IEC機能安全規格の改訂動向 : 安全側故障割合(SFF)の要求事項について

概要

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The standard of functional safety requires the subsystems of safety-related system(SRS) to conform with architectural constraints consisting of both random hardware-fault tolerance and safe failure fraction(SFF) constraints as denoted in Part 2 of the standard. The architectural constraints put limitations on the claim that the subsystems can have the highest safety-integrity level(SIL). Therefore, the constraints are highly important requirements as well as those on SIL in the standard. However, the constraints look like themselves to contradict logically the SIL requirements in Part 1 of the standard. Thus, in the present paper how and why the SFF constraints do not bring about logical coherency in the standard is discussed and examined.
社団法人電子情報通信学会の論文
2007-01-25