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Robin Clark 2010-10-12 18:13:55 +01:00
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fmmd_concept/fmmd_concept.tex
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@ -19,8 +19,8 @@ modular.}
\section{Introduction} \section{Introduction}
There are three methodologies in common use for failure mode modelling. There are four methodologies in common use for failure mode modelling.
These are FTA, FMEA These are FTA, FMEA, FMECA
and FMEDA (a form of statistical analysis). and FMEDA (a form of statistical analysis).
These methodologies have several draw backs. These methodologies have several draw backs.
@ -221,10 +221,13 @@ to smaller and smaller functional modules \cite{maikowski}.
\end{itemize} \end{itemize}
\section{Proposed Methodology} \section{Proposed Methodology \\ Failure Mode Modular De-Composition (FMMD)}
The proposed methodology will be bottom-up. to fulfill the logical de-composition requirement The proposed methodology will be bottom-up.
it must build {\fg}s from the bottom-up. These are minimal collections of components Thiure that all component failure modes are handled.
The bottom-up approach also fulfills the logical de-composition requirement.
FMMD builds {\fg}s of components from the bottom-up.
Thus the {\fg}s are minimal collections of components
that work together to perform a simple function. that work together to perform a simple function.
We can perform a failure mode effects analysis on each of the component failure We can perform a failure mode effects analysis on each of the component failure
modes within the {\fg}. We can thus ensure that all component failure modes modes within the {\fg}. We can thus ensure that all component failure modes
@ -236,9 +239,24 @@ When we have out set of symptoms, we can now create
a {\dc}. The {\dc} will have as its set of failures a {\dc}. The {\dc} will have as its set of failures
modes, the collected symptoms of the {\fg}. modes, the collected symptoms of the {\fg}.
Because we can now have a {\dc} we can use these to form Because we can now have a {\dcs} we can use these to form
new {\fg}s and we can build a hierarchical model of the system failure modes. new {\fg}s and we can build a hierarchical model of the system failure modes.
Advantages
\begin{itemize}
\item It can be checked, automatically that, all component failure modes have been considered in the model.
\item Because we are modelling with {\fgs} and {\dcs} these can be generic, i.e. mechanical, electronic or software components.
\item The {\dcs} are re-usable, in that commonly used modules can be re-used in other designs/projects.
\item It will have a formal basis, that is to say, it should be able to produce mathematical proofs
for its results (MTTF and the causes for SYSTEM level faults).
\item Overall reliability and danger evaluation statistics can be computed.
\item A graphical representation based on Euler diagrams is proposed.
\item From the top down the failure mode model should will a logical de-composition of the functionality, by
chosing {\fg}s this happens as a natural consequence.
\end{itemize}
%%- \section{building blocks of a safety critical systen} %%- \section{building blocks of a safety critical systen}