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OK CH2 needs all the 'we' and 'our' sentences

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re-written. Ballcocks. AND CH4, caryy on with AF comments.
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Robin Clark 2013-09-06 18:48:10 +01:00
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submission_thesis/CH3_FMEA_criticism/copy.tex
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@ -21,12 +21,12 @@ our lives safer. This chapter aims to look for the deficiencies in current FMEA
and look for ways in which it could be performed better and more efficiently. and look for ways in which it could be performed better and more efficiently.
A major problem is with the scope of A major problem is with the scope of
examination---i.e. which/how~many components should we check against a particular failure mode---to examination---i.e. which/how~many components should be checked against a particular failure mode---to
apply for FMEA analysis. apply for FMEA analysis.
% %
Checking all combinations quickly leads to a state explosion problem: Checking all possible combinations of {\fms} against all components quickly leads to a state explosion problem. %:
defining limits for the number of components to check for against a given {\bc} %defining limits for the number of components to check for against given {\bc}
{\fm} could address this. %{\fms} could address this.
% %
The difficulties of integrating software The difficulties of integrating software
and hardware in FMEA failure models mean that FMEA is showing its age: designed and hardware in FMEA failure models mean that FMEA is showing its age: designed
@ -63,7 +63,7 @@ traceable reasoning) FMEA models are presented.
Finally we conclude with a list of deficiencies in current FMEA methodologies and present a wish list Finally we conclude with a list of deficiencies in current FMEA methodologies and present a wish list
for an improved methodology. for an improved methodology.
\section{Historical Origins of FMEA: {\bc} {\fm} to system level failure/symptom paradigm} \section{Historical Origins of FMEA and the {\bc} {\fm} to system level failure/symptom paradigm}
\subsection{FMEA: {\bc} {\fm} to system level failure modelling} \subsection{FMEA: {\bc} {\fm} to system level failure modelling}
FMEA traces it roots to the 1940s when it was used to identify the most costly FMEA traces it roots to the 1940s when it was used to identify the most costly
@ -145,12 +145,12 @@ This can be seen as an indicator of the lack of
cause to effect precision possible when analysing cause to effect precision possible when analysing
large systems using FMEA. large systems using FMEA.
% %
Ideally this relationship would be one to one. Ideally this relationship would be many ({\bc} {\fms}) to one (system level symptoms).
% %
This would be beneficial in terms of validating This would be beneficial in terms of validating
precision of analysis, and for by-products of precision of analysis, and for by-products of
the process such as developing diagnostic fault trees from the process such as developing diagnostic fault trees~\cite{cbds}[Ch 6.2] from
FMEA analyses. FMEA results.
\section{Comparison Complexity} \section{Comparison Complexity}
%\section{Reasoning Distance used to measure Comparison Complexity} %\section{Reasoning Distance used to measure Comparison Complexity}
@ -177,16 +177,17 @@ other system level symptoms.
% Were we to compare the reasoning distance with the theoretical maximum, the sum of all failure % Were we to compare the reasoning distance with the theoretical maximum, the sum of all failure
% modes in a system, multiplied by the number of components in it, we could arrive at a maximum % modes in a system, multiplied by the number of components in it, we could arrive at a maximum
% reasoning distance, which we can use as a comparison complexity figure. % reasoning distance, which we can use as a comparison complexity figure.
If the reasoning distance is compared with the theoretical maximum, i.e. If a reasoning distance used is compared with the theoretical maximum, i.e.
as defined in equation~\ref{eqn:fmea_single}, this can be used as a comparison complexity figure. as defined in equation~\ref{eqn:fmea_single},
comparison complexity figures can be produced.
% %
% This figure would mean we could compare the maximum number of checks (i.e. exhaustive %rigorous % This figure would mean we could compare the maximum number of checks (i.e. exhaustive %rigorous
% analysis) with the number actually performed. % analysis) with the number actually performed.
This figure would mean this maximum number of checks (i.e. exhaustive %rigorous Comlexity comparision means this maximum number of checks (i.e. exhaustive %rigorous
analysis) could be compared to the number actually performed. analysis) could be compared to the number actually performed.
% %
In effect a yard~stick for the efficiency, in terms of work, In effect a yard~stick for the amount of work performed
for a particular analysis technique. for a particular FMEA analysis technique/strategy.
\paragraph{The ideal of exhaustive FMEA (XFMEA).} \paragraph{The ideal of exhaustive FMEA (XFMEA).}
% %

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submission_thesis/CH4_FMMD/instance_diagram_NONINVAMP.dia
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