ANALOG SYSTEM-LEVEL FAULT-DIAGNOSIS BASED ON A SYMBOLIC METHOD IN THEFREQUENCY-DOMAIN

Concurrently, a symbolic approach for analog system-level fault diagno sis and a systematic approach to maximize the fault location capabilit y are proposed. This unified approach is realized as a result of combi ning the simulation before test (SBT) fault dictionary diagnosis metho d with a symbolic approach. The traditional SBT fault dictionary metho d is often costly and inefficient because of a high number of simulati ons, but it can become very efficient when a symbolic approach is empl oyed. This symbolic approach only requires one analysis for circuit to pology to generate the network transfer function and a parameter subst itution to obtain the frequency response (or time response) of the sys tem. An efficient program is developed to deal with the frequency resp onses of the system to provide the optimum testing point set, and to a utomatically generate the fault dictionary. The ''distance'' between t he measurement data and the frequency responses from the fault diction ary is evaluated to determine the diagnosis results. A practical examp le is presented in order to illustrate the main features of this propo sed analog system fault diagnosis approach.