General inspection strategy for fault diagnosis—minimizing the inspection costs

In this paper, a general inspection strategy for system fault diagnosis is presented. The procedure presented in this paper, is an improvement of methods described in papers by Wang [Fault tree diagnosis based on Shannon entropy. Reliab. Engng System Safety, 34 (1991) 143–167], Wang & Cooke [Optimal inspection sequence in fault diagnosis. Reliab. Engng System Safety, 37 (1992) 207–210] and Najmus-Saqib & Ishaque [Inspection strategy in fault diagnosis with unequal effort.Reliab. Engng System Safety, 43 (1994) 275–280]. This general strategy provides the optimal inspection procedure when the inspections require unequal effort and the minimum cut set probabilities are unequal. This feature makes the procedure described in this paper more useful for practical applications than the most recent procedure presented in the paper by Najmus-Saqib & Ishaque, which requires the minimum cut set probabilities to be equal. The inspection strategy described in this paper is based on first inspecting the basic event that will provide the maximum information gain per unit cost invested. The information gain is measured by the decrease of Shannon entropy. A detailed tutorial example is presented.