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