Multi-paradigm modelling for cyber–physical systems: a descriptive framework

The complexity of cyber–physical systems (CPSS) is commonly addressed through complex workflows, involving models in a plethora of different formalisms, each with their own methods, techniques, and tools. Some workflow patterns, combined with particular types of formalisms and operations on models in these formalisms, are used successfully in engineering practice. To identify and reuse them, we refer to these combinations of workflow and formalism patterns as modelling paradigms. This paper proposes a unifying (Descriptive) Framework to describe these paradigms, as well as their combinations. This work is set in the context of Multi-Paradigm Modelling (MPM), which is based on the principle to model every part and aspect of a system explicitly, at the most appropriate level(s) of abstraction, using the most appropriate modelling formalism(s) and workflows. The purpose of the Descriptive Framework presented in this paper is to serve as a basis to reason about these formalisms, workflows, and their combinations. One crucial part of the framework is the ability to capture the structural essence of a paradigm through the concept of a paradigmatic structure. This is illustrated informally by means of two example paradigms commonly used in CPS: Discrete Event Dynamic Systems and Synchronous Data Flow. The presented framework also identifies the need to establish whether a paradigm candidate follows, or qualifies as, a (given) paradigm. To illustrate the ability of the framework to support combining paradigms, the paper shows examples of both workflow and formalism combinations. The presented framework is intended as a basis for characterisation and classification of paradigms, as a starting point for a rigorous formalisation of the framework (allowing formal analyses), and as a foundation for MPM tool development

Reliability and security in wellbeing monitoring embedded systems

Dissertação para obtenção do Grau de Mestre em Engenharia Informática e de ComputadoresAo longo dos últimos anos, a fiabilidade e a segurança dos sistemas embebidos utilizados em áreas críticas, como a saúde e o sector automóvel, têm suscitado um interesse crescente na comunidade científica e ganho maior consciencialização entre o público em geral. Esta tese aborda a modelação e a implementação de uma arquitetura software fiável e segura para um sistema embebido focado na aquisição e processamento de sinais fisiológicos, em particular o eletrocardiograma (ECG). O trabalho realizado visou o CardioWheel, um projeto em curso desenvolvido pela CardioID Technologies, destinado a aplicações nas áreas da saúde e do automóvel. As particularidades destas áreas quanto aos seus requisitos de segurança e proteção dos utilizadores servem de caso de estudo para mostrar as vantagens da arquitetura desenvolvida. Assim, no estudo realizado foi feito o levantamento dos requisitos do sistema que foram utilizados para projetar a máquina de estados da arquitetura em UML, a qual foi validada formalmente utilizando a ferramenta Uppaal e o modelo de autómatos finitos temporizados. Também foi feita uma análise de ameaças à arquitetura para validar os aspetos relacionados com a segurança. A arquitetura foi desenvolvida para microcontroladores ESP32 usando o ecossistema ESP-IDF e o FreeRTOS, para o que foram consideradas camadas independentes de hardware. A camada de comunicação é baseada no protocolo Bluetooth Low Energy (BLE) e permite a transmissão dos dados do nó final para um gateway e, posteriormente, para um servidor na nuvem. A operação de atualização de firmware usando o componente Over-The-Air (OTA) foi também implementada e validada quanto à sua segurança. A arquitetura foi, inicialmente, avaliada e validada usando um protótipo laboratorial. Posteriormente, foi utilizada para realizar uma pequena série de produção do CardioWheel em que se utilizaram as estratégias de validação propostas no contexto do projeto ESCEL KDT Valu3s. Também foi realizado um ensaio pré-médico no Hospital de Santa Marta usando o CardioWheel com a arquitetura proposta, que permitiu validar a sua fiabilidade e capacidades quando comparado com um eletrocardiógrafo clínico.Recently, the reliability and cybersecurity aspects of embedded systems for critical domains, such as health and automotive, has increased interest in the research community and awareness to the general public. This thesis addresses the modelling and the implementation of a reliable and secure software architecture for an embedded system aimed at the acquisition and processing of physiological signals, in particular the electrocardiogram (ECG). The work focused CardioWheel, an ongoing project developed by CardioID Technologies, targeting health and automotive applications. These domains demand special requirements for safety and security, and serve as a showcase for the proposed architecture. Accordingly, suitable requirements were first established and the architecture state machine was developed using UML and formally validated using Uppaal and Timed Automata modelling. Then, the threat analysis of the architecture was conducted. Finally, the implementation was realized for an ESP32 microcontroller using the FreeRTOS, the ESP-IDF ecosystem, and specially developed hardware independent layers. The communication layer is based on Bluetooth Low Energy (BLE) and allows the transmission of the data from the end-node to a gateway and finally to the cloud. The system has a Over-The-Air (OTA) component that enables the update of the firmware and the security of this operation was also validated. The proposed architecture was firstly validated using a laboratory prototype. Then, it was deployed to build a small production series of CardioWheel incorporating validation strategies proposed within the context of the ESCEL KDT Valu3s project. Also, a pre-medical trial was conducted at the Hospital de Santa Marta, confirming the reliability and capabilities of our system against a clinical ground-truth.N/

Towards a new methodology for design, modelling, and verification of reconfigurable distributed control systems based on a new extension to the IEC 61499 standard

In order to meet user requirements and system environment changes, reconfigurable control systems must dynamically adapt their structure and behaviour without disrupting system operation. IEC 61499 standard provides limited support for the design and verification of such systems. In fact, handling different reconfiguration scenarios at runtime is difficult since function blocks in IEC 61499 cannot be changed at run-time. Hence, this thesis promotes an IEC 61499 extension called reconfigurable function block (RFB) that increases design readability and smoothly switches to the most appropriate behaviour when a reconfiguration event occurs. To ensure system feasibility after reconfiguration, in addition to the qualitative verification, quantitative verification based on probabilistic model checking is addressed in a new RFBA approach. The latter aims to transform the designed RFB model automatically into a generalised reconfigurable timed net condition/event system model (GRTNCES) using a newly developed environment called RFBTool. The GR-TNCES fits well with RFB and preserves its semantic. Using the probabilistic model checker PRISM, the generated GR-TNCES model is checked using defined properties specified in computation tree logic. As a result, an evaluation of system performance and an estimation of reconfiguration risks are obtained. The RFBA methodology is applied on a distributed power system case study.Dynamische Anforderungen und Umgebungen erfordern rekonfigurierbare Anlagen und Steuerungssysteme. Rekonfiguration ermöglicht es einem System, seine Struktur und sein Verhalten an interne oder externe Änderungen anzupassen. Die Norm IEC 61499 wurde entwickelt, um (verteilte) Steuerungssysteme auf Basis von Funktionsbausteinen zu entwickeln. Sie bietet jedoch wenig Unterstützung für Entwurf und Verifikation. Die Tatsache, dass eine Rekonfiguration das System-Ausführungsmodell verändert, erschwert die Entwicklung in IEC 61499 zusätzlich. Daher schlägt diese Dissertation rekonfigurierbare Funktionsbausteine (RFBs) als Erweiterung der Norm vor. Ein RFB verarbeitet über einen Master-Slave-Automaten Rekonfigurationsereignisse und löst das entsprechende Verhalten aus. Diese Hierarchie trennt das Rekonfigurationsmodell vom Steuerungsmodell und vereinfacht so den Entwurf. Die Funktionalität des Entwurfs muss verifiziert werden, damit die Ausführbarkeit des Systems nach einer Rekonfiguration gewährleistet ist. Hierzu wird das entworfene RFB-Modell automatisch in ein generalised reconfigurable timed net condition/event system übersetzt. Dieses wird mit dem Model-Checker PRISM auf qualitative und quantitative Eigenschaften überprüft. Somit wird eine Bewertung der Systemperformanz und eine Einschätzung der Rekonfigurationsrisiken erreicht. Die RFB-Methodik wurde in einem Softwarewerkzeug umgesetzt und in einer Fallstudie auf ein dezentrales Stromnetz angewendet

Foundations of Multi-Paradigm Modelling for Cyber-Physical Systems

This open access book coherently gathers well-founded information on the fundamentals of and formalisms for modelling cyber-physical systems (CPS). Highlighting the cross-disciplinary nature of CPS modelling, it also serves as a bridge for anyone entering CPS from related areas of computer science or engineering. Truly complex, engineered systems—known as cyber-physical systems—that integrate physical, software, and network aspects are now on the rise. However, there is no unifying theory nor systematic design methods, techniques or tools for these systems. Individual (mechanical, electrical, network or software) engineering disciplines only offer partial solutions. A technique known as Multi-Paradigm Modelling has recently emerged suggesting to model every part and aspect of a system explicitly, at the most appropriate level(s) of abstraction, using the most appropriate modelling formalism(s), and then weaving the results together to form a representation of the system. If properly applied, it enables, among other global aspects, performance analysis, exhaustive simulation, and verification. This book is the first systematic attempt to bring together these formalisms for anyone starting in the field of CPS who seeks solid modelling foundations and a comprehensive introduction to the distinct existing techniques that are multi-paradigmatic. Though chiefly intended for master and post-graduate level students in computer science and engineering, it can also be used as a reference text for practitioners

Methodologies synthesis

This deliverable deals with the modelling and analysis of interdependencies between critical infrastructures, focussing attention on two interdependent infrastructures studied in the context of CRUTIAL: the electric power infrastructure and the information infrastructures supporting management, control and maintenance functionality. The main objectives are: 1) investigate the main challenges to be addressed for the analysis and modelling of interdependencies, 2) review the modelling methodologies and tools that can be used to address these challenges and support the evaluation of the impact of interdependencies on the dependability and resilience of the service delivered to the users, and 3) present the preliminary directions investigated so far by the CRUTIAL consortium for describing and modelling interdependencies