Title Participants Abstract "Digital twins for continuous deployment in model-based systems engineering of cyber-physical systems" "Joost Mertens, Joachim Denil" "Cyber-Physical Systems (CPS) are required to operate over a longer lifetime. As such, their requirementscan change, requiring updates to the system to be be rolled out continuously (Continuous Deployment)throughout the system’s lifetime. The DevOps methodology provides a structured, quality assuringway to do so, as it integrates Development and Operations of a system in a continuous cycle. DevOpsis generally applied in software development, however in the design of CPS, which follows a Model-Based Systems Engineering (MBSE) approach, it is not. This is because many challenges remain in theapplication of DevOps in MBSE. Our focus is on creating the foundations for continuous deployment ofsafety-critical CPS using digital twins of the CPS." "Optimizing simulated-assisted verification of safety properties of cyber-physical systems" "Mehrdad Moradi" "The validation of the safety properties of Cyber-Physical Systems (CPS) requires tremendous effort, as the complexity of cyber-physical systems is increasing. A well-known approach for the safety validation of CPS is Fault Injection (FI). Fault injection is a testing technique that aids in understanding how the system behavioral when stressed in an unusual way. The goal of fault injection is to find a catastrophic fault that can cause the system to fail by injecting faults into it. These catastrophic faults are less likely to occur, and finding them requires tremendous labor and cost, as fault space is enormous and multidimensional. Therefore, traditional fault injection methods are not effective in terms of number of found faults and severity of them. In this thesis, we utilize simulation-based fault injection in the system models, which enables the test engineer to identify the fault in the early phase of system development. We first performed a systematic literature review to categorize the existing methods, fault models, metrics for system models. Then, we propose a fault injection method to inject faults into the MATLAB/Simulink model as white-box models using model transformation. We also worked on the fault injection in black-box models, which is based on Functional Mock-up Interface (FMI). Next, we investigated multiple methods to increase the efficiency (in terms of total number of critical faults and run time execution) of fault injection using sensitivity analysis, reinforcement learning (RL), and the Generative Adversarial Network (GAN). These methods utilize high-level domain knowledge of the model under test to set up the fault injection simulation. The proposed methods automatically configure faults in the model under test and find catastrophic faults that can violate the safety properties of the model in the early stage of system development. We compared the proposed method (RL-based and GAN-based) with random-based fault injection, and our proposed method outperformed random-based fault injection in terms of the severity or number of faults found. We also demonstrated our method in Hazard Analysis and Risk Assessment (HARA), specified in ISO 26262 (functional safety standard in automotive), identifies malfunctions that could lead to hazards, and rates their risks." "Teaching the fundamentals of the modelling of cyber-physical systems" "Yentl Van Tendeloo, Hans Vangheluwe" "Current Cyber-Physical Systems are becoming too complex to model and simulate using the usual approaches. This complexity is not only due to a large number of components, but also by the increasing diversity of components and problem aspects. In this paper, we report on over a decade of experience in teaching the modelling and simulation of complex Cyber-Physical Systems, at both McGill University, and the University of Antwerp. We tackle complexity through the use of multiple formalisms, each specialized for a specific domain and problem. Modelling and simulation is used throughout the complete development process. Students are introduced to all fundamental problems encountered when modelling and simulating Cyber-Physical Systems. Students will be able to both create a meaningful model in the formalism, as well as create a minimal simulation kernel for it. Our approach results in a deep understanding of the formalism, particularly the advantages and disadvantages, without focussing on tool-specific issues. In the end, students are capable of choosing the most appropriate formalism for a problem, and making an informed decision on which tool to use. Due to the variety of formalisms, students can successfully apply the gained knowledge in a wide spectrum of domains." "Co-optimization of cyber-physical systems" "Yon Vanommeslaeghe" "The term cyber-physical system (CPS) is generally used to describe a system that integrates software (cyber) and physical components, allowing this software to monitor and interact with the physical world through sensors and actuators. Due to the nature of these CPS, i.e., the combination of the “cyber” and the physical, their design and development inherently involves engineers from multiple engineering domains. As these systems become more complex, so does their design and development. Not only do engineers need to take into account more and more design parameters and objectives, and their interdependencies within their own domain, but the different engineering domains involved in the design also become more and more intertwined. While this introduces new challenges throughout the development process, in this dissertation, we focus on three specific stages: (i) detailed design, (ii) system integration, and (iii) system validation. First, regarding the detailed design stage, we consider the increasing number of dependencies within and across different engineering domains. We demonstrate how ontologies can be used to model the dependencies between design parameters and objectives, both within and across different engineering domains, and how this information can be used to manually or automatically determine efficient design space exploration (DSE) strategies for a system under design. Second, regarding the system integration stage, we explicitly consider the embedded deployment of control or monitoring algorithms. Here, we demonstrate how co-simulation can be used to evaluate the impact of embedded platform effects on application behavior earlier in the development process. We present an approach to co-simulate embedded platform models, modeled using the discrete event system specification (DEVS) formalism, and application models, contained in functional mock-up units (FMUs), focusing on multi-core specific aspects, such as shared resources. Finally, a common way of managing the complexity of CPS design and development is to employ model-based systems engineering (MBSE) techniques. However, models are always an abstraction of the real-world systems they represent, which introduces uncertainty at the model level. Similarly, variations in real-world system parameters can introduce additional uncertainty. This complicates system validation, as this uncertainty can cause discrepancies in system behavior between simulation and the real world. Regarding this, we demonstrate how uncertainty affects the predicted system behavior and subsequent real-world validation of a CPS, (co-)optimized using a model-based DSE approach. Based on this, we present a possible process for model calibration, design-space exploration, and system validation, which specifically takes into account uncertainty." "Multi-paradigm modelling of cyber-physical systems" "Hans Vangheluwe" "The networking of multi-physics (mechanical, electical, hydraulic, biochemical, ...) with computational systems (control systems, signal processing, logical inferencing, planning, ... ) processes, interacting with often uncertain environments, with human actors, in a socio-economic context, leads to so-called Cyber-Physical Systems (CPS). Cyber-physical systems are reaching a hitherto unseen level of complexity. To date, no unifying theory nor systematic design methods, techniques and tools exist for such systems. Individual (mechanical, electrical, network or software) engineering disciplines only offer partial solutions. Multi-paradigm Modelling (MPM) proposes to model every part and aspect of such complex systems explicitly, at the most appropriate level(s) of abstraction, using the most appropriate modelling formalism(s). This includes the explicit modelling of the often complex engineering workflows. Modelling language engineering, including model transformation languages, and the study of the semantics of these languages, are used to realize MPM. MPM is seen as an effective answer to the challenges of designing CPS. This presentation introduces some of the challenges of collaborative development of CPS as well as possible multi-paradigm modelling solutions such as (in-)consistency management and cosimulation." "Validity frames for the model-based development of cyber-physical systems" "Engineering Cyber-Physical Systems has become increasingly complex, e.g. due to the vastly increasing performance and safety demands. This makes it harder to correctly develop such systems. One way to tackle this development complexity, is adhering to Model-Based Systems Engineering (MBSE) approaches, which enable the use of (system) models throughout almost the complete engineering process. Within MBSE, physics-based models, models representing the physical behavior of the system, are commonly used. The value of such models is tightly coupled to how well the model reflects the system’s physical behavior and the correct model use, within it’s known valid range. If models are used outside this validity range, the produced model behavior is untrustworthy, as we do not know if it’s correct, slightly off or even completely wrong. By ignoring a model’s validity, we cannot reason about the trustworthiness off the produced model behavior, making them unusable for further engineering activities such as preliminary system analysis. Within this dissertation, we point the importance of the model validity and propose the Validity Frame concept as enabler for explicit model validity reasoning and usage. This theoretical Validity Frame concept is practically elaborated and the use is demonstrated on different academic applications." "Ontological reasoning for consistency in the design of cyber-physical systems" "Ken Vanherpen, Istvan David, Paul De Meulenaere, Pieter J. Mosterman, Martin Torngren, Ahsan Qamar, Hans Vangheluwe" "The design of Cyber-Physical Systems (CPS) involves a multitude of stakeholders. Each of these stakeholders has a specific view on the system under design. Unfortunately, when designers create artefacts in their different views in a concurrent manner, the integration of the different views may reveal inconsistencies. This leads to time consuming, iterative design processes where inconsistencies are resolved, in turn possibly creating new ones. It is hence necessary to reason explicitly about the view-specific properties that depend on, and influence properties of other views. This enables consistency during integration and reduces the development time and effort. In this paper we formalise the interrelationships between the different views, in the context of different design processes, to allow designers to meaningfully and efficiently manage inconsistencies. Our formalisation introduces ontological domain properties and their relations as the link between the view-specific properties used by the stakeholders. Thus, our approach combines the state of the art of Model-Based Systems Engineering (MBSE) and Semantic Web. The relevance of this approach is demonstrated by means of a motivating example." "Integrated process safety and process security risk assessment of industrial cyber-physical systems in chemical plants" "Shuaiqi Yuan, Ming Yang, Genserik Reniers" "Aligned with the development needs of Industry 4.0, industrial cyber-physical systems (ICPSs) are widely applied to chemical facilities to facilitate so-called intelligent production processes. Meanwhile, emerging cyber-tophysical (C2P) risks are introduced due to the vulnerability of ICPSs to cyberattacks. An integrated safety and security risk assessment of chemical facilities equipped with industrial cyber-physical systems becomes challenging, particularly in performing a probabilistic/quantitative risk assessment. Targeting this gap, this study develops a systematic approach to construct accident scenarios concerning both safety hazards and security threats and performs a probabilistic risk assessment of chemical facilities considering the interdependency between safety-associated events and security-associated events. In the proposed approach, bow-tie technique is used to perform a safety risk analysis, and meanwhile, the possible dangerous scenarios caused by physical attacks and C2P attacks are also identified and integrated into the bow-tie diagram. Particularly, attack impact modeling of C2P attacks helps to identify dangerous attack modes, and a time-to-compromise (TTC) based method is used to quantify the vulnerability of ICPSs to C2P attacks. Then, a Bayesian network (BN) model is developed to perform an integrated safety and security risk analysis. An illustrative case study is used in this study to give guidance on performing integrated safety and security risk assessment of ICPSs and validate the feasibility of the proposed approach." "Development of autonomous cyber-physical systems using intelligent agents and LEGO technology" "Burak Karaduman, Geylani Kardas" "Cyber-physical systems (CPS) have attracted various embedded technologies and researchers from low-level where the practitioners implement their systems using high-level programming languages where the multiple paradigms also overlap. As CPSs merge with numerous disciplines, heterogeneity emerges, and increasing complexity requires abstractions to program CPSs. Moreover, it is feasible to benefit from the suitable technologies that facilitate programming the physical parts of CPS. LEGO might prefer creating concrete use cases as composable technology, while embedded technology allows running the software to establish CPS. However, workflow, architecture, design alternatives, and abstraction should be defined to achieve this combination. Once low-level control is merged with agent-based programming, then this infrastructure can pave the way for applying intelligent-based solutions to tackle the high-level problems of CPS. This chapter introduces the architecture, a development workflow, and a set of agent-based CPSs to describe how LEGO technology-based CPS can be developed where software agents are integrated into the design, conforming to the provided architecture." "Applications of model-driven engineering in cyber-physical systems" "Mustafa Abshir Mohamed, Moharram Challenger, Geylani Kardas" "Engineers face significant challenges in developing cyber-physical systems (CPS) due to their heterogeneous nature, i.e. the need for knowledge and skills from a wide range of academic and industrial disciplines, the integration of the artifacts of these disciplines and fields, and the difficulty of maintaining such heterogeneous artifacts should be taken into account. The development of CPS mostly needs a unified methodology that permits efficient raise of the abstraction level to overcome issues of heterogeneity induced by the multidisciplinary nature of the system. Model-driven engineering (MDE) is believed to be an alternative solution to overcome the challenges faced while developing CPS. This paper presents a systematic mapping study on using the MDE paradigm in CPS development and management. 140 research papers published during the period 2010–2018 are evaluated. The study mainly enables to find out the followed approaches when applying MDE for CPS, addressed CPS challenges, application domains and presented case studies. Results showed that the number of publications in this field is continuously increasing in recent years. Results also showed that metamodeling and model-based approaches are mostly adopted by the researchers affiliated to Europe, while DSL-based approach is adopted mostly by USA affiliated researchers. Only 45% of the studies consider a specific CPS application domain in which Smart Manufacturing is the most addressed domain followed by Critical Infrastructure, Health Care and Medicine. Moreover, the majority of the studies present case studies as the main evaluation method for the proposed MDE solutions. Conducting empirical evaluations is mostly missing. The results also revealed that various CPS challenges are addressed, and the most addressed ones are the complexity and interoperability aspects of CPS. Reporting on what previous researches have accomplished, as well as current research efforts and open challenges related to this field can guide researchers and developers in their further work on CPS design and implementation."