..
This commit is contained in:
parent
584b23bd3b
commit
3c24ddd24a
@ -3,86 +3,94 @@
|
||||
%\label{sec:symptom_abstraction}
|
||||
\label{sec:algorithmfmmd}
|
||||
|
||||
This section decribes the algorithm for performing one step of
|
||||
FMMD analysis
|
||||
analysing a {\fg} and determining from it a {\dc}.
|
||||
Algorithms using set theory describe the process.
|
||||
It begins with an overview of the FMMD process, and then contrasts and compares it
|
||||
to diagnostic analysis (fault finding).
|
||||
This discussion is followed by justification for using a bottom-up, forward search
|
||||
approach, along with modularisation.
|
||||
A theoretical example of FMMD using set theory is given.
|
||||
The algorithm for performing FMMD is then presented.
|
||||
This chapter defines the process for performing one stage of the FMMD process i.e.
|
||||
from forming a {\fg} to creating a {\dc}.
|
||||
%This section decribes the algorithm for performing one step of
|
||||
%FMMD analysis
|
||||
%analysing a {\fg} and determining from it a {\dc}.
|
||||
%
|
||||
%Algorithms using set theory describe the process.
|
||||
%An overview of the FMMD process is presented and it is then compared to
|
||||
%diagnostic analysis (fault finding).
|
||||
%This is followed by justification for using a bottom-up, forward search
|
||||
%approach, along with modularisation.
|
||||
A theoretical example of FMMD using set theory is given following on to
|
||||
a description of the process presented as an algorithm.
|
||||
%for performing FMMD is then presented.
|
||||
|
||||
%
|
||||
\section{FMMD as a process.}
|
||||
|
||||
In FMMD we take a group of components with a functional purpose, apply
|
||||
FMEA, and then determine how the {\fg} can fail.
|
||||
We determine the common symptoms of failure of the {\fg}, and then
|
||||
create a new {\dc} which has, as its failure modes, the symptoms we determined.
|
||||
|
||||
\paragraph{FMMD and failure mode models.}
|
||||
|
||||
In essence, we take a {\fg} (a collection of components),
|
||||
and apply FMEA analysis locally on this {\fg}.
|
||||
%
|
||||
In this way, we determine how that {\fg} can fail.
|
||||
We can then go further and consider these to
|
||||
be symptoms of failure of the {\fg}.
|
||||
Because component failures will often manifest themselves as the same symptoms of failure,
|
||||
we are able to collect common symptoms of failure for the {\fg}.
|
||||
%
|
||||
%
|
||||
With the collected common symptoms, we can treat the {\fg}
|
||||
as a component in its own right.
|
||||
This new component being derived from the {\fg}.
|
||||
%
|
||||
In the field of safety engineering this derived component corresponds 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.
|
||||
%
|
||||
Once the failure modes have been determined for a sub-system/{\dc},
|
||||
this {\dc} can be combined with others to form {\fgs} to model higher level sub-systems/{\dcs}.
|
||||
%
|
||||
In this way a hierarchy to represent the fault behaviour
|
||||
of a system can be built from the bottom~up. This process can continue
|
||||
until there is a complete hierarchy representing the failure mode
|
||||
behaviour of the entire system under analysis.
|
||||
%FMMD hierarchy
|
||||
Using the FMMD technique, the hierarchy is built from the bottom up to
|
||||
ensure complete failure mode coverage.
|
||||
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 generic failure mode model.
|
||||
\fmmdgloss
|
||||
%
|
||||
From the fault data model, automatic generation
|
||||
of FTA \cite{nasafta} (Fault Tree Analysis) and minimal cuts sets \cite{nucfta} are possible.
|
||||
Also statistical reliability/probability of failure~on~demand \cite{en61508} and MTTF (Mean Time to Failure) calculations can be produced
|
||||
automatically\footnote{Where component failure mode statistics are available \cite{mil1991}}.
|
||||
%
|
||||
This chapter focuses on the process of converting {\fgs} to {\dcs}, or building the `blocks' of the FMMD hierarchy.
|
||||
We can term this stage in FMMD analysis as the `symptom extraction' process.
|
||||
The symptom extraction or abstraction process, is the key process in creating an FMMD hierarchy.
|
||||
}
|
||||
% \section{FMMD as a process.}
|
||||
%
|
||||
% % In FMMD we take a group of components with a functional purpose, apply
|
||||
% % FMEA, and then determine how the {\fg} can fail.
|
||||
% % We determine the common symptoms of failure of the {\fg}, and then
|
||||
% % create a new {\dc} which has, as its failure modes, the symptoms we determined.
|
||||
%
|
||||
% \paragraph{FMMD and failure mode models.}
|
||||
%
|
||||
% To perform FMMD a {\fg} (a collection of components) is chosen
|
||||
% FMEA is applied to it.
|
||||
% %
|
||||
% %In this way, we determine how that {\fg} can fail.
|
||||
% This gives us a set of failure modes for the {\fg}.
|
||||
% %
|
||||
% The {\fg} is not viewed as a component, or module,
|
||||
% and the FMEA results considered
|
||||
% be its symptoms of failure.
|
||||
% %
|
||||
% Because component failures will often manifest themselves as the same symptoms of failure,
|
||||
% we are able to collect common symptoms of failure for the {\fg}.
|
||||
% %
|
||||
% %
|
||||
% With the collected common symptoms, we can treat the {\fg}
|
||||
% as a component in its own right. We term this a `{\dc}'.
|
||||
% %This new component being derived from the {\fg}.
|
||||
% %
|
||||
% %The `{dc}' can be thought of as 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.
|
||||
% %
|
||||
% Once the failure modes have been determined for a sub-system/{\dc},
|
||||
% this {\dc} can be combined with others to form {\fgs} to model higher level sub-systems/{\dcs}.
|
||||
% %
|
||||
% In this way a hierarchy to represent the fault behaviour
|
||||
% of a system can be built from the bottom~up. This process can continue
|
||||
% until there is a complete hierarchy representing the failure mode
|
||||
% behaviour of the entire system under analysis.
|
||||
% %FMMD hierarchy
|
||||
% Using the FMMD technique, the hierarchy is built from the bottom up to
|
||||
% ensure complete failure mode coverage.
|
||||
% 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 generic failure mode model.
|
||||
% \fmmdgloss
|
||||
% %
|
||||
% %From the fault data model, automatic generation
|
||||
% %of FTA \cite{nasafta} (Fault Tree Analysis) and minimal cuts sets \cite{nucfta} are possible.
|
||||
% %Also statistical reliability/probability of failure~on~demand \cite{en61508} and MTTF (Mean Time to Failure) calculations can be produced
|
||||
% %automatically\footnote{Where component failure mode statistics are available \cite{mil1991}}.
|
||||
% %
|
||||
% This chapter focuses on the process of converting {\fgs} to {\dcs}, or building the `blocks' of the FMMD hierarchy.
|
||||
% We can term this stage in FMMD analysis as the `symptom abstraction' process.
|
||||
% %The symptom abstraction or abstraction process, is the key process in creating an FMMD hierarchy.
|
||||
% }
|
||||
\vspace{40pt}
|
||||
%\today
|
||||
\paragraph{Mutual exclusive property of the failure modes of a {\dc}}
|
||||
Because the symptoms have been collected from
|
||||
identical failure effects of the {\fg} they are mutually exclusive.
|
||||
That is to say no failure mode effects of a component of a {\fg}
|
||||
can be shared by a {\dc} failure mode.
|
||||
This ensures the mutually exclusive, or unitary state failure mode property, meaning
|
||||
the failure modes of a {\dc} are suitable for use in higher level {\fgs}.
|
||||
|
||||
\subsection{Diagnostic analysis and Failure Mode Analysis}
|
||||
Fault finding is a closely related discipline to failure mode analysis.
|
||||
In diagnostic analysis, we generally start with a high level --- or system ---failure type.
|
||||
We trace this from the top, de-composing the systems until we come to
|
||||
a component or sub-system that has caused the failure.
|
||||
While there are similarities between diagnostic failure mode tracing and static failure mode analysis
|
||||
it is important to discuss the differences between them.
|
||||
%
|
||||
% %\today
|
||||
% \paragraph{Mutual exclusive property of the failure modes of a {\dc}}
|
||||
% Because the symptoms have been collected from
|
||||
% identical failure effects of the {\fg} they are mutually exclusive.
|
||||
% That is to say no failure mode effects of a component of a {\fg}
|
||||
% can be shared by a {\dc} failure mode.
|
||||
% This ensures the mutually exclusive, or unitary state failure mode property, meaning
|
||||
% the failure modes of a {\dc} are suitable for use in higher level {\fgs}.
|
||||
%
|
||||
% \subsection{Diagnostic analysis and Failure Mode Analysis}
|
||||
% Fault finding is a closely related discipline to failure mode analysis.
|
||||
% In diagnostic analysis, we generally start with a high level --- or system ---failure type.
|
||||
% We trace this from the top, de-composing the systems until we come to
|
||||
% a component or sub-system that has caused the failure.
|
||||
% While there are similarities between diagnostic failure mode tracing and static failure mode analysis
|
||||
% it is important to discuss the differences between them.
|
||||
% %
|
||||
%\subsection{Static Analysis}
|
||||
%
|
||||
%In the field of safety critical engineering, to comply with
|
||||
@ -105,80 +113,80 @@ it is important to discuss the differences between them.
|
||||
%FMMD can model electrical, mechanical and software failures using a common notation,
|
||||
%and can thus model an integrated electro-mechanical software controlled system.
|
||||
%
|
||||
\subsection{Top Down or Natural Trouble Shooting}
|
||||
We firstly look at the `natural' trouble shooting process.
|
||||
Fault finding is instinctively performed from the top-down.
|
||||
A faulty piece of equipment is examined and will have a
|
||||
symptom or specific fault.
|
||||
%
|
||||
The suspected area or sub-system within the
|
||||
equipment will be looked into next.
|
||||
%
|
||||
The trouble shooter will look for behaviour that is unusual or incorrect
|
||||
to determine the next area or sub~system to look into, each time
|
||||
moving to a more detailed lower level.
|
||||
Specific measurements
|
||||
and checks will be made, and finally a component or a low level sub-system
|
||||
will be found to be faulty.
|
||||
A natural fault finding process is thus top~down.
|
||||
Top down formal fault isolation/finding techniques for electronics are described in \cite{maikowski}.
|
||||
Fault tree analysis is a top down static failure mode analysis technique~\cite{nucfta,nasafta}.
|
||||
%%
|
||||
%% to fool the graphics insertion to make it compatible
|
||||
%% with thesis and papaer level directories.
|
||||
%%
|
||||
%% ln -s . symptom_ex_process
|
||||
%%
|
||||
|
||||
%% insert diagram here
|
||||
|
||||
\begin{figure}[h]
|
||||
\centering
|
||||
\includegraphics[width=300pt,bb=0 0 587 445,keepaspectratio=true]{./CH4_FMMD/top_down_de_comp.png}
|
||||
% top_down_de_comp.jpg: 587x445 pixel, 72dpi, 20.71x15.70 cm, bb=0 0 587 445
|
||||
\caption{Top Down Failure De-Composition Diagram}
|
||||
\label{fig:tdh}
|
||||
\end{figure}
|
||||
|
||||
%%
|
||||
%% FMEA and FTA and safety engineering people used the term SUB_SYSTEM ALOT
|
||||
%% this study needs to use this term to keep the interested/in context.
|
||||
The term `sub-system' is typically used in top down methodologies.
|
||||
It has two equivalents in FMMD.
|
||||
Both {\fg} and {\dc} correspond to the top down concept of a `sub-system'.
|
||||
In FMMD a {\fg} becomes a {\dc} after analysis.
|
||||
The term sub-system will be used alongside both {\fg} and {\dc} where necessary.
|
||||
|
||||
\subsection{Top-Down System De-Composition}
|
||||
|
||||
A top down fault analysis system will take a system and divide it into
|
||||
several sub-systems, and determine the safety dependencies
|
||||
of the System on those sub-systems. In the case of large complicated
|
||||
systems, the sub-systems themselves may be broken down into simpler sub-systems.
|
||||
A top down hierarchy is shown in figure \ref{fig:tdh}.
|
||||
|
||||
\subsection{FMMD - Bottom~up Analysis}
|
||||
The FMMD methodology does not follow the `natural fault finding' or top down approach,
|
||||
it instead works from the bottom up.
|
||||
Starting with a collection of base~components that form
|
||||
a simple functional group, the effect of all component error modes are
|
||||
examined, as to their effect on the functional group.
|
||||
%
|
||||
The effects on the functional group can then be collected as common symptoms,
|
||||
and now we may treat the functional group as a component, as it has a known set of failure modes.
|
||||
%
|
||||
By reusing the `components' derived from functional~groups, an entire
|
||||
hierarchical failure mode model of the system can be built.
|
||||
That is to say, using derived components in higher level functional groups,
|
||||
a hierarchy is naturally formed.
|
||||
%
|
||||
By working from the bottom up, we can trace all possible sources
|
||||
that could cause a particular mode of equipment failure.
|
||||
This means that at the design stage of a product all component failure
|
||||
modes must be considered. A benefit of FMMD is complete failure mode coverage.
|
||||
This also means that it is possible to obtain statistical estimates based on the known reliabilities
|
||||
of components~\cite{mil1991}.
|
||||
%It also means that every component failure mode must at the very least be considered.
|
||||
% \subsection{Top Down or Natural Trouble Shooting}
|
||||
% We firstly look at the `natural' trouble shooting process.
|
||||
% Fault finding is instinctively performed from the top-down.
|
||||
% A faulty piece of equipment is examined and will have a
|
||||
% symptom or specific fault.
|
||||
% %
|
||||
% The suspected area or sub-system within the
|
||||
% equipment will be looked into next.
|
||||
% %
|
||||
% The trouble shooter will look for behaviour that is unusual or incorrect
|
||||
% to determine the next area or sub~system to look into, each time
|
||||
% moving to a more detailed lower level.
|
||||
% Specific measurements
|
||||
% and checks will be made, and finally a component or a low level sub-system
|
||||
% will be found to be faulty.
|
||||
% A natural fault finding process is thus top~down.
|
||||
% Top down formal fault isolation/finding techniques for electronics are described in \cite{maikowski}.
|
||||
% Fault tree analysis is a top down static failure mode analysis technique~\cite{nucfta,nasafta}.
|
||||
% %%
|
||||
% %% to fool the graphics insertion to make it compatible
|
||||
% %% with thesis and papaer level directories.
|
||||
% %%
|
||||
% %% ln -s . symptom_ex_process
|
||||
% %%
|
||||
%
|
||||
% %% insert diagram here
|
||||
%
|
||||
% \begin{figure}[h]
|
||||
% \centering
|
||||
% \includegraphics[width=300pt,bb=0 0 587 445,keepaspectratio=true]{./CH4_FMMD/top_down_de_comp.png}
|
||||
% % top_down_de_comp.jpg: 587x445 pixel, 72dpi, 20.71x15.70 cm, bb=0 0 587 445
|
||||
% \caption{Top Down Failure De-Composition Diagram}
|
||||
% \label{fig:tdh}
|
||||
% \end{figure}
|
||||
%
|
||||
% %%
|
||||
% %% FMEA and FTA and safety engineering people used the term SUB_SYSTEM ALOT
|
||||
% %% this study needs to use this term to keep the interested/in context.
|
||||
% The term `sub-system' is typically used in top down methodologies.
|
||||
% It has two equivalents in FMMD.
|
||||
% Both {\fg} and {\dc} correspond to the top down concept of a `sub-system'.
|
||||
% In FMMD a {\fg} becomes a {\dc} after analysis.
|
||||
% The term sub-system will be used alongside both {\fg} and {\dc} where necessary.
|
||||
%
|
||||
% \subsection{Top-Down System De-Composition}
|
||||
%
|
||||
% A top down fault analysis system will take a system and divide it into
|
||||
% several sub-systems, and determine the safety dependencies
|
||||
% of the System on those sub-systems. In the case of large complicated
|
||||
% systems, the sub-systems themselves may be broken down into simpler sub-systems.
|
||||
% A top down hierarchy is shown in figure \ref{fig:tdh}.
|
||||
%
|
||||
% \subsection{FMMD - Bottom~up Analysis}
|
||||
% The FMMD methodology does not follow the `natural fault finding' or top down approach,
|
||||
% it instead works from the bottom up.
|
||||
% Starting with a collection of base~components that form
|
||||
% a simple functional group, the effect of all component error modes are
|
||||
% examined, as to their effect on the functional group.
|
||||
% %
|
||||
% The effects on the functional group can then be collected as common symptoms,
|
||||
% and now we may treat the functional group as a component, as it has a known set of failure modes.
|
||||
% %
|
||||
% By reusing the `components' derived from functional~groups, an entire
|
||||
% hierarchical failure mode model of the system can be built.
|
||||
% That is to say, using derived components in higher level functional groups,
|
||||
% a hierarchy is naturally formed.
|
||||
% %
|
||||
% By working from the bottom up, we can trace all possible sources
|
||||
% that could cause a particular mode of equipment failure.
|
||||
% This means that at the design stage of a product all component failure
|
||||
% modes must be considered. A benefit of FMMD is complete failure mode coverage.
|
||||
% This also means that it is possible to obtain statistical estimates based on the known reliabilities
|
||||
% of components~\cite{mil1991}.
|
||||
% %It also means that every component failure mode must at the very least be considered.
|
||||
|
||||
|
||||
%{
|
||||
@ -237,20 +245,28 @@ of components~\cite{mil1991}.
|
||||
|
||||
\nocite{safeware}
|
||||
\section{Overview of the FMMD analysis Process}
|
||||
|
||||
The FMMD process is described in chapter~\ref{sec:chap4}
|
||||
With the FMEA results for a {\fg} common symptoms of failure can be determined. This is termed `symptom~abstraction'.
|
||||
% TO DO: separate these two:
|
||||
|
||||
\paragraph{FMMD analysis Objective.}
|
||||
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 a functional~group can fail, we can treat it as a component or sub-system
|
||||
%
|
||||
% \paragraph{FMMD analysis Objective.}
|
||||
% 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 a functional~group can fail, we can treat it as a component or sub-system
|
||||
% with its own set of failure modes.
|
||||
Once the failure symptoms for a {\fg} are known, the {\fg} can be treated as a component or sub-system
|
||||
with its own set of failure modes.
|
||||
This process allows us to modularise and simply FMEA analysis of systems.
|
||||
The FMEA process is reviewed here, introducing
|
||||
formal definitions that will be used in the description of FMMD
|
||||
presented as an algorithm.
|
||||
|
||||
|
||||
\paragraph{FMEA applied to the Functional Group.}
|
||||
As the functional~group contains a set of components, the failure~modes
|
||||
that we have to consider are all the failure modes of its components, as
|
||||
developed in the function definition $fm : \;\mathcal{FG} \rightarrow \mathcal{F}$.
|
||||
developed in the function definition $fm : \;\mathcal{G} \rightarrow \mathcal{F}$.
|
||||
The aim here is to build `test cases', combinations of failure~modes
|
||||
to use as failure~mode analysis scenarios.
|
||||
%Each failure mode (or combination of) investigated is termed a `test case'.
|
||||
@ -260,16 +276,21 @@ The component failure modes in each test case
|
||||
are examined with respect to their effect on the functional~group.
|
||||
%
|
||||
The aim of this analysis is to find out how the functional~group fails given
|
||||
the test case conditions, for each test case.
|
||||
each test case.
|
||||
%
|
||||
The goal of the process is to produce a set of failure modes from the perspective of the user of the functional~group.
|
||||
%
|
||||
In other words, if a designer is handed a piece of circuitry to use, he need not be concerned with
|
||||
the failure modes of its components. He is handed it as a derived component, which has
|
||||
a set of failure mode symptoms. The designer can now treat this piece of circuitry as a black box, or {\dc}.
|
||||
the failure modes of its components.
|
||||
%
|
||||
He is handed it as a derived component, which has a set of failure mode symptoms.
|
||||
%
|
||||
The designer can now treat this piece of circuitry as a black box, or {\dc}.
|
||||
|
||||
\paragraph{Environmental Conditions or Applied States.}
|
||||
\paragraph{Environmental Conditions or Operational States.}
|
||||
|
||||
Each test case must be considered for all applied/operational states and
|
||||
Each test case must be considered for all %applied/
|
||||
operational states and
|
||||
%in the for the case of each applied states or
|
||||
environmental conditions to which it may be exposed. In this way, all possible
|
||||
failure mode behaviour due to all the conditions that can be applied to a test case will be examined.
|
||||
@ -310,42 +331,43 @@ will both cause the same failure symptom; $no\_sound$ !
|
||||
|
||||
\paragraph{Collection of Symptoms.}
|
||||
%Looking at the
|
||||
examining failure from the
|
||||
functional group perspective failure modes, we collect
|
||||
some of these into common `symptoms' where possible.
|
||||
%
|
||||
Some test cases may cause
|
||||
unique failure modes at the functional group level. These can be termed
|
||||
lone symptoms.
|
||||
%
|
||||
The common symptoms of failure and lone~symptoms are identified and collected.
|
||||
% examining failure from the
|
||||
% functional group perspective failure modes, we collect
|
||||
% some of these into common `symptoms' where possible.
|
||||
% %
|
||||
% Some test cases may cause
|
||||
% unique failure modes at the functional group level. These can be termed
|
||||
% lone symptoms.
|
||||
% %
|
||||
% The common symptoms of failure and lone~symptoms are identified and collected.
|
||||
% %
|
||||
% We can now create a new component and consider the symptoms as its failure modes.
|
||||
Common symptoms of failure of the {\fg} are collected.
|
||||
%
|
||||
We can now create a new component and consider the symptoms as its failure modes.
|
||||
%
|
||||
We call this new component a `{\dc}'.
|
||||
%
|
||||
%Note that here, b
|
||||
Because the process is bottom up, we can ensure that all failure modes
|
||||
from the components in a functional~group have been handled\footnote{Software can check that all
|
||||
failure modes have been included in at least one test case, and modelled individually.
|
||||
Because the FMMD process is bottom up, we can ensure that all failure modes
|
||||
from the components in a {\fg} have been considered.
|
||||
%\footnote{Software can check that all failure modes have been included in at least one test case, and modelled individually. For Double
|
||||
%Simultaneous fault mode checking, all valid double failure modes can be checked for coverage as well.}.
|
||||
%
|
||||
For Double
|
||||
Simultaneous fault mode checking, all valid double failure modes can be checked for coverage as well.}.
|
||||
%
|
||||
Were any failure~modes missed, the failure mode model could be %dangerously
|
||||
Were failure~modes to be missed, the resulting failure mode model would be %dangerously
|
||||
incomplete.
|
||||
%
|
||||
It is possible here for an automated system to flag un-handled failure modes,
|
||||
which solves the main failing of top~down methodologies
|
||||
It is possible here for an automated system to flag un-handled failure modes.
|
||||
%which solves the main failing of top~down methodologies
|
||||
%\cite{topdownmiss},
|
||||
that of not
|
||||
guaranteeing to model all component failure modes.
|
||||
%that of not
|
||||
%guaranteeing to model all component failure modes.
|
||||
%\ref{requirement at the start}
|
||||
|
||||
|
||||
\section{The Process}
|
||||
\section{A single stage of the FMMD process}
|
||||
|
||||
\paragraph{To analyse a base level Derived~Component/sub-system}
|
||||
%\paragraph{To analyse a base level Derived~Component/sub-system}
|
||||
|
||||
To summarise:
|
||||
|
||||
@ -365,12 +387,17 @@ form `test cases'.
|
||||
\item Using the `test cases' as scenarios to examine the effects of component failures,
|
||||
we determine the failure~mode behaviour of the functional group.
|
||||
%
|
||||
This is a human process, involving detailed analysis of the component failure modes in the test case on the {\fg}.
|
||||
Where specific environment conditions, or applied states are germane to the {\fg}, these must be examined
|
||||
This is a human process, applying FMEA for each test case.
|
||||
%
|
||||
Where specific environment conditions, or operational states are germane to the {\fg}, these must also be examined
|
||||
for each test case.
|
||||
\item Collect common~symptoms by determining which test cases produce the same fault symptoms {\em from the perspective of the functional~group}.
|
||||
\item The common~symptoms are now the fault mode behaviour of the {\fg}. i.e. given the {\fg} as a `black box' the symptoms are the ways in which it can fail.
|
||||
\item A new `derived component' can now be created where each common~symptom, or lone symptom, is a failure~mode of this new component.
|
||||
%
|
||||
\item Collect common~symptoms by determining which test cases produce the same fault symptoms {\em from the perspective of the {\fg}}.
|
||||
%
|
||||
\item The common~symptoms are now the fault mode behaviour of the {\fg}.
|
||||
i.e. given the {\fg} as a `black box' the symptoms are the ways in which it can fail.
|
||||
%
|
||||
\item A new `{\dc}' can now be created where each common~symptom, or lone symptom, is a failure~mode of this new component.
|
||||
\end{itemize}
|
||||
|
||||
|
||||
@ -543,8 +570,10 @@ consider DC as being in the set of components i.e. $DC \in \mathcal{C}$
|
||||
|
||||
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
|
||||
|
||||
\subsection{Defining the analysis process \\ as a function}
|
||||
\subsection{Defining the analysis process as a function}
|
||||
|
||||
We define one stage of the FMMD process, taking a {\fg} and deriving a {\dc}
|
||||
by the symbol `D'.
|
||||
Where $\mathcal{FG}$ is the set of all sets of functional groups, and $\mathcal{DC}$
|
||||
is the set of all derived components, we can define the symptom abstraction process thus:
|
||||
$$
|
||||
@ -577,7 +606,7 @@ because we can obtain a failure mode set,
|
||||
(the failure mode set we have named $DCFM$).
|
||||
|
||||
Thus we can now move up another abstraction level by applying
|
||||
symptom abstraction/extraction to the functional group
|
||||
symptom abstraction to the {\fg}
|
||||
$FG_{derived}$ shown in equation \ref{eqn:fgderived}.
|
||||
|
||||
\begin{equation}
|
||||
@ -662,7 +691,7 @@ $$
|
||||
\derivec : \mathcal{FG} \rightarrow \mathcal{DC} .
|
||||
$$
|
||||
|
||||
The next section describes the details of the symptom extraction process.
|
||||
The next section describes the details of the symptom abstraction process.
|
||||
|
||||
}
|
||||
|
||||
@ -671,26 +700,26 @@ The next section describes the details of the symptom extraction process.
|
||||
%\section{A Formal Algorithmic Description of `Symptom Abstraction'}
|
||||
\section{Algorithmic Description}
|
||||
\label{sec:symptomabs}
|
||||
The algorithm for {\em symptom extraction} is described in
|
||||
The algorithm for {\em symptom abstraction} is described in
|
||||
this section
|
||||
%describes the symptom abstraction process
|
||||
using set theory and procedural descriptions.
|
||||
%
|
||||
The {\em symptom abstraction process} (given the symbol `$\derivec$') takes a functional group $FG$
|
||||
The {\em symptom abstraction process} (given the symbol `$\derivec$', D for derive) takes a functional group $FG$
|
||||
and a new derived~component/sub-system $DC$.
|
||||
%The sub-system $SS$ is a collection
|
||||
%of failure~modes of the sub-system.
|
||||
Note that
|
||||
$DC$ is a derived component at a higher level of fault analysis abstraction
|
||||
than the functional~group from which it was derived.
|
||||
%Thus,
|
||||
$DC$ can now be treated
|
||||
as a component with a known set of failure modes.
|
||||
% Note that
|
||||
% $DC$ is a derived component at a higher level of fault analysis abstraction
|
||||
% than the functional~group from which it was derived.
|
||||
% %Thus,
|
||||
% $DC$ can now be treated
|
||||
% as a component with a known set of failure modes.
|
||||
|
||||
|
||||
\paragraph{Enumerating abstraction levels}
|
||||
\label{sec:abstractionlevel}
|
||||
We can assign an attribute of abstraction level $\abslev$ to
|
||||
As described in section~\ref{sec:alpha} we can assign an attribute of abstraction level $\abslev$ to
|
||||
components, where $\abslev$ is a natural number, ($\abslev \in \mathbb{N}_0$).
|
||||
For a base component, let the abstraction level be zero.
|
||||
If we apply the symptom abstraction process $\derivec$,
|
||||
@ -776,15 +805,15 @@ The function $fm$ applied to a component returns the failure modes for that comp
|
||||
Thus its domain is the set of all components $\mathcal{C}$ and its range
|
||||
is the powerset of all failure modes $\mathcal{P}\,\mathcal{F}$.
|
||||
|
||||
$$ fm : \mathcal{C} \rightarrow \mathcal{P}\,\mathcal{\FG} $$
|
||||
$$ fm : \mathcal{C} \rightarrow \mathcal{P}\,\mathcal{F} $$
|
||||
|
||||
A {\fg} is a collection of components such that $\mathcal{\FG} \in \mathcal{P}\,\mathcal{C}$.
|
||||
A {\fg} is a collection of components $G$ such that $\mathcal{G} \in \mathcal{P}\,\mathcal{C}$.
|
||||
|
||||
The function $fm$ can be overloaded with a functional group $\mathcal{\FG}$ as its domain
|
||||
The function $fm$ can be overloaded with a {\fg} $\mathcal{G}$ as its domain
|
||||
and the power-set of all failure modes as its range.
|
||||
|
||||
|
||||
$$ fm: \mathcal{\FG} \rightarrow \mathcal{P}\,\mathcal{F} $$
|
||||
$$ fm: \mathcal{\FG} \rightarrow \mathcal{P}\,\mathcal{G} $$
|
||||
|
||||
%
|
||||
%%Let $FG$ be the set of components in the functional group under analysis, and $c$
|
||||
@ -855,7 +884,7 @@ the failure modes for a particular test case have been chosen by
|
||||
a human operator and are additional to those chosen by the automated process (i.e they are
|
||||
special case test cases involving multiple failure modes)
|
||||
The function \textbf{unitary state} means that all test
|
||||
cases can have no pairs of failure modes sourced from the same component.
|
||||
cases can have no pairs of failure modes sourced from the same component, see section~\ref{sec:unitarystate}.
|
||||
|
||||
\label{sec:completetest}
|
||||
|
||||
|
@ -826,7 +826,7 @@ FMMD analysis tables from chapter~\ref{sec:chap6}.
|
||||
\end{tabular}
|
||||
\end{table}
|
||||
}
|
||||
\clearpage/pr
|
||||
\clearpage
|
||||
|
||||
\subsection{Gnuplot script for hypothetical XFMEA FMMD reasoning distance comparision}
|
||||
\label{sec:gnuplotxfmeafmmdcomp}
|
||||
|
Loading…
Reference in New Issue
Block a user