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Added FMEA section

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Robin Clark 2011-05-10 18:41:33 +01:00
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noninvopamp/noninvopamp.tex
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@ -280,8 +280,8 @@ We can now derive a `component' to represent this amplifier configuration (see f
%failure mode contours). %failure mode contours).
%\clearpage %\clearpage
\clearpage
\section{Failure Mode as a Directed Acyclic Graph} \section{Failure Modes from non inverting amplifier as a Directed Acyclic Graph (DAG)}
We can now represent the FMMD analysis as a directed graph, see figure \ref{fig:noninvdag0}. We can now represent the FMMD analysis as a directed graph, see figure \ref{fig:noninvdag0}.
With the information structured in this way, we can trace the high level failure mode symptoms With the information structured in this way, we can trace the high level failure mode symptoms
@ -411,7 +411,7 @@ back to their potential causes.
%\clearpage
\section{Extracting Fault Trees from the DAG} \section{Extracting Fault Trees from the DAG}
@ -525,13 +525,88 @@ The FTA diagram directly derived from the FMMD DAG is shown in figure \ref{fig:n
%\clearpage %\clearpage
show an example fault tree, showing the causes and logical (only OR's here) %show an example fault tree, showing the causes and logical (only OR's here)
\section{Extracting FMEA Analysis from the DAG} \subsection{Information missing in FTA}
Extract for each component failure mode the system level cause to expand: Each FTA deals only with one symptom.
\subsubsection{Further refinements}
to expand: Cuts sets and minimal cut sets.
\clearpage
\section{Assisting FMEA reports from the DAG}
A design FMEA, or potential failure mode and effects analysis
will typically require the designer to look at the possible effects
of all the component failure modes in the system under investigation.
\ifthenelse {\boolean{paper}}
{
%FMEA - brief description for paper...
Design FMEA is methodology for assessing potential reliability/dangerous condition early
in the development cycle.
FMEA is used to identify potential failure modes,
determine their effect on the operation of the product,
and identify actions to mitigate the failures.
FMEA relies anticipating what {\em might} go wrong with a product.
While anticipating every failure mode is not possible, a development team should
collate as complete a list of potential failure modes as possible.
With an FMMD sourced failure mode to symptom mapping, this
list should be more complete. It will for instance include
not only an entry every component failure mode, but has a formal
reasoning process behind it, which leads to the symptom.
}
{
See section \ref{pfmea} for an overview of FMEA.
FMEA relies anticipating what {\em might} go wrong with a product.
While anticipating every failure mode is not possible, a development team should
collate as complete a list of potential failure modes as possible.
With an FMMD sourced failure mode to symptom mapping, this
list should be more complete. It will for instance include
not only an entry every component failure mode, but has a formal
reasoning process behind it, which leads to the symptom.
}
We have from the DAG model, a direct path from each component failure
mode to potential symptoms. This allows us to partially fill in
the FMEA report. The detectability and severity of the symptom
are subjective. Given component failure rates, the probability
of the the potential cause occurring can be calculated, using the FMD-91~\cite{fmd91} and MIL1991~\cite{mil1991}
component failure mode statistical references.
\begin{table}[ht]
\caption{Non Inverting Amplifier: Failure Mode Effects Analysis: Single Faults} % title of Table
\centering % used for centering table
\begin{tabular}{||l|l|c|l|c|c|c||}
\hline \hline
\textbf{Item} & \textbf{Potential Failure} & \textbf{ Sev } & \textbf{Potential} & \textbf{prob} & \textbf{det} & \textbf{RPN} \\
\textbf{Function} & \textbf{mode} & \textbf{ /cost }& \textbf{Cause} & \textbf{/occ } & \textbf{} & \\\hline
\hline
Non Inverting & $AMP_{high}$ & & $R1_{short} $ & & & \\
Amplifier & $AMP_{low}$ & & $R1_{open} $ & & & \\
Circuit & $AMP_{low}$ & & $R2_{short} $ & & & \\
& $AMP_{high}$ & & $R2_{open}$ & & & \\
& $AMP_{lowpass}$ & & $OPAMP_{lowslew}$ & & & \\
& $AMP_{low}$ & & $OPAMP_{latchdown}$ & & & \\
& $AMP_{high}$ & & $OPAMP_{latchup}$ & & & \\
& $AMP_{low}$ & & $OPAMP_{noop} $ & & & \\
\hline
\hline
\hline
\end{tabular}
\label{ampfmea}
\end{table}
\subsection{Information missing in FMEA}
to expand: Each FMEA looses the reasoning in the FMMD Hierarchy/DAG for linking
the symptoms to the potential causes.
FMEA can miss symptoms especially where a component failure mode may cause more than one top-level symptom.
\section{Extracting FMECA from the DAG}
Work out the alpha and beta values !!! Work out the alpha and beta values !!!