Many-valued logic and qualitative modelling of electrical circuits

Several authors have reported previous work on qual-itative modelling of electrical systems by assumin g steady-state conditions and reducing circuits to net-works of resistive elements. This has been very suc-cessful in certain applications, particularly for Failure Mode Effects Analysis in automotive electrical systems. In support of this work we have concentrated on sim-ple, minimal models that maintain structural isomor-phism with the real system; the motivation being t o provide an accessible conceptual structure for ease o f use by engineering staff. However, a number of difficul-ties remain and solutions to these would increase th e applicability of the method. In this paper we introduce further developments that address several of the remaining important issues and provide solutions to some recent obstacles. After de-scribing a series of problems, we draw on the field o f many-valued logic for inspiration and investigate som e qualitative analogies. The results of a new labelling scheme show the advantages of a 5 valued quantity space for resistance. This is shown to resolve previousl y ambiguous cases and opens up considerably more mod-elling possibilities. The interpretation of the labelling scheme can be tailored to the application domain, giv-ing powerful modelling options