From 27f11dc4f4fec0e6e52a5cc4862981fc8dbaba14 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Tue, 26 Oct 2010 15:25:06 +0100 Subject: [PATCH] as given to Hazel to proof read --- fmmd_concept/fmmd_concept.tex | 23 +++++++++++++++++++++-- 1 file changed, 21 insertions(+), 2 deletions(-) diff --git a/fmmd_concept/fmmd_concept.tex b/fmmd_concept/fmmd_concept.tex index c43f9e3..58f8b52 100644 --- a/fmmd_concept/fmmd_concept.tex +++ b/fmmd_concept/fmmd_concept.tex @@ -342,7 +342,7 @@ to smaller and smaller functional modules \cite{maikowski}. \end{itemize} -\section{Proposed Methodology \\ Failure Mode Modular De-Composition (FMMD)} +\section{} \paragraph{New methodology Must be bottom-up} In order to ensure that all component failure modes have been covered @@ -363,7 +363,16 @@ in \cite{maikowski}. This top down technique de-composes by functionality. Simpler and simpler functional blocks are discovered as we delve further into the way the system works and is built. +\paragraph{Design Decision: Methodology Mus be Bottom-up} +In oder to ensure that all component failure modes are handled, +this methodology must statrt at the bottom, with base component failure modes. +In this way automated checking can be applied to all component failure modes +to ensure none have been inadvertantly excluded from the process. + \paragraph{Need for a `bottom-up' system de-composition} +There is an apparent conflict here. The natural way to +de-compose a system is from the top down. +% What is required here is to mimic this top-down de-composition with a bottom up technique. @@ -381,14 +390,24 @@ This means that we have to tie base component failure modes to SYSTEM level errors. This is the `possibility to miss failure mode effects at SYSTEM level' critism of the FTA, FMEDA and FMECA methodologies. +\paragraph{Design Decision: Methodolgy must reduce and collate errors at each functional group stage} +SYSTEMS typically have far fewer failure modes then the sum of its comonent failure modes. +Many SYSTEM level errors may be caused by a variety of component level errors. +At each fucntional group collection, there must be a process to collect +common symptoms and reduce the number of failure modes to handle. \paragraph{How to build a SYSTEM failure behaviour model} The next problem is how to we build a failure mode model that converges to a finite set of SYSTEM level failure modes. % -It would be better would be to analyse the failure mode behaviour in each +It would be better would be to analyse the failure mode behaviour of each functional group, and determine the ways in which it, rather than its components, can fail. +% +By doing this, the natural process whereby symptoms of the {\fg}, +which can potentially be caused by more then one +component failure mode, become the target for reducing the number +of failure modes to handle as we traverse up the hierarchy. \paragraph{Component failures and {\fg} failure symptoms}