A multi-level, multi-purpose qualitative network flow analysis technique

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Student thesis: Master's ThesisMaster of Philosophy

Original languageEnglish
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Award date2011
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Abstract

Research at Aberystwyth into qualitative simulation of electrical circuits has been
word-leading for nearly two decades. During that time, the Advanced Reasoning
Group has developed a variety of electrical circuit simulators. The most successful, CIRQ, has been deployed for more than ten years in industrially useful design analysis systems, and has undergone a range of improvements over that time. MCIRQ is a more advanced version of CIRQ that was developed on the Design for the Whole Vehicle, Whole Lifecycle EPSRC Project at Aberystwyth. It is able to reason about circuits with multiple levels of qualitative resistance, and to indicate the different levels of current activity in the circuit. It showed great promise of being able to assist the design analysis systems in producing improved analysis reports, but was never deployed industrially because it was not able to analyse as wide a set of circuits as the original CIRQ software. This thesis describes a reimplementation of MCIRQ for use with both electrical and fluid flow systems. It extends the theory of electrical qualitative analysis in several ways, and makes several improvements to the original version of MCIRQ: It replaces the Forward-Reverse labelling system of path finding with Series- Parallel reduction system to determine current magnitude and direction.
It improves the Star-Delta Reduction algorithm to deal with problem cases that do not occur in well-formed electrical circuits, but which do occur in the circuits with failure that are dealt with in failure analysis work. It extends MCIRQ to deal with many bridge circuits that were impossible to resolve in the previous version of MCIRQ. It introduces a principled strategy for resolving the direction of current flow within the circuit. The overall effect of these improvements is to transform MCIRQ into a qualitative analysis tool that can be used for real world applications. The thesis illustrates the kinds of analysis that can now be done by MCIRQ that was impossible before. The new MCIRQ has been employed on the ASTRAEA project. It has made possible applications of design analysis for engineering systems that could not have been addressed by any of the previous circuit analysers, notably in the domain of systems with both electrical and hydraulic aspects