A Target Failure Measure for Solving Discontinuous Functional Safety Assessment of E/E/PE Safety-Related Systems

IEC 61508 is used for target failure measures, such as the average probability of a dangerous failure on demand, [Formula: see text], for low-demand operation mode and the probability of a dangerous failure per hour, PFH, for high-demand operation mode when assessing the functional safety of E/E/PE safety-related systems. It is known that this regulation leads to discontinuous functional safety assessment and the problem of evaluation accuracy around the boundary of these operation mode. We newly propose a target failure measure which enables us to conduct the functional safety assessment continuously regardless of the operation mode for a single channel structure of the E/E/PE safety-related systems. A numerical experiment is conducted to consider the difference between our approach and the IEC 61508-based approach.