This commit is contained in:
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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@ -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.
\end{itemize}
\section{Re-Factoring the UML Model}
The UML models thus far in this
\ifthenelse {\boolean{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.
This section re-organises and rationalises the UML model.
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
\section{Re-Factoring the UML Model}
The terms used in FMMD and the UML data model are refined in the
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
using a common notation.
The author believes it addresses many short comings in current static failure mode analysis methodologies.
\vspace{60pt}
\today
%\today

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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
of detected and undetected system failure modes to
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
%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.
To take an example from a K type thermocouple, the offset of 1.86mV
%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
\subsection{Undetected Failure Mode: Incorrect Reading}
@ -500,7 +500,7 @@ We can surmise the symptoms in a list.
%\clearpage
\subsection{OP-AMP FIT Calculations}
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
%$\frac{failures}{{10}^6}$
${failures}/{{10}^6}$ % 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
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.
\section{Conclusions}

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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
do-while etc.
At a program flow stage, the software may initiate actions. Typically, in an embedded
system, a micro controller will read from external sensors, and then apply
Generally the flow of data follows a pattern of afferent, transform and efferent.
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.
More generally the flow of data follows a pattern of afferent, transform and efferent.
\subsection{Afferent, Transform and Afferent Data Flow}