Ambiguities and Deviations in Qualitative Circuit Analysis

Lee M.H., Bell J. and Coghill G.M., Ambiguities and Deviations in Qualitative Circuit Analysis, in Proc. QR?2001, 15th Int. Workshop on Qualitative Reasoning, San Antonio, Texas, May 2001, pp51-58.

Qualitative electrical circuit models have now been developed by the QR community to the extent that they can be found in commercial software products. Our own work, including this paper, deals with steady-state models applied to design analysis tasks in automotive electrical systems. Our previous method using three valued resistance networks has been very successful in certain applications, particularly those that address the effects of structural circuit changes. More recently we have introduced a many-valued model that allows the effects of value changes to be analysed. In this paper we describe two innovations: a method for the resolution of flow directions and a new treatment of deviations. Both of these are based on a many-valued resistance model with an order-of-magnitude relation. The first technique generalises previous methods and the second offers a new functionality for such models.