An Advanced Modeling Approach For Cyclic Safety Mechanisms In A Fault Tree Analysis


A technical paper titled “Best Practices for Advanced Modeling of Safety Mechanisms in an FTA” was published by researchers at University of Stuttgart, Robert Bosch GmbH, Audi AG, and Porsche AG.


“To cope with the megatrends electrification, automated driving, and connectivity, new functionalities and electric and/or electronic systems must be developed, which require a safe power supply. This leads to increased functional safety requirements for the power supply system, particularly regarding availability. Fault tolerance measures can be implemented to comply with a safety goal (SG) specifying a safety-related availability requirement. To verify an architecture concerning the residual risk of an SG violation, several quantitative target values are provided in ISO 26262. This technical elaboration presents a systematic and holistic approach how to gain benefit in the quantitative evaluation from cyclic safety mechanisms (SMs)– in a fault tolerant item– which have a fault handling time interval (FHTI) longer than the fault tolerant time interval. Modelling cyclic SMs only based on conventional AND-gates is not sufficient. Instead, the fault sequence is differentiated to enable ISO 26262-compliance. Within this paper, an innovative approach including its mathematical background is presented how cyclic SMs can be modelled in a fault tree analysis– with focus on multiple-point faults. The results are verified by a Monte-Carlo-Simulation. Besides the scalability of the approach regarding the number of considered cyclic SMs, the relevant FHTI of each cyclic SM can be considered in a traceable and comprehensible manner.”

Find the technical paper here. Published: June 2023.

P. Kilian et al., “Best Practices for Advanced Modeling of Safety Mechanisms in an FTA,” in IEEE Access, vol. 11, pp. 60109-60129, 2023, doi: 10.1109/ACCESS.2023.3284751.

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