Fault Tree Ring Closure Normalization for Minimal Cutsets
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Solution Overview
Problem
Existing fault tree analysis methods face challenges in handling ring closures, which can prevent the determination of minimal cutsets and complicate safety assurance in safety-critical systems, particularly in multi-component control or actuator systems.
Innovation Solution
A computer-implemented method for modeling multi-component systems using fault trees, detecting ring closures, replacing edges with variables to create a placeholder tree, and determining normalized representations through cutsets and disjunctive or conjunctive graphs to address the complexities introduced by ring closures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fault tree analysis is applied to multi-component control systems with loops, then safety assurance capability is improved, but the analysis becomes problematic and minimal cutsets cannot be determined due to ring closures
Solution Approach 1:
The patent segments the fault tree analysis process into distinct phases: identifying ring closures, temporarily replacing them with placeholder variables to create an acyclic intermediate representation, performing minimal cutset analysis on the simplified structure, and then reconstructing the complete analysis by substituting placeholders with their original ring closure definitions. This segmentation allows the analysis to proceed on manageable portions rather than the entire complex structure at once.
Solution Approach 2:
The patent introduces an intermediate representation of the fault tree where ring closures are replaced with placeholder variables. This intermediate form serves as a mediator between the original complex fault tree with rings and the final analysis results, enabling standard minimal cutset algorithms to be applied without modification while still capturing the essence of the original system's failure modes.
2Measurement precision
If ring closures are present in the fault tree, then the system modeling accuracy is improved, but computational efficiency deteriorates and error determination becomes impossible
Solution Approach 1:
The patent performs preliminary identification and marking of all ring closures in the fault tree before initiating the minimal cutset analysis. By pre-processing the fault tree structure to identify cyclic dependencies and replace them with placeholders, the system prepares an optimized intermediate representation that eliminates computational inefficiencies ahead of time, allowing standard algorithms to run efficiently on the acyclic structure.
Data Source
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AI summary
One or more ring closures (180) of a fault tree (101, 102) are detected. For each one of the one or more ring closures (180): at least one respective edge (146) of the respective ring closure (180) is replaced in the fault tree (101, 102) by a respective variable (611) to obtain a placeholder fault tree (601) and a normalized representation of the placeholder fault tree (601) is determined.