From be082d9311588c7b16fa4051b42a177a2b7b6be1 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Sun, 7 Apr 2013 10:11:20 +0100 Subject: [PATCH] Added links to MUTEX in there Very important to stress the results from one stage of FMMD analysis create a {\dc} with mut ex failure modes. --- submission_thesis/CH2_FMEA/copy.tex | 16 ++++++++++++++-- submission_thesis/CH4_FMMD/copy.tex | 9 +++++++++ 2 files changed, 23 insertions(+), 2 deletions(-) diff --git a/submission_thesis/CH2_FMEA/copy.tex b/submission_thesis/CH2_FMEA/copy.tex index 457ff4b..3347b9f 100644 --- a/submission_thesis/CH2_FMEA/copy.tex +++ b/submission_thesis/CH2_FMEA/copy.tex @@ -625,16 +625,28 @@ approach in looking for system failures. In this section we examine some fundamental concepts and underlying philosophies of FMEA. +\paragraph{Failure modes of a component and mutual exclusivity.} +It is desirable that the failure modes for a component are mutually exclusive, were a component able +to fail in several ways at the same time, this would complicate analysis. +It would mean having to consider combinations of internal component failures +as separate failure modes. This concept is discussed in sections ~\ref{ch4:mutex} +and ~\ref{ch7:mutex}. +% +In general failure modes +for simple components are mutually exclusive +but large and complex components (such as integrated circuits), especially where they contain separate modules, +could have non mutually exclusive failure modes and these need spacial handling, see section~\ref{ch3:mutex}. \paragraph{The signal path.} % C Garret does not like the terms afferent and efferent here, try to think of something else Most electronic systems are used to process a signal: with signal processing -there is usually a clear afferent to transform to efferent path. +there is usually a clear path from the signal coming into the system, it being processed in some way, and a resultant effect on +an output or control signal. % afferent to transform to efferent path. % That is, there is an input, some processing and an output. % -We define the signal path as the components used to process the signal. +For the purpose of FMEA, we define the signal path as the components used to process the signal. % Some circuits have feedback loops or even circular signal paths, but it is normal for a signal path to exist. diff --git a/submission_thesis/CH4_FMMD/copy.tex b/submission_thesis/CH4_FMMD/copy.tex index 03c1076..5922815 100644 --- a/submission_thesis/CH4_FMMD/copy.tex +++ b/submission_thesis/CH4_FMMD/copy.tex @@ -2204,6 +2204,15 @@ in the model. With the above condition true, we term this a `complete' FMMD failure model. Ensuring this condition is described in section~\ref{sec:completetest}. +\paragraph{Mutual exclusivity of {\dc} failure modes.} +It is a desirable feature of a component that its failure modes +are mutually exclusive. +This also applies to {\dcs} produced in the FMMD process. +In the FMMD process symptoms are are collected, i.e no component failure modes may be shared +by a symptom within a {\fg}, and therefore the failure modes of a {\dc} are mutually exclusive. +Thus FMMD naturally produces {\dc} failure modes that are mutually exclusive. +This property is examined in more detail in section~\ref{ch7:mutex}. + \paragraph{State explosion problem of FMEA solved by FMMD.} % Because FMMD considers failure modes within functional groups;