The term hydrobatics refers to the agile maneuvering of underwater vehicles. Hydrobatic capabilities in autonomous underwater vehicles (AUVs) can enable increased maneuverability without a sacrifice in efficiency and speed. This means innovative robot designs and new use case scenarios are possible. Benefits and technical challenges related to hydrobatic AUVs are explored in this thesis. The dissertation contributes to new knowledge in simulation, control and field applications, and provides a structured approach to realize hydrobatic capabilities in real world impact areas. Three impact areas are considered - environmental monitoring, ocean production and security. A combination of agility in maneuvering and efficiency in performance is crucial for successful AUV applications. To achieve such performance, two technical challenges must be solved. First, these AUVs have fewer control inputs than degrees of freedom, which leads to the challenge of underactuation. The challenge is described in detail and solution strategies that use optimal control and model predictive control (MPC) are highlighted. Second, the flow around an AUV during hydrobatic maneuvers transitions from laminar to turbulent flow at high angles of attack. This renders flight dynamics modelling difficult. A full 0-360 degree envelope flight dynamics model is therefore derived, which combines a multi-fidelity hydrodynamic database with a generalized component-buildup approach. Such a model enables real-time (or near real-time) simulations of hydrobatic maneuvers including loops, helices and tight turns. Next, a cyber-physical system (CPS) is presented -- it safely transforms capabilities derived in simulation to real-world use cases in the impact areas described. The simulator environment is closely integrated with the robotic system, enabling pre-validation of controllers and software before hardware deployment. The small and hydrobatic SAM AUV (developed in-house at KTH as part of the Swedish Maritime Robotics Center) is used as a test platform. The CPS concept is validated by using the SAM AUV for the search and detection of a submerged target in field operating conditions. Current research focuses on further exploring underactuated control and motion planning. This includes development of real-time nonlinear MPC implementations running on AUV hardware, as well as intelligent control through feedback motion planning, system identification and reinforcement learning. Such strategies can enable real-time robust and adaptive control of underactuated systems. These ideas will be applied to demonstrate new capabilities in the three impact areas. / Termen hydrobatik avser förmåga att utföra avancerade manövrer med undervattensfarkoster. Syftet är att, med bibehållen fart och räckvidd, utvigda den operationella förmågan i manövrering, vilket möjliggör helt nya användningsområden för maximering av kostnadseffektivitet. I denna avhandling undersöks fördelar och tekniska utmaningar relaterade till hydrobatik som tillämpas på undervattensrobotar, vanligen kallade autonoma undervattensfarkoster (AUV). Avhandlingen bidrar till ny kunskap i simulering, reglering samt tillämpning i experiment av dessa robotar genom en strukturerad metod för att realisera hydrobatisk förmåga i realistiska scenarier.  Tre nyttoområden beaktas - miljöövervakning, havsproduktion och säkerhet. Inom dessa nyttoområden har ett antal scenarios identifierats där en kombination av smidighet i manövrerbarhet samt effektivitet i prestanda är avgörande för robotens förmåga att utföra sin uppgift. För att åstadkomma detta måste två viktiga tekniska utmaningar lösas. För det första har dessa AUVer färre styrytor/trustrar än frihetsgrader, vilket leder till utmaningen med underaktuering. Utmaningen beskrivs i detalj och lösningsstrategier som använder optimal kontroll och modellprediktiv kontroll belyses. För det andra är flödet runt en AUV som genomför hydrobatiska manövrar komplext med övergång från laminär till stark turbulent flöde vid höga anfallsvinklar. Detta gör flygdynamikmodellering svår. En full 0-360 graders flygdynamikmodell härleds därför, vilken kombinerar en multi-tillförlitlighets hydrodynamisk databas med en generaliserad strategi för komponentvis-superpositionering av laster. Detta möjliggör prediktering av hydrobatiska manövrar som t.ex. utförande av looping, roll, spiraler och väldigt snäva svängradier i realtids- eller nära realtids-simuleringar. I nästa steg presenteras ett cyber-fysikaliskt system (CPS) – där funktionalitet som härrör från simuleringar kan överföras till de verkliga användningsområdena på ett effektivt och säkert sätt. Simulatormiljön är nära integrerad i robot-miljön, vilket möjliggör förvalidering av reglerstrategier och mjukvara innan hårdvaruimplementering. En egenutvecklad hydrobatisk AUV (SAM) används som testplattform. CPS-konceptet valideras med hjälp av SAM i ett realistiskt sceanrio genom att utföra ett sökuppdrag av ett nedsänkt föremål under fältförhållanden. Resultaten av arbetet i denna licentiatavhandling kommer att användas i den fortsatta forskningen som fokuserar på att ytterligare undersöka och utveckla ny metodik för reglering av underaktuerade AUVer. Detta inkluderar utveckling av realtidskapabla ickelinjära MPC-implementeringar som körs ombord, samt AI-baserade reglerstrategier genom ruttplaneringsåterkoppling, autonom systemidentifiering och förstärkningsinlärning. Sådan utveckling kommer att tillämpas för att visa nya möjligheter inom de tre nyttoområdena. / SMaRC

Detecting anomalies in computer-based systems, including Cyber-Physical Systems (CPS), has attracted a large interest recently. Behavioral anomalies represent deviations from what is regarded as the nominal expected behavior of the system. Both Process science and Data science can yield satisfactory results in detecting behavioral anomalies. Within Process Mining, Conformance Checking addresses data retrieval and the connection of data to behavioral models with the aim to detect behavioral anomalies. Nowadays, computer-based systems are increasingly complex and require appropriate validation, monitoring, and maintenance techniques. Within complex computer-based systems, the European Rail Traffic Management System/European Train Control System (ERTMS/ETCS) represents the specification of a standard Railway System integrating heterogeneous hardware and software components, with the aim of providing international interoperability with trains seemingly interacting within standardized infrastructures. Compliance with the standard as well as expected behavior is essential, considering the criticality of the system in terms of performance, availability, and safety. To that aim, a Process Mining Conformance Checking process can be employed to validate the requirements through run-time model-checking techniques against design-time process models. A Process Mining Conformance Checking methodology has been developed and applied with the goal of validating the behavior exposed by an ERTMS/ETCS system during the execution of specific scenarios. The methodology has been tested and demonstrated correct classification of valid behaviors exposed by the ERTMS/ETCS system prototype. Results also showed that the Fitness metric developed in the methodology allows the detection of latent errors in the system before they can generate any failures.

Cette thèse porte sur le développement d'approches compositionnelles et efficaces de synthèse de contrôleurs pour les systèmes cyber-physiques (CPS). En effet, alors que les techniques de conception des CPS basées sur des modèles ont fait l'objet de nombreuses études au cours de la dernière décennie, leur scalabilité reste problématique. Dans cette thèse, nous contribuons à rendre de telles approches plus évolutives.La première partie est axée sur les approches compositionnelles. Un cadre général pour le raisonnement compositionnel en utilisant des contrats d’hypothèse-garantie est proposé. Ce cadre est ensuite combiné avec des techniques de contrôle symbolique et appliqué à un problème de synthèse de contrôleur pour des systèmes échantillonnés, distribués et multipériodiques, où l'approche symbolique est utilisé pour synthétiser un contrôleur imposant un contrat donné. Ensuite, une nouvelle approche de calcul compositionnel des abstractions symboliques est proposée, basée sur la notion de composition approchée et permettant de traiter des abstractions hétérogènes.La deuxième partie de la thèse porte sur des techniques efficaces d'abstraction et de synthèse de contrôleurs. Deux nouvelles techniques de calcul d’abstractions sont proposées pour les systèmes à commutation incrémentalement stables. La première approche est basée sur l'échantillonnage multi-niveaux où nous avons établi l'existence d'un paramètre optimal d'échantillonnage qui aboutit à un modèle symbolique avec un nombre minimal de transitions. La deuxième approche est basée sur un échantillonnage événementiel, où la durée des transitions dans le modèle symbolique est déterminée par un mécanisme déclencheur, ce qui permet de réduire le conservatisme par rapport au cas périodique. La combinaison avec des techniques de synthèse de contrôleurs paresseux est proposée permettant la synthèse à un coût de calcul réduit. Enfin, une nouvelle approche de synthèse paresseuse a été développée pour les systèmes de transition monotones et les spécifications de sécurité dirigées. Plusieurs études de cas sont considérées dans cette thèse, telles que la régulation de la température dans les bâtiments, le contrôle des convertisseurs de puissance, le pilotage des véhicules et le contrôle de la tension dans les micro-réseaux DC. / This thesis focus on the development of compositional and efficient controller synthesis approaches for cyber-physical systems (CPS). Indeed, while model-based techniques for CPS design have been the subject of a large amount of research in the last decade, scalability of these techniques remains an issue. In his thesis, we contribute to make such approaches more scalable.The focus of the first part is on compositional approaches. A general framework for compositional reasoning using assume-guarantee contracts is proposed. This framework is then combined with symbolic control techniques and applied to a controller synthesis problem for multiperiodic distributed sampled-data systems, where symbolic approaches have been used to synthesize controllers enforcing a given assume-guarantee contract. Then, a new approach to the compositional computation of symbolic abstractions is proposed based on the notion of approximate composition, allowing to deal with heterogeneous abstractions and arbitrary interconnections.The second part is about efficient abstraction and controller synthesis techniques. Two new abstractions schemes have been developed for incrementally stable switched systems. The first approach is based on multirate sampling where we established the existence of an optimal multirate sampling parameter that results in a symbolic model with a minimal number of transitions. The second approach is based on event-based sampling, where the duration of transitions in the symbolic model is determined by some triggering mechanism, which makes it possible to reduce the conservatism with respect to the periodic case. Combination with lazy controller synthesis techniques has been proposed allowing the synthesis at a reduced computational cost. Finally, a new lazy approach has been develop for monotone transition systems and directed safety specifications. Several case studies have been considered in this thesis such as temperature regulation in buildings, control of power converters, vehicle platooning and voltage control in DC micro-grids.

L'électronique a connu une évolution incontestable ces dernières années. Les progrès réalisés, notamment dans l'électronique numérique et l'intégration des circuits, ont abouti à des systèmes plus performants, miniatures et à faible consommation énergétique. Les évolutions technologiques, alliant les avancées de l'informatique et des technologies numériques et leur intégration de plus en plus poussée au sein d'objets multiples, ont permis le développement d'un nouveau paradigme de systèmes qualifiés de systèmes cyber-physiques. Ces systèmes sont massivement déployés de nos jours grâce à l'expansion des applications liées à l'Internet Des Objets (IDO). Les systèmes cyber-physiques s'appuient, entre autre, sur le déploiement massif de capteurs communicants sans fil autonomes, ceux-ci présentent plusieurs avantages : * Flexibilité dans le choix de l'emplacement. Ils permettent l'accès à des zones dangereuses ou difficiles d'accès. * Affranchissement des câbles qui présentent un poids, un encombrement et un coût supplémentaire. * Elimination des problèmes relatifs aux câbles (usure, étanchéité...) * Facilité de déploiement de réseaux de capteurs Cependant, ces capteurs sans fils nécessitent une autonomie énergétique afin de fonctionner. Les techniques conventionnelles telles que les batteries ou les piles, n'assurent le fonctionnement des capteurs que pour une durée limitée et nécessitent un changement périodique. Ceci présente un obstacle dans le cas où les capteurs sans fils sont placés dans un endroit où l'accès est impossible. Il est donc nécessaire de trouver un autre moyen d'approvisionner l'énergie de façon permanente à ces réseaux de capteurs sans fil. L'intégration et la miniaturisation des systèmes électroniques ont permis la réalisation de systèmes à faible consommation, ce qui a fait apparaître d'autres techniques en termes d'apports énergétiques. Parmi ces possibilités se trouvent la récupération d'énergie électromagnétique et le transfert d'énergie sans fil (TESF). En effet, l'énergie électromagnétique est de nos jours, omniprésente sur notre planète, l'utiliser donc comme source d'énergie pour les systèmes électroniques semble être une idée plausible et réalisable. Cette thèse s'inscrit dans ce cadre, elle a pour objectif la conception et la fabrication de systèmes de récupération d'énergie électromagnétique pour l'alimentation de réseaux de capteurs sans fil. Le circuit de récupération d'énergie électromagnétique est appelé " Rectenna ", ce mot est l'association de deux entités qui sont " antenne " et " rectifier " qui désigne en anglais le " redresseur ". L'antenne permet de récupérer l'énergie électromagnétique ambiante et le redresseur la convertit en un signal continu (DC) qui servira par la suite à alimenter les capteurs sans fil. Dans ce manuscrit, plusieurs rectennas seront présentées, pour des fréquences allant des bandes GSM 868MHz, 915MHz, passant par l'UMTS à 2GHZ et WIFI à 2,45GHz, et allant jusqu'aux bandes Ku et Ka. / The electronic domain has known a significant expansion the last decades, all the advancements made has led to the development of miniature and efficient electronic devices used in many applications such as cyber physical systems. These systems use low-power wireless sensors for: detection, monitoring and so on. The use of wireless sensors has many advantages: * The flexibility of their location, they allow the access to hazardous areas. * The realization of lighter system, less expensive and less cumbersome. * The elimination of all the problems associated to the cables (erosion, impermeability...) * The deployment of sensor arrays. Therefore, these wireless sensors need to be supplied somehow with energy to be able to function properly. The classic ways of supplying energy such as batteries have some drawbacks, they are limited in energy and must be replaced periodically, and this is not conceivable for applications where the wireless sensor is placed in hazardous places or in places where the access is impossible. So, it is necessary to find another way to permanently provide energy to these wireless sensors. The integration and miniaturization of the electronic devices has led to low power consumption systems, which opens a way to another techniques in terms of providing energy. Amongst the possibilities, we can find the Wireless Power Transfer (WPT) and Energy Harvesting (EH). In fact, the electromagnetic energy is nowadays highly available in our planet thanks to all the applications that use wireless systems. We can take advantage of this massive available quantity of energy and use it to power-up the low power wireless sensors. This thesis is incorporated within the framework of WPT and EH. Its objective is the conception and realization of electromagnetic energy harvesters called "Rectenna" in order to supply energy to low power wireless sensors. The term "rectenna" is the combination of two words: Antenna and Rectifier. The Antenna is the module that captures the electromagnetic ambient energy and converts it to a RF signal, the rectifier is the RF circuit that converts this RF signal into a continuous (DC) signal that is used to supply the wireless sensors. In this manuscript, several rectennas will be presented, for different frequencies going from the GSM frequencies (868 MHz, 915 MHz) to the Ku/Ka bands.

The ongoing effort for an efficient, sustainable, and automated interaction between humans, machines, and our environment will make cyber-physical systems (CPS) an integral part of the industry and our daily lives. At their core, CPS integrate computing elements, communication networks, and physical processes that are monitored and controlled through sensors and actuators. New and innovative applications become possible by extending or replacing static and expensive cable-based communication infrastructures with wireless technology. The flexibility of wireless CPS is a key enabler for many envisioned scenarios, such as intelligent factories, smart farming, personalized healthcare systems, autonomous search and rescue, and smart cities. High dependability, efficiency, and adaptivity requirements complement the demand for wireless and low-cost solutions in such applications. For instance, industrial and medical systems should work reliably and predictably with performance guarantees, even if parts of the system fail. Because emerging CPS will feature mobile and battery-driven devices that can execute various tasks, the systems must also quickly adapt to frequently changing conditions. Moreover, as applications become ever more sophisticated, featuring compact embedded devices that are deployed densely and at scale, efficient designs are indispensable to achieve desired operational lifetimes and satisfy high bandwidth demands. Meeting these partly conflicting requirements, however, is challenging due to imperfections of wireless communication and resource constraints along several dimensions, for example, computing, memory, and power constraints of the devices. More precisely, frequent and correlated message losses paired with very limited bandwidth and varying delays for the message exchange significantly complicate the control design. In addition, since communication ranges are limited, messages must be relayed over multiple hops to cover larger distances, such as an entire factory. Although the resulting mesh networks are more robust against interference, efficient communication is a major challenge as wireless imperfections get amplified, and significant coordination effort is needed, especially if the networks are dynamic. CPS combine various research disciplines, which are often investigated in isolation, ignoring their complex interaction. However, to address this interaction and build trust in the proposed solutions, evaluating CPS using real physical systems and wireless networks paired with formal guarantees of a system’s end-to-end behavior is necessary. Existing works that take this step can only satisfy a few of the abovementioned requirements. Most notably, multi-hop communication has only been used to control slow physical processes while providing no guarantees. One of the reasons is that the current communication protocols are not suited for dynamic multi-hop networks. This thesis closes the gap between existing works and the diverse needs of emerging wireless CPS. The contributions address different research directions and are split into two parts. In the first part, we specifically address the shortcomings of existing communication protocols and make the following contributions to provide a solid networking foundation: • We present Mixer, a communication primitive for the reliable many-to-all message exchange in dynamic wireless multi-hop networks. Mixer runs on resource-constrained low-power embedded devices and combines synchronous transmissions and network coding for a highly scalable and topology-agnostic message exchange. As a result, it supports mobile nodes and can serve any possible traffic patterns, for example, to efficiently realize distributed control, as required by emerging CPS applications. • We present Butler, a lightweight and distributed synchronization mechanism with formally guaranteed correctness properties to improve the dependability of synchronous transmissions-based protocols. These protocols require precise time synchronization provided by a specific node. Upon failure of this node, the entire network cannot communicate. Butler removes this single point of failure by quickly synchronizing all nodes in the network without affecting the protocols’ performance. In the second part, we focus on the challenges of integrating communication and various control concepts using classical time-triggered and modern event-based approaches. Based on the design, implementation, and evaluation of the proposed solutions using real systems and networks, we make the following contributions, which in many ways push the boundaries of previous approaches: • We are the first to demonstrate and evaluate fast feedback control over low-power wireless multi-hop networks. Essential for this achievement is a novel co-design and integration of communication and control. Our wireless embedded platform tames the imperfections impairing control, for example, message loss and varying delays, and considers the resulting key properties in the control design. Furthermore, the careful orchestration of control and communication tasks enables real-time operation and makes our system amenable to an end-to-end analysis. Due to this, we can provably guarantee closed-loop stability for physical processes with linear time-invariant dynamics. • We propose control-guided communication, a novel co-design for distributed self-triggered control over wireless multi-hop networks. Self-triggered control can save energy by transmitting data only when needed. However, there are no solutions that bring those savings to multi-hop networks and that can reallocate freed-up resources, for example, to other agents. Our control system informs the communication system of its transmission demands ahead of time so that communication resources can be allocated accordingly. Thus, we can transfer the energy savings from the control to the communication side and achieve an end-to-end benefit. • We present a novel co-design of distributed control and wireless communication that resolves overload situations in which the communication demand exceeds the available bandwidth. As systems scale up, featuring more agents and higher bandwidth demands, the available bandwidth will be quickly exceeded, resulting in overload. While event-triggered control and self-triggered control approaches reduce the communication demand on average, they cannot prevent that potentially all agents want to communicate simultaneously. We address this limitation by dynamically allocating the available bandwidth to the agents with the highest need. Thus, we can formally prove that our co-design guarantees closed-loop stability for physical systems with stochastic linear time-invariant dynamics.:Abstract Acknowledgements List of Abbreviations List of Figures List of Tables 1 Introduction 1.1 Motivation 1.2 Application Requirements 1.3 Challenges 1.4 State of the Art 1.5 Contributions and Road Map 2 Mixer: Efficient Many-to-All Broadcast in Dynamic Wireless Mesh Networks 2.1 Introduction 2.2 Overview 2.3 Design 2.4 Implementation 2.5 Evaluation 2.6 Discussion 2.7 Related Work 3 Butler: Increasing the Availability of Low-Power Wireless Communication Protocols 3.1 Introduction 3.2 Motivation and Background 3.3 Design 3.4 Analysis 3.5 Implementation 3.6 Evaluation 3.7 Related Work 4 Feedback Control Goes Wireless: Guaranteed Stability over Low-Power Multi-Hop Networks 4.1 Introduction 4.2 Related Work 4.3 Problem Setting and Approach 4.4 Wireless Embedded System Design 4.5 Control Design and Analysis 4.6 Experimental Evaluation 4.A Control Details 5 Control-Guided Communication: Efficient Resource Arbitration and Allocation in Multi-Hop Wireless Control Systems 5.1 Introduction 5.2 Problem Setting 5.3 Co-Design Approach 5.4 Wireless Communication System Design 5.5 Self-Triggered Control Design 5.6 Experimental Evaluation 6 Scaling Beyond Bandwidth Limitations: Wireless Control With Stability Guarantees Under Overload 6.1 Introduction 6.2 Problem and Related Work 6.3 Overview of Co-Design Approach 6.4 Predictive Triggering and Control System 6.5 Adaptive Communication System 6.6 Integration and Stability Analysis 6.7 Testbed Experiments 6.A Proof of Theorem 4 6.B Usage of the Network Bandwidth for Control 7 Conclusion and Outlook 7.1 Contributions 7.2 Future Directions Bibliography List of Publications

Denna rapport närmar sig cyberfysiska system (CPS) ur både användnings- och utvecklingsperspektiv, med särskilt fokus på utmaningarna i en sjukhusmiljö. Vikten av en kontinuerlig utveckling för att optimera teknologins prestanda och användbarhet betonas, och de specifika utmaningar som är unika för en sjukhusmiljö belyses. Studien undersöker hantering av komplexitet kopplat till CPS i form av automatiserade transportsystem på Nya Karolinska Universitetssjukhuset, Stockholm, Sverige. Målet är att ge framtida sjukhusprojekt en klar beskrivning av erfarenheterna av att utveckla och hantera CPS i sjukhusmiljö. Genom att titta på både möjligheter och utmaningar kommer rapporten att bidra till en ökad förståelse för CPS och dess förmåga att förbättra vården. Resultaten visar att utmaningarna inkluderar höga säkerhetskrav, integrering med personal, noga övervakning för att undvika driftstörningar och behovet av samarbete och flexibilitet. Rapporten drar slutsatsen att samarbete, proaktiv inställning och kontinuerlig utveckling är nödvändiga för att optimera prestanda och användbarhet hos CPS. Användare och kunder bör också vara aktiva i att dokumentera och rapportera systemets beteende för en kontinuerlig förbättring. Utvecklingen av CPS inom sjukhusmiljöer kräver också kontinuerlig testning och utbildning av personal samt ett koordinerat och strategiskt förhållningssätt för att säkerställa god samverkan mellan systemets olika aspekter. / This report approaches CPS technology from both usage and development perspectives, with a particular focus on the challenges in a hospital environment. The importance of continuous development to optimize the technology's performance and usability is explored, as well as the specific challenges that are unique to a hospital environment. The study investigates the complexity management of CPS in the form of automated transport systems at the New Karolinska University Hospital in Stockholm, Sweden. The goal is to provide future hospital projects with a clear description of the experiences of developing and managing CPS in a hospital environment. By looking at both opportunities and challenges, the report contributes to a greater understanding of CPS and its ability to improve health care. The study shows that the challenges include high security requirements, integration with staff, careful monitoring to avoid disruptions, and the need for cooperation and flexibility. The report concludes that cooperation, proactive attitude and continuous development are necessary to optimize the performance and usability of CPS. Users and customers should be active in documenting and reporting the system's behavior for continuous improvement. The development of CPS in hospital environments also requires continuous testing and training of staff and a coordinated and strategic approach to ensure cooperation between the system's different aspects.

<p>The progressive integration of microcontrollers into various domains has transformed traditional mechanical systems into modern cyber-physical systems. However, the beginning of this transformation predated the era of hyper-interconnectedness that characterizes our contemporary world. As such, the principles and visions guiding the design choices of this transformation had not accounted for many of today's security challenges. Many designers had envisioned their systems to operate in an air-gapped-like fashion where few security threats loom. However, with the hyper-connectivity of today's world, many CPS find themselves in uncharted territory for which they are unprepared.</p> <p><br></p> <p>An example of this evolution is the Controller Area Network (CAN). CAN emerged during the transformation of many mechanical systems into cyber-physical systems as a pivotal communication standard, reducing vehicle wiring and enabling efficient data exchange. CAN's features, including noise resistance, decentralization, error handling, and fault confinement mechanisms, made it a widely adopted communication medium not only in transportation but also in diverse applications such as factories, elevators, medical equipment, avionic systems, and naval applications.</p> <p><br></p> <p>The increasing connectivity of modern vehicles through CD players, USB sticks, Bluetooth, and WiFi access has exposed CAN systems to unprecedented security challenges and highlighted the need to bolster their security posture. This dissertation addresses the urgent need to enhance the security of modern cyber-physical systems in the face of emerging threats by proposing a proactive vulnerability identification and defense construction approach and applying it to CAN as a lucid case study. By adopting this proactive approach, vulnerabilities can be systematically identified, and robust defense mechanisms can be constructed to safeguard the resilience of CAN systems.</p> <p><br></p> <p>We focus on developing vulnerability scanning techniques and innovative defense system designs tailored for CAN systems. By systematically identifying vulnerabilities before they are discovered and exploited by external actors, we minimize the risks associated with cyber-attacks, ensuring the longevity and reliability of CAN systems. Furthermore, the defense mechanisms proposed in this research overcome the limitations of existing solutions, providing holistic protection against CAN threats while considering its performance requirements and operational conditions.</p> <p><br></p> <p>It is important to emphasize that while this dissertation focuses on CAN, the techniques and rationale used here could be replicated to secure other cyber-physical systems. Specifically, due to CAN's presence in many cyber-physical systems, it shares many performance and security challenges with those systems, which makes most of the techniques and approaches used here easily transferrable to them. By accentuating the importance of proactive security, this research endeavors to establish a foundational approach to cyber-physical systems security and resiliency. It recognizes the evolving nature of cyber-physical systems and the specific security challenges facing each system in today's hyper-connected world and hence focuses on a single case study. </p>

Increasingly flexible and efficient industrial processes and automation systems are developed by integrating computational systems and physical processes, thereby forming large heterogeneous systems of cyber-physical systems. Such systems depend on particular data models and payload formats for communication, and making different entities interoperable is a challenging problem that drives the engineering costs and time to deployment. Interoperability is typically established and maintained manually using domain knowledge and tools for processing and visualization of symbolic metadata, which limits the scalability of the present approach. The vision of next generation automation frameworks, like the Arrowhead Framework, is to provide autonomous interoperability solutions. In this thesis the problem to automatically establish interoperability between cyber-physical systems is reviewed and formulated as a mathematical optimisation problem, where symbolic metadata and message payloads are combined with machine learning methods to enable message translation and improve system of systems utility. An autoencoder based implementation of the model is investigated and simulation results for a heating and ventilation system are presented, where messages are partially translated correctly by semantic interpolation and generalisation of the latent representations. A maximum translation accuracy of 49% is obtained using this unsupervised learning approach. Further work is required to improve the translation accuracy, in particular by further exploiting metadata in the model architecture and autoencoder training protocol, and by considering more advanced regularization methods and utility optimization. / Productive 4.0

<p dir="ltr">In the contemporary digital era, Advanced Persistent Threat (APT) attacks are evolving, becoming increasingly sophisticated, and now perilously targeting critical cyber-physical systems, notably Industrial Control Systems (ICS). The intersection of digital and physical realms in these systems enables APT attacks on ICSs to potentially inflict physical damage, disrupt critical infrastructure, and jeopardize human safety, thereby posing severe consequences for our interconnected world. Provenance tracing techniques are essential for investigating these attacks, yet existing APT attack forensics approaches grapple with scalability and maintainability issues. These approaches often hinge on system- or application-level logging, incurring high space and run-time overheads and potentially encountering difficulties in accessing source code. Their dependency on heuristics and manual rules necessitates perpetual updates by domain-knowledge experts to counteract newly developed attacks. Additionally, while there have been efforts to verify the safety of Programming Logic Controller (PLC) code as adversaries increasingly target industrial environments, these works either exclusively consider PLC program code without connecting to the underlying physical process or only address time-related physical safety issues neglecting other vital physical features.</p><p dir="ltr">This dissertation introduces two novel frameworks, ATLAS and ARCHPLC, to address the aforementioned challenges, offering a synergistic approach to fortifying cybersecurity in the face of evolving APT and ICS threats. ATLAS, an effective and efficient multi-host attack investigation framework, constructs end-to-end APT attack stories from audit logs by combining causality analysis, Natural Language Processing (NLP), and machine learning. Identifying key attack patterns, ATLAS proficiently analyzes and pinpoints attack events, minimizing alert fatigue for cyber analysts. During evaluations involving ten real-world APT attacks executed in a realistic virtual environment, ATLAS demonstrated an ability to recover attack steps and construct attack stories with an average precision of 91.06%, a recall of 97.29%, and an F1-score of 93.76%, providing a robust framework for understanding and mitigating cyber threats.</p><p dir="ltr">Concurrently, ARCHPLC, an advanced approach for enhancing ICS security, combines static analysis of PLC code and data mining from ICS data traces to derive accurate invariants, providing a comprehensive understanding of ICS behavior. ARCHPLC employs physical causality graph analysis techniques to identify cause-effect relationships among plant components (e.g., sensors and actuators), enabling efficient and quantitative discovery of physical causality invariants. Supporting patching and run-time monitoring modes, ARCHPLC inserts derived invariants into PLC code using program synthesis in patching mode and inserts invariants into a dedicated monitoring program for continuous safety checks in run-time monitoring mode. ARCHPLC adeptly detects and mitigates run-time anomalies, providing exceptional protection against cyber-physical attacks with minimal overhead. In evaluations against 11 cyber-physical attacks on a Fischertechnik manufacturing plant and a chemical plant simulator, ARCHPLC protected the plants without any false positives or negatives, with an average run-time overhead of 14.31% in patching mode and 0.4% in run-time monitoring mode.</p><p dir="ltr">In summary, this dissertation provides invaluable solutions that equip cybersecurity professionals to enhance APT attack investigation, enabling them to identify and comprehend complex attacks with heightened accuracy. Moreover, these solutions significantly bolster the safety and security of ICS infrastructure, effectively protecting critical systems and strengthening defenses against cyber-physical attacks, thereby contributing substantially to the field of cybersecurity.</p>

In this dissertation research, we design and analyze resilient cyber-physical systems (CPSs) under high network dynamics, adversarial attacks, and various uncertainties. We focus on three key system attributes to build resilient CPSs by developing a suite of the autonomous cyber defense mechanisms. First, we consider network adaptability to achieve the resilience of a CPS. Network adaptability represents the network ability to maintain its security and connectivity level when faced with incoming attacks. We address this by network topology adaptation. Network topology adaptation can contribute to quickly identifying and updating the network topology to confuse attacks by changing attack paths. We leverage deep reinforcement learning (DRL) to develop CPSs using network topology adaptation. Second, we consider the fault-tolerance of a CPS as another attribute to ensure system resilience. We aim to build a resilient CPS under severe resource constraints, adversarial attacks, and various uncertainties. We chose a solar sensor-based smart farm as one example of the CPS applications and develop a resource-aware monitoring system for the smart farms. We leverage DRL and uncertainty quantification using a belief theory, called Subjective Logic, to optimize critical tradeoffs between system performance and security under the contested CPS environments. Lastly, we study system resilience in terms of system recoverability. The system recoverability refers to the system's ability to recover from performance degradation or failure. In this task, we mainly focus on developing an automated intrusion response system (IRS) for CPSs. We aim to design the IRS with effective and efficient responses by reducing a false alarm rate and defense cost, respectively. Specifically, We build a lightweight IRS for an in-vehicle controller area network (CAN) bus system operating with DRL-based autonomous driving. / Doctor of Philosophy / In this dissertation research, we design and analyze resilient cyber-physical systems (CPSs) under high network dynamics, adversarial attacks, and various uncertainties. We focus on three key system attributes to build resilient CPSs by developing a suite of the autonomous cyber defense mechanisms. First, we consider network adaptability to achieve the resilience of a CPS. Network adaptability represents the network ability to maintain its security and connectivity level when faced with incoming attacks. We address this by network topology adaptation. Network topology adaptation can contribute to quickly identifying and updating the network topology to confuse attacks by changing attack paths. We leverage deep reinforcement learning (DRL) to develop CPSs using network topology adaptation. Second, we consider the fault-tolerance of a CPS as another attribute to ensure system resilience. We aim to build a resilient CPS under severe resource constraints, adversarial attacks, and various uncertainties. We chose a solar sensor-based smart farm as one example of the CPS applications and develop a resource-aware monitoring system for the smart farms. We leverage DRL and uncertainty quantification using a belief theory, called Subjective Logic, to optimize critical tradeoffs between system performance and security under the contested CPS environments. Lastly, we study system resilience in terms of system recoverability. The system recoverability refers to the system's ability to recover from performance degradation or failure. In this task, we mainly focus on developing an automated intrusion response system (IRS) for CPSs. We aim to design the IRS with effective and efficient responses by reducing a false alarm rate and defense cost, respectively. Specifically, We build a lightweight IRS for an in-vehicle controller area network (CAN) bus system operating with DRL-based autonomous driving.