Research On Fault Diagnosis Approach At Subnetwork Level In Large Analog Circuits

To the complicated circuits and systems, all kinds of fault diagnosis approaches at element level have been not competent for the need of fault diagnosis in engineering yet. Based on the network decomposition approach the fault diagnosis approach at subnetwork level decomposes the large scale circuit into several subnetworks and then diagnoses the subnetworks respectively. So it can simplify the computation. It is fast and effective. Especially, where there are physical or functional blocks and subnetworks which are indiscerptible in the network, it shows its practical value.This paper researches the fault diagnosis approach at subnetwork level in large analog circuits on the aspects as follows:(l)When the network decomposition approach was proposed, the tearing nodes only can chose the accessible nodes and the decomposition of the circuit is not discretional, so the development and application of the fault diagnosis approach at subnetwork level is astricted. This paper introduces a modified network decomposition approach of circuit which breaks through the restrict that all the tearing nodes must be accessible and makes the decomposition of network flexible. This paper introduces the condition in topology that the circuit is solvable when the tearing nodes include inaccessible nodes, discusses the suitable self-testing conditions and mutual-testing conditions for all kinds of decomposition cases in which circuit satisfies solvability conditions and reseaches deeply the hierachical search approach that can search the faulty subnetwork in large analog circuit fast.(2)Because the diagnosis speed of logical analysis is slow, this paper presents logical diagnosis matrix approach. Based on it, the paper introduces Bidirectional Associative Memory Neural Network (BAMN) and stores the logic diagnosis matrix in the BAMN. If only the actual diagnosis code is input to BAMN, fault messages will be quickly obtained in the export terminal of BAMN and the faulty subnetwork is located. So the speed of fault diagnosis at subnetwork level is improved further.(3)Interval mathematics is a powerful tool for the analysis of tolerance in analog circuits. The paper introduces the basic theory of interval mathematics, based on which the paper presents a criterion that diagnoses the fault of tolerant circuits and the self-testing conditions and mutual-testing conditions that diagnose the fault of tolerant subnetwork. It solves the problem that the faults of tolerant circuits are diagnosed...