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Robin Clark 2011-05-10 18:57:47 +01:00
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noninvopamp/noninvopamp.tex
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@ -542,10 +542,16 @@ to expand: Cuts sets and minimal cut sets.
A design FMEA, or potential failure mode and effects analysis A design FMEA, or potential failure mode and effects analysis
will typically require the designer to look at the possible effects will typically require the designer to look at the possible effects
of all the component failure modes in the system under investigation. of all the component failure modes in the system under investigation.
FMEA uses the terms `potential causes' and `potential failure modes'.
In an FMMD sense, the `potential causes' are component level failure modes
and the `potential failure modes' are top-level symptoms.
\ifthenelse {\boolean{paper}} \ifthenelse {\boolean{paper}}
{ {
%FMEA - brief description for paper... %FMEA - brief description for paper...
Design FMEA is methodology for assessing potential reliability/dangerous condition early Design FMEA is methodology for assessing potential reliability/dangerous conditions early
in the development cycle. in the development cycle.
FMEA is used to identify potential failure modes, FMEA is used to identify potential failure modes,
determine their effect on the operation of the product, determine their effect on the operation of the product,
@ -553,6 +559,7 @@ and identify actions to mitigate the failures.
FMEA relies anticipating what {\em might} go wrong with a product. FMEA relies anticipating what {\em might} go wrong with a product.
While anticipating every failure mode is not possible, a development team should While anticipating every failure mode is not possible, a development team should
collate as complete a list of potential failure modes as possible. collate as complete a list of potential failure modes as possible.
With an FMMD sourced failure mode to symptom mapping, this With an FMMD sourced failure mode to symptom mapping, this
list should be more complete. It will for instance include list should be more complete. It will for instance include
not only an entry every component failure mode, but has a formal not only an entry every component failure mode, but has a formal
@ -564,16 +571,19 @@ FMEA relies anticipating what {\em might} go wrong with a product.
While anticipating every failure mode is not possible, a development team should While anticipating every failure mode is not possible, a development team should
collate as complete a list of potential failure modes as possible. collate as complete a list of potential failure modes as possible.
With an FMMD sourced failure mode to symptom mapping, this With an FMMD sourced failure mode to symptom mapping, this
list should be more complete. It will for instance include list should be more complete.
It will for instance include
not only an entry every component failure mode, but has a formal not only an entry every component failure mode, but has a formal
reasoning process behind it, which leads to the symptom. reasoning process behind it, which leads to the symptom.
} }
We have from the DAG model, a direct path from each component failure We have from the DAG model, a direct path from each component failure
mode to potential symptoms. This allows us to partially fill in mode to top-level symptoms. This allows us to partially fill in
the FMEA report. The detectability and severity of the symptom the FMEA report. The detectability and severity of the symptom
are subjective. Given component failure rates, the probability 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} of the the potential cause occurring can be calculated, given suitable
component failure mode statistical references. component failure mode statistical references (e.g. FMD-91~\cite{fmd91} and MIL1991~\cite{mil1991}).
\begin{table}[ht] \begin{table}[ht]
\caption{Non Inverting Amplifier: Failure Mode Effects Analysis: Single Faults} % title of Table \caption{Non Inverting Amplifier: Failure Mode Effects Analysis: Single Faults} % title of Table
@ -601,6 +611,11 @@ component failure mode statistical references.
\label{ampfmea} \label{ampfmea}
\end{table} \end{table}
With the partially filled in table the FMEA report only now needs the severity/cost,
probability/occurrence and detectability fields filled in to obtain the
$RPN$ numbers that define the order of importance of failure modes in FMEA.
\subsection{Information missing in FMEA} \subsection{Information missing in FMEA}
to expand: Each FMEA looses the reasoning in the FMMD Hierarchy/DAG for linking to expand: Each FMEA looses the reasoning in the FMMD Hierarchy/DAG for linking