2026 年 21 巻 3 号 p. 26-00064
The functional resonance analysis method (FRAM) is one of most brilliant methods in complex systems to conduct the risk analysis and/or accident analysis. To conduct the risk assessment which consists of the risk analysis and risk reduction on the control of gaseous fuel flow, the semi-quantitative FRAM was adopted in this research. The accumulated coupling variability was newly propounded, and the expected values obtained by simple calculations were used to evaluate variabilities semi-quantitatively. The accumulated coupling variability was closely related with risk, and then we analyzed the sensitivity of output variability of each function to the accumulated coupling variability of the top event. Significant functions, which had large values in sensitivity, i.e. greatly affected the risk of system, were identified through the risk analysis. The accumulated coupling variability of the top event, corresponding to the risk of system, was effectively suppressed, based on the semi-quantitative results derived from the risk analysis. We proposed the effective measure of risk reduction in this research. Using the expected values in the semi-quantitative FRAM, the risk analysis was conducted with reasonable accuracy, considerably reducing the effort and time spent on evaluations. Compared with the downlink functional coupling variability as the representative of previous methods, the superiority of the proposed method was confirmed.
