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moved approvals FMEA to the end

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Robin Clark 2011-09-30 11:10:30 +01:00
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146
presentations/fmea/fmea_pres.tex
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@ -131,41 +131,6 @@ double failure scenarios (for burner lock-out scenarios).
\end{frame}
\section{FMEA used for Saftey Critical Aprovals}
\begin{frame}
\frametitle{Safety Critical Approvals FMEA}
Experts from Approval House and Equipement Manufacturer
discuss selected component failure modes
judged to be in critical sections of the product.
\begin{figure}[h]
\centering
\includegraphics[width=100pt,keepaspectratio=true]{./tech_meeting.png}
% tech_meeting.png: 350x299 pixel, 300dpi, 2.97x2.53 cm, bb=0 0 84 72
\caption{FMEA Meeting}
\label{fig:tech_meeting}
\end{figure}
\end{frame}
\begin{frame}
\frametitle{Safety Critical Approvals FMEA}
\begin{figure}[h]
\centering
\includegraphics[width=70pt,keepaspectratio=true]{./tech_meeting.png}
% tech_meeting.png: 350x299 pixel, 300dpi, 2.97x2.53 cm, bb=0 0 84 72
\caption{FMEA Meeting}
\label{fig:tech_meeting}
\end{figure}
\begin{itemize}
\pause \item Impossible to look at all component failures let alone apply FMEA rigorously.
\pause \item In practise, failure scenarios for critical sections are contested, and either justified or extra safety measures implemented.
\pause \item Meeting notes or minutes only.
\end{itemize}
\end{frame}
\section{PFMEA - Production FMEA : 1940's to present}
@ -345,6 +310,7 @@ if it can be shown that selfchecking will detect failure modes.
\end{frame}
\begin{frame}
\frametitle{ FMEDA - Failure Modes Effects and Diagnostic Analysis}
Failure modes are classified as Safe or Dangerous according
to the putative system level failure they will cause.
The Failure modes are also classified as Detected or
@ -356,6 +322,7 @@ is represented by lambda variables
(i.e. $\lambda_{SD}$, $\lambda_{SU}$, $\lambda_{DD}$, $\lambda_{DU}$).
\end{frame}
\begin{frame}
\frametitle{ FMEDA - Failure Modes Effects and Diagnostic Analysis}
\textbf{Diagnostic Coverage.}
The diagnostic coverage is simply the ratio
of the dangerous detected probabilities
@ -369,6 +336,7 @@ $$ DiagnosticCoverage = \Sigma\lambda_{DD} / \Sigma\lambda_D $$
\begin{frame}
\frametitle{ FMEDA - Failure Modes Effects and Diagnostic Analysis}
The diagnostic coverage for safe failures, where $\Sigma\lambda_{SD}$ represents the percentage of
safe detected base component failure modes,
and $\Sigma\lambda_S$ the total number of safe base component failure modes,
@ -388,9 +356,49 @@ $$ SFF = \big( \Sigma\lambda_S + \Sigma\lambda_{DD} \big) / \big( \Sigma\lambda_
\end{frame}
\begin{frame}
\frametitle{ FMEDA - Failure Modes Effects and Diagnostic Analysis}
SIL Levels are how they are calculated
\end{frame}
\section{FMEA used for Safety Critical Approvals}
\begin{frame}
\frametitle{Safety Critical Approvals FMEA}
Experts from Approval House and Equipment Manufacturer
discuss selected component failure modes
judged to be in critical sections of the product.
\begin{figure}[h]
\centering
\includegraphics[width=100pt,keepaspectratio=true]{./tech_meeting.png}
% tech_meeting.png: 350x299 pixel, 300dpi, 2.97x2.53 cm, bb=0 0 84 72
\caption{FMEA Meeting}
\label{fig:tech_meeting}
\end{figure}
\end{frame}
\begin{frame}
\frametitle{Safety Critical Approvals FMEA}
\begin{figure}[h]
\centering
\includegraphics[width=70pt,keepaspectratio=true]{./tech_meeting.png}
% tech_meeting.png: 350x299 pixel, 300dpi, 2.97x2.53 cm, bb=0 0 84 72
\caption{FMEA Meeting}
\label{fig:tech_meeting}
\end{figure}
\begin{itemize}
\pause \item Impossible to look at all component failures let alone apply FMEA rigorously.
\pause \item In practise, failure scenarios for critical sections are contested, and either justified or extra safety measures implemented.
\pause \item Meeting notes or minutes only.
\end{itemize}
\end{frame}
\section{FMEA - General Criticism}
\begin{frame}
\frametitle{FMEA - General Criticism}
@ -402,42 +410,60 @@ $$ SFF = \big( \Sigma\lambda_S + \Sigma\lambda_{DD} \big) / \big( \Sigma\lambda_
\pause \item FMEA type methodologies were designed for simple electro-mechanical systems of the 1940's to 1960's.
\end{itemize}
FMEDA is a modern extension of FMEA, in that it will allow for
self checking features, and provides detailed recommendations for computer/software architecture,
but
%FMEDA is a modern extension of FMEA, in that it will allow for
%self checking features, and provides detailed recommendations for computer/software architecture,
%but
\end{frame}
\begin{frame}
\frametitle{FMEA - Better Metodology - Wish List}
\begin{itemize}
\pause \item State explosion
\pause \item Rigorous
\pause \item Reasoning Traceable
\pause \item re-useable
\pause \item
\end{itemize}
%FMEDA is a modern extension of FMEA, in that it will allow for
%self checking features, and provides detailed recommendations for computer/software architecture,
%but
\end{frame}
\section{Failure Mode Modular De-Composition}
\subsection{FMEA and complexity of each failure scenario analysis}
\begin{frame}
Consider the FMEA type methodologies
where we look at all the failure modes in a system, and then
see how they can affect all other components within it,
to determine its system level symptom or failure mode.
We need to look at a large number of failure scenarios
to do this completely (all failure modes against all components).
This is represented in equation~\ref{eqn:fmea_state_exp},
where $N$ is the total number of components in the system, and
$cfm$ is the number of failure modes per component.
\begin{equation}
\label{eqn:fmea_state_exp}
N.(N-1).cfm % \\
%(N^2 - N).cfm
\end{equation}
% Consider the FMEA type methodologies
% where we look at all the failure modes in a system, and then
% see how they can affect all other components within it,
% to determine its system level symptom or failure mode.
% We need to look at a large number of failure scenarios
% to do this completely (all failure modes against all components).
% This is represented in equation~\ref{eqn:fmea_state_exp},
% where $N$ is the total number of components in the system, and
% $cfm$ is the number of failure modes per component.
%
% \begin{equation}
% \label{eqn:fmea_state_exp}
% N.(N-1).cfm % \\
% %(N^2 - N).cfm
% \end{equation}
The FMMD methodology breaks the analysis down into small stages,
by making the analyst choose functional groups, and then when analysed the groups
are treated as components to be used for a higher stage.
This is designed to address the state explosion (where $O$ is order
by making the analyst choose functional groups of components, which are then when analysed.
When analysed, we will have a set of symptoms of failure for the functional group.
We can then create a derived~component,
to represent the functional group.
We can use derived components to form `higher~level' functional groups.
This addresses the state explosion (where $O$ is order
of complexity) $O=N^2$ inherent in equation~\ref{eqn:fmea_state_exp}.
\end{frame}
\begin{frame}
We can view the functional groups in FMMD as forming a hierarchy.
If for the sake of example we consider each functional group to
be three components, figure~\ref{fig:three_tree} shows
@ -451,7 +477,7 @@ how the levels work and converge to a top or system level.
\label{fig:three_tree}
\end{figure}
\clearpage
\end{frame}
We can represent the number of failure scenarios to check in an FMMD hierarchy
with equation~\ref{eqn:anscen}.
@ -498,7 +524,7 @@ group is the same for equation~\ref{eqn:fmea_state_exp22}
and equation~\ref{eqn:anscen}.
\clearpage
\section{Example}
%\section{Example}
To see the effects of reducing `state~explosion' we need to look at a larger system.
Let us take a system with 3 levels and apply these formulae.