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OK prob final version....

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Robin Clark 2012-10-08 21:44:04 +01:00
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39
presentations/System_safety_2012/fmmd_software_pres.tex
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@ -52,8 +52,8 @@
\begin{frame} \begin{frame}
\frametitle{FMEA} \frametitle{FMEA}
We now talk about Failure Mode Effects Analysis, and the different ways it is applied. We now talk about Failure Mode Effects Analysis, and the different ways it is applied.
These techniques are discussed, and then %These techniques are discussed, and then
a refinement(FMMD) is proposed, which is essentially a modularisation of the FMEA process. %a refinement(FMMD) is proposed, which is essentially a modularisation of the FMEA process.
% %
\begin{itemize} \begin{itemize}
@ -596,7 +596,7 @@ judged to be in critical sections of the product.
\begin{itemize} \begin{itemize}
\pause \item FMEA type methodologies were designed for simple electro-mechanical systems of the 1940's to 1960's. \pause \item FMEA type methodologies were designed for simple electro-mechanical systems of the 1940's to 1960's.
\pause \item Reasoning Distance - component failure to system level symptom \pause \item Reasoning Distance - component failure to system level symptom : \pause Software controlled systems have another layer of reasoning distance
\pause \item State explosion - impossible to perform rigorously \pause \item State explosion - impossible to perform rigorously
\pause \item Difficult to re-use previous analysis work \pause \item Difficult to re-use previous analysis work
\pause \item Very Difficult to model simultaneous failures. \pause \item Very Difficult to model simultaneous failures.
@ -617,8 +617,8 @@ judged to be in critical sections of the product.
\pause \item State explosion \pause \item State explosion
\pause \item Rigorous (total coverage) \pause \item Rigorous (total coverage)
\pause \item Reasoning Traceable \pause \item Reasoning Traceable \pause ideally across disciplines \pause Mechanical \pause Electrical \pause Software
\pause \item Re-useable \pause \item Re-usable
\pause \item Simultaneous failures \pause \item Simultaneous failures
%\pause \item %\pause \item
\end{itemize} \end{itemize}
@ -1071,7 +1071,7 @@ missed in an analysis.
\pause \item SFMEA maps variable corruption for {\fms} --- \pause \item SFMEA maps variable corruption for {\fms} ---
\pause this means a large number of combinations --- \pause automated SFMEA \pause this means a large number of combinations --- \pause automated SFMEA
\pause databases \pause databases
\pause tracking the relationships between variable corruption tracking the relationships between variable corruption
and system failure modes and system failure modes
%\pause \item %Because of the large number of combinations for considering all variables as corruptible %\pause \item %Because of the large number of combinations for considering all variables as corruptible
% automated SFMEA % automated SFMEA
@ -1150,7 +1150,7 @@ in a clear and modular model.
\end{figure} \end{figure}
\begin{itemize} \begin{itemize}
\pause \item Pre condition violations are analogous to component failure modes \pause \item Pre condition violations are analogous to component failure modes
\pause \item Post condition violations are analogous to symptoms of failure of the function \pause derived component failure modes \pause \item Post condition violations are analogous to symptoms of failure of the function \pause i.e. the derived component failure modes
\end{itemize} \end{itemize}
\end{frame} \end{frame}
@ -1225,7 +1225,8 @@ General Failure behaviour of {\ft} signalling
\pause \pause
Yourdon, afferent---transform---efferent data flow, in an embedded system our Yourdon, afferent---transform---efferent data flow, in an embedded system our
sensors---data processing/software---actuators. sensors---data processing/software---actuators.
So the electronics are the bottom. \pause
So the electronics are the below software in a modular hierarchy....
\end{frame} \end{frame}
@ -1350,9 +1351,9 @@ We must now look at the software.
\caption{Context Diagram for {\ft} loop} \caption{Context Diagram for {\ft} loop}
\label{fig:ftcontext} \label{fig:ftcontext}
\end{figure} \end{figure}
We consider two software functions, $ fm(Read\_ADC) = \{ CHAN\_NO, VREF \} $ which is called by We consider two software functions, $Read\_ADC()$ which returns a value from the ADC, which is called by
$ fm(read\_4\_20\_input) = \{ VRNGE \} .$ \pause $ Read\_4\_20\_input() .$ which returns a pro-mil value for the input. \pause
As $Read\_ADC$ is the function called it is lower in the call tree hierarchy. \pause As $Read\_ADC$ is the function called it is lower in the call tree hierarchy. \pause
We form a {\fg} with $CMATV$ and this software function. We form a {\fg} with $CMATV$ and this software function.
\end{frame} \end{frame}
@ -1363,7 +1364,7 @@ We form a {\fg} with $CMATV$ and this software function.
\frametitle{FMMD - Example integrated hardware/software system --- {\ft} input} \frametitle{FMMD - Example integrated hardware/software system --- {\ft} input}
\begin{figure}[h] \begin{figure}[h]
\centering \centering
\includegraphics[width=120pt]{./read_adc.jpg} \includegraphics[width=140pt]{./read_adc.jpg}
% read_adc.jpg: 452x514 pixel, 96dpi, 11.96x13.60 cm, bb=0 0 339 386 % read_adc.jpg: 452x514 pixel, 96dpi, 11.96x13.60 cm, bb=0 0 339 386
\caption{Software Function: \textbf{read\_ADC}} \caption{Software Function: \textbf{read\_ADC}}
\label{fig:read_ADC()} \label{fig:read_ADC()}
@ -1426,6 +1427,7 @@ Pre-conditions
We could term the failure modes of this function as We could term the failure modes of this function as
\{ ADC\_TIMEOUT\_OCCURS, INCORRECT\_MUX\_CHAN, INCORRECT\_VREF \} \{ ADC\_TIMEOUT\_OCCURS, INCORRECT\_MUX\_CHAN, INCORRECT\_VREF \}
\pause \pause
\\
We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it interface directly with: CMATV. We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it interface directly with: CMATV.
\end{frame} \end{frame}
@ -1501,7 +1503,7 @@ We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it
\begin{frame} \begin{frame}
\begin{figure}[h] \begin{figure}[h]
\centering \centering
\includegraphics[width=160pt]{./read_4_20_input.jpg} \includegraphics[width=200pt]{./read_4_20_input.jpg}
% read_4_20_input.jpg: 452x514 pixel, 96dpi, 11.96x13.60 cm, bb=0 0 339 386 % read_4_20_input.jpg: 452x514 pixel, 96dpi, 11.96x13.60 cm, bb=0 0 339 386
\caption{Read 4 to 20mA input function} \caption{Read 4 to 20mA input function}
\label{fig:read_4_20_input} \label{fig:read_4_20_input}
@ -1524,7 +1526,7 @@ We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it
This function has one pre-condition, the voltage range ($0.88V \leftrightarrow 4.4V$) This function has one pre-condition, the voltage range ($0.88V \leftrightarrow 4.4V$)
and one postcondition {\ft} current mapped to per-mil integer output. and one postcondition {\ft} current mapped to per-mil integer output.
\pause
We could term the failure mode of this function, voltage out of range, as We could term the failure mode of this function, voltage out of range, as
\{ VRNGE \}. \{ VRNGE \}.
@ -1548,7 +1550,7 @@ We could term the failure mode of this function, voltage out of range, as
1: $RI_{VRGE}$ & voltage & $OUT\_OF\_$ \\ 1: $RI_{VRGE}$ & voltage & $OUT\_OF\_$ \\
& outside range & $RANGE$ \\ \hline & outside range & $RANGE$ \\ \hline
2: $RADC_{VV_ERR}$ & voltage & $VAL\_ERR$ \\ 2: $RADC_{VV\_ERR}$ & voltage & $VAL\_ERR$ \\
& incorrect & \\ \hline & incorrect & \\ \hline
@ -1596,10 +1598,11 @@ $$fm(R420I) = \{OUT\_OF\_RANGE, VAL\_ERR\} .$$
\pause \item Each {\fg} to {\dc} transition represents a documented \pause \item Each {\fg} to {\dc} transition represents a documented
reasoning stage. reasoning stage.
\pause \item Unlike SFMEA software failure modes naturally link with hardware failure modes \pause \item Unlike SFMEA software failure modes naturally link with hardware failure modes
\pause \item Added efficiency benefits \pause \item Added efficiency benefits\pause---smaller reasoning distances\pause---less checking for RFMEA
\pause \item Additionally, using FMMD we can determine a failure model for the hardware/software interface~\cite{sfmeainterface}. \pause \item Additionally, using FMMD we can determine a failure model for the hardware/software interface.%~\cite{sfmeainterface}.
\end{itemize} \end{itemize}
\end{frame}
\begin{frame}
Questions ? Questions ?
%The FMMD method has been demonstrated using the industry standard {\ft} %The FMMD method has been demonstrated using the industry standard {\ft}