abstract: Testing and Verification of Cyber-Physical Systems (CPS) is a challenging problem. The challenge arises as a result of the complex interactions between the components of these systems: the digital control, and the physical environment. Furthermore, the software complexity that governs the high-level control logic in these systems is increasing day by day. As a result, in recent years, both the academic community and the industry have been heavily invested in developing tools and methodologies for the development of safety-critical systems. One scalable approach in testing and verification of these systems is through guided system simulation using stochastic optimization techniques. The goal of the stochastic optimizer is to find system behavior that does not meet the intended specifications. In this dissertation, three methods that facilitate the testing and verification process for CPS are presented: 1. A graphical formalism and tool which enables the elicitation of formal requirements. To evaluate the performance of the tool, a usability study is conducted. 2. A parameter mining method to infer, analyze, and visually represent falsifying ranges for parametrized system specifications. 3. A notion of conformance between a CPS model and implementation along with a testing framework. The methods are evaluated over high-fidelity case studies from the industry. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2017

Leading industrial nations invest to try to increase advanced manufacturing and innovation to catch up in a free-market world. One common vision for these investments has been Industry 4.0. In short can this topic be described as the internet moving into the industry. The concept is relatively new and has become one of the most discussed topics during the last couple of years in many manufacturing conferences. However, the industry is so far lacking a clear definition of the concept, and much of the focus is on laboratory experiments rather than industrial applications. The research that has been conducted so far has not involved the process industry, where this thesis will operate. The purpose of this study is to contribute to the understanding of how Industry 4.0 can be related to the pulp and paper industry by contextualizing the concept, and function as a “door-opener” for further research. Potentials, sustainability aspects and a concrete example has been used to comprehend this. The study has been designed with a qualitative approach through semi-structured interviews at the specific case company Stora Enso, Skoghall. As the concept of Industry 4.0 not yet has an explicit definition the start of the thesis was therefore to create a theoretical framework of the theory to relate to during the rest of the study. The findings of the research show that Industry 4.0 in the pulp and paper industry focuses on Availability through possibilities of prediction and response improvement. The concept should emphasis on keeping the production ongoing with fever break-downs and increased Quality of the products. Communication improvements will be essential in reaching the new industry level, with connecting the whole plant as a crucial part. The thesis contributes with a first insight to what Industry 4.0 will mean to the pulp and paper industry and how it contextualizes in the sector. / Framträdande industriella nationer investerar idag för att öka den avancerade tillverkningen och antalet innovationer för att hänga med i den fria marknaden. En gemensam vision för de här investeringarna är Industri 4.0. I korta drag kan det beskrivas som att internet flyttar in i industrin. Konceptet är relativt nytt och har kommit att bli ett av de mest diskuterade områdena under de senaste åren på tillverkningskonferenser. Industrin saknar dock en tydlig definition av konceptet, och mycket av fokus gällande ämnet hamnar på laborationsexperiment istället för praktiska applikationer. Vidare finns det ett behov av att titta på hur detta ser ut i processindustrin eftersom detta ännu inte granskats, vilket kommer vara området för uppsatsen. Syftet med denna studie är att bidra till förståelsen för hur Industri 4.0 kan relateras till pappersindustrin genom att kontextualisera konceptet och verkasom en ”dörr-öppnare” för vidare forskning. Möjligheter, hållbarhetsaspekter och ett konkret exempel har använts för att skapa förståelse för detta. Studien har designats med ett kvalitativt angreppssätt med semi-strukturerade intervjuer på det specifika fallet, Stora Enso Skoghall. Eftersom konceptet Industri 4.0 ännu saknar en tydlig definition började studien med att skapa ett teoretiskt ramverk för att kunna relatera till detta genom arbetet. Resultaten visar att Industri 4.0 i pappersindustrin fokuserar på Tillgänglighet genom ökade prediktions- och åtgärdsmöjligheter. Konceptet borde lägga vikt vid att hålla igång produktionen med färre avbrott och ökad Kvalitet på produkterna. Kommunikationsförbättringar kommer bli essentiella för att nå den nya nivån av industri, där integrationen av hela fabriken kommer spela en stor roll. Examensarbetet bidrar med en första inblick i vad Industri 4.0 kommer betyda för pappersindustrin och hur det kontextualiseras i branschen.

abstract: Critical infrastructures in healthcare, power systems, and web services, incorporate cyber-physical systems (CPSes), where the software controlled computing systems interact with the physical environment through actuation and monitoring. Ensuring software safety in CPSes, to avoid hazards to property and human life as a result of un-controlled interactions, is essential and challenging. The principal hurdle in this regard is the characterization of the context driven interactions between software and the physical environment (cyber-physical interactions), which introduce multi-dimensional dynamics in space and time, complex non-linearities, and non-trivial aggregation of interaction in case of networked operations. Traditionally, CPS software is tested for safety either through experimental trials, which can be expensive, incomprehensive, and hazardous, or through static analysis of code, which ignore the cyber-physical interactions. This thesis considers model based engineering, a paradigm widely used in different disciplines of engineering, for safety verification of CPS software and contributes to three fundamental phases: a) modeling, building abstractions or models that characterize cyberphysical interactions in a mathematical framework, b) analysis, reasoning about safety based on properties of the model, and c) synthesis, implementing models on standard testbeds for performing preliminary experimental trials. In this regard, CPS modeling techniques are proposed that can accurately capture the context driven spatio-temporal aggregate cyber-physical interactions. Different levels of abstractions are considered, which result in high level architectural models, or more detailed formal behavioral models of CPSes. The outcomes include, a well defined architectural specification framework called CPS-DAS and a novel spatio-temporal formal model called Spatio-Temporal Hybrid Automata (STHA) for CPSes. Model analysis techniques are proposed for the CPS models, which can simulate the effects of dynamic context changes on non-linear spatio-temporal cyberphysical interactions, and characterize aggregate effects. The outcomes include tractable algorithms for simulation analysis and for theoretically proving safety properties of CPS software. Lastly a software synthesis technique is proposed that can automatically convert high level architectural models of CPSes in the healthcare domain into implementations in high level programming languages. The outcome is a tool called Health-Dev that can synthesize software implementations of CPS models in healthcare for experimental verification of safety properties. / Dissertation/Thesis / Ph.D. Computer Science 2012

abstract: The cyber-physical systems (CPS) are emerging as the underpinning technology for major industries in the 21-th century. This dissertation is focused on two fundamental issues in cyber-physical systems: network interdependence and information dynamics. It consists of the following two main thrusts. The first thrust is targeted at understanding the impact of network interdependence. It is shown that a cyber-physical system built upon multiple interdependent networks are more vulnerable to attacks since node failures in one network may result in failures in the other network, causing a cascade of failures that would potentially lead to the collapse of the entire infrastructure. There is thus a need to develop a new network science for modeling and quantifying cascading failures in multiple interdependent networks, and to develop network management algorithms that improve network robustness and ensure overall network reliability against cascading failures. To enhance the system robustness, a "regular" allocation strategy is proposed that yields better resistance against cascading failures compared to all possible existing strategies. Furthermore, in view of the load redistribution feature in many physical infrastructure networks, e.g., power grids, a CPS model is developed where the threshold model and the giant connected component model are used to capture the node failures in the physical infrastructure network and the cyber network, respectively. The second thrust is centered around the information dynamics in the CPS. One speculation is that the interconnections over multiple networks can facilitate information diffusion since information propagation in one network can trigger further spread in the other network. With this insight, a theoretical framework is developed to analyze information epidemic across multiple interconnecting networks. It is shown that the conjoining among networks can dramatically speed up message diffusion. Along a different avenue, many cyber-physical systems rely on wireless networks which offer platforms for information exchanges. To optimize the QoS of wireless networks, there is a need to develop a high-throughput and low-complexity scheduling algorithm to control link dynamics. To that end, distributed link scheduling algorithms are explored for multi-hop MIMO networks and two CSMA algorithms under the continuous-time model and the discrete-time model are devised, respectively. / Dissertation/Thesis / Ph.D. Electrical Engineering 2012

State estimation problem for power systems has long been a fundamental issue that demands a variety of methodologies dependent on the system settings. With recent introduction of advanced devices of phasor measurement units (PMUs) and dedicated communication networks, the infrastructure of power grids has been greatly improved. Coupled with the infrastructure improvements are three emerging issues for the state estimation problems, namely, the coexistence of both traditional and PMU measurements, the incomplete information resulting from delayed, missing and quantized measurements due to communication constraints, and the cyber-attacks on the communication channels. Three challenging problems are faced when dealing with the three issues in the state estimation program of power grids: 1) how to include the PMU measurements in the state estimator design, 2) how to account for the phenomena of incomplete information occurring in the measurements and design effective state estimators resilient to such phenomena, and 3) how to identify the system vulnerability in state estimation scheme and protect the estimation system against cyber-attacks. In this thesis, with the aim to solve the above problems, we develop several state estimation algorithms which tackle the issues of mixed measurements and incomplete information, and examine the cyber-security of the dynamic state estimation scheme. • To improve the estimation performance of power grids including PMU measurements, a hybrid extended Kalman filter and particle swarm optimization algorithm is developed, which has the advantages of being scalable to the numbers of the installed PMUs and being compatible with existing dynamic state estimation software as well. • Two kinds of network-induced phenomena, which leads to incomplete information of measurements, are considered. Specifically, the phenomenon of missing measurements is assumed to occur randomly and the missing probability is governed by a random variable, and the quantized nonlinear measurement model of power systems is presented where the quantization is assumed to be of logarithmic type. Then, the impact of the incomplete information on the overall estimation performance is taken into account when designing the estimator. Specifically, a modified extended Kalman filter is developed which is insensitive to the missing measurements in terms of acceptable probability, and a recursive filter is designed for the system with quantized measurements such that an upper bound of the estimation error is guaranteed and also minimized by appropriately designing the filter gain. • With the aim to reduce or eliminate the occurrence of the above-mentioned network-induced phenomena, we propose an event-based state estimation scheme with which communication transmission from the meters to the control centre can be greatly reduced. To ensure the estimation performance, we design the estimator gains by solving constrained optimization problems such that the estimation error covariances are guaranteed to be always less than a finite upper bound. • We examine the cyber-security of the dynamic state estimation system in power grids where the adversary is able to inject false data into the communication channels between PMUs and the control centre. The condition under which the attacks cause unbounded estimation errors is found. Furthermore, for system that is vulnerable to cyber-attacks, we propose a system protection scheme through which only a few (rather than all) communication channels require protection against false data injection attacks.

Cyber-Physical-Human Systems (CPHSs) are the integration, mostly focused on the interactions, of cyber, physical and humans elements that work together towards the achievement of the objectives of the system. Users continuously rely on CPHSs to fulfil personal goals, thus becoming active, relevant, and necessary components of the designed system. The gap between humans and technology is getting smaller. Users are increasingly demanding smarter and personalized applications, capable of understanding and acting upon changing situations. However, humans are highly dynamic, their decisions might not always be predictable, and they expose themselves to unforeseeable situations that might impact their interactions with their physical and cyber elements. The problem addressed in this dissertation is the support of CPHSs' user-centric requirements at runtime. Therefore, this dissertation focuses on the investigation of runtime models and infrastructures for: (1) understanding users, their personal goals and changing situations, (2) causally connecting the cyber, physical and human components involved in the achievement of users' personal goals, and (3) supporting runtime adaptation to respond to relevant changes in the users' situations. Situation-awareness and runtime adaptation pose significant challenges for the engineering of user-centric CPHSs. There are three challenges associated with situation-awareness: first, the complexity and dynamism of users' changing situations require specifications that explicitly connect users with personal goals and relevant context. Second, the achievement of personal goals entails comprehensive representations of user's tasks and sequences and measurable outcomes. Third, situation-awareness implies the analysis of context towards an understanding of users' changing conditions. Therefore, there is a need for representations and reasoning techniques to infer emerging situations. There are three challenges associated with runtime adaptation: first, the dynamic nature of CPHSs and users require runtime models to make explicit the components of CPHSs and their interactions. Second, the definition of architectural and functional requirements of CPHSs to support runtime user-centric awareness and adaptation. Finally, the design and implementation of runtime adaptation techniques to support dynamic changes in the specification of the CPHSs' runtime models. The four contributions of this dissertation add to the body of knowledge for the development of smart applications centred around the achievement of users' personal goals. First, we propose a definition and architectural design for the implementation of user-centric smart cyber-physical-human applications (UCSAs). Our design proposes a context-aware self-adaptive system supported by a runtime infrastructure to manage CRUD operations. Second, we propose two models at runtime (MARTs): (1) our Galapagos Metamodel, which defines the concepts of a UCSA; and (2) our Galapagos Model, which supports the specification of evolving tasking goals, personal interactions, and the relevant contexts. Third, we propose our operational framework, which defines model equivalences between human-readable and machine-readable, available runtime operations and semantics, to manage runtime operations on MARTs. Finally, we propose our processing infrastructure for models at runtime (PRIMOR), which is a component-based system responsible for providing reading access from software components to the MARTs, executing model-related runtime operations, and managing the propagation of changes among interconnected MARTs and their realities. To evaluate our contributions, we conducted a literature review of models and performed a qualitative analysis to demonstrate the novelty of our approach by comparing it with related approaches. We demonstrated that our models satisfy MARTs characteristics, therefore making them proper models at runtime. Furthermore, we performed an experimental analysis based on our case study on online grocery shopping for the elderly. We focused our analysis on the runtime operations specified in the framework as supported by the corresponding MART (accuracy and scalability), and our infrastructure to manage runtime operation and growing MARTs (performance). / Graduate

The existing closed-loop sensor networks are based on architectures that are designed and implemented for one specific application and require dedicated sensing and computational resources. This prevents the sharing of these networks. In this work, we propose an architecture of virtualization to allow sharing of closed-loop sensor networks. We also propose a scheduling approach that will manage requests from competing applications and evaluate their impact on system utilization against utilization achieved by more traditional, dedicated sensor networks. These algorithms are evaluated through trace-driven simulations, where the trace data is taken from CASA’s closed-loop weather radar sensor network. Results from this evaluation show that the proposed scheduling algorithms applied in a shared network result in cost savings, that are the result of being able to multiplex applications onto a single network as opposed to running each application on an dedicated sensor network.

<div>Cyber-Physical Systems (CPSs) consist of physical and computational components usually interconnected through the internet. This type of systems have found applications in robotic surgery, smart medical services, driverless cars, smart power grids as well as in modern homes and offices. For a CPS to function properly, a reliable and secure communications between the system physical and cyber elements is of utmost importance. Malicious attacks during control signals and output measurements transmission between the physical plant and the control center must be addressed, which is the main research problem studied in this thesis.</div><div><br></div><div>A novel robust observer was proposed to synthesize a combined controller-observer compensator for a class of CPSs with sparse malicious attacks and arbitrary disturbances. The compensator consists of a controller, a norm approximator, and an unknown input observer (UIO). The proposed observer was compared with a norm-based observer given in the literature to show its advantage. To further enhance the proposed observer's performance against arbitrary disturbances, design methods were given that use fictitious output measurements and error correcting code (ECC) approach. The design of the UIO was extended to a bank of UIOs in order to improve the observer's performance against sparse malicious attacks.</div><div><br></div><div>The proposed observer can be used in the design of UIO-based fault detection and isolation (FDI) algorithms as well as in the distributed fault-tolerant control of large-scale interconnected systems. The results of this thesis can be applied to the design of controller-observer compensators for CPSs with modeling uncertainties.</div>

Endpoint devices are integral in the realisation of any industrial cyber-physical system (ICPS) application. As part of the work of promoting safer and more secure industrial Internet of Things (IIoT) networks and devices, the Industrial Internet Consortium (IIC) and the OpenFog Consortium have developed security framework specifications detailing security techniques and technologies that should be employed during the design of an IIoT network. Previous work in establishing cryptographic services on platforms intended for wireless sensor networks (WSN) and the Internet of Things (IoT) has concluded that security mechanisms cannot be implemented using software libraries owing to the lack of memory and processing resources, the longevity requirements of the processor platforms, and the hard real-time requirements of industrial operations. Over a decade has passed since this body of knowledge was created, however, and IoT processors have seen a vast improvement in the available operating and memory resources while maintaining minimal power consumption. This study aims to update the body of knowledge regarding the provision of security services on an IoT platform by conducting a detailed analysis regarding the performance of new generation IoT platforms when running software cryptographic services. The research considers execution time, power consumption and memory occupation and works towards a general, implementable design of a secure, IIoT edge device. This is realised by identifying security features recommended for IIoT endpoint devices; identifying currently available security standards and technologies for the IIoT; and highlighting the trade-offs that the application of security will have on device size, performance, memory requirements and monetary cost. / Dissertation (MSc)--University of Pretoria, 2017. / Electrical, Electronic and Computer Engineering / MSc / Unrestricted

Smartness of technical systems relies also on appropriate actuators and sensors. Different to the prevalent definition of smartness to be embedded machine intelligence, in this paper elegance and simplicity of solutions is postulated be a more uniform and useful characterization. This is discussed in view of the current trends towards cyber physical systems and the role of components and subsystems, as well as of models for their effective realization. Current research on actuators and sensing in the fluid power area has some emphasis on simplicity and elegance of solution concepts and sophisticated modeling. This is demonstrated by examples from sensorless positioning, valve actuation, and compact hydraulic power supply.