diff --git a/presentations/fmea/fmea_pres.tex b/presentations/fmea/fmea_pres.tex index b883409..941f73e 100644 --- a/presentations/fmea/fmea_pres.tex +++ b/presentations/fmea/fmea_pres.tex @@ -45,20 +45,42 @@ \begin{frame} - + \frametitle{ FMEA Example: Milli-volt reader} Example: Let us consider a system, in this case a milli-volt reader, consisting of instrumentation amplifiers connected to a micro-processor that reports its readings via RS-232. +\begin{figure} + \centering + \includegraphics[width=175pt]{./mvamp.png} + % mvamp.png: 561x403 pixel, 72dpi, 19.79x14.22 cm, bb=0 0 561 403 +\end{figure} + + +\end{frame} + + +\begin{frame} + \frametitle{FMEA Example: Milli-volt reader} Let us perform an FMEA and consider how one of its resistors failing could affect it. -For the sake of example let us choose a resistor in an OP-AMP -reading the milli-volt source and that if it were to go open, we would have a gain -of 1 from the amplifier. +For the sake of example let us choose resistor R1 in the OP-AMP gain circuitry. +\begin{figure} + \centering + \includegraphics[width=175pt]{./mvamp.png} + % mvamp.png: 561x403 pixel, 72dpi, 19.79x14.22 cm, bb=0 0 561 403 +\end{figure} +\end{frame} + + + + +\begin{frame} + \frametitle{FMEA Example: Milli-volt reader} \begin{itemize} \pause \item \textbf{F - Failures of given component} The resistor could fail by going OPEN or SHORT (EN298 definition). \pause \item \textbf{M - Failure Mode} Consider the component failure mode OPEN - \pause \item \textbf{E - Effects} This will disconnect the feedback loop in the amplifier causing a LOW READING + \pause \item \textbf{E - Effects} This will disconnect the feedback loop in the amplifier, driving the minus input HIGH causing a LOW READING \pause \item \textbf{A - Analysis} The reading will be out of normal range, and we will have an erroneous milli-volt reading \end{itemize} \end{frame} @@ -83,26 +105,28 @@ approach in looking for system failures. Consider the analysis where we look at all the failure modes in a system, and then see how they can affect all other components within it. - - -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. \end{frame} -\begin{frame} + \begin{frame} \frametitle{Rigorous Single Failure FMEA} - +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 the equation below. %~\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_single} N.(N-1).cfm % \\ %(N^2 - N).cfm \end{equation} +\end{frame} + +\begin{frame} +\frametitle{Rigorous Single Failure FMEA} This would mean an order of $N^2$ number of checks to perform to perform `rigorous~FMEA'. Even small systems have typically 100 components, and they typically have 3 or more failure modes each. @@ -330,7 +354,7 @@ safety Integrity. For Hardware FMEDA does force the user to consider all components in a system -by requiring that a MTTF value is assigned. +by requiring that a MTTF value is assigned for each failure~mode. This MTTF may be statistically mitigated (improved) if it can be shown that selfchecking will detect failure modes. \end{frame} @@ -421,8 +445,8 @@ FMEDA is a modern extension of FMEA, in that it will allow for self checking features, and provides detailed recommendations for computer/software architecture. It also has a simple final result, a Safety Integrity Level (SIL) from 1 to 4 (where 4 is safest). -FMEA can be used as a term simple to mean Failure Mode Effects Analysis, and is -part of product approval for many regulated products in the EU and the USA... +%FMEA can be used as a term simple to mean Failure Mode Effects Analysis, and is +%part of product approval for many regulated products in the EU and the USA... \end{frame} @@ -672,7 +696,9 @@ not all the components in the system. \textbf{traceability} Because each reasoning stage contains associations ($FailureMode \mapsto Sypmtom$) we can trace the `reasoning' from base level component failure mode to top level/system -failure. +failure, by traversing the tree. + + \end{frame} \begin{frame} diff --git a/presentations/fmea/mvamp.dia b/presentations/fmea/mvamp.dia new file mode 100644 index 0000000..ccf9f9a Binary files /dev/null and b/presentations/fmea/mvamp.dia differ