A method for fault diagnosis of nonlinear circuits

Abstract

Purpose The purpose of this paper is to develop a method for multiple soft fault diagnosis of nonlinear circuits including fault detection, identification of faulty elements and estimation of their values in real circumstances. Design/methodology/approach The method for fault diagnosis proposed here uses a measurement test leading to a system of nonlinear equations expressing the measured quantities in terms of the circuit parameters. Nonlinear functions, which appear in these equations are not given in explicit analytical form. The equations are solved using a homotopy concept. A key problem of the solvability of the equations is considered locally while tracing the solution path. Actual faults are selected on the basis of the observation that the probability of faults in fewer number of elements is greater than in a larger number of elements. Findings The results indicate that the method is an effective tool for testing nonlinear circuits including bipolar junction transistors and junction field effect transistors. Originality/value The homotopy method is generalized and associated with a restart procedure and a numerical algorithm for solving differential equations. Testable sets of elements are found using the singular value decomposition. The procedure for selecting faulty elements, based on the minimal fault number rule, is developed. The method comprises both theoretical and practical aspects of fault diagnosis.

Soft fault diagnosis of non‐linear circuits having multiple DC solutions

“…For this purpose values of : 0.5, 1.0, 1.5,…, 5.0 V were selected and the corresponding values of were determined. The test was implemented into the diagnostic method proposed in the reference [22] assuming the measurement accuracy 0.1 mV and all resistors ,…, were diagnosed. Six values of each of the resistor were chosen from the range of its nominal value and every time ten sets of the fault‐free parameter values were randomly selected from the tolerance range .…”

“…Note 1 : Now we show that the test based on a multivalued characteristic (Fig. 17) included in the diagnostic method [22] makes the method useless. For this purpose, we chose values of the input voltages 0.5, 1.0, 1.5,…, 5.0, all in volts.…”

“…Numerous methods devoted to soft fault diagnosis have been developed in the last decades, e.g. [4, 5, 9, 10, 13, 16, 17, 21, 22, 25, 28]. Most works in this area concentrate on single fault diagnosis, e.g.…”

“…The method [22] is based on a measurement test carried out in a DC state, similarly as described in Section 2, leading to the test equation having the form (2). To solve this equation a homotopy concept is used and the Newton homotopy equation h(x, t) = f (x) − (1 − t) f (x 0 ) = 0 is written, where x 0 is a vector consisting of nominal parameters and t is a scalar variable.…”

Bulletin of the Polish Academy of Sciences: Technical Sciences

“…May require expensive test equipment and/or processing (thus testing) time [10][11][12]. Lately, methods utilizing sophisticated information analysis (or complex design-for-testability of circuit) are used to read as much information from circuit as possible: wavelet transform, evolutionary optimization or artificial intelligence [13][14][15][16][17][18][19].…”