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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Structural Equation Modeling of Writing Proficiency Using Can-Do Questionnaires

Kobayashi, Wakako January 2017 (has links)
The purposes of this study were to validate the writing section of the Eiken Can-Do Questionnaires used in this study and the second purpose was to determine the effects of ten affective orientations (i.e., Desire to Write English, Attitude Toward Learning to Write English, Motivational Intensity, Instrumental Orientation for Writing in English, L2 Writing Anxiety, L2 Writing Self-Confidence, Willingness to Communicate in L2 Writing, Self-Esteem, Cognitive Competence, and General Self-Worth), on the participants’ responses to the Eiken Can-Do Questionnaires. This purpose is valuable because little is known about the relationship between Can-Do Questionnaire and affective variables investigated in this study. The final purpose of this study was to develop Can-Do Questionnaires as an internal measure for a university writing class. The participants of this study were 204 university students studying in two private universities in Tokyo, Japan. The first instrument was the writing section of the Eiken Can-Do Questionnaire; this questionnaire served as the outside measure in this study. The second, six out of nine essays written by the students were assessed as a measure of their writing ability in English. The Affective Orientation Questionnaire was administered to measure ten Affective Orientations. The questionnaire and essay data were analyzed using the Rasch rating scale. All of the participants completed the Background Questionnaire and Affective Orientation Questionnaire in April 2010 and 2011 and completed the writing section of the Eiken Can-do Questionnaire in April, July, and December 2010 and 2011. six writing assignments were produced by 179 out of the 204 participants wrote during the 2010 and 2011 academic year, and the relationships among the variables were analyzed using Structural Equation Modeling. The results indicated that the use of the Eiken Can-Do Questionnaires as the proficiency level measure was appropriate for this group of university students. The Eiken Can-Do Questionnaires were predictors of Motivation and L2 Self-Confidence. Motivation was a predictor of WTC in L2 Writing. Therefore, it should be noted that the Eiken Can-Do Questionnaires had an indirect effect with WTC in L2 Writing. The result implies that through having Eiken Can-Do questionnaires and Classroom Can-do Questionnaires to achieve their future goals, their English classes and their future learning objectives were connected.  It is necessary to provide students with adequate practice and guidance in using the Eiken Can-Do Questionnaires in order to promote a deeper understanding of their purposes and uses. / Teaching & Learning
272

Designing Security Defenses for Cyber-Physical Systems

Foruhandeh, Mahsa 04 May 2022 (has links)
Legacy cyber-physical systems (CPSs) were designed without considering cybersecurity as a primary design tenet especially when considering their evolving operating environment. There are many examples of legacy systems including automotive control, navigation, transportation, and industrial control systems (ICSs), to name a few. To make matters worse, the cost of designing and deploying defenses in existing legacy infrastructure can be overwhelming as millions or even billions of legacy CPS systems are already in use. This economic angle, prevents the use of defenses that are not backward compatible. Moreover, any protection has to operate efficiently in resource constraint environments that are dynamic nature. Hence, the existing approaches that require ex- pensive additional hardware, propose a new protocol from scratch, or rely on complex numerical operations such as strong cryptographic solutions, are less likely to be deployed in practice. In this dissertation, we explore a variety of lightweight solutions for securing different existing CPSs without requiring any modifications to the original system design at hardware or protocol level. In particular, we use fingerprinting, crowdsourcing and deterministic models as alternative backwards- compatible defenses for securing vehicles, global positioning system (GPS) receivers, and a class of ICSs called supervisory control and data acquisition (SCADA) systems, respectively. We use fingerprinting to address the deficiencies in automobile cyber-security from the angle of controller area network (CAN) security. CAN protocol is the de-facto bus standard commonly used in the automotive industry for connecting electronic control units (ECUs) within a vehicle. The broadcast nature of this protocol, along with the lack of authentication or integrity guarantees, create a foothold for adversaries to perform arbitrary data injection or modification and impersonation attacks on the ECUs. We propose SIMPLE, a single-frame based physical layer identification for intrusion detection and prevention on such networks. Physical layer identification or fingerprinting is a method that takes advantage of the manufacturing inconsistencies in the hardware components that generate the analog signal for the CPS of our interest. It translates the manifestation of these inconsistencies, which appear in the analog signals, into unique features called fingerprints which can be used later on for authentication purposes. Our solution is resilient to ambient temperature, supply voltage value variations, or aging. Next, we use fingerprinting and crowdsourcing at two separate protection approaches leveraging two different perspectives for securing GPS receivers against spoofing attacks. GPS, is the most predominant non-authenticated navigation system. The security issues inherent into civilian GPS are exacerbated by the fact that its design and implementation are public knowledge. To address this problem, first we introduce Spotr, a GPS spoofing detection via device fingerprinting, that is able to determine the authenticity of signals based on their physical-layer similarity to the signals that are known to have originated from GPS satellites. More specifically, we are able to detect spoofing activities and track genuine signals over different times and locations and propagation effects related to environmental conditions. In a different approach at a higher level, we put forth Crowdsourcing GPS, a total solution for GPS spoofing detection, recovery and attacker localization. Crowdsourcing is a method where multiple entities share their observations of the environment and get together as a whole to make a more accurate or reliable decision on the status of the system. Crowdsourcing has the advantage of deployment with the less complexity and distributed cost, however its functionality is dependent on the adoption rate by the users. Here, we have two methods for implementing Crowdsourcing GPS. In the first method, the users in the crowd are aware of their approximate distance from other users using Bluetooth. They cross validate this approximate distance with the GPS-derived distance and in case of any discrepancy they report ongoing spoofing activities. This method is a strong candidate when the users in the crowd have a sparse distribution. It is also very effective when tackling multiple coordinated adversaries. For method II, we exploit the angular dispersion of the users with respect to the direction that the adversarial signal is being transmitted from. As a result, the users that are not facing the attacker will be safe. The reason for this is that human body mostly comprises of water and absorbs the weak adversarial GPS signal. The safe users will help the spoofed users find out that there is an ongoing attack and recover from it. Additionally, the angular information is used for localizing the adversary. This method is slightly more complex, and shows the best performance in dense areas. It is also designed based on the assumption that the spoofing attack is only terrestrial. Finally, we propose a tandem IDS to secure SCADA systems. SCADA systems play a critical role in most safety-critical infrastructures of ICSs. The evolution of communications technology has rendered modern SCADA systems and their connecting actuators and sensors vulnerable to malicious attacks on both physical and application layers. The conventional IDS that are built for securing SCADA systems are focused on a single layer of the system. With the tandem IDS we break this habit and propose a strong multi-layer solution which is able to expose a wide range of attack. To be more specific, the tandem IDS comprises of two parts, a traditional network IDS and a shadow replica. We design the shadow replica as a deterministic IDS. It performs a workflow analysis and makes sure the logical flow of the events in the SCADA controller and its connected devices maintain their expected states. Any deviation would be a malicious activity or a reliability issue. To model the application level events, we leverage finite state machines (FSMs) to compute the anticipated states of all of the devices. This is feasible because in many of the existing ICSs the flow of traffic and the resulting states and actions in the connected devices have a deterministic nature. Consequently, it leads to a reliable and free of uncertainty solution. Aside from detecting traditional network attacks, our approach bypasses the attacker in case it succeeds in taking over the devices and also maintains continuous service if the SCADA controller gets compromised. / Doctor of Philosophy / Our lives are entangled with cyber-physical systems (CPSs) on a daily basis. Examples of these systems are vehicles, navigation systems, transportation systems, industrial control systems, etc. CPSs are mostly legacy systems and were built with a focus on performance, overlooking security. Security was not considered in the design of these old systems and now they are dominantly used in our everyday life. After numerous demonstration of cyber hacks, the necessity of protecting the CPSs from adversarial activities is no longer ambiguous. Many of the advanced cryptographic techniques are far too complex to be implemented in the existing CPSs such as cars, satellites, etc. We attempt to secure such resource constraint systems using simple backward compatible techniques in this dissertation. We design cheap lightweight solutions, with no modifications to the original system. In part of our research, we use fingerprinting as a technique to secure passenger cars from being hacked, and GPS receivers from being spoofed. For a brief description of fingerprinting, we use the example of two identical T-shirts with the same size and design. They will always have subtle differences between them no matter how hard the tailor tried to make them identical. This means that there are no two T-shirts that are exactly identical. This idea, when applied to analog signalling on electric devices, is called fingerprinting. Here, we fingerprint the mini computers inside a car, which enables us to identify these computers and prevent hacking. We also use the signal levels to design fingerprints for GPS signals. We use the fingerprints to distinguish counterfeit GPS signals from the ones that have originated from genuine satellites. This summarizes two major contributions in the dissertation. Our earlier contribution to GPS security was effective, but it was heavily dependent on the underlying hardware, requiring extensive training for each radio receiver that it was protecting. To remove this dependence of training for the specific underlying hardware, we design and implement the next framework using defenses that require application-layer access. Thus, we proposed two methods that leverage crowdsourcing approaches to defend against GPS spoofing attacks and, at the same time, improve the accuracy of localization for commodity mobile devices. Crowdsourcing is a method were several devices agree to share their information with each other. In this work, GPS users share their location and direction information, and in case of any discrepancy they figure that they are under attack and cooperate to recover from it. Last, we shift the gear to the industrial control systems (ICSs) and propose a novel IDS to protect them against various cyber attacks. Unlike the conventional IDSs that are focused on one of the layers of the system, our IDS comprises of two main components. A conventional component that exposes traditional attacks and a second component called a shadow replica. The replica mimics the behavior of the system and compares it with that of the actual system in a real-time manner. In case of any deviation between the two, it detects attacks that target the logical flow of the events in the system. Note that such attacks are more sophisticated and difficult to detect because they do not leave any obvious footprints behind. Upon detection of attacks on the original controller, our replica takes over the responsibilities of the original ICS controller and provides service continuity.
273

3D computational fluid dynamics study of a drying process in a can making industry

Tanthadiloke, S., Chankerd, W., Suwatthikul, A., Lipikanjanakul, P., Mujtaba, Iqbal, Kittisupakorn, P. 05 August 2016 (has links)
Yes / In the drying process of a can making industry, the drying efficiency of a thermal drying oven can be improved by adjusting the volumetric air flow rate of the blower. To maximize drying efficiency, an optimal flow rate is needed. Consequently, a three-dimensional computational fluid dynamics (CFD) is used to provide simulation according to the response of air velocity, air temperature and evaporated solvent concentration with respect to changes in volumetric air flow rate in the drying oven. An experimental study has been carried out to determine the evaporation rate of the solvent. To validate the models, the process data obtained from the CFD is compared with that obtained from actual data. In the accurate models, the simulation results demonstrate that the decrease in volumetric air flow rate provides no major discrepancy of the air velocity patterns in all dimensions and decreases the maximum temperature in the oven. Consequently, this decrease in volumetric air flow rate rapidly increases the evaporated solvent concentration in the beginning and then gradually decreases over the length of the oven. In addition, further reduction of the flow rate gives lower heat loss of the oven up to 83.67%. / The authors would like to thank The Thailand Research Fund (TRF) under The Royal Golden Jubilee Ph.D. Program (PHD/0158/2550), The Institutional Research Grant (The Thailand Research Fund) (IRG 5780014) and Chulalongkorn University (Contract No. RES_57_411_21_076) for financial support to this work.
274

Online Message Delay Prediction for Model Predictive Control over Controller Area Network

Bangalore Narendranath Rao, Amith Kaushal 28 July 2017 (has links)
Today's Cyber-Physical Systems (CPS) are typically distributed over several computing nodes communicating by way of shared buses such as Controller Area Network (CAN). Their control performance gets degraded due to variable delays (jitters) incurred by messages on the shared CAN bus due to contention and network overhead. This work presents a novel online delay prediction approach that predicts the message delay at runtime based on real-time traffic information on CAN. It leverages the proposed method to improve control quality, by compensating for the message delay using the Model Predictive Control (MPC) algorithm in designing the controller. By simulating an automotive Cruise Control system and a DC Motor plant in a CAN environment, it goes on to demonstrate that the delay prediction is accurate, and that the MPC design which takes the message delay into consideration, performs considerably better. It also implements the proposed method on an 8-bit 16MHz ATmega328P microcontroller and measures the execution time overhead. The results clearly indicate that the method is computationally feasible for online usage. / Master of Science / In today’s world, most complicated systems such as automobiles employ a decentralized modular architecture with several nodes communicating with each other over a shared medium. The Controller Area Network (CAN) is the most widely accepted standard as far as automobiles are concerned. The performance of such systems gets degraded due to the variable delays (jitters) incurred by messages on the CAN. These delays can be caused by messages of higher importance delaying bus access to the messages of lower importance, or due to other network related issues. This work presents a novel approach that predicts the message delays in real-time based on the traffic information on CAN. This approach leverages the proposed method to improve the control quality by compensating for the message delay using an advanced controller algorithm called Model Predictive Control (MPC). By simulating an automotive Cruise Control system and a DC motor plant in a CAN environment, this work goes on to demonstrate that the delay prediction is accurate, and that the MPC design which takes the message delay into consideration, performs considerably better. It also implements the proposed approach on a low end microcontroller (8bit, 16MHz ATmega328P) and measures the time taken for predicting the delay for each message (execution overhead). The obtained results clearly indicate that the method is computationally feasible for use in a real-time scenario.
275

Integrating Service Tools on Embedded Displays

Danforth, Jesper, Kassab, Ghaith January 2024 (has links)
The machines and vehicles of today are very advanced with several electronic controlunits (ECUs) tasked with monitoring and performing various tasks. These ECUs com-municate with each other via the onboard Control Area Network (CAN bus). When anerror occurs or the need for maintenance arises, an external computer needs to be con-nected to the control area network (CAN bus) to enable, among others, troubleshootingand maintenance of the various ECUs connected to the system.The central question we explore in this thesis is whether it’s feasible and practical tomove the service system library for these machines onto an existing resource-constrainedECU with a display already present within the system, thereby eliminating the need foran external computer. This solution streamlines maintenance processes by increasing themaintainability of the machines and vehicles when an external computer is not availableand reduces downtime by lowering the Mean Time To Diagnose (MTTD).In the end, a majority of the main functions of the service library were integrated intoan ECU with a display, only missing the ability to flash new firmware to other deviceswithin the CAN bus system. This proves that the theory behind the project is correct, andwith more time the missing feature could have been implemented.
276

Enclosing and Mounting an Electronic Component on Articulated Haulers : A proposition on how to protect, and where to place, an intelligent node on the environmentally harsh exterior of construction equipment with respect to multiple parameters

Sintorn, Johan January 2016 (has links)
As is the case with many other manufacturers of vehicles, Volvo Construction Equipment has a constantly increasing amount of electric and electronic equipment in their articulated haulers. These are of great use in modern machines, bringing functions, and safety that were not possible before, but they also bring more cables to handle. In the case of the articulated haulers a quite thick cable harness of about 15 meters in length reaches from the driver’s cabin in the front to the components in the far back end of the vehicle. This is not only a lot of long cables to handle both during assembly and service, but the nature of signals traveling in cables is that the voltage gets weaker with distance. This phenomenon has to be accounted for by measuring devices dependent on the voltage. It has been suggested that a device referred to as an intelligent node, or ICCS-module, which communicates digitally via CAN could be installed in the back of the articulated haulers. This module would be independent of the mentioned drop in voltage. The ICCS-module will be receiving a small bundle of cables being routed from the driver’s cabin. From it cables would go out to a majority of the components in its vicinity. The components connected to the node would not need to have any other cables. This thesis is focused on the mechanical aspects of installing this ICCS-module. Having electric and electronic equipment on construction vehicles is a challenge when it comes to protecting the device from the harsh environment that is the hauler’s exterior. It will have to withstand being immersed in water for long periods of time, greatly varying temperatures, vibrations and shocks as well as being hit by projectiles. The placement as well as the design of the enclosure should be chosen with respect to both the devices length of life and how well it fulfils its intended role and achieves the expected results. To produce an enclosure and find a placement aiming to satisfy these conditions, a traditional product development process were executed. The articulated haulers as well as relevant literature were researched. Concepts were generated and evaluated by both the author and by employees at Volvo Construction Equipment until a final concept for the enclosure and placement were found. The enclosure were then designed in detail specifying the material, manufacturing techniques, controlled for thermodynamic circumstances, modelled in Catia V5 and controlled for vibrations. It was concluded that the enclosure should be able protect the ICCS-module after some more development and that the placement and cable routing results in a much shorter total cable length.
277

Análise da norma ISO11783 e sua utilização na implementação do barramento do implemento de um monitor de semeadora. / Analysis of ISO11783 and its usage in the implementation of a Planter Monitor implement bus network.

Guimarães, Alexandre de Almeida 19 February 2003 (has links)
A utilização de eletrônica embarcada na agricultura tem crescido rapidamente, tornando necessária a utilização de diversos módulos a bordo da máquina (trator e implemento). Considerando-se os impactos relacionados a esta tendência, alternativas tecnológicas devem ser geradas e devidamente exploradas, especialmente sobre os sistemas de controle e o cabeamento requeridos. As arquiteturas eletro-eletrônicas devem garantir o mínimo de custo de implementação e tempo de manutenção. Os sistemas de controle devem operar maximizando a disponibilidade das informações, o que implica a necessidade de troca de dados entre estes diversos sistemas de controle e, portanto, a existência de um protocolo de comunicação serial internacionalmente padronizado. Neste contexto, este trabalho aborda os diversos protocolos de comunicação serial - como o RS232, o RS485 e o CAN (Controller Area Network) - e as suas normas específicas, voltadas às aplicações agrícolas, como a ISO11783 e a DIN 9684, comparando-as. Dessa análise resulta a indicação da ISO11783, norma baseada no protocolo CAN, como a mais interessante para as aplicações agrícolas. Essa norma é estudada em detalhes, o que permite a criação de um roteiro de estudo e implementação do referido protocolo. Finalmente, é desenvolvida uma aplicação deste protocolo, considerando-se uma rede de comunicação de dados de um Monitor de Semeadora, a fim de demonstrar sua aplicação prática. / The use of on-board electronics in agriculture has grown quickly, requiring many electronic modules on-board machines (tractor and implement). Considering the trend related impacts, alternative technologies should be developed and used properly, especially on control systems and on the required wiring harness. Electro-electronic architectures should provide minimum implementation cost and maintenance related time. Control systems should operate maximizing the availability of information that implies on the necessity of data exchange among these variety of control systems and also, on the existence of an international standardized serial communication protocol. Considering that, this documentation covers many serial communication protocols - as RS232, RS485 and CAN (Controller Area Network) - and the agricultural applications related standards as ISO11783 and DIN 9684, comparing them. This analysis results in the indication of ISO11783, a CAN Bus based standard, as the most interesting to agricultural applications. This standard is analyzed in details, making possible the development of a protocol related study and implementation guideline. Finally, a protocol related application is developed for a Planter Monitor implement bus network, looking forward to demonstrating an ISO11783 real implementation.
278

Influence des fautes transitoires sur la fiabilité d'un système contrôlé en réseau / Impact of transient faults on the reliability evaluation of a networked control system

Ghostine, Rony 12 June 2008 (has links)
Ce travail s'inscrit dans le cadre de l'évaluation de la sûreté de fonctionnement des systèmes commandés en réseau (SCR). La capacité des systèmes de commandes à compenser les effets de certaines défaillances de composants amène à redéfinir le concept de défaillances du système. La conséquence est que l'évaluation de la fiabilité prévisionnelle du système est dépendante de l'évaluation fonctionnelle et devient impossible avec les méthodes traditionnelles de la sûreté de fonctionnement. Pour surmonter ces difficultés, une approche basée sur la modélisation en vue de la simulation est proposée. Nous avons choisi les Réseaux d'activités stochastiques (SAN) largement connus dans la modélisation des protocoles de communication ainsi que dans les études de la sûreté de fonctionnement. Dans un premier temps, nous avons cherché à identifier l'incidence de deux types de défaillances fugitives : la perte d'un échantillon d'une part et le retard d'un échantillon dans la boucle de régulation d'autre part. Après, nous simulons le comportement en présence des deux types de perturbations simultanément, mettant en évidence des effets cumulatifs. Si on tient compte maintenant du fait que l'origine des pertes ou retards est due à la présence du réseau, il faut l'introduire dans le modèle. On introduit alors dans le modèle global du système la représentation SAN d'un réseau CAN et l'injection des défaillances dans celui-ci. La méthode de Monte Carlo est utilisée pour estimer les indicateurs de sûreté de fonctionnement et on montre l'influence de certains facteurs comme la charge du réseau par exemple. Nous avons proposé une méthode et les outils associés pour approcher cette évaluation par simulation et ainsi apporter une aide à la conception des systèmes satisfaisant à des exigences critiques sur certains paramètres de performance / Achieved work in this thesis deals with dependability evaluation of networked controlled system (NCS). The ability of control system to offset the effects of some components’ failure leads to redefine the concept of system failure. Consequently the reliability evaluation is dependent on functional parameters and becomes impossible with traditional dependability methods. This work aims at bringing a contribution relative to this aspect. To overcome these difficulties, an approach based on both modelling and simulation is proposed. We choose to work with stochastic activity network (SAN) widely used in modelling communication protocols as well as in dependability studies. First we sought to identify the incidence of two types of transient faults: loss of samples and delay within the control loop. Next we simulate the behaviour in the presence of two types of disturbances at the same time highlighting the cumulative effects. In fact the origin of the loss or delay information inside the control loop is due to the presence of the network, this aspect must be taken into account, that is why we introduce a new model representing the Controller Area Network (CAN) and injection of possible perturbations. Monte-Carlo method is used to estimate dependability parameters showing the influence of some factors such as network load for example. We have proposed a method and associated tools to approach this evaluation by simulation and thus provide assistance in designing systems to meet requirements on certain performance parameters
279

Schedulability analysis for the design of reliable and cost-effective automotive embedded systems / Analyses d'ordonnancalité pour la conception de systèmes embarqués automobiles fiables et optimisés

Khan, Dawood Ashraf 29 November 2011 (has links)
Automobile système embarqué est une architecture distribuée de l'ordinateur des applications basées sur. La prolifération des systèmes embarqués dans une automobile a apporté de nombreux avantages,tels que le remplacement du système mécanique ancienne avec capteur électronique en réseau et desactionneurs, par exemple, dans des applications telles suspensions adaptatives. Le remplacement des systèmes mécaniques avec ceux électroniques et l'intégration de nouvelles fonctionnalités dans l'électronique soulève une grave préoccupation, c'est de fournir des garanties que ces systèmes embarqués seront en mesure d'effectuer, même dans des environnements difficiles, en particulier dans un système critique pour la sécurité comme un automobile. De plus, ceux-ci l'actualité informatique applications à la demande, imposée par un processus physique.Par exemple, pour éviter un événement catastrophique comme un accident de la demande de freinage doit répondre aux contraintes de minutage. Ce qui implique que la durée de temps entre l'instance de l'application du frein (à la pédale de frein) et l'instance de l'actionnement au niveau des roues d'un véhicule automobile doit être inférieure à la limite. En outre, l'application de freinage est généralement répartie sur le nombre de nœuds, qui sont embarqués communicants les uns avec les autres en utilisant une ressource de communication partagée. Par conséquent, il est important que nous fournissons des garanties que la demande, individuellement et collectivement, est atteinte de ses contrainte temporelle; qui est dans la composition de plusieurs nœuds embarqués. En outre, la prolifération des applications informatiques est également livré avec une hétérogénéité croissante et la complexité de l'architecture intégrée, ce qui conduira à l'augmentation de la complexité de l'analyse pour les systèmes automobiles.Par conséquent, il ya un besoin croissant d'assurer que ces systèmes automobiles embarqués répondre à des contraintes temporelles et de fournir des garanties de sécurité au cours de leur fonctionnement normal ou lors de situations critiques. Cette thèse vise à développer les analyses d'ordonnançabilité pour systèmes automobiles et les réseaux intégrés, avec le but de faciliter,d'une manière rentable et fiable, la conception et l'analyse des systèmes embarqués automobiles. Les analyses sont élaborées et appliquées dans le contexte de l'automobile; de ​​façon à réduire le risque d'échec en raison de délai: les limites du matériel; frais généraux de mise en œuvre, et les interférences dues à la circulation probaliste / Automotive embedded system is a distributed architecture of computer-based applications. The proliferation of embedded systems in an automobile has brought numerous benefits; such as replacement of old mechanical system with networked electronic sensor and actuators, for example, in applications like adaptive suspensions. The replacement of mechanical systems with electronic onesand the integration of new functionality in electronics raises a serious concern; that is to provide guarantees that these embedded systems will be able to perform, even in harsh environments, particularly in a safety-critical system like an automobile.Moreover, these computer-based applications demand timeliness, imposed by a physical process. For example, to avoid a catastrophic event like a crash the braking application has to meet thetiming-constraints. This implies that the time duration between the instance of application of the brake (at brake pedal) and the instance of actuation at the wheels of an automobile should be less than the deadline. Moreover, the braking application is usually spread over number of embedded nodes, which are communicating with each other using a shared communication resource. Therefore, it is important that we provide some guarantees that an application, individually and collectively, is meeting its timing constraint; that is in the composition of multiple embedded nodes. Moreover, theproliferation of computer-based applications also comes with an increasing heterogeneity and complexity of the embedded architecture; which lead to the increase in the complexity of the analysis for the automotive systems Therefore, there is an increasing need to ensure that these automotive embedded systems meet temporal constraints and provide safety guarantees during their normal operation or during critical situations. This thesis aims at developing the schedulability analyses for automotive systems and embedded networks; with the aim to facilitate, in a cost-effective and reliable manner, the design and analysis of automotive embedded systems. The analyses are developed and applied in the automotive context; so as to reduce the risk of deadline failure due to: hardware limitations ; implementation overheads; and nterference due to probabilistic traffic
280

Vérification des contraintes temporelles de bout-en-bout dans le contexte AutoSar / Verification of end-to-end real-time constraints in the context of AutoSar

Monot, Aurélien 26 October 2012 (has links)
Les systèmes électroniques embarqués dans les véhicules ont une complexité sans cesse croissante. Cependant, il est crucial d'en maîtriser le comportement temporel afin de garantir la sécurité ainsi que le confort des passagers. La vérification des contraintes temporelles de bout-en-bout est donc un enjeu majeur lors de la conception d'un véhicule. Dans le contexte de l'architecture logicielle AUTOSAR standard dans les véhicules, nous décomposons la vérification d'une contrainte de bout-en-bout en sous-problèmes d'ordonnancement sur les calculateurs et sur les réseaux de communication que nous traitons ensuite séparément. Dans un premier temps, nous présentons une approche permettant d'améliorer l'utilisation des calculateurs exécutant un grand nombre de composants logiciels, compatible avec l'introduction progressive des plateformes multi-coeurs. Nous décrivons des algorithmes rapides et efficaces pour lisser la charge périodique sur les calculateurs multi-coeurs en adaptant puis en améliorant une approche existant pour les bus CAN. Nous donnons également des résultats théoriques sur l'efficacité des algorithmes dans certains cas particuliers. Enfin, nous décrivons les possibilités d'utilisation de ces algorithmes en fonction des autres tâches exécutées sur le calculateur. La suite des travaux est consacrée à l'étude des distributions de temps de réponse des messages transmis sur les bus CAN. Dans un premier temps nous présentons une approche de simulation basée sur la modélisation des dérives d'horloges des calculateurs communicant sur le réseau. Nous montrons que nous obtenons des distributions de temps de réponse similaires en réalisant une longue simulation avec des dérives d'horloge ou en faisant un grand nombre de courtes simulations sans dérives d'horloge. Nous présentons enfin une technique analytique pour évaluer les distributions de temps de réponse des trames CAN. Nous présentons différents paramètres d'approximation permettant de réduire le nombre très important de calculs à effectuer en limitant la perte de précision. Enfin, nous comparons expérimentalement les résultats obtenus par analyse et simulation et décrivons les avantages et inconvénients respectifs de ces approches / The complexity of electronic embedded systems in cars is continuously growing. Hence, mastering the temporal behavior of such systems is paramount in order to ensure the safety and comfort of the passengers. As a consequence, the verification of end-to-end real-time constraints is a major challenge during the design phase of a car. The AUTOSAR software architecture drives us to address the verification of end-to-end real-time constraints as two independent scheduling problems respectively for electronic control units and communication buses. First, we introduce an approach, which optimizes the utilization of controllers scheduling numerous software components that is compatible with the upcoming multicore architectures. We describe fast and efficient algorithms in order to balance the periodic load over time on multicore controllers by adapting and improving an existing approach used for the CAN networks. We provide theoretical result on the efficiency of the algorithms in some specific cases. Moreover, we describe how to use these algorithms in conjunction with other tasks scheduled on the controller. The remaining part of this research work addresses the problem of obtaining the response time distributions of the messages sent on a CAN network. First, we present a simulation approach based on the modelisation of clock drifts on the communicating nodes connected on the CAN network. We show that we obtain similar results with a single simulation using our approach in comparison with the legacy approach consisting in numerous short simulation runs without clock drifts. Then, we present an analytical approach in order to compute the response time distributions of the CAN frames. We introduce several approximation parameters to cope with the very high computational complexity of this approach while limiting the loss of accuracy. Finally, we compare experimentally the simulation and analytical approaches in order to discuss the relative advantages of each of the two approaches

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