A design and implementation methodology for diagnostic systems

A methodology for design and implementation of diagnostic systems is presented. Also discussed are the advantages of embedding a diagnostic system in a host system environment. The methodology utilizes an architecture for diagnostic system development that is hierarchical and makes use of object-oriented representation techniques. Additionally, qualitative models are used to describe the host system components and their behavior. The methodology architecture includes a diagnostic engine that utilizes a combination of heuristic knowledge to control the sequence of diagnostic reasoning. The methodology provides an integrated approach to development of diagnostic system requirements that is more rigorous than standard systems engineering techniques. The advantages of using this methodology during various life cycle phases of the host systems (e.g., National Aerospace Plane (NASP)) include: the capability to analyze diagnostic instrumentation requirements during the host system design phase, a ready software architecture for implementation of diagnostics in the host system, and the opportunity to analyze instrumentation for failure coverage in safety critical host system operations

Towards a resilient networked service system

Large service systems today are of highly network structures. In this thesis, these large service systems are called networked service systems. The network nature of these systems has no doubt brought mass customized services but has also created challenges in the management of their safety. The safety of service systems is an important issue due to their critical influences on the functioning of society. Traditional safety engineering methods focus on maintaining service systems in a safe state, in particular aiming to maintain systems to be reliable and robust. However, resilience cannot be absent from safety out of many recent disasters that occur in society. The goal of this thesis is to improve the resilience of networked service systems. Four major works have been performed to achieve this goal. First, a unified definition of service systems was proposed and its relationship to other system concepts was unfolded. Upon the new definition, a domain model of service systems was established by a FCBPSS framework, followed by developing a computational model. Second, a definition of resilience for service systems was proposed, based on which the relationship among three safety properties (i.e., reliability, robustness and resilience) was clarified, followed by developing a framework for resilience analysis. Third, a methodology of resilience measurement for service systems was proposed by four measurement axioms along with corresponding mathematical models. The methodology focused on the potential ability of a service system to create optimal rebalancing solutions. Two typical service systems, transportation system and enterprise information system, were employed to validate the methodology. Fourth, a methodology of enhancing resilience for service systems was proposed by integrating three types of reconfigurations of systems, namely design, planning and management, along with the corresponding mathematical model. This methodology was validated by an example of transportation system. Several conclusions can be drawn from the work above: (1) a service system has a unique characteristic that it meets humans' demand directly, and its safety relies on the balance between the supplies and demands; (2) different from reliability and robustness, the resilience of a service system focuses on the rebalancing ability from imbalanced situations; (3) it makes sense to measure the resilience of a service system only for a particular imbalanced situation and based on evaluation of rebalancing solutions; and (4) integration of design, planning and management is an effective approach for improvement of the resilience for a service system. The contributions of this thesis can be summarized. Scientifically, this thesis work has improved our understanding of service systems and their resilience property; furthermore, this work has advanced the state of knowledge of safety science in particular having successfully responded to two questions: is a service system safe and how to make a service system safer? Technologically or methodologically, the work has advanced the knowledge for modeling and optimization of networked service systems in particular with multiple layer models along with the algorithms for integrated decision making on design, planning, and management

Uncertainty management in multidisciplinary design of critical safety systems

Managing the uncertainty in multidisciplinary design of safety-critical systems requires not only the availability of a single approach or methodology to deal with uncertainty but a set of different strategies and scalable computational tools (that is, by making use of the computational power of a cluster and grid computing). The availability of multiple tools and approaches for dealing with uncertainties allows cross validation of the results and increases the confidence in the performed analysis. This paper presents a unified theory and an integrated and open general-purpose computational framework to deal with scarce data, and aleatory and epistemic uncertainties. It allows solving of the different tasks necessary to manage the uncertainty, such as uncertainty characterization, sensitivity analysis, uncertainty quantification, and robust design. The proposed computational framework is generally applicable to solve different problems in different fields and be numerically efficient and scalable, allowing for a significant reduction of the computational time required for uncertainty management and robust design. The applicability of the proposed approach is demonstrated by solving a multidisciplinary design of a critical system proposed by NASA Langley Research Center in the multidisciplinary uncertainty quantification challenge problem

Model Based Functional Safety – How Functional Is It?

As the engineering world embraces Model Based System Engineering (MBSE), the system safety discipline should also enfold and support MBSE methodology and approaches. The need for Model Based Functional safety, as part of the established system safety and software safety process, is becoming apparent due to existing and developing system design complexity. This paper is intended to show how valuable Model Based Functional Safety approaches can be when evaluating safety signification functions of complex software-intensive integrated systems. Using models can improve the accuracy during the Functional Hazard Analysis (FHA) and can help validate Fault Tree Analyses (FTA) and subsequent system safety analysis (SSA) process and results because the model focuses on the architecture, the physical system, the computer system, as well as the applicable software/middleware/Programmable Logic Devices (PLDs). Model Based Functional Safety may utilize use cases, structural architecture models, activity diagrams, sequence diagrams, functional flow diagrams, and state/mode models to depict safety attributes and to influence explicit safety requirements. SysML may be used to depict critical functions, functional threads, safety features, and expected behavior. Such augmented models (safety models) can also be used to analyze potential off nominal failure conditions and system behavior for various scenarios when conducting FHAs and subsequently detailed system and software safety analyses. This paper will provide an example of the MBSE framework and concepts for tool use in the functional safety analysis and the utilization of attributed models and artifacts to supplement system safety documentation

Building safe software

Murphy is a set of techniques and tools under investigation for their potential in enhancing the safety of software. This paper describes some of the work which has been done and some which is planned

Civil aircraft advanced avionics architectures - an insight into saras avionics, present and future perspective

Traditionally, the avionics architectures being implemented are of federated nature, which means that each avionics function has its own independent, dedicated fault-tolerant computing resources. Federated architecture has great advantage of inherent fault containment and at the same time envelops a potential risk of massive use of resources resulting in increase in weight, looming, cost and maintenance as well. With the drastic advancement in the computer and software technologies, the aviation industry is gradually moving towards the use of Integrated Modular Avionics (IMA) for civil transport aircraft, potentially leading to multiple avionics functions housed in each hardware platform. Integrated Modular Avionics is the most important concept of avionics architecture for next generation aircrafts. SARAS avionics suite is purely federated with almost glass cockpit architecture complying to FAR25. The Avionics activities from the inception to execution are governed by the regulations and procedures under the review of Directorate General of Civil Aviation (DGCA). Every phase of avionics activity has got its own technically involvement to make the system perfect. In addition the flight data handling, monitoring and analysis is again a thrust area in the civil aviation industry leading to safety and reliability of the machine and the personnel involved. NAL has been in this area for more than two decades and continues to excel in these technologies

Integrated Safety and Security Risk Assessment Methods: A Survey of Key Characteristics and Applications

Over the last years, we have seen several security incidents that compromised system safety, of which some caused physical harm to people. Meanwhile, various risk assessment methods have been developed that integrate safety and security, and these could help to address the corresponding threats by implementing suitable risk treatment plans. However, an overarching overview of these methods, systematizing the characteristics of such methods, is missing. In this paper, we conduct a systematic literature review, and identify 7 integrated safety and security risk assessment methods. We analyze these methods based on 5 different criteria, and identify key characteristics and applications. A key outcome is the distinction between sequential and non-sequential integration of safety and security, related to the order in which safety and security risks are assessed. This study provides a basis for developing more effective integrated safety and security risk assessment methods in the future

The thematic network SAFER EURORO : an integrated approach to safe European roro ferry design

For a period of more than 10 years, a safety culture approach has been promoted through the theme'Design for Safety,' which aims at integrating safety cost effectively in the ship design process. There isa considerable wealth of information amassed over these years of research and development on safetycriticalareas. One of the main elements of the research and development (R&D) work is the assurance ofsafety within the ship design process, in the continuous search for improving the current state of affairs.Through bold steps in the direction advocated by 'Design for Safety,' it is slowly but steadily beingrecognized that this approach can greatly contribute to the overall cost-effective improvement of safety inshipping while nurturing the evolution of proper practice in the field. On this background, the paper attempts a thorough overview of related R&D developments over the lastdecade. Particular emphasis is placed on the developments that have taken place as part of the activitiesof the Thematic Network SAFER EURORO and associated research projects, which have led to thedevelopment of a recent major research initiative, the Integrated Project SAFEDOR, which is expected tolead research development in the area for the years to come