Increasing global competition, market uncertainties and high product variance are a few of the factors posing challenges to the existing manufacturing industry. Having a quick response to market fluctuations and adapting to changing customer demands while maintaining shorter lead times and low costs are a few of the major challenges. The main focus of this thesis is on Evolvable Production Systems, which is one of the promising solutions to deal with the emerging manufacturing challenges by changing the conventional manufacturing systems towards a more flexible, intelligent and adaptable approach. Although promising, further research is needed in several directions for a wider industrial acceptance of EPS. The directions include but are not limited to methodological aspects, tool support, etc. throughout the development lifecycle. This thesis aims to provide a basis for a holistic model-based development methodology for evolvable production systems. One of the main contributionsof this work is the identification of major architectural elements (i.e stakeholders,concerns, viewpoints and views) and their dependencies on each other.This work shall serve as a basis for establishing a well-defined architectural framework for EPS. The second important contribution of this thesis is the development of a domain specific modeling language (EPS- DSL) based on the existing EPS ontology. The DSM platform does not only store the domain knowledge in the form of models but also provides support for the re-use of these models, i.e. enables utilization of the domain ontology during system development. Moreover, the automatic code generation support for the module library presented in this work, significantly reduces the risks of information discrepancies when transferring data from one abstraction level to another. The existing EPS ontology is also evaluated from a holistic perspective and resulted in contributing a few improvement suggestions for achieving a seamless model-based development approach. Evaluation of Simulink/SimEvents as a modeling and simulation tool for EPS is the third main contribution of this thesis. One of the main advantages of evaluating this tool for EPS is the opportunity to analyze the complete system behavior on a single modeling platform. The integration of agent-based system behavior (discrete event) with dynamic system behavior (continuous &amp; discrete time) provides a holistic modeling approach and implies less information inconsistencies. / <p>QC 20160429</p>

In Model-Based Testing (MBT) the main goal is to test a system by designing models which describe the functionality of the system to test. Subsequently, test cases are obtained from the model, and these test cases can be executed automatically. Experience has shown that the learning curve for learning MBT can be steep - especially for people who do not have previous programming experience. This is because the language used to design models uses programming language concepts. In this thesis we describe a tool which automatically generates models, given an initial set of requirements. The advantage of this tool is that users do not need to learn a model-based testing language to design models, but instead they must learn to use a high-level of abstraction and a Graphical User Interface to specify their test cases. We demonstrate the value of the tool by using it to design models that generate test cases for telecommunications system, but show that this tool can be adapted for use in testing similar systems. The application of this tool can facilitate traditional phase-based software development methods, by saving a considerable amount of time and resources. In addition, when applied to agile software development, the reduced time required for testing because of the use of our tool helps shortening the feedback loops between designing and testing, thus increasing team efficiency within every iteration. / I Model-Based Testing (MBT) är det huvudsakliga målet att testa ett system genom modeller som beskriver systemets unktionalitet för att testa. Därefter erhålls testfall från modellen, och dessa testfall kan utföras automatiskt. Erfarenheten har visat att inlärningskurvan för lärande MBT kan vara branta - särskilt för personer som inte har tidigare erfarenhet av programmering. Detta beror på det språk som används för användning programmeringsspråk begrepp. I denna avhandling beskriver vi ett verktyg som automatiskt genererar modellerna, med tanke på en första uppsättning krav. Fördelen med detta verktyg är att användarna inte behöver lära sig en modellbaserad testning av språket att konstruera modeller, utan de måste lära sig att använda en hög nivåav abstraktion och ett grafiskt användargränssnitt för att ange sina testfall. Vi demonstrerar värdet av verktyget genom att använda den för att konstruera modeller som genererar testfall för telekommunikationssystem, men visar att detta verktyg kan anpassas för användning vid testning av liknande system. Tillämpningen av detta verktyg kan underlätta traditionella fas-baserade metoder mjukvaruutveckling, genom att spara en avsevärd tid och resurser. Dessutom, när det tillämpas på Agile Software utveckling, minskade tid som krävs för att testa på grund av användningen av vårt verktyg hjälper förkorta återkopplingar mellan design och testning, vilket ökar teamet effektiviteten inom varje iteration. / En Model-Based Testing (MBT), el objetivo principal es testear un sistema mediante el diseño de modelos que describan su funcionalidad. En consecuencia, estos modelos generan test cases que pueden ser ejecutados automáticamente en dicho sistema. La experiencia nos muestra que la curva de aprendizaje en el caso de MBT puede ser pronunciada, especialmente para aquellos sin ninguna experiencia previa en programación. Esto se debe a que los lenguajes usados para diseñar modelos usan conceptos intrínsecos a los lenguajes de programación. En este Proyecto Fin de Carrera, describimos una herramienta que genera automáticamente modelos, dado un conjunto de requisitos inicial. La ventaja que ofrece esta herramienta es que los usuarios no requieren el aprendizaje de ninguno lenguaje de modelado a la hora de diseñar modelos, sino que tan solo deben aprender a utilizar una Interfaz de Usuario Gráfica (GUI), a un alto nivel de abstracción, para especificar sus test cases. Demostramos el valor de esta herramienta mediante su aplicación en un nuevo sistema de telecomunicaciones en fase de pruebas de Ericsson, mostrando al mismo tiempo que puede ser utilizada en el testeo de sistemas similares. La aplicación de esta herramienta puede facilitar los métodos de desarrollo de software tradicionales mediante el ahorro de una cantidad considerable de tiempo y recursos. Además, aplicada a métodos de desarrollo ágil de software, el tiempo reducido requerido para el testing a causa del uso de esta herramienta ayuda a acortar los plazos entre diseño y testing, y en consecuencia, incrementando la eficiencia del equipo en cada iteración.

Post-implantation facial nerve stimulation is a common side-effect of cochlear electrical stimulation. Facial nerve stimulation can often be resolved through adjustments in speech processor fitting but, in some instances, exhibit limited benefit or may have a detrimental effect on speech perception. In this study, the apical reference stimulation mode was investigated as a potential intervention to facial nerve stimulation. Firstly, a model refinement software tool was developed to improve the accuracy of models created by an automated workflow. Secondly, the refined model of the human cochlea, facial nerve and electrode array, coupled with a neural model, was used to predict excitations of auditory and facial nerve fibres. Finally, psychoacoustic tests were used to determine auditory comfort and threshold levels for the apical reference stimulation mode while simultaneously capturing electromyography data. The refinement tool illustrated an improved accuracy compared to measured data. Models predicted a desirable outcome for apical reference stimulation, as facial nerve fibre thresholds were higher and auditory thresholds were lower, in direct comparison to conventional monopolar stimulation. Psychoacoustic tests illustrated decreased auditory thresholds and increased dynamic range during apical reference stimulation. Furthermore, apical reference stimulation resulted in lower electromyography energy levels, compared to conventional monopolar stimulation, which suggests a reduction in facial nerve stimulation. Subjective feedback corroborated that apical reference stimulation alleviated facial nerve stimulation. This suggests that apical reference stimulation may be a viable strategy to alleviate facial nerve stimulation considering the improvements in dynamic range and auditory thresholds, complemented with a reduction in facial nerve stimulation / Dissertation (MEng (Bioengineering))--University of Pretoria, 2019. / NRF / Electrical, Electronic and Computer Engineering / MEng (Bioengineering) / Unrestricted

Akzeptanztests werden in Scrum-Projekten durchgeführt, um umgesetzte Anforderungen iterativ und inkrementell gegen die Erwartungen des Product Owners zu prüfen. Dazu müssen Testartefakte kontinuierlich spezifiziert, gewartet und ausgeführt werden. Im Projektverlauf werden die Durchführung und Wartung des Testprozesses zunehmend zu zeit- und ressourcenkritischen Aufgaben, die mit einer manuellen Testdurchführung nicht mehr zu bewerkstelligen sind. Es wird ein ausgereifter Testautomatisierungsansatz benötigt. In dieser Arbeit wurde ein Testverfahren entworfen, welches die Vorteile des Model-Based Testing (MBT) mit anderen Test-First-Ansätzen, wie dem Behavior-Driven Development und Acceptance Test-Driven Development kombiniert, um die automatisierte Durchführung von Akzeptanztests im Scrum-Vorgehen zu integrieren. Dafür wurde untersucht, wie Anforderungen in Form von User Storys für die Testmodellentwicklung formalisiert werden können, wie die Rückverfolgbarkeit vom Testfall zur Anforderung und zurück gewährleistet werden kann und wie abstrakte Testfälle für die automatische Testdurchführung konkretisiert werden können. Zudem wurden ein Automatisierungs- und Durchführungsansatz für die Nutzung von GraphWalker mit Selenium als Adapterschicht zur Graphical User Interface (GUI)-Testautomatisierung sowie Möglichkeiten der Nutzung von Zustandsmodellen zur Modellierung fachlich oder logisch unerwünschter Pfade dargelegt. Das Testverfahren wurde prototypisch bei einem Fallbeispiel implementiert, um konkrete Anwendungsfälle umzusetzen und Rückschlüsse aus der praktischen Anwendung ziehen zu können. Die Ergebnisse der Arbeit zeigen, dass sich das konzipierte Testverfahren für die Automatisierung von Akzeptanztests eignet und das Vorgehen sowohl von Forschenden als auch Praktizierenden zur Implementierung eines MBT-Verfahrens verwendet werden kann.

Increased use of data is influencing the existing practices in the engineering domain,including that of systems engineering. Complex products and systems (CoPS), along with its predominant methodology of development, Model-based systems engineering(MBSE), is no exception to this. This thesis explores the possible integration of the emerging data driven methods and the established model-based methods in the context of CoPS development. It also explores what the implications of such an integration could be for the organizations building such systems, the system integrators. To analyse the current state of the art in CoPS development and model based methods as well as the emerging trends in data driven methods, this research employs an integrative literature review method. The literature search concluded in 71 selected articles to be reviewed. These articles where divided over three main categories, CoPS, Model-based systems engineering (MBSE) and data driven methods.The results of the analysis suggest that data driven methods and the model-based methods complement rather than compete throughout the innovation life cycle of CoPS. The findings indicate that an integration of the methods is beneficial to the architectural, systemic, and component level innovation in CoPS. MBSE and data driven methods could however have different levels of influence in these three types of innovation. The findings indicate that MBSE could have more influence in architectural innovations, while data driven methods could be more influential in systemic and component innovation. The continuous innovation in the use phase of system is also seen to be improved by this integration. The system integrators benefit from the improved project to project learning resulting from the integration which enhances their economy of repetition. An integrated method could also increase the speed of which decisions can be made while still maintaining reliability in the system. The results indicate that the number of iterations could increase due to the increased feedback of data and the learnings gained from it, which could pose some challenge to the existing project management methods. Further research is needed to find out what are the full benefits of an integrated method and identify other potential conflicts.

The growing need for ocean surveillance and exploration has pushed the development of novel autonomous underwater vehicle (AUV) technology. A current trend is to make use of bio-inspired propulsor to increase the overall system efficiency and performance, an improvement that has deep implications in the dynamics of the system. The goal of this dissertation is to propose a generic robust control framework specific for bio-inspired autonomous underwater vehicles (BIAUV). These vehicles utilize periodic oscillation of a flexible structural component to generate thrust, a propulsion mechanism that can be tuned to operate under resonance and consequently improve the overall system efficiency. The control parameter should then be selected to keep the system operating in such a condition. Another important aspect is to have a controller design technique that can address the time-varying behaviors, structured uncertainties and system nonlinearities. To address these needs a robust, model-based, nonlinear controller design technique is presented, called digital sliding mode controller (DSMC), which also takes into account the discrete implementation of these laws using microcontrollers. The control law is implemented in the control of a jellyfish-inspired autonomous underwater vehicle. / Ph. D.

Les systèmes réactifs sont modélisés avec différents types d'automates, tels que les systèmes de transitions symboliques à entrée sortie (IOSTS). L'exécution symbolique d'un IOSTS permet la génération de cas de test qui peuvent être exécutés sur une implantation concrète, afin de déterminer si elle est conforme à son modèle. Dans ce document, nous étendons les IOSTS avec des appels de fonctions utilisateur et analysons leur impact sur le système entier et viceversa. Cette thèse comble l'écart entre une approche basée sur le modèle où les fonctions utilisateur sont abstraites et une approche basée sur le code où les petits morceaux de code sont considérés séparément, indépendamment de la façon dont ils sont combinés. Selon le niveau de connaissance que nous avons sur ces fonctions, elles sont modélisées soit par une spécification complète, soit par une spécification partielle, soit juste comme des boîtes noires fournies sans aucune connaissance. Premièrement, lorsque les fonctions sont partiellement connues, nous utilisons des bouchons définis par des tables contenant des tuples représentatifs des données d'entrée/sortie. L'approche proposée emprunte au test "concolic", l'idée de mélanger l'exécution symbolique avec l'information obtenue à partir d'exécutions concrètes des fonctions (tables). Deuxièmement, si l'utilisateur est prêt à fournir d'autres spécifications, il serait intéressant d'utiliser des représentations plus complètes pour les fonctions. Par conséquent, nous proposons d'abstraire des comportements des fonctions par des contrats pré/post. Ensuite, nous étendons l'exécution symbolique en analysant les fonctions via leurs contrats. Enfin, lorsque les fonctions appelées sont complètement inconnues, nous présentons une approche pour extraire de nouveaux contrats pour eux en explorant les contraintes issues de l'exécution symbolique de l'IOSTS. De tels contrats reflètent les contraintes des fonctions qui rendent possible un certain comportement (exigence). / Reactive systems are modeled with various kinds of automata, such as Input Output Symbolic Transition Systems (IOSTS). Symbolic execution over an IOSTS allows test cases generation that can be executed on a concrete implementation, in order to determine whether it is conforming to its model. In this dissertation, we aim at extending the IOSTS framework with explicit user-defined function calls and analyze their impact on a whole system and vice-versa. The thesis bridges the gap between a model-based approach in which user-defined functions are abstracted away and a code-based approach in which small pieces of code are considered separately regardless of the way they are combined. According to the level of knowledge we have about these functions, they are modeled either by a complete specification, a partial specification, or even just as black-boxes provided without any knowledge. First, when functions are partially known, we use function stubs defined by tables containing representative input/output data tuples. The proposed approach borrows from concolic testing, the idea of mixing symbolic execution with information obtained from instrumented concrete executions (function tables). Second, if the user is willing to provide further specifications, it would be interesting to use more complete representations for called functions. Hence, we propose to abstract function behaviors by means of pre/post contracts. Then we extend symbolic execution by analyzing the functions through their contracts. Finally, when called functions are completely unknown, we present an approach to extract new contracts for them by exploring constraints coming from the IOSTS symbolic execution. Such contracts reflect constraints on the functions that make some behavior (requirement) feasible.

No description available.

The control of batch pulp digesters is hampered by insufficient measurements as well as nonlinearity and weak correlation between consecutive cooks. This makes a model-based approach to control attractive. Due to the age of the industry, many legacy controllers are in place on digesters around the world. The theoretical variance obtained by Monte Carlo modelling of a new controller is used as a benchmark for performance comparison between an old control system (S-factor) and a new model based controller developed by the University of Pretoria (the UP controller). This study covers the development of the controller, Monte Carlo modelling of the old and new controllers and in-situ testing of the UP controller on an operating digester. During Monte Carlo simulation, the UP controller outperformed the legacy controller, obtaining a theoretical overall variance of 3,07 (which will be used as the baseline for performance measurement) while also showing larger responses to tuning factors. The S-factor performed at 6,8 times the theoretical optimum variance during in situ testing, while the UP controller performed at 3,9 times the theoretical optimum (43% better than the S-factor controller). An average error 90% lower than that of the S-factor controller was obtained when using the UP controller. Additional benefits of the new controller include easy inclusion of new measurements and clear relations between the tuning parameters used and the conditions in the digester. / Dissertation (MEng (Control))--University of Pretoria, 2003. / Chemical Engineering / unrestricted

The need to secure critical infrastructure (CI) systems against attacks is a topic that has been discussed recently in literature. Many examples of attacks against CI exist, such as the physical attack on the Pacific Gas and Electric Metcalf substation in 2013 that caused millions of dollars in damage or the Stuxnet cyber-attack which was identified in 2010 that caused damage to Iran’s nuclear program and alerted the world to the existence of cyber weapons. As a result of these types of events in which vulnerabilities in CI are exploited, it is important to have a comprehensive systems approach for assessing the vulnerabilities in CI systems. This dissertation seeks to provide a method for engineers to use system and human architectures to perform vulnerability assessment (VA) and decision analysis to enable decision makers to make tradeoffs on how to use their resources to protect CI against attacks.There are several gaps in literature in how to use system and human architectures to perform VA to protect CI from damage. First, no method exists that uses a model based approach and human and system architectures to perform a comprehensive analysis of CI to develop decision analysis models to aid decision makers in determining the most effective use of security resources to secure their CI systems. It is important that such models be comprehensive by including industry standards, system and human architectures, attack scenarios, subject matter expert opinion and models for analysis to help decision makers determine the best security investments. Second, there is not an established method to develop detailed mathematical models from an operational activity diagram that represents an attack scenario. This is important because the translation from architecture to high fidelity models will enable CI asset owners to make tradeoffs on security resource use. Finally, there is no method to evaluate the role of humans in a CI VA based on human views of the system. This dissertation provides an approach to use human and system architectures to perform VA and decision analysis to fill these gaps.