Fundamental Study on Safety Assessment of Intelligent and Integrated Systems

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The main objective of this research is to develop methodology to assess the safety of intelligent systems which are operated and controlled by use of highly sophisticated information processing technology.In the first year of the project, since the reliability and safety of the intelligent systems depend on the correctness of their stored knowledge, two types of supporting methods to maintain the reliability of stored ruyes in rule-based failure diagnosis systems are developed.In the second year, several failure diagnosis methods for dynamic and static systems are developed and investigated based on an error-risk criterion. One of the methods developed, for example, considers 1) sequences of monitored values of inspection items, 2) errors in monitored values, 3) reliability characteristics of the system, and 4) subjective evaluation of losses caused by system abnormal events.In the third year, human factors together with human error propagation processes in operation and decision making are focused on. Firstly, a new consistency index is proposed to the pair-wise comparison matrix which is extensively used in the Analytic Hierarchy Processes (AHP) for obtaining the relative importance of alternatives. By computer simulation of AHP processes, the properties of the proposed index are examined in comparison with the conventional index. Secondly, to analyze the effect of human errors in a team of multiple members who execute a given task, a general framework based on a human behavior model is proposed and an illustrative example of a tank-filling task for a team of three members is made to show the details of the proposed method. Thirdly, decision making by a hierarchical team which consists of a primary decision maker and his subordinates is discussed. After general decision making rules are derived by use of an expected error-risk criterion, their properties are exploited in detail.