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Robin Clark 2011-01-07 09:39:25 +00:00
parent ec6f388a31
commit 74b160a927
3 changed files with 16 additions and 11 deletions
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9
fmmd_concept/fmmd_concept.tex
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@ -1200,12 +1200,13 @@ chosing {\fg}s and working bottom-up this hierarchical trait will occur as a nat
\item It is possible to model multiple failure modes. \item It is possible to model multiple failure modes.
\end{itemize} \end{itemize}
\section{Re-Factoring the UML Model}
The UML models thus far in this
\ifthenelse {\boolean{paper}} \ifthenelse {\boolean{paper}}
{ {
%paper %paper
\pagebreak[4]
\section{Re-Factoring the UML Model}
The UML models thus far in this
have been used to develop the data relationships required to perform FMMD analysis. have been used to develop the data relationships required to perform FMMD analysis.
This section re-organises and rationalises the UML model. This section re-organises and rationalises the UML model.
We want to be able to use {\dcs} in functional groups. We want to be able to use {\dcs} in functional groups.
@ -1225,6 +1226,7 @@ The re-factored UML diagram is shown in figure \ref{fig:refactored_uml}.
} }
{ {
% chapter % chapter
\section{Re-Factoring the UML Model}
The terms used in FMMD and the UML data model are refined in the The terms used in FMMD and the UML data model are refined in the
chapter \ref{defs}. chapter \ref{defs}.
} }
@ -1243,5 +1245,4 @@ provides the background for the need for a new methodology for
static analysis that can span the mechanical electrical and software domains static analysis that can span the mechanical electrical and software domains
using a common notation. using a common notation.
The author believes it addresses many short comings in current static failure mode analysis methodologies. The author believes it addresses many short comings in current static failure mode analysis methodologies.
\vspace{60pt} %\today
\today

8
fmmd_design_aide/fmmd_design_aide.tex
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@ -77,7 +77,7 @@ The `undetectable' failure modes undertsandably, are the most worrying for the s
EN61058, the statistically based European Norm, using ratios EN61058, the statistically based European Norm, using ratios
of detected and undetected system failure modes to of detected and undetected system failure modes to
classify the sytems safety levels and describes sub-clasifications classify the sytems safety levels and describes sub-clasifications
for detected and undetected failure modes \cite{en61508}. for detected and undetected failure modes~\cite{en61508}.
%It is these that are, generally the ones that stand out as single %It is these that are, generally the ones that stand out as single
%failure modes. %failure modes.
@ -231,7 +231,7 @@ and this error symptom, `low\_reading' would mean our plant could
beleive that the temperature reading is lower than it actually is. beleive that the temperature reading is lower than it actually is.
To take an example from a K type thermocouple, the offset of 1.86mV To take an example from a K type thermocouple, the offset of 1.86mV
%from the potential divider represents amplified to %from the potential divider represents amplified to
would represent $\approx \; 46\,^{\circ}{\rm C}$ \cite{eurothermtables} \cite{aoe}. would represent $\approx \; 46\,^{\circ}{\rm C}$~\cite{eurothermtables}~\cite{aoe}.
%\clearpage %\clearpage
\subsection{Undetected Failure Mode: Incorrect Reading} \subsection{Undetected Failure Mode: Incorrect Reading}
@ -500,7 +500,7 @@ We can surmise the symptoms in a list.
%\clearpage %\clearpage
\subsection{OP-AMP FIT Calculations} \subsection{OP-AMP FIT Calculations}
The DOD electronic reliability of components The DOD electronic reliability of components
document MIL-HDBK-217F\cite{mil1992}[5.1] gives formulae for calculating document MIL-HDBK-217F~\cite{mil1991}[5.1] gives formulae for calculating
the the
%$\frac{failures}{{10}^6}$ %$\frac{failures}{{10}^6}$
${failures}/{{10}^6}$ % looks better ${failures}/{{10}^6}$ % looks better
@ -553,7 +553,7 @@ failures per Billion (${10}^9$) hours of operation} of 1.
The switching transistor will be operating at a low frequency The switching transistor will be operating at a low frequency
and well within 50\% of it maximum voltage. and well within 50\% of it maximum voltage.
MIL-HDBK-217F\cite{mil1992}[6-25] gives an exmaple MIL-HDBK-217F~\cite{mil1991}[6-25] gives an exmaple
transistor in these environmental conditions, and assigns an FIT value of 11. transistor in these environmental conditions, and assigns an FIT value of 11.
\section{Conclusions} \section{Conclusions}

10
sw_as_plds/sw_as_plds.tex
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@ -42,11 +42,15 @@ Transitioning between one stage and another depends on decisions made from
variable states. This corresponds to the standard software structures, if-then-else variable states. This corresponds to the standard software structures, if-then-else
do-while etc. do-while etc.
At a program flow stage, the software may initiate actions. Typically, in an embedded Generally the flow of data follows a pattern of afferent, transform and efferent.
system, a micro controller will read from external sensors, and then apply That is to say data is input, processed and data is output.
%At a program flow stage, the software may initiate actions.
In a safety critical control system
typically, an embedded
electro-mechanical system, a micro controller will read from external sensors, and then apply
outputs to control the equipment under supervision. outputs to control the equipment under supervision.
More generally the flow of data follows a pattern of afferent, transform and efferent.
\subsection{Afferent, Transform and Afferent Data Flow} \subsection{Afferent, Transform and Afferent Data Flow}