From 3b897e85d2125ebbf53f895fe2185852e73d6d40 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Mon, 8 Oct 2012 21:44:04 +0100 Subject: [PATCH] OK prob final version.... --- .../System_safety_2012/fmmd_software_pres.tex | 39 ++++++++++--------- 1 file changed, 21 insertions(+), 18 deletions(-) diff --git a/presentations/System_safety_2012/fmmd_software_pres.tex b/presentations/System_safety_2012/fmmd_software_pres.tex index b8f6aec..4f3ed15 100644 --- a/presentations/System_safety_2012/fmmd_software_pres.tex +++ b/presentations/System_safety_2012/fmmd_software_pres.tex @@ -52,8 +52,8 @@ \begin{frame} \frametitle{FMEA} We now talk about Failure Mode Effects Analysis, and the different ways it is applied. -These techniques are discussed, and then -a refinement(FMMD) is proposed, which is essentially a modularisation of the FMEA process. +%These techniques are discussed, and then +%a refinement(FMMD) is proposed, which is essentially a modularisation of the FMEA process. % \begin{itemize} @@ -596,7 +596,7 @@ judged to be in critical sections of the product. \begin{itemize} \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 Difficult to re-use previous analysis work \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 Rigorous (total coverage) - \pause \item Reasoning Traceable - \pause \item Re-useable + \pause \item Reasoning Traceable \pause ideally across disciplines \pause Mechanical \pause Electrical \pause Software + \pause \item Re-usable \pause \item Simultaneous failures %\pause \item \end{itemize} @@ -1071,7 +1071,7 @@ missed in an analysis. \pause \item SFMEA maps variable corruption for {\fms} --- \pause this means a large number of combinations --- \pause automated SFMEA \pause databases - \pause tracking the relationships between variable corruption + tracking the relationships between variable corruption and system failure modes %\pause \item %Because of the large number of combinations for considering all variables as corruptible % automated SFMEA @@ -1150,7 +1150,7 @@ in a clear and modular model. \end{figure} \begin{itemize} \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{frame} @@ -1225,7 +1225,8 @@ General Failure behaviour of {\ft} signalling \pause Yourdon, afferent---transform---efferent data flow, in an embedded system our 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} @@ -1350,9 +1351,9 @@ We must now look at the software. \caption{Context Diagram for {\ft} loop} \label{fig:ftcontext} \end{figure} -We consider two software functions, $ fm(Read\_ADC) = \{ CHAN\_NO, VREF \} $ which is called by -$ fm(read\_4\_20\_input) = \{ VRNGE \} .$ \pause -As $Read\_ADC$ is the function called it is lower in the call tree hierarchy. \pause +We consider two software functions, $Read\_ADC()$ which returns a value from the ADC, which is called by +$ 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 We form a {\fg} with $CMATV$ and this software function. \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} \begin{figure}[h] \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 \caption{Software Function: \textbf{read\_ADC}} \label{fig:read_ADC()} @@ -1426,6 +1427,7 @@ Pre-conditions We could term the failure modes of this function as \{ ADC\_TIMEOUT\_OCCURS, INCORRECT\_MUX\_CHAN, INCORRECT\_VREF \} \pause +\\ We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it interface directly with: CMATV. \end{frame} @@ -1501,7 +1503,7 @@ We now create a {\fg} called RADC consisting of read\_ADC() and the hardware it \begin{frame} \begin{figure}[h] \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 \caption{Read 4 to 20mA input function} \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 ($0.88V \leftrightarrow 4.4V$) 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 \{ VRNGE \}. @@ -1548,7 +1550,7 @@ We could term the failure mode of this function, voltage out of range, as 1: $RI_{VRGE}$ & voltage & $OUT\_OF\_$ \\ & outside range & $RANGE$ \\ \hline - 2: $RADC_{VV_ERR}$ & voltage & $VAL\_ERR$ \\ + 2: $RADC_{VV\_ERR}$ & voltage & $VAL\_ERR$ \\ & incorrect & \\ \hline @@ -1596,10 +1598,11 @@ $$fm(R420I) = \{OUT\_OF\_RANGE, VAL\_ERR\} .$$ \pause \item Each {\fg} to {\dc} transition represents a documented reasoning stage. \pause \item Unlike SFMEA software failure modes naturally link with hardware failure modes - \pause \item Added efficiency benefits - \pause \item Additionally, using FMMD we can determine a failure model for the hardware/software interface~\cite{sfmeainterface}. + \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}. \end{itemize} - +\end{frame} +\begin{frame} Questions ? %The FMMD method has been demonstrated using the industry standard {\ft}