A Hybrid Modular Approach for Dynamic Fault Tree Analysis (original) (raw)
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Dynamic Fault Tree Analysis Based on Petri Nets
—In traditional Dynamical Fault Tree analysis, it is necessary to modularize DFT tree firstly so as to obtain static subtrees and dynamic subtrees. Generally, Binary Decision Diagram (BDD) and Markov chains are utilized in the DFT to process static and dynamic subtrees, respectively. However, due to the possibility of state combinatorial explosion problem in Markov chain, it is difficult to analyze system with DFT in some cases. This paper investigated Petri net method in DFT in order to solve this problem. An example of processor system is analyzed with the proposed Petri net based DFT, which contains many dynamic logic gates in two classes. The analysis results show that the proposed method can overcome the state combinatorial explosion problem and guarantee high accuracy.
Dynamic Fault Tree Analysis: State-of-the-Art in Modeling, Analysis, and Tools
2020
YesSafety and reliability are two important aspects of dependability that are needed to be rigorously evaluated throughout the development life-cycle of a system. Over the years, several methodologies have been developed for the analysis of failure behavior of systems. Fault tree analysis (FTA) is one of the well-established and widely used methods for safety and reliability engineering of systems. Fault tree, in its classical static form, is inadequate for modeling dynamic interactions between components and is unable to include temporal and statistical dependencies in the model. Several attempts have been made to alleviate the aforementioned limitations of static fault trees (SFT). Dynamic fault trees (DFT) were introduced to enhance the modeling power of its static counterpart. In DFT, the expressiveness of fault tree was improved by introducing new dynamic gates. While the introduction of the dynamic gates helps to overcome many limitations of SFT and allows to analyze a wide ra...
Combining various solution techniques for dynamic fault tree analysis of computer systems
Proceedings Third IEEE International High-Assurance Systems Engineering Symposium (Cat. No.98EX231)
Fault trees provide a conceptually simple modeling framework to represent system-level reliability in terms of interactions between component reliabilities. DIFtree [1] effectively combines the best static fault tree solution technique (Binary Decision Diagrams) with Markov solution techniques for dynamic fault trees. DIFtree includes advanced techniques for modeling coverage; coverage modeling has been shown to be critical to the analysis of fault tolerant computer systems. DIFtree is based on a divideand-conquer technique for modularizing the system level fault tree into independent sub-trees; different solution techniques can be used for sub-trees. In this paper we extend the DIFtree analysis capability to model several different distributions of time to failure, including fixed probabilities (no time component), exponential (constant hazard rate), Weibull (time varying hazard rate), and log normal. Our approach extends both the BDD and Markov analytical approaches and incorporates simulation as well.
Reliability analysis of non repairable systems using stochastic Petri nets
[1988] The Eighteenth International Symposium on Fault-Tolerant Computing. Digest of Papers
Many real-life systems are typically involved in sequence-dependent failure behaviors. Such systems can be modeled by dynamic fault trees (DFTs) with priority AND gates, in which the occurrence of the top events depends on not only combinations of basic events but also their failure sequences. To the author's knowledge, the existing methods for reliability assessment of DFTs with priority AND gates are mainly Markov-state-space-based, inclusion-exclusion-based, Monte Carlo simulation-based, or sequential binary decision diagram-based approaches. Unfortunately, all these methods have their shortcomings. They either suffer the problem of state space explosion or are restricted to exponential components time-to-failure distributions or need a long computation time to obtain a solution with a high accuracy. In this article, a novel method based on dynamic binary decision tree (DBDT) is first proposed. To build the DBDT model of a given DFT, we present an adapted format of the traditional Shannon's decomposition theorem. Considering that the chosen variable index has a great effect on the final scale of disjoint calculable cut sequences generated from a built DBDT, which to some extent determines the computational efficiency of the proposed method, some heuristic branching rules are presented. To validate our proposed method, a case study is analyzed. The results indicate that the proposed method is reasonable and efficient.
An open-source application to model and solve dynamic fault tree of real industrial systems
2011
In recent years, a new generation of modeling tools for the risk assessment have been developed. The concept of "dynamic" was exported also in the field of reliability and techniques like dynamic fault tree, dynamic reliability block diagrams, boolean logic driven Markov processes, etc., have become of use. But, despite the promises of researchers and the efforts of end-users, the dynamic paradox hangs: risk assessment procedures are not as straight as they were with the traditional static methods and, what is worse, it is difficult to assess the reliability of these results. Far from deny the importance of the scientific achievement, we have tested and cursed some of these dynamic tools realizing that none of them was appropriate to solve a real case. In this context, we decided to develop a new DFT reliability solver, based on the Monte Carlo simulative approach. The tool is greatly powerful because it is written with Matlab® code, hence is open-source and can be extended. In this first version, we have implemented the most used dynamic gates (PAND, SEQ, FDEP and SPARE), the existence of repeated events and the possibility to simulate different cumulative distribution function of failure (Weibull, negative exponential CDF and constant). The tool is provided with a snappy graphic user interface written in Java®, which allows an easy but efficient modeling of any fault tree schema. The tool has been tested with many literature cases of study and results encourage other developments.
Expert Systems with Applications, 2012
With the aim of a more effective representation of reliability assessment for real industry, in the last years concepts like dynamic fault trees (DFT) have gained the interest of many researchers and engineers (dealing with problems concerning safety management, design and development of new products, decision analysis and project management, maintenance of industrial plant, etc.). With the increased computational power of modern calculators is possible to achieve results with low modeling efforts and calculating time. Supported by the strong mathematical basis of state space models, the DFT technique has increased its popularity. Nevertheless, DFT analysis of real application has been more likely based on a specific case to case resolution procedure that often requires a great effort in terms of modeling by the human operator. Moreover, limitations like the state space explosion for increasing number of components, the constrain of using exponential distribution for all kind of basic events constituting any analyzed system and the ineffectiveness of modularization for DFT which exhibit dynamic gates at top levels without incurring in calculation and methodological errors are faces of these methodologies. In this paper we present a high level modeling framework that exceeds all these limitations, based on Monte Carlo simulation. It makes use of traditional DFT systemic modeling procedure and by replicating the true casual nature of the system can produce relevant results with low effort in term of modeling and computational time. A Simulink library that integrates Monte Carlo and FT methodologies for the calculation of DFT reliability has been developed, revealing new insights about the meaning of spare gates.
Quantitative Analysis of Dynamic Fault Trees Based on the Structure Function
Quality and Reliability Engineering International, 2014
This paper presents a probabilistic model of dynamic gates which allows to perform the quantitative analysis of any dynamic fault tree (DFT) from its structure function. Both these probabilistic models and the quantitative analysis which can be performed thanks to them can accommodate any failure distribution of basic events. We illustrate our approach on a DFT example from the literature.
Reliability analysis of complex technical systems using the fault tree modularization technique
1980
CHAPTER 2 TIME DEPENDENT FAULT TREE ANALYSIS 62 2.1 Introduction 62 2.2 Class 1 Components: Time Independent Components 63 2.3 Class 2 Components: Nonrepairable Components 66 6 Page 2.4 Class 3 Components: Repairable Components 2.5 Class 4 Components: Periodically Tested Components 2.6 General Time Dependent Relations for the Evaluation of Fault Trees by Using the Modular Concept 2.7 General Relations for Time Dependent Simple Modules Consisting of Only Repairable Components (Class 3 Components) 2.8, General Relationships for a Time-Dependent Simple Module Consisting of Only Non-Repairable Components (Class 2 Components) CHAPTER 3 REDUCTION OF LARGE FAULT TREES BASED ON THE VESELY-FUSSELL IMPORTANCE MEASURES 3.1 Introduction 3.2 Importance Measures and the Use of PL-MOD to Calculate the V-F Importance Measures 3.3 Use of the Code PL-MOD for Reducing Large Fault Trees 103 3.4 Reductions of LPRS and HPIS Fault Trees 104 CHAPTER 4 MONTE-CARLO SIMULATION OF TOP EVENT PROBABILITY 109 4.1 Introduction 109 4.2 The Log-Normal Distribution 111 4.2.1 Justification for Use of Log-Normal Distribution 111 4.2.2 Characteristics and Some of the Mathematical Concepts of Log-Normal Distribution 111 4.3 Mathematical Concepts used in PL-MODMC for the Monte-Carlo Simulation 113 4.4 Distribution Models for the Modules of a Coherent System Fault Tree 121