Investigation of Fault Diagnosis by Transfer Function Techniques

摘要

The program under this contract was directed toward demonstrating the feasibility of fault diagnosis by transfer function techniques for linear electronic circuits. The objective was to be able to diagnose faults to the component level using only available input and output terminals and a minimum number of internal test points. The methodology was to formulate and implement the theories, techniques and computer program required to generate a test procedure to diagnose a general class of linear electronic circuits. The technique investigated is that of observing changes in the breakpoint frequencies and amplitudes of the normal frequency response curves of the circuit under test and relating these changes to the faulty elements so that they may be diagnosed. The validity of this technique is based upon the fact that the breakpoint information together with the gain at any frequency serves to uniquely identify the transfer function of the system. The application of topological formulas to the generation of the symbolic transfer function of the circuit under test, and numerical evaluation of the generated function under normal and simulated failure conditions is the specific technique employed. The computer program developed provides as output data the test procedure for a given circuit and a complete fault dictionary for correlation of circuit failures to the faulty component. The program has been applied to a number of small linear electronic circuits, the results of which demonstrate the feasibility of the fault diagnosis tech-nique. An analysis of the results for a single stage audio amplifier circuit is included.