Determine the Masking Fault Sets in Complex Systems

Fault isolation could be categorized into two classes, the single fault isolation and the multiple faults isolation. By using the hidden fault set and the masking fault set concept, M. Shakeri et. al proposed a simple algorithm to isolate multiple faults in a complex system. In this paper, we will propose a method of identifying the minimum masking fault set. The method starts with the assumption that a suboptimal sequential single fault diagnosis tree was already obtained, and we will show how to proceed, staring from the parent node consisting of all the possible failure sources, all the way down to obtain the minimum masking fault set at each final leaf node. We give two examples in the paper to verify our proposed method. We first use the example given by K.R. Pattipati et. al to find the minimum masking fault set at each individual leaf node, the result is then compared with that obtained by M. Shakeri et. al. It is shown that our result is consistent with that obtained by M. Shakeri et. al. In the second example, we apply our method to a more complicated model, and employ the sequential single fault diagnosis tree generated by TEAMS Engineering tool from Qualtech Systems Inc., which is able to provide masking fault set information as well. We thus determine the minimum masking fault set for the isolated failure source using our proposed method, and compare the result with that obtained by TEAMS Engineering tool.