Optimal periodic testing policy for a system with self-testing

Let us consider a system such as a logic circuit with self-testing in which fault detection is possible by checking the output code during the usual operating cycles. However, in the case of a system with incomplete self-testing properties, a fault may not be detected immediately when it occurs. Hence, even if the system has an input code providing an output code to detect a fault, the fault cannot easily be discovered if the input code does not occur frequently. Therefore, it is necessary to perform testing periodically. However, there is a possibility of degrading system performance if unnecessarily many tests are performed. In the present study, the loss cost per unit time from the occurrence of a fault to its detection is introduced and the expected cost when periodic testing is performed is analytically derived. Also, the optimum periodic test interval minimizing the expected cost is discussed. Specific numerical examples for a system whose failure distribution has an exponential are given and discussed. (C) 2004 Wiley Periodicals, Inc.