A simulation research on gradual faults in analog circuits for PHM

Prognostic and Health Management (PHM) is a key technology for condition-based maintenance and autonomic support, and electronic systems are one of the main application areas in PHM. An electronic system generally consists of digital circuits and analog circuits. However, it seems an aporia concerning the methods of the fault diagnosis and prognosis for analog circuits in current status. For real-time diagnosis and prognosis, various suitable intelligent algorithms are needed, and appropriate data is also needed to select and evaluate the intelligent algorithms. Since the real data are not easy to obtain, instead, simulation data can be considered. In addition, hard faults like open or short circuits are not usual but the gradual failures such as parameters shifting, usually happens. So, it is more valuable to simulate gradual failures and get their data for detecting the applicability of various diagnostic and prognosis algorithms. A voltage-controlled function generator, which wholly consists of analog circuits, is used for the case study in this chapter. First one or more resistors as the coming failure components are selected and defined according to the circuit diagram in the sensitive areas which are determined by thermal analysis, vibration analysis and life analysis. Then, a set of simulation data at different test points is obtained by the Multisim software through gradually varying resistance values of the defined failure resistors while simulating the tolerances of the other normal components by Monte Carlo method at the same time. At last, an experiment was carried out to prove the feasibility of the above simulation method by using the real rheostats instead of the defined failure resistors, and a set of test data at different test points is obtained.