Complex Critical Systems Research Articles

CONCEPTION AND APPLICATION OF DEPENDABLE INTERNET OF THINGS BASED SYSTEMS

Context. The problem is in the design, development, maintenance and commisioning of interoperable dependable systems using on the Internet of Things based on von Neumann paradigm of “building reliable systems from unreliable components” for dependable service-oriented systems and infrastructures.Objective. The goals of the paper are in the development of concepts and principles and assessment technologies for creation and maintenance of complex critical systems based on Internet of Things (IoT) as well as implementation of research in various domains.Method. In the paper the concept of development of dependable systems on the basis of the Internet of things is described. The multisectoral analysis of methods and models of reliability and cybersecurity (dependability) evaluation of information and control systems of critical applications using the Internet of things has been performed for different domains: power, healthcare, industrial, etc. The analysis has shown that some software failures and malfunctions, cyberattacks and consequences of influence of attacks are identical for all domains, but there are specific features for each domain, which are necessary to consider at working out of methodology of maintenance of denepdability of reliability of systems of critical applications using the Internet of things.Results. The developed conception, methods, tools and technologies for the creation and implementation of dependable information & control systems for critical applications based on the Internet of Things.Conclusions. The paper proposes a conception that includes a set of scientific and applied tasks for the development of methods, tools and technologies for the creation and implementation of dependable information & analytical and information & control systems for critical applications based on the Internet of Things. The prospects for further research may include the detailing of the developed models, methods and technologies to ensure the dependability of complex information & control systems for critical applications based on the Internet of Things.

On the Calculation of Functional Safety Parameters of Technical Systems

Now the scientific methodology is created, the theory and practice of the analysis and synthesis of functional safety of responsible electronic programmable devices and systems at all stages of their life cycle are developed. The basics of the methodology are fixed by standards. Methods of analysis and synthesis of functional safety are strictly formalized. They are based on the calculations of functional safety indicators with respect to failures of constituent elements and, especially, dangerous and protective failures of the system. Known methods of calculation are focused on determining the intensity and probability of dangerous failures. The objective of the proposed method lies in the fact that, in graph form, without resorting to the solution of the system of equations in the operator transformations to establish the distribution function of time until the threat or security failure, or any unhealthy condition of the system. These distribution functions determine all the necessary indicators of mean time (and, if necessary, the variance of this time) to a dangerous or protective failure. The proposed semi-Markov (Markov) operator method allows to solve a number of problems of calculation and prediction of functional safety of critical (responsible) systems. The method is formalized and suitable for subsequent computer implementation. This fact testifies to the expediency of further development of graph methods, convenient for the study of the safety of complex critical systems, devoid of the shortcomings of the proposed method in terms of the complexity of the preparatory work to determine the analytical expressions of transition probabilities in the Laplace - Stieltjes transformations. The given example of using the method has an independent value – it allows you to assess the advantages and disadvantages of ensuring functional safety by building a two-channel system without restarting the channels

Design and development of automated high temperature motor test facility

With increasing applications in high performance actuation systems as in aerospace and nuclear industries, demand for motors operating at an ambient temperature of 100°C and above has increased. Hence, it is highly necessary to validate the performance of motors at high temperature before their integration into complex critical systems. Most commercial test benches for motor available today, are designed for operation only at normal temperature. This paper describes the design, physical structure, operating principle and data acquisition system of automated test facility developed for testing stepper motors, brushed DC motors and brushless servo motors at room temperature as well as at elevated temperatures. To make the entire measurement system automated, a graphical user interface based on C# software is developed. Through the experiments on standard motors, quality of the design, performance of test bench and implementation of control modes are validated. The results obtained show a successful intercommunication between modules such as control, drive, measurement, data acquisition and display as per the required performance.

Distributed Diagnosis of Electric Aircraft Powertrain

Electrically powered autonomous aircraft are being increasingly considered for intra-city short-haul air-taxi services to fly human passengers between different locations. As a result, it is critical to incorporate safety under autonomous operations into system operations by enabling such autonomous aircraft to make accurate estimates of its current health state and take the right decisions to complete its mission successfully. The first step to assess health state of the entire aircraft is for the aircraft to be able to assess the health of its individual critical systems, (e.g electrical powertrain) for it to be able to fly and reach its destination in a safe manner. The fundamental components of a powertrain in an electrically powered aircraft include key electrical components such as batteries, motors, and power electronics (e.g., electronic speed controllers). A model-based diagnosis approach of complex critical systems enables their safe and efficient operation. Typically, such model-based schemes are centralized approaches that suffer from inherent disadvantages such as computational complexity, single point of failure, and scalability issues. Distributing the diagnosis task addresses these issues. To this end, this paper presents the results of implementing a distributed diagnostics approach to a representative electric aircraft powertrain. In particular, we focus on the implementation of a distributed diagnosis framework to a quadrotor vehicle. The simulation experiments demonstrate how the distributed diagnosis algorithm correctly and efficiently diagnose faults in the rotorcraft’s electric powertrain.

Testing Situation Awareness Network for the Electrical Power Infrastructure

The contemporary electrical power infrastructure is exposed to new types of threats. The cause of such threats is related to the large number of new vulnerabilities and architectural weaknesses introduced by the extensive use of the Information and Communication Technologies (ICT) in such complex critical systems. The power grid interconnection with the Internet exposes the grid to new types of attacks, such as Advanced Persistent Threats (APT) or Distributed-Denial-of-Service (DDoS) attacks. When addressing this situation the usual cyber security technologies are prerequisite, but not sufficient. To counter evolved and highly sophisticated threats such as the APT or DDoS, state-of-the-art technologies including Security Incident and Event Management (SIEM) systems, extended Intrusion Detection/Prevention Systems (IDS/IPS) and Trusted Platform Modules (TPM) are required. Developing and deploying extensive ICT infrastructure that supports wide situational awareness and allows precise command and control is also necessary. In this paper the results of testing the Situational Awareness Network (SAN) designed for the energy sector are presented. The purpose of the tests was to validate the selection of SAN components and check their operational capability in a complex test environment. During the tests' execution appropriate interaction between the components was verified.

Optimized task allocation on private cloud for hybrid simulation of large-scale critical systems

Simulation represents a powerful technique for the analysis of dependability and performance aspects of distributed systems. For large-scale critical systems, simulation demands complex experimentation environments and the integration of different tools, in turn requiring sophisticated modeling skills. Moreover, the criticality of the involved systems implies the set-up of expensive testbeds on private infrastructures. This paper presents a middleware for performing hybrid simulation of large-scale critical systems. The services offered by the middleware allow the integration and interoperability of simulated and emulated subsystems, compliant with the reference interoperability standards, which can provide greater realism of the scenario under test. The hybrid simulation of complex critical systems is a research challenge due to the interoperability issues of emulated and simulated subsystems and to the cost associated with the scenarios to set up, which involve a large number of entities and expensive long running simulations. Therefore, a multi-objective optimization approach is proposed to optimize the simulation task allocation on a private cloud.

A MULTIFORMALISM MODULAR APPROACH TO ERTMS/ETCS FAILURE MODELING

European Railway Traffic Management System/European Train Control System (ERTMS/ETCS) is a recent standard aimed at improving performance, safety and inter-operability of modern railways. In order to be compliant to ERTMS/ETCS, a railway signalling system must meet strict nonfunctional requirements on system level failure modes. In this paper, a multiformalism model is employed to perform an availability analysis of an ERTMS/ETCS reference architecture at early phases of its development cycle. At this aim, a bottom-up analysis is performed from subsystem failure models (expressed by means of Generalized Stochastic Petri Nets, Fault Trees and Repairable Fault Trees) up to the overall system model. The modular approach, here used, allows to evaluate the influence of basic design parameters on the probability of system-level failure modes and demonstrates that system availability is within the bound required by the ERTMS/ETCS specification. The results show that the multiformalism modeling approach helps to cope with complexity, eases the verification of availability requirements and can be successfully applied to the analysis of complex critical systems.

SYRMA: a tool for a system approach to risk management in mission critical systems

Managing risks and taking steps to reduce risks at acceptable level are considered as strategic objectives for organisations in almost any application domain. It is widely recognised that a system-oriented approach is needed to effectively manage risks in complex and mission critical systems. Well-known standard approaches to risk management exist and some frameworks and best practices have reached a high level of completeness and suitability in the different possible application scenarios. Nonetheless, we realised that poor support is offered towards the adoption of system-oriented approaches to risk management. This paper proposes a web-based application, named systemic risk management SYRMA, to effectively support a system approach to risk management, especially in the case of complex and mission critical systems. SYRMA is based on a conceptual model that identifies main entities in risk management and their relations with resources of the target organisation. Identified relationships among model entities facilitate the provision of a synoptic overview of incidents, possible risks and risk-related information. Finally, we describe how SYRMA has been implemented as a prototype for the healthcare sector.

A survey of safety-oriented model-driven and formal development approaches

Numerous model-driven and formal approaches have been proposed to facilitate development of complex critical systems. To address safety concerns, these approaches incorporate safety analysis techniques at different stages of the system development process. In this paper, we overview the approaches that have been recently proposed to integrate safety analysis into model-driven and formal development of critical systems. Moreover, we identify several criteria for classifying and comparing these approaches. Our survey aims at guiding industry practitioners as well as identifying promising research directions in the area.

SMT-based scenario verification for hybrid systems

Hybrid automata are a widely used framework to model complex critical systems, where continuous physical dynamics are combined with discrete transitions. The expressive power of Satisfiability Modulo Theories (SMT) solvers can be used to symbolically model networks of hybrid automata, using formulas in the theory of reals, and SAT-based verification algorithms, such as bounded model checking and k-induction, can be naturally lifted to the SMT case. In this paper, we tackle the important problem of scenario-based verification, i.e. checking if a network of hybrid automata accepts some desired interactions among the components, expressed as Message Sequence Charts (MSCs). We propose a novel approach, that exploits the structure of the scenario to partition and drive the search, both for bounded model checking and k-induction. We also show how to obtain information explaining the reasons for infeasibility in the case of invalid scenarios. The expressive power of the SMT framework allows us to exploit a local time semantics, where the timescales of the automata in the network are synchronized upon shared events. The approach fully leverages the advanced features of modern SMT solvers, such as incrementality, unsatisfiable core extraction, and interpolation. An experimental evaluation demonstrates the effectiveness of the approach in proving both feasibility and unfeasibility, and the adequacy of the automatically generated explanations.

A Recovery-Oriented Approach for Software Fault Diagnosis in Complex Critical Systems

This paper proposes an approach to software faults diagnosis in complex fault tolerant systems, encompassing the phases of error detection, fault location, and system recovery. Errors are detected in the first phase, exploiting the operating system support. Faults are identified during the location phase, through a machine learning based approach. Then, the best recovery action is triggered once the fault is located. Feedback actions are also used during the location phase to improve detection quality over time. A real world application from the Air Traffic Control field has been used as case study for evaluating the proposed approach. Experimental results, achieved by means of fault injection, show that the diagnosis engine is able to diagnose faults with high accuracy and at a low overhead.

Vulnerability of complex critical systems: case water supply and distribution networks

Management of complex, interdependent critical infrastructures demands systematic continuity evaluations and capability building for abnormal as well as normal conditions. The changing risk and threat environment creates new vulnerabilities that require an extensive approach to control weak points and support the undisturbed and reliable functions of critical infrastructures. The water contamination case is used to illustrate the complexity of today’s changing risk environment. It also showed that without well-established risk analysis the aftermath could be drastic due to the inadequate link between risk analysis and continuity plans.

Integrated HSEE management systems for industry: A case study in gas refinary

The aim of this study was to depict a framework for development of integrated intelligent human engineering environment in complex critical systems. Conventional health, safety and environment (HSE) are a widely used approach to enhance reliability and safety of complex systems. The integrated health, safety, environment and ergonomics management system (HSEE‐MS) is defined however as integration of conventional HSE with ergonomics. To show the need for and superiority of HSEE over conventional HSE, a gas treatment company in Iran was studied. Evaluation of ergonomics was carried out by 195 male employees responding to questionnaires. The integrated HSEE system introduces a unique, effective and systemic mechanism, which integrates the structure of the human and organizational systems with a conventional HSE system. It is utilized to enhance reliability, availability, maintainability and safety through the proposed integrated framework of this study.

Managing technology for highly complex critical modular systems: The case of automotive by-wire systems

The motor vehicle industry has experienced the adoption of several new complex technologies that affect the approach with which OEMs, suppliers tackle product complexity. Nonetheless, the implications of these complex technologies have the potential to change the way automotive OEMs and suppliers relate to each other. This paper addresses the fact that technological specialization produces a complex electronic/electric vehicle architecture; which creates an interdependency among all members of the automotive innovation networks, a fact that has not been addressed in existing literature. For this in-depth case study, the specific examples of brake-by-wire and steer-by-wire systems were selected as subjects.

The HiVe Writer

Critical systems require assurance that key security, safety or mission requirements are met. Tools are necessary to provide this assurance. The HiVe Writer supports model-based documentation for complex critical systems. The HiVe Writer forms the functional foundation for the ambitious HiVe (Hierarchical Verification Environment) project which aims to provide a unified framework in which entire design projects can be described with the highest level of assurance. The primary innovation in the HiVe Writer is a centrally-managed design model: any design, explanatory and technical documents created within the tool are constrained to be consistent with this design model and therefore with each other. This paper gives a detailed description of the HiVe Writer, showing how it supports model-based editing of structured technical documents and, in particular, requirements formulation.

Formal Fault Tree Analysis - Practical Experiences

Safety is an important requirement for many modern systems. To ensure safety of complex critical systems, well-known safety analysis methods have been formalized. This holds in particular for automation sytsems and transportation systems. In this paper we present the formalization of one of the most wide spread safety analysis methods: fault tree analysis (FTA). Formal FTA allows to rigorously reason about completeness of a faulty tree. This means it is possible to prove whether a certain combination of component failures is critical for system failure or not. This is a big step forward as informal reasoning on cause-consequence relations is very error-prone.We report on our experiences with a real world case study from the domain of railroads. The here presented case study is – to our knowledge – the first complete formal fault tree analysis for an infinite state system. Until now only finite state systems have been analyzed with formal FTA by using model checking.

Risk management of complex critical systems

It is crucial to examine the changing panorama of vulnerabilities and criticalities in our increasingly interconnected world. Understanding the meaning of complexity and its implications allows us to see the interconnectedness of the world for enhanced risk management in technical and social systems. In this respect, a framework to assess complex systems is necessary to understand vulnerabilities and risks. We explain how this framework can provide a quick, higher-level view and preliminary risk management screening prior to proceeding into specific and costly analyses.

OVERCOMING THE CHRISTMAS TREE SYNDROME

We propose a new computational approach to logic-based systems that should reason in a fast but logically sound and complete manner about large-scale complex critical devices and systems that can exhibit unexpected faulty behaviors. The approach is original from at least two points of view. First, it makes use of local search techniques while preserving logical deductive completeness. Second, it proves experimentally efficient for very large knowledge bases thanks to new heuristics in the use of local search techniques.