diff --git a/logic_diagram/logic_diagram.tex b/logic_diagram/logic_diagram.tex index cf5a3e7..dd68b6b 100644 --- a/logic_diagram/logic_diagram.tex +++ b/logic_diagram/logic_diagram.tex @@ -391,51 +391,73 @@ and unused available zones. \section{Context, functional groups, failure modes and symptoms} +The intended application of these diagrams, is to model failure modes +of collection of components, or {\fgs}. The aim is to +create a derived component that represents the {\fg}. +PLD diagrams are designed to aid this process. +% Asterisks represent combinations of failure +%modes. These are failure mode scenarios, or `test~cases'. + \input{shortfg} \subsection{Symptom Collection} +\paragraph{Failure Mode Modular De-Composition (FMMD).} The methodology using these propositional logic diagrams is concerned with taking functional groups of components, analysing how the functional group can fail, and then deriving a failure mode model for the functional group so that we can treat it as a component in its own right, or as a `derived component' +\paragraph{From component failure modes to {\fg} failure modes.} We represent the failure modes of the components within a {\fg} as contours in the diagram. The test cases represent combinations of component failure modes -within the functional group. -The test cases, when analysed can be grouped into $SMG$s. -The SMG, Symptomatically merged group, is a collection of test -cases where the failure symptom is the same. +within the functional group. These are drawn as asterisks on the diagram. % -Each SMG +The test cases, when analysed can be grouped into $SMG$s. +The $SMG$, Symptomatically merged group, is a collection of test +cases where their failure symptoms, from the perspective of the {\fg}, is the same. +% +Each $SMG$ defines a failure mode behaviour of the functional group as though the {\fg} were considered as a high level component. % As we may be interested in treating the functional group -and a component to model higher levels of design, or failure mode abstraction, +as a {\dc} to model higher levels of design, or failure mode abstraction, we can derive a new diagram from the $SMG$s. Each $SMG$ represents a failure mode of the functional group, therefore in the higher level diagram -each SMG is represented by a contour. +each $SMG$ is represented by a contour. { \definition{ \label{SMGderivation} %A diagram can be drawn to represent the collection of $SMG$s. The diagram $d$ represents $SMG$s as graphs of asterisks connected with joining lines. -A new diagram can be derived from this, replacing each SMG with a contour in the new diagram. +A new diagram can be derived from this, replacing each $SMG$ with a contour in the new diagram. This diagram is at one higher level of failure~mode abstraction than the diagram that it was produced from. This diagram is the `symptom collection' diagram derived form $d$. } } -\subsection{Derived Component} +\paragraph{Derived Component.} The diagram $d$ represents the failure modes of a functional group, with the joining lines defining the its symptom collection. -The `symptom collection' respresents the functional group -at a higher level of failure mode abstraction. It represents the -{\fg} as a higher level component, or {\textbf{derived component}}, with a defined set of failure modes. +The `symptom collection' represents the functional group +at a higher level of failure mode abstraction. That is to say, +the contours in the new diagram represent the ways in which the {\fg} considered +as an entity can fail. The new represents the +{\fg} as a higher level component, or {\textbf{derived component}}, with its own set of failure modes. + +\ifthenelse {\boolean{paper}} +{ +% ref symptom extraction process paper HERE +} +{ +Chapter \ref{chap:sympex} describes the symptom abstraction process, detailing algorithms and +validation and consistency checks applied. +} + \section{Example Diagrams} @@ -503,7 +525,7 @@ sub-system failures, for instance two fuel shutdown safety valves failing to clo % reference gas shutoff valve closure example % -\clearpage +%\clearpage \subsection { Logical XOR example } \begin{figure}[h] @@ -556,7 +578,7 @@ under analysis. -\clearpage +%\clearpage \subsection {Labels and usage} %In diagram \ref{fig:ld_meq} Z and W were labelled but were not necessary for the final expression @@ -624,7 +646,7 @@ of $ R = b \oplus c $. In failure analysis, this could be considered to be a functional~group with three failure states $a$,$b$ and $c$. It has three SMG's Q,R and P. Thus there are three ways in which this functional~group is considered to fail. -\clearpage +%\clearpage @@ -688,9 +710,10 @@ by the FMMD software tool. -\clearpage +%\clearpage +\pagebreak[3] \subsection { Inhibit Failure } % @@ -914,6 +937,15 @@ The act of collecting common symptoms by joining lines is seen more intuitive than lists of logic equations. % seen as BY ME ! HA ! It also neatly by-passes the problem of having test cases which could inadvertently be placed into more than one $SMG$. +\ifthenelse {\boolean{paper}} +{ +% explain unitary state failure modes here? I'd rather not have to in the `paper' version.... 16MAR2011 +} +{ +Having $SMG$s share test~cases would violate the concept of unitary state +failure modes (see \ref{sec:unitarystate}). +} + Syntax checking (looking for contradictions and tautologies), as well as detecting errors of omission are automated in the FMMD tool. @@ -954,7 +986,7 @@ configuration is being termed \textbf{pair-wise intersection} of contours, in th A PLD editor can be set to ensure that each diagram has a test case for every double simultaneous failure instance. -\clearpage +\pagebreak[3] \section{N Simultaneous Errors} There are systems where it may be necessary to model for N simultaneous failures. @@ -1013,4 +1045,5 @@ The test case AFE represents the condition where all four engines have failed \c %\theend - +%\pagebreak[4] +\clearpage \ No newline at end of file diff --git a/logic_diagram/paper.tex b/logic_diagram/paper.tex index 392089a..04f7a1f 100644 --- a/logic_diagram/paper.tex +++ b/logic_diagram/paper.tex @@ -23,8 +23,8 @@ %\fancyfoot[LE,RO]{\thepage} \cfoot{Page \thepage\ of \pageref{LastPage}} \rfoot{\today} -\lhead{Propositional Logic Diagram FMMD} - +\lhead{Propositional Logic Diagram } +\rhead{FMMD - Failure Mode Modular De-Composition} % numbers at outer edges \pagenumbering{arabic} % Arabic page numbers hereafter \author{R.P.Clark} diff --git a/shortfg.tex b/shortfg.tex index 906af52..25d6583 100644 --- a/shortfg.tex +++ b/shortfg.tex @@ -8,7 +8,7 @@ of components `functional groups'. % For instance we may have a handful of components brought together to perform a simple function -like amplifying a signal or a power supply. +like a `signal amplifier' or a `power supply'. % The components in a {\fg} can be considered to be `functionally~adjacent' to each other, in that