Merge branch 'master' of dev:/home/robin/git/thesis

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Robin Clark 2011-11-16 09:06:14 +00:00
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@ -825,7 +825,7 @@ mode (i.e. one or more failure modes that caused it).
%
\subsection{FMMD Hierarchy}
\;
By applying stages of analysis to higher and higher abstraction
levels, we can converge to a complete failure mode model of the system under analysis.
Because the symptom abstraction process is defined as surjective (from component failure modes to symptoms)
@ -970,9 +970,18 @@ its range as the number of checks to perform to satisfy a rigorous FMEA inspecti
This can be simplified if we can determine the total number of failure modes in the system $fT$, (i.e. $ fT = \sum_{n=1}^{|fg|} {|fm(c_n)|}$);
equation~\ref{eqn:rd} becomes $$ RD(fg) = fT.(|fg|-1).$$
Equation~\ref{eqn:rd} can also be expressed as
\begin{equation}
\label{eqn:rd2}
%$$
RD(fg) = {|fg|}.{|fm(c_n)|}.{(|fg|-1)} .
%$$
\end{equation}
\pagebreak[4]
\subsection{Reasoning Distance Examples}(c-1)
\subsection{Reasoning Distance Examples}
The potential divider discussed in section~\ref{potdivfmmd} has a four failure modes and two components and therefore has an $RD$ of 4.
$$RD(potdiv) = \sum_{n=1}^{2} |2|.(|1|) = 4 $$
@ -1032,17 +1041,17 @@ Starting at the top, we have a {\fg} with three derived components, each of whic
three failure modes.
Thus the number of checks to make in the top level is $3^0.3.2.3=18$.
On the level below that, we have three {\fgs} each with a
an identical number of checks, $3^1.3.2.3=56$.{\fg}
an identical number of checks, $3^1.3.2.3=56$.%{\fg}
On the level below that we have nine {\fgs}, $3^2.3.2.3=168$.
Adding these together gives $242$ checks to make to perform RFMEA \textbf{within}
{\fgs}.
Adding these together gives $242$ checks to make to perform FMMD (i.e. RFMEA \textbf{within the}
{\fgs}).
If we were to take the system represented in figure~\ref{fig:three_tree}, and
apply RFMEA on it as a whole system, we can use equation~\ref{eqn:rd},
$ RD(fg) = \sum_{n=1}^{|fg|} |fm(c_n)|.(|fg|-1)$, where $|fg|$ is 27, $fm(c_n)$ is 3
and $(|fg|-1)$ is 26.
This gives:
$ RD(fg) = \sum_{n=1}^{27} |3|.(|27|-1) = 2106$
$RD(fg) = \sum_{n=1}^{27} |3|.(|27|-1) = 2106$.
In order to get general equations with which to compare RFMEA with FMMD
we can re-write equation~\ref{eqn:rd} in terms of the number of levels
@ -1069,6 +1078,26 @@ We can now use equation~\ref{eqn:anscen} and \ref{eqn:fmea_state_exp22} to comp
the two approaches, for the work required to perform rigorous checking.
For instance, having four levels
of FMMD analysis, with these fixed numbers,
%(in addition to the top zeroth level)
will require 81 base level components.
$$
%\begin{equation}
\label{eqn:fmea_state_exp22}
3^4.(3^4-1).3 = 81.(81-1).3 = 19440 % \\
%(N^2 - N).f
%\end{equation}
$$
$$
%\begin{equation}
% \label{eqn:anscen}
\sum_{n=0}^{3} {3}^{n}.3.3.(2) = 720
%\end{equation}
$$
\subsection{Exponential squared to Exponential}
can I say that ?

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