From 9ea027ac14512db2c26d8d83fe2185583ce93411 Mon Sep 17 00:00:00 2001 From: Robin Date: Sun, 30 May 2010 18:57:41 +0100 Subject: [PATCH] . --- symptom_ex_process/symptom_ex_process.tex | 202 +++++----------------- 1 file changed, 42 insertions(+), 160 deletions(-) diff --git a/symptom_ex_process/symptom_ex_process.tex b/symptom_ex_process/symptom_ex_process.tex index 72789e8..ffc1bb9 100644 --- a/symptom_ex_process/symptom_ex_process.tex +++ b/symptom_ex_process/symptom_ex_process.tex @@ -7,29 +7,25 @@ its component parts. %, and the failure modes of those parts. -The technique uses a graphical notation, based on Euler\cite{eulerviz} and Constraint -diagrams\cite{constraint} to model failure modes and failure mode common symptom collection. -The technique is designed for making building blocks for a hierarchical fault model. +%The technique uses a graphical notation, based on Euler\cite{eulerviz} and Constraint diagrams\cite{constraint} to model failure modes and failure mode common symptom collection. The technique is designed for making building blocks for a hierarchical fault model. Once the failure modes have been determined for a sub-system, that sub-system may be treated as a `component' or `black box' and used in conjunction with other such analysed sub-systems, to model higher level sub-systems. In this way a hierarchy to represent the fault behaviour of a system can be built. - - %FMMD hierarchy The hierarchy is built from the bottom up. Starting with component failure modes at the bottom. Because the process is bottom-up, syntax checking and tracking can ensure that no component failure mode can be overlooked. Once a hierarchy is in place it can be converted into a fault data model. - +% From the fault data model, automatic generation of FTA\cite{nasafta} (Fault Tree Analysis) and mimimal cuts sets\cite{nucfta} are possible. Also statistical reliability\cite{en61508} and MTTF (Mean Time to Failure) calculations can be produced automatically, where component failure mode statistics are available\cite{mil1991}. - +% This paper focuses on the process of building the blocks that are used in the hierarchy. \end{abstract} @@ -100,7 +96,7 @@ A sub-system will be composed of component parts, which may themselves be sub-systems. However each `component part' will have a fault/failure behaviour and it should always be possible to obtain a set of failure modes -for each `component'. +for each `component'. In FMMD terms a sub-system is a derived component. If we look at the sound system again as an example; the CD~player could fail in serveral distinct ways, no matter @@ -153,7 +149,7 @@ Currently this sort of information is generally only available for generic comp System & A product designed to \\ & work as a coherent entity \\ \hline Sub-system & A part of a system, \\ - & sub-systems may contain sub-systems \\ \hline +-or- derived component & sub-systems may contain sub-systems \\ \hline Failure mode & A way in which a System, \\ & Sub-system or component can fail \\ \hline Functional Group & A collection of sub-systems and/or \\ @@ -173,73 +169,43 @@ Base Component & Any bought in component, which \\ \paragraph{symptom abstraction described} -The objective of `symptom abstraction' is to analyse the functional~group and find out what will happen to it, -when specified component failure modes occur. -Once we know how it fails as a functional~group, we can treat it as a component or sub-system +The objective of `symptom abstraction' is to analyse the functional~group and find +how it can fail +when specified components within it fail. +Once we know how functional~group can fail, we can treat it as a component or sub-system with its own set of failure modes. +\paragraph{FMEA applied to the functional Group} +As the functional~group is a set of components, the failure~modes +that we have to consider are all the failure modes of its components. Each failure mode (or combination of) investigated is termed a `test case'. Each `test case' is analysed. The component failure modes are examined with respect to their effect on the functional~group. +\paragraph{Symptom identification and collection} When all `test~cases' have been analysed a second phase is applied. - +% This looks at the results of the `test~cases' as symptoms -of the sub-system. - In this way `test~case~results' are grouped as common symptoms, from the perspective of the sub-system. - To go back to the CD~player example, a failed +of the sub-system. +Single component failures within the functional~group may cause unique symptoms. +However, many failures, when looked at from the perspective of the functional group, will have the same symptoms. +These can be collected as `common symptoms'. +To go back to the CD~player example, a failed output stage, and a failed internal audio amplifier, will both cause the same failure; $no\_sound$ ! +\paragraph{Collection of Symptoms} +The common symptoms of failure are identified and collected. +we can now consider the functional~group as a component and the common symptoms as its failure modes. - -\paragraph{symptom abstraction represented on the diagram} -This process can be applied using a diagram. -From the collection of parts for the sub-system under analysis, a set of failure -modes for each component is obtained. A diagram is then drawn with -each component failure mode represented by a contour. -Component failure mode combinations are -chosen for `test cases'.\footnote{Combinations of component failure modes can be represented by overlapping contours} - -A `test case' is represented on the diagram as a point or asterisk, -in a region enclosed by the contours representing the failure modes it investigates. - -The effect on the sub-system of each test case is analysed. -%It is then represented on the diagram by an asterisk on the contour representing the failure mode. -The `test~case~results' are archived. -When all test cases have been analysed, we switch our attention to a higher abstraction level. -% We treat the sub-system as a black box, or as a component part itsself. -% We can now look at the test case results from the perspective of a `user' -% of this sub-system. -% -% +% \paragraph{symptom abstraction represented on the diagram} This process can be applied using a diagram. From the collection of parts for the sub-system under analysis, a set of failure modes for each component is obtained. A diagram is then drawn with each component failure mode represented by a contour. Component failure mode combinations are chosen for `test cases'.\footnote{Combinations of component failure modes can be represented by overlapping contours} A `test case' is represented on the diagram as a point or asterisk, in a region enclosed by the contours representing the failure modes it investigates. The effect on the sub-system of each test case is analysed. %It is then represented on the diagram by an asterisk on the contour representing the failure mode. The `test~case~results' are archived. When all test cases have been analysed, we switch our attention to a higher abstraction level. % We treat the sub-system as a black box, or as a component part itsself. % We can now look at the test case results from the perspective of a `user' % of this sub-system. % % % We treat the sub-system as a `black box' and view the effects of the component failure % at the sub-system level. This mean we are not interested so much in what the compoent does, % but how the sub-system reacts when it fails in a certain way. % % Each `test case' is labelled from the perspective of the failure as seen at sub-system level. -% -We can now try to simplfy by determining common symptoms. -A common symptom, in this context, is defined as faults caused by different -component failure modes that have the same effect from the perspective -of a `user' of the sub-system. - -Test case results can now viewed as failure modes of the sub-sytem or `black box', and grouped together -where there are common symptoms. -These are grouped together by joining them with lines. These lines form collected groups (or `spiders'). -See figure \ref{fig:gensubsys3}. -% -It can be seen now that each {\em lone test case} and {\em spider} on the -diagram is a distinct failure mode of the sub-system. -This means that these failure modes represent the fault behaviour of the sub-system. -We can now treat this sub-system as a component in its own right, or in other words, -we have derived a failure mode model at a higher level of abstraction. - -We can now draw a new diagram to represent the failure modes of the sub-system. -Each spider or lone test case, becomes a contour representing a failure mode -of the sub-system in this new diagram (see figure \ref{fig:gensubsys4}. - - +% We can now try to simplfy by determining common symptoms. A common symptom, in this context, is defined as faults caused by different component failure modes that have the same effect from the perspective of a `user' of the sub-system. Test case results can now viewed as failure modes of the sub-sytem or `black box', and grouped together where there are common symptoms. These are grouped together by joining them with lines. These lines form collected groups (or `spiders'). See figure \ref{fig:gensubsys3}. +% It can be seen now that each {\em lone test case} and {\em spider} on the diagram is a distinct failure mode of the sub-system. This means that these failure modes represent the fault behaviour of the sub-system. We can now treat this sub-system as a component in its own right, or in other words, we have derived a failure mode model at a higher level of abstraction. We can now draw a new diagram to represent the failure modes of the sub-system. Each spider or lone test case, becomes a contour representing a failure mode of the sub-system in this new diagram (see figure \ref{fig:gensubsys4}. \section{The Process : To analyse a base level sub-system} @@ -249,15 +215,14 @@ To sumarise: \item Determine a minimal functional group \item Obtain list of components in the functional group \item Collect the failure modes for each component - \item Draw these as contours on a diagram - \item Where multiple failures are examined use overlapping contours - \item For each region on the diagram, make a test case - \item Examine each test case and determine the effect of the component failure modes on the behaviour of the functional group +% \item Draw these as contours on a diagram +% \item Where si,ultaneous failures are examined use overlapping contours +% \item For each region on the diagram, make a test case + \item Examine each failure mode of all the components in the functional~group, and determine its effect on the failure behaviour of the functional group \item Collect common symptoms. Imagine you are handed this functional group as a `black box', a sub-system to use. -Determine which test cases produce the same fault symptoms. Join common symptoms with lines connecting them (sometimes termed a `spider'). - \item The lone test cases and the spiders are now the fault mode behaviour of the sub-system. - \item A new diagram can now be drawn where each spider, or lone test case from the original diagram -is represented as a contour. These contours represent the failure modes of the sub-system. +Determine which test cases produce the same fault symptoms.% Join common symptoms with lines connecting them (sometimes termed a `spider'). + \item The lone test cases and the common~symptoms are now the fault mode behaviour of the sub-system/derived~component. + \item A new `derived component' can now be created where each common~symptom, or lone test case is a failure~mode of this new component \end{itemize} @@ -291,53 +256,7 @@ thus - -The failure modes of the components can be represented as contours on -on the diagram in \ref{fig:gensubsys1}. -\begin{figure} - \centering - \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/synmptom_abstraction.jpg} - % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 -\label{fig:gensubsys1} - \caption{$FG_{cfm}$ Component Failure modes represented as contours} -\end{figure} - -% % DIAGRAM WITH SPIDER -% \begin{figure} -% \centering -% \includegraphics[scale=20]{./synmptom_abstraction.jpg} -% % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 -% \label{fig:gensubsys2} -% \caption{$SS_{cfm}$ Component Failure modes represented as contours} -% \end{figure} - - -We can now look at the effects that component failure modes have -on the sub-system. -This process involves examining `test cases'. Each `test case' represents the fault behaviour -of the sub-system due to particular combinations of component fault modes. - -Each test case can be represented on the diagram as a labeled point. -The labeled point will reside in a region on the diagram -enclosed by the contours representing particular component fault modes. -The label will indicate the fault symptom from the perspective of the sub-system. -For the sake of example, only single component failure modes are considered. -We can now assign a test~case to each contour, and mark it on the diagram. - -% \begin{figure}[h+] -% \centering -% \includegraphics[scale=20]{./symptom_abstraction2.jpg} -% % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 -% \label{fig:gensubsys2} -% \caption{Component Failure modes with analysed test cases} -% \end{figure} -\begin{figure} - \centering - \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/symptom_abstraction2.jpg} - % symptom_abstraction2.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 - \label{fig:gensubsys2} - \caption{Component Failure modes with analysed test cases} -\end{figure} +% The failure modes of the components can be represented as contours on on the diagram in \ref{fig:gensubsys1}. \begin{figure} \centering \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/synmptom_abstraction.jpg} % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 \label{fig:gensubsys1} \caption{$FG_{cfm}$ Component Failure modes represented as contours} \end{figure} % % DIAGRAM WITH SPIDER % \begin{figure} % \centering % \includegraphics[scale=20]{./synmptom_abstraction.jpg} % % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 % \label{fig:gensubsys2} % \caption{$SS_{cfm}$ Component Failure modes represented as contours} % \end{figure} We can now look at the effects that component failure modes have on the sub-system. This process involves examining `test cases'. Each `test case' represents the fault behaviour of the sub-system due to particular combinations of component fault modes. Each test case can be represented on the diagram as a labeled point. The labeled point will reside in a region on the diagram enclosed by the contours representing particular component fault modes. The label will indicate the fault symptom from the perspective of the sub-system. For the sake of example, only single component failure modes are considered. We can now assign a test~case to each contour, and mark it on the diagram. % \begin{figure}[h+] % \centering % \includegraphics[scale=20]{./symptom_abstraction2.jpg} % % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 % \label{fig:gensubsys2} % \caption{Component Failure modes with analysed test cases} % \end{figure} \begin{figure} \centering \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/symptom_abstraction2.jpg} % symptom_abstraction2.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 \label{fig:gensubsys2} \caption{Component Failure modes with analysed test cases} \end{figure} \par \vspace{0.3cm} @@ -355,49 +274,26 @@ $c\_2$ & $fs\_7$ \\ \hline \vspace{0.3cm} - -The sub-system fault symptoms are now represented on the diagram as in figure \ref{fig:gensubsys2}. - -A second stage of analysis is now applied. -Empirically, it is often noticed that a sub-system will fail in the same way due to a variety of reasons. -To the `user' of the sub-system, it does not matter which component or combination of components has failed. -The sub-system can thus be considered to have its own set of failure modes. -This stage of the analysis is to determine these, to collect `like symptoms'. -This is performed on the diagram by linking the test cases with lines to form `spiders' - +% The sub-system fault symptoms are now represented on the diagram as in figure \ref{fig:gensubsys2}. A second stage of analysis is now applied. Empirically, it is often noticed that a sub-system will fail in the same way due to a variety of reasons. To the `user' of the sub-system, it does not matter which component or combination of components has failed. The sub-system can thus be considered to have its own set of failure modes. This stage of the analysis is to determine these, to collect `like symptoms'. This is performed on the diagram by linking the test cases with lines to form `spiders' For the sake of example let us consider the fault symptoms $SP1 = \{fs_2, fs_4, fs_5\}$ to be an identical failure mode at the {\em sub-system} level. These can then be joined to form a spider. Likewise let $SP2 = \{fs_1, fs_3, fs_7\}$ be an identical failure mode at the {\em sub-system} level. Let $\{fs_6\}$ be a distinct failure mode at {\em sub-system} level. -The diagram can now be drawn as in figure \ref{fig:gensubsys3}. +% The diagram can now be drawn as in figure \ref{fig:gensubsys3}. % \begin{figure}[h+] % \centering % \includegraphics[scale=20]{./symptom_abstraction3.jpg} % % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 % \label{fig:gensubsys3} % \caption{Common failure modes collected as `Spiders'} % \end{figure} \begin{figure}[h+] \centering \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/symptom_abstraction3.jpg} % symptom_abstraction3.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 \label{fig:gensubsys3} \caption{Common failure modes collected as `Spiders'} \end{figure} -% \begin{figure}[h+] -% \centering -% \includegraphics[scale=20]{./symptom_abstraction3.jpg} -% % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 -% \label{fig:gensubsys3} -% \caption{Common failure modes collected as `Spiders'} -% \end{figure} -\begin{figure}[h+] - \centering - \includegraphics[width=3in,height=3in,bb=0 0 513 541]{symptom_abstraction/symptom_abstraction3.jpg} - % symptom_abstraction3.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 - \label{fig:gensubsys3} -\caption{Common failure modes collected as `Spiders'} -\end{figure} +We have now in $SP1$, $SP2$ and $fs_6$ the three ways in which this sub-system can fail. +In other words we have derived failure modes for this sub-system. +The third stage of the process could be applied automatically. +Each common symptom becomes a failure mode of +a newly created derived component. -The third stage of the process can be applied automatically. -Each `spider' or `lone test case' becomes a contour -in the new diagram (see figure \ref{fig:gensubsys4}. The result of this will be, a set of failure modes for the sub-system, as though it were a {\em black box} or a {\em component} to be used in higher level designs. -We have now in $SP1$, $SP2$ and $fs_6$ the three ways in which this sub-system can fail. -In other words we have derived failure modes for this sub-system. %\section{The Process : To analyse a base level sub-system} @@ -442,7 +338,7 @@ In other words we have derived failure modes for this sub-system. % is represented as a contour. These contours represent the failure modes of the sub-system. % \end{itemize} -This sub-system may now therfore, be represented as three separate failure modes. +This sub-system or derived~component may now therefore, be represented as three separate failure modes. We may now treat this sub-system as we would a component with a known set of failure modes. The failure modes of the Sub-system $SS$ are now the set $SS_{fm} = \{ SP1, Sp2, fs_6 \}$. @@ -466,23 +362,9 @@ The derivation of $SS_{fm}$ is represented graphically using the `$\bowtie$' sym % % synmptom_abstraction.jpg: 570x601 pixel, 80dpi, 18.10x19.08 cm, bb=0 0 513 541 % \label{fig:gensubsys3} % \caption{Deriving a new diagram} -% \end{figure} -% - -\begin{figure}[h+] - \centering - \includegraphics[width=3in,height=3in,bb=0 0 376 410]{symptom_abstraction/symptom_abstraction4.jpg} - % symptom_abstraction4.jpg: 418x455 pixel, 80dpi, 13.27x14.45 cm, bb=0 0 376 410 - \caption{Deriving a new diagram} - \label{fig:gensubsys4} -\end{figure} -The derived diagram in figure \ref{fig:gensubsys4} shows the functional group of components $A,B,C$ -analysed as a sub-system. The result is a set of fault modes that define the fault mode behaviour of that sub-system. - - -This sub-system, with its three error modes, can now be treated as a component (although at a higher level of abstraction) +This sub-system or derived~component, with its three error modes, can now be treated as a component (although at a higher level of abstraction) with known failure modes.