Model-based and simulation-driven methods for the reliability and safety analysis of systems

Abstract

In several industrial domains such as automotive, railway, avionics, satellite, health care and energy, a great variety of systems are currently designed and developed by organizing and integrating existing components (which in turn can be regarded as systems),that pool their resources and capabilities together to create a new system which is able to o er more functionalities and performances than those o ered by the simple sum of its components. Typically, the design and management of such systems, whose properties cannot be immediately de ned, derived and easily analyzed starting from the properties of their parts when they are considered in stand-alone, require to identify and face with some important research issues. In particular, the integration of system components is a challenging task whose criticality rises as the heterogeneity and complexity of the components increase. Thus, suitable engineering methods, tools and techniques need to be exploited to prevent and manage the risks arising from the integration of system components and, mainly, to avoid their occurrence in the advanced phases of the system development process which may result in a signi cant increase in the entire project costs. To overcome these issues the adoption of the Systems Engineering approach represents a viable solution as it provides a wide set of methods and practices which allow the de nition of the system architecture and behavior at di erent abstraction level in terms of its components and their interactions. Moreover, systems requirements are constantly traced during the di erent system development phases so to clearly specify how a system component concurs to the ful llment of the requirements. However, in the Systems Engineering eld, even though great attention has been devoted to functional requirements analysis and traceability, there is still a lack of methods which speci cally address these issues for non-functional requirements. As a consequence, the analysis concerning if and how non-functional requirements are met by the system under development is not typically executed contextually to the design of the system but still postponed to the last stages of the development process with a high risk of having to revise even basic design choices and with a consequent increase in both completion tim and development costs. Among all system requirements, Reliability and Safety are important non-functional requirements. Especially for mission-critical systems, there is a strong demand for new and more powerful analysis tools and techniques able not only to verify the reliability indices and safety of a system but also to exibly evaluate the system performances and compare di erent design choices. In this context, the research aimed to promote the use of exible methods for the analysis of non-functional requirements by focusing on the de nition of: (i) model-based method for system reliability analysis centered on popular SysML/UML-based languages for systems modeling and on de-facto standard platforms for the simulation of multi-domain dynamic and embedded systems (Mathworks Simulink); (ii) a methodological process for supporting the safety analysis, along with an approach for performing the Fault Tree Analysis of cyber-physical systems, mainly based on the Modelica language and OpenModelica simulation environment. Furthermore, in order to support the representation of system requirements and thus enable their veri cation and validation during the design stages, a meta-model for modeling requirements of physical systems as well as di erent approaches for extending the Modelica language have been proposed. Moreover, an algorithm, which allows trace and evaluate requirements violation through simulation, has been de ned. Finally, the e ectiveness of the proposed methods and approaches, especially in the modeling and analysis of both the expected and dysfunctional system behavior, is the result of an intensive experimentation in several industrial domains such automotive, avionics and satellite