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symptom_ex_process/symptom_ex_process.tex
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@ -14,8 +14,8 @@ and then determining how that functional group can fail.
% %
With this information, we can treat the functional group With this information, we can treat the functional group
as a component in its own right. as a component in its own right.
This new component is a derived component. This new component is a derived from the functional~group.
For a top down technique this would correspond to a low~level sub-system. In the field of safety engineering this derived component correspond to a low~level sub-system.
%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/derived~component, Once the failure modes have been determined for a sub-system/derived~component,
@ -56,8 +56,8 @@ and then determining how that functional group can fail.
% %
With this information, we can treat the functional group With this information, we can treat the functional group
as a component in its own right. as a component in its own right.
This new component is a derived component. This new component is a derived from the functional~group.
For a top down technique this would correspond to a low~level sub-system. In the field of safety engineering this derived component correspond to a low~level sub-system.
%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/derived~component, Once the failure modes have been determined for a sub-system/derived~component,
@ -90,6 +90,24 @@ This chapter focuses on the process of building the blocks, the symptom extracti
\section{Fault Finding and Failure Mode Analysis} \section{Fault Finding and Failure Mode Analysis}
\subsection{Static Analysis}
In the field of safety critical engineering; to comply with
European Law a product must be certified under the approriate `EN' standard.
Typically environmental stress, EMC, electrical stressing, endurance tests,
software~inspections and project~management quality reviews are applied\cite{sccs}.
Static testing is also applied. This is theoretical analysis of the design of the product from the safety
perspective.
Three main techniques are currently used,
Statistical failure models, FMEA (Failure mode Effects Analysis) and FTA (Fault Tree Analysis).
The FMMD technique is aimed primarily as design verification for
safety critical systems.
However, FMMD also provides the mathematical frame work
to assist in the production of these three results of static analysis.
From the model created by the FMMD technique, the three above failure mode
descriptions can be derived.
\subsection{Top Down or natural trouble shooting} \subsection{Top Down or natural trouble shooting}
It is interesting here to look at the `natural' trouble shooting process. It is interesting here to look at the `natural' trouble shooting process.
Fault finding is intinctively performed from the top-down. Fault finding is intinctively performed from the top-down.
@ -103,6 +121,7 @@ Specific measurements
and checks will be made, and finally a component or a low level sub-system and checks will be made, and finally a component or a low level sub-system
will be found to be faulty. will be found to be faulty.
A natural fault finding process is thus top~down. A natural fault finding process is thus top~down.
Top down fault isolation/finding techniques are described in \ref{NETWORKDECOMPOSITION}.
\subsection{FMMD - Bottom~up Analysis} \subsection{FMMD - Bottom~up Analysis}
The FMMD technique does not follow the `natural fault finding' or top down approach, The FMMD technique does not follow the `natural fault finding' or top down approach,
it instead works from the bottom up. it instead works from the bottom up.
@ -121,33 +140,18 @@ This also means that we can obtain statistical estimates based on the known reli
of the components. of the components.
%It also means that every component failure mode must at the very least be considered. %It also means that every component failure mode must at the very least be considered.
\subsection{Static Analysis}
In the field of safety critical engineering; to comply with
European Law a product must be certified under the approriate `EN' standard.
Typically environmental stress, EMC, electrical stressing, endurance tests,
software~inspections and project~management quality reviews are applied\cite{sccs}.
Static testing is also applied. This is theoretical analysis of the design of the product from the safety
perspective.
Three main techniques are currently used,
Statistical failure models, FMEA (Failure mode Effects Analysis) and FTA (Fault Tree Analysis).
The technique outlined here aims to provide a mathematical frame work
to assist in the production of these three results of static analysis.
From the model created by the FMMD technique, the three above failure mode
descriptions can be derived.
{
The aims are
\begin{itemize}
\item To automate the process where possible
\item To apply a documented trail for each analysis phase (determination of functional groups, and analysis of component failure modes on those groups)
\item To use a modular approach so that analysed sub-systems can be re-used
\item Automatically ensure no failure mode is unhandled
\item To produce a data model from which FTA, FMEA and statistical failure models may be obtained automatically
\end{itemize}
}
%{
%The aims are
%\begin{itemize}
% \item To automate the process where possible
% \item To apply a documented trail for each analysis phase (determination of functional groups, and analysis of component failure modes on those groups)
% \item To use a modular approach so that analysed sub-systems can be re-used
% \item Automatically ensure no failure mode is unhandled
% \item To produce a data model from which FTA, FMEA and statistical failure models may be obtained automatically
%\end{itemize}
%}
%
\subsection{Systems, functional groups, sub-systems and failure modes} \subsection{Systems, functional groups, sub-systems and failure modes}
@ -168,7 +172,8 @@ A sub-system will be composed of components, which
may themselves be sub-systems. However each `component' may themselves be sub-systems. However each `component'
will have a fault/failure behaviour and it should will have a fault/failure behaviour and it should
always be possible to obtain a set of failure modes always be possible to obtain a set of failure modes
for each `component'. In FMMD terms a sub-system is a derived component. for each `component'.
%In FMMD terms a sub-system is a derived component.
If we look at the sound system example, If we look at the sound system example,
the CD~player could fail in several distinct ways, the CD~player could fail in several distinct ways,
@ -196,8 +201,13 @@ We can define a functional~group as a set of components that interact
to perform a specific function. to perform a specific function.
When we have analysed the fault behaviour of a functional group, we can treat it as a `black box'. When we have analysed the fault behaviour of a functional group, we can treat it as a `black box'.
We can now call our functional~group a sub-system or a derived~component. The fault behaviour will consist of a set of `symptoms' caused by combinations
The goal here is to know how it will behave under fault conditions ! of the component failure modes.
We can make a new `component' derived from the functional~group.
The symptoms are the failure modes of this new `derived component'.
%We can now call our functional~group a sub-system or a derived~component.
%The goal here is to know how it will behave under fault conditions !
%Imagine buying one such `sub~system' from a very honest vendor. %Imagine buying one such `sub~system' from a very honest vendor.
%One of those sir, yes but be warned it may fail in these distinct ways, here %One of those sir, yes but be warned it may fail in these distinct ways, here
%in the honest data sheet the set of failure modes is listed! %in the honest data sheet the set of failure modes is listed!