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bib cites are case sensitive! bib entries are not. confusiion...

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Robin Clark 2010-08-30 09:56:35 +01:00
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78
component_failure_modes_definition/component_failure_modes_definition.tex
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@ -587,45 +587,45 @@ of failure modes within components, but also ensuring that combinations across c
do not involve any pairs of failure modes within the same component. do not involve any pairs of failure modes within the same component.
A recursive algorithm and proof is described in appendix \ref{chap:vennccps}. A recursive algorithm and proof is described in appendix \ref{chap:vennccps}.
\paragraph{Practicality} %%\paragraph{Practicality}
Functional Group may consist, typically of four or five components, which typically %%Functional Group may consist, typically of four or five components, which typically
have two or three failure modes each. Taking a worst case of mutiplying these %%have two or three failure modes each. Taking a worst case of mutiplying these
by a factor of five (the number of failure modes and components) would give %%by a factor of five (the number of failure modes and components) would give
$25 \times 15 = 375$ %%$25 \times 15 = 375$
%%
%%
%%
\begin{verbatim} %%\begin{verbatim}
%%
# define a factorial function %%# define a factorial function
# gives 1 for negative values as well %%# gives 1 for negative values as well
define f(x) { %%define f(x) {
if (x>1) { %% if (x>1) {
return (x * f (x-1)) %% return (x * f (x-1))
} %% }
return (1) %% return (1)
%%
} %%}
define u1(c,x) { %%define u1(c,x) {
return f(c*x)/(f(1)*f(c*x-1)) %% return f(c*x)/(f(1)*f(c*x-1))
} %%}
define u2(c,x) { %%define u2(c,x) {
return f(c*x)/(f(2)*f(c*x-2)) %% return f(c*x)/(f(2)*f(c*x-2))
} %%}
%%
define uc(c,x) { %%define uc(c,x) {
return c * f(x)/(f(2)*f(x-2)) %% return c * f(x)/(f(2)*f(x-2))
} %%}
%%
# where c is number of components, and x is number of failure modes %%# where c is number of components, and x is number of failure modes
# define function u to calculate combinations to check for double sim failure modes %%# define function u to calculate combinations to check for double sim failure modes
define u(c,x) { %%define u(c,x) {
f(c*x)/(f(1)*f(c*x-1)) + f(c*x)/(f(2)*f(c*x-2)) - c * f(c)/(f(2)*f(c-2)) %%f(c*x)/(f(1)*f(c*x-1)) + f(c*x)/(f(2)*f(c*x-2)) - c * f(c)/(f(2)*f(c-2))
} %%}
%%
%%
\end{verbatim} %%\end{verbatim}
%%
\pagebreak[1] \pagebreak[1]
\section{Component Failure Modes \\ and Statistical Sample Space} \section{Component Failure Modes \\ and Statistical Sample Space}

2
components_as_plds/components_as_plds.tex
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@ -50,7 +50,7 @@ all possible failure modes, and where appropriate, how
these failure modes will affect other components in the circuit. these failure modes will affect other components in the circuit.
Safety analysis of components forming critical circuitry, Safety analysis of components forming critical circuitry,
is currently performed using scenario based test cases\cite{EN298}, % \cite{gastec}, \cite{tuv}. is currently performed using scenario based test cases\cite{en298}, % \cite{gastec}, \cite{tuv}.
These involve experts checking a circuit for failure modes on a circuit and how these will These involve experts checking a circuit for failure modes on a circuit and how these will
affect the system, based on their expertise. affect the system, based on their expertise.
Because this is a human process, Because this is a human process,

12
introduction/introduction.tex
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@ -13,8 +13,6 @@ both the
deterministic deterministic
and and
probablistic approaches. probablistic approaches.
%specific `simultaneous failures'\cite{EN298},\cite{EN230},\cite{EN12067}
%and the probability to dangerous fault approach\cite{EN61508}.
The visual notation developed was initially designed for electronic fault modelling. The visual notation developed was initially designed for electronic fault modelling.
However, it was realised that it could be applied to mechanical and software domains as well. However, it was realised that it could be applied to mechanical and software domains as well.
@ -166,7 +164,7 @@ One is a general number of acceptable failures per hour\footnote{The common metr
hours of operation} of operation or hours of operation} of operation or
a given statistical failure on demand. a given statistical failure on demand.
This is the probablistic approach and is embodied in the European Standard This is the probablistic approach and is embodied in the European Standard
EN61508 \cite{EN61508} (international standard IOC1508). EN61508 \cite{en61508} (international standard IOC1508).
\paragraph{Deterministic safety Measures} \paragraph{Deterministic safety Measures}
The second philosophy, applied to application specific standards, is to investigate The second philosophy, applied to application specific standards, is to investigate
@ -405,7 +403,7 @@ to reduce the possibility of this last condition.
\section{Motivation for developing a formal methodology} \section{Motivation for developing a formal methodology}
A feature of many safety critical systems specifications, A feature of many safety critical systems specifications,
including EN298, EN230 \cite{EN298} \cite{EN230} including EN298, EN230 \cite{en298} \cite{en230}
is to demand, is to demand,
at the very least that single failures of hardware at the very least that single failures of hardware
or software cannot or software cannot
@ -455,7 +453,7 @@ for individual component failures and their effects on other components when the
For a very small system with say 1000 failure modes this would demand a potential of 500,000 For a very small system with say 1000 failure modes this would demand a potential of 500,000
checks for any automated checking process. checks for any automated checking process.
\vskip 0.3cm \vskip 0.3cm
European legislation\cite{EN298} directs that a system must be able to react to two component failures European legislation\cite{en298} directs that a system must be able to react to two component failures
and not go into a dangerous state. and not go into a dangerous state.
\vskip 0.3cm \vskip 0.3cm
This raises an interesting problem from the point of view of formal modelling. Here we have a binary cross product of all components This raises an interesting problem from the point of view of formal modelling. Here we have a binary cross product of all components
@ -496,8 +494,8 @@ overdosed 6 people between 1985 and 1987.
An earlier computerised version of the therac-25 (the therac-20) used the same software but kept the An earlier computerised version of the therac-25 (the therac-20) used the same software but kept the
hardware interlocks from the previous manual operation machines. The hardware interlocks hardware interlocks from the previous manual operation machines. The hardware interlocks
on the therac-20 functioned correctly and the faulty software in it caused no accidents. on the therac-20 functioned correctly and the faulty software in it caused no accidents.
A safety study for the device, using Fault Tree Analysis% \cite{nucfta} A safety study for the device, using Fault Tree Analysis % \cite{nucfta}
carried out in 1983 carried out in 1983
excluded the software \cite{safeware}[App. A]. excluded the software \cite{safeware}[App. A].

10
symptom_ex_process/process.tex
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@ -10,7 +10,7 @@ when specified components within it fail.
Once we know how a functional~group can fail, we can treat it as a component or sub-system Once we know how a functional~group can fail, we can treat it as a component or sub-system
with its own set of failure modes. with its own set of failure modes.
\paragraph{fmEA applied to the Functional Group} \paragraph{FMEA applied to the Functional Group}
As the functional~group is a set of components, the failure~modes 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. 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 failure mode (or combination of) investigated is termed a `test case'.
@ -62,9 +62,11 @@ To sumarise:
% \item Obtain the list of components in the functional group % \item Obtain the list of components in the functional group
\item Collect the failure modes of each component into a flat set. \item Collect the failure modes of each component into a flat set.
\item Choose all single instances (and optional selected combinations\footnote{ \item Choose all single instances (and optional selected combinations\footnote{
Some specific combinations of failure modes might be included, or with EN298 \cite{en298} Some specific combinations of failure modes might be included. For instance where
all possible double failure mode conditions} of the failure modes to a very reliable part is duplicated but very critical, like the 4 engines on a 747
aircraft.}) of the failure modes to
form `test cases'. form `test cases'.
\item If required create test cases from all valid double failure mode combinations within the {\fg}.
% \item Draw these as contours on a diagram % \item Draw these as contours on a diagram
% \item Where si,ultaneous failures are examined use overlapping contours % \item Where si,ultaneous failures are examined use overlapping contours
% \item For each region on the diagram, make a test case % \item For each region on the diagram, make a test case
@ -93,7 +95,7 @@ statistics and evironmental factors in a variety of sources. \cite{mil1991}
\ifthenelse {\boolean{paper}} \ifthenelse {\boolean{paper}}
{ {
\subsection{Define Failure mode function fm} \subsection{Define Failure mode function $fm$}
} }
{ {
To re-cap from the definitions chapter \ref{chap:definitions}. To re-cap from the definitions chapter \ref{chap:definitions}.