellte Konzept umfasst dabei zwei wesentliche Problemstellungen: Bewertung der Robustheit Methode für robuste Systeme zur Laufzeit In Abhängigkeit der technischen Kennzahl, Robustheit, wird eine optimale Entscheidungsstrategie gewählt und so das Systemverhalten gesteuert. Mit der Integration eines Robustheitskonzepts insbesondere für den Systembetrieb soll anhand der Berücksichtigung der Systemeigenschaft Robustheit zur Laufzeit ein Beitrag zum Qualitätszuwachs bei Systemen geleistet werden. / Complex IT-systems are deeply embedded in the infrastructure of the society. The integration of these systems is important for plenty of areas such as the transportation system, the financial system or the health care system. For a long time, the functional aspects of the invention had been put forward. But lately the non-functional characteristics of IT-systems such as robustness have developed to essential key factors in many fields. A lot of systems are being exposed to environmental disturbances are showing during the stage of operation. This research work purpose is to develop a concept of robustness to increase system robustness. The robustness of embedded systems is supposed to be analyzed towards disturbances and terms of usage that were caused by the environment. Thereby the concept targets two main issues: measurement of the robustness and methods for robust systems concerning its duration. Depending on the value of robustness a proper decision is made in order to control the behavior of the system. Through an integration of the above mentioned concept, a rise of quality regarding the robustness of the system is pursued respecting its period of operation.

In die Infrastruktur unserer Gesellschaft sind komplexe IT-Systeme fest eingebettet. Die Verbreitung und Verstetigung von IT-Systemen betrifft zentrale Bereiche unserer Gesellschaft beispielsweise Verkehrs-, Finanz- oder Gesundheitssystem. Lange Zeit standen funktionale Aspekte bei der Entwicklung informationstechnischer Systeme im Vordergrund. In den letzten Jahren haben sich jedoch nichtfunktionale Eigenschaften von IT-Systemen wie Robustheit zu unverzichtbaren Schlüsseleigenschaften in einer Vielzahl von Anwendungsfeldern entwickelt. Systeme während der Betriebsphase sind Veränderungen der gegebenen Einsatz- und Betriebsbedingungen durch Störungen der Umgebung oder auch Verschleißerscheinungen ausgesetzt. Ziel der Forschungsarbeit ist es ein Konzept für die Systemeigenschaft Robustheit zu entwickeln. Für ein gegebenes System mit einem definierten Funktionsziel ist zu analysieren, inwieweit es robust hinsichtlich Störungen der Einsatzbedingungen, verursacht durch Ereignisse der Umgebung, ist und folglich trotzdem das Funktionsziel erfüllt. Das vorgestellte Konzept umfasst dabei zwei wesentliche Problemstellungen: Bewertung der Robustheit und Methode für robuste Systeme zur Laufzeit. In Abhängigkeit der technischen Kennzahl, Robustheit, wird eine optimale Entscheidungsstrategie gewählt und so das Systemverhalten gesteuert. Mit der Integration eines Robustheitskonzepts insbesondere für den Systembetrieb soll anhand der Berücksichtigung der Systemeigenschaft Robustheit zur Laufzeit ein Beitrag zum Qualitätszuwachs bei Systemen geleistet werden. / Complex IT-systems are deeply embedded in the infrastructure of the society. The integration of these systems is important for plenty of areas such as the transportation system, the financial system or the health care system. For a long time, the functional aspects of the invention had been put forward. But lately the non-functional characteristics of IT-systems such as robustness have developed to essential key factors in many fields. A lot of systems are being exposed to environmental disturbances are showing during the stage of operation. This research work purpose is to develop a concept of robustness to increase system robustness. The robustness of embedded systems is supposed to be analyzed towards disturbances and terms of usage that were caused by the environment. Thereby the concept targets two main issues: measurement of the robustness and methods for robust systems concerning its duration. Depending on the value of robustness a proper decision is made in order to control the behavior of the system. Through an integration of the above mentioned concept, a rise of quality regarding the robustness of the system is pursued respecting its period of operation.

A method for performing robust optimal design that combines the efficiency of experimental designs and the accuracy of nonlinear programming (NLP) has been developed, called Search-and-Zoom. Two case studies from the RF and communications industry, a high-frequency micro-strip band-pass filter (BPF) and a rectangular, directional patch antenna, were used to show that sensitivity optimization could be effectively performed in this industry and to compare the computational efficiency of traditional NLP methods (using fmincon solver in MATLAB R2013a) and they hybrid method Search-and-Zoom. The sensitivity of the BPF's S11 response was reduced from 0.06666 at the (non-robust) nominal optimum to 0.01862 at the sensitivity optimum. Feasibility in the design was improved by reducing the likelihood of violating constraints from 20% to nearly 0%, assuming RSS (i.e., normally-distributed) input tolerances and from 40% to nearly 0%, assuming WC (i.e., uniformly-distributed) input tolerances. The sensitivity of the patch antenna's S11 function was also improved from 0.02068 at the nominal optimum to 0.0116 at the sensitivity optimum. Feasibility at the sensitivity optimum was estimated to be 100%, and thus did not need to be improved. In both cases, the computation effort to reach the sensitivity optima, as well as the sensitivity optima with RSS and WC feasibility robustness, was reduced by more than 80% (average) by using Search-and-Zoom, compared to the NLP solver.

This thesis studies robustness against large-scale failures in communications networks. If failures are isolated, they usually go unnoticed by users thanks to recovery mechanisms. However, such mechanisms are not effective against large-scale multiple failures. Large-scale failures may cause huge economic loss. A key requirement towards devising mechanisms to lessen their impact is the ability to evaluate network robustness. This thesis focuses on multilayer networks featuring separated control and data planes. The majority of the existing measures of robustness are unable to capture the true service degradation in such a setting, because they rely on purely topological features. One of the major contributions of this thesis is a new measure of functional robustness. The failure dynamics is modeled from the perspective of epidemic spreading, for which a new epidemic model is proposed. Another contribution is a taxonomy of multiple, large-scale failures, adapted to the needs and usage of the field of networking. / Esta tesis estudia la robustez contra fallos de gran escala en redes de comunicaciones. Si los fallos son aislados, usualmente pasan inadvertidos para los usuarios gracias al uso de mecanismos de recuperación. Sin embargo, tales mecanismos no son efectivos contra fallos múltiples de gran escala. Los fallos de gran escala pueden causar grandes pérdidas económicas. Un requisito clave a la hora de diseñar mecanismos efectivos para reducir los efectos negativos es la habilidad de evaluar la robustez de la red. Esta tesis se centra en redes multinivel que poseen planos de control y de datos separados. La mayoría de las medidas de robustez existentes no capturan correctamente la verdadera degradación de los servicios en tales escenarios porque basan la evaluación en propiedades puramente topológicas. Una de las contribuciones de esta tesis es una nueva métrica de robustez funcional. La dinámica de los fallos se modela desde la perspectiva de la propagación de epidemias, para lo cual un nuevo modelo epidémico es propuesto. Otra contribución es una taxonomía de los fallos múltiples de gran escala, adaptado a las necesidades y uso del campo de las redes de comunicaciones.

No description available.

This thesis concerns optimization of structures considering various uncertainties. The overall objective is to find methods to create solutions that are optimal both in the sense of handling the typical load case and minimising the variability of the response, i.e. robust optimal designs. Traditionally optimized structures may show a tendency of being sensitive to small perturbations in the design or loading conditions, which of course are inevitable. To create robust designs, it is necessary to account for all conceivable variations (or at least the influencing ones) in the design process. The thesis is divided in two parts. The first part serves as a theoretical background to the second part, the two appended articles. This first part includes the concept of robust design, basic statistics, optimization theory and meta modelling. The first appended paper is an application of existing methods on a large industrial example problem. A sensitivity analysis is performed on a Scania truck cab subjected to impact loading in order to identify the most influencing variables on the crash responses. The second paper presents a new method that may be used in robust optimizations, that is, optimizations that account for variations and uncertainties. The method is demonstrated on both an analytical example and a Finite Element example of an aluminium extrusion subjected to axial crushing. / ROBDES

Master of Science / Department of Statistics / Weixin Yao / In this report, we investigate a robust estimation of the number of components in the mixture of regression models using trimmed information criterion. Compared to the traditional information criterion, the trimmed criterion is robust and not sensitive to outliers. The superiority of the trimmed methods in comparison with the traditional information criterion methods is illustrated through a simulation study. A real data application is also used to illustrate the effectiveness of the trimmed model selection methods.

Master of Science / Department of Statistics / Weixin Yao / Mixtures of factor analyzers have been popularly used to cluster the high dimensional data. However, the traditional estimation method is based on the normality assumptions of random terms and thus is sensitive to outliers. In this article, we introduce a robust estimation procedure of mixtures of factor analyzers using the trimmed likelihood estimator (TLE). We use a simulation study and a real data application to demonstrate the robustness of the trimmed estimation procedure and compare it with the traditional normality based maximum likelihood estimate.

No description available.