Andrew comments included into CH4

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Robin Clark 2012-06-09 16:58:47 +01:00
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@ -598,11 +598,11 @@ This is represented in the DAG in figure \ref{fig:fg1adag}.
\end{figure} \end{figure}
We can now formulate a `derived component' to represent this potential divider. We can now formulate a `derived component' to represent this potential divider:
This can be named \textbf{PD}. we name this \textbf{PD}.
This {\dc} will have two failure modes. This {\dc} will have two failure modes.
We can use the symbol $\derivec$ to represent the process of taking the analysed We use the symbol $\derivec$ to represent the process of taking the analysed
{\fg} and creating from it, a {\dc}. The creation of the {\dc} \textbf{PD} is {\fg} and creating from it a {\dc}. The creation of the {\dc} \textbf{PD} is
represented in figure~\ref{fig:dc1}. represented in figure~\ref{fig:dc1}.
We then represent the {\dc} as a DAG in figure \ref{fig:dc1dag}. We then represent the {\dc} as a DAG in figure \ref{fig:dc1dag}.
@ -694,7 +694,7 @@ We can represent these failure modes on a DAG (see figure~\ref{fig:op1dag}).
%} %}
%\clearpage %\clearpage
%\paragraph{Modelling the OP amp with the potential divider.} %\paragraph{Modelling the OP amp with the potential divider.}
We now merge the OP amp and the {\dc} {\em PD}, to We now collect the OP amp and the {\dc} {\em PD}, to
form a {\fg} to represent the non-inverting amplifier. form a {\fg} to represent the non-inverting amplifier.
% %
%We have the failure modes of the {\dc} for the potential divider, %We have the failure modes of the {\dc} for the potential divider,
@ -703,6 +703,7 @@ form a {\fg} to represent the non-inverting amplifier.
%We can now create a {\fg} for the non-inverting amplifier %We can now create a {\fg} for the non-inverting amplifier
%by bringing together the failure modes from \textbf{opamp} and \textbf{PD}. %by bringing together the failure modes from \textbf{opamp} and \textbf{PD}.
% %
The two components in this new {\fg} have failure modes.
Each of these failure modes will be given a {\fc} for analysis, Each of these failure modes will be given a {\fc} for analysis,
and this is represented in table \ref{tbl:ampfmea1}. and this is represented in table \ref{tbl:ampfmea1}.
@ -884,11 +885,15 @@ represents the failure mode behaviour of the non-inverting amplifier.
\label{fig:dc2} \label{fig:dc2}
\end{figure} \end{figure}
We can now examine the {\dc} {\em INVAMP} by drawing it as a DAG. We can now examine the failure mode relationships in the {\dc} {\em INVAMP} by drawing it as a DAG.
%expand the {\em PD} {\dc} and have a full FMMD failure %mode %expand the {\em PD} {\dc} and have a full FMMD failure %mode
%model %model
We can traverse this DAG, and thus determine all possible causes for We can traverse this DAG, tracing the top level symptoms down to the leaves of the tree (the leaves being {\bc} failure modes),
and thus determine all possible causes for
the three high level symptoms, i.e. the failure~modes of the non-inverting amplifier {\em INVAMP}. the three high level symptoms, i.e. the failure~modes of the non-inverting amplifier {\em INVAMP}.
Knowing all possible causes for a top level event/failure~mode
is extremely useful. Were the top level event to be classified as catastrophic for instance, we could use this information
to strengthen components that could cause the top level event/failure.
% %
Figure \ref{fig:noninvdag1} shows a fully expanded DAG, from which we can derive information Figure \ref{fig:noninvdag1} shows a fully expanded DAG, from which we can derive information
to assist in building models for FTA, FMEA, FMECA and FMEDA failure mode analysis methodologies. to assist in building models for FTA, FMEA, FMECA and FMEDA failure mode analysis methodologies.
@ -999,7 +1004,7 @@ It could be something %quite complicated
like an %integrated like an %integrated
micro-controller, or quite simple like the resistor. micro-controller, or quite simple like the resistor.
% %
We can define a We can identify a
component by its name, a manufacturer's part number and perhaps component by its name, a manufacturer's part number and perhaps
a vendor's reference number. a vendor's reference number.
@ -1017,8 +1022,8 @@ We, in fact, need to go a little further than the above definition of a part,
and say that we want to define an atomic entity. % used as a building block. and say that we want to define an atomic entity. % used as a building block.
%The term component, in American English, can mean a building block or a part. %The term component, in American English, can mean a building block or a part.
%In British-English a component generally is given to mean the definition for part above. %In British-English a component generally is given to mean the definition for part above.
We define {\bc} to be the lowest level of component that we use as a building block. We define {\bc} to be the lowest level---or entities we begin with in our analysis---of component that we use as a building block.
This is a choice made by the analyst. This is a choice made by the analyst, often guided by the standards to which the analysis is being performed to.
% %
Both op-amps and transistors have published statistical failure rates and yet an op-amp is constructed from transistors. Both op-amps and transistors have published statistical failure rates and yet an op-amp is constructed from transistors.
% %
@ -1036,7 +1041,7 @@ to which we are approving/analysing a system.
%% FUCKING STEREO SUB_SYSTEM EXAMPLE, THE FUCKING CHILDRENS SECTION %% FUCKING STEREO SUB_SYSTEM EXAMPLE, THE FUCKING CHILDRENS SECTION
\subsection{Systems, functional groupings, components and failure modes: sound system example} \subsection{definition of terms: sound system example.}
%000000elpful here to define the terms, `system', `functional~group', `component', `base~component', `symptom' and `derived~component/sub-system'. %000000elpful here to define the terms, `system', `functional~group', `component', `base~component', `symptom' and `derived~component/sub-system'.
%These are listed in table~\ref{tab:symexdef}. %These are listed in table~\ref{tab:symexdef}.
@ -1051,7 +1056,7 @@ This is now used as an example to describe terms used in FMMD.
% %
For instance a stereo amplifier separate/slave is a component. For instance a stereo amplifier separate/slave is a component.
%The %The
whole sound system consists perhaps of the following `components': A whole sound system consists perhaps of the following components:
CD-player, tuner, amplifier~separate, loudspeakers and ipod~interface. CD-player, tuner, amplifier~separate, loudspeakers and ipod~interface.
%Thinking like this is a top~down analysis approach %Thinking like this is a top~down analysis approach
@ -1084,9 +1089,10 @@ These collections are termed `{\fgs}'.
% %
For instance, the circuitry that powers the laser diode For instance, the circuitry that powers the laser diode
to illuminate the CD might contain a handful of components, and as such would make a good candidate to illuminate the CD might contain a handful of components, and as such would make a good candidate
as one of the base level {\fgs}. as one of the base level {\fgs}. It is a good candidate because
it performs a well defined function and it could be considered a design module.
\paragraph{Functional group to {\dc} process outline.} \paragraph{Functional grouping to {\dc} process outline.}
%In choosing the lowest level (base component) sub-systems we would look %In choosing the lowest level (base component) sub-systems we would look
%for the smallest `functional~groups' of components within a system. %for the smallest `functional~groups' of components within a system.
We can define a {\fg} as a set of components that interact We can define a {\fg} as a set of components that interact
@ -1151,7 +1157,7 @@ Currently, failure mode information is generally only available for generic com
% number of well defined ways. % number of well defined ways.
For common {\bcs} For common {\bcs}
there is established literature for the failure modes for the system designer to consider (often with accompanying statistical there is established literature for the failure modes for the system designer to consider (often with accompanying statistical
failure rates)~\cite{mil1991}~\cite{en298}~\cite{fmd91}. failure rates)~\cite{mil1991,en298,fmd91}.
% %
For instance, a simple resistor is generally considered For instance, a simple resistor is generally considered
to fail in two ways, it can go open circuit or it can short. to fail in two ways, it can go open circuit or it can short.
@ -1318,13 +1324,13 @@ A flat set is a set containing just failure modes and not sets of failure modes~
%for the {\fg}. %for the {\fg}.
% %
Each of these failure modes, and optionally combinations of them, are Each of these failure modes, and optionally combinations of them, are
formed into `test~cases' which are formed into failure~scenarios which are
analysed for their effect on the failure mode behaviour of the `{\fg}'. analysed for their effect on the failure mode behaviour of the `{\fg}'.
% %
Once we have the failure mode behaviour of the {\fg}, we can determine its symptoms of failure. Once we have the failure mode behaviour of the {\fg}, we can determine its symptoms of failure.
%for the {\fg}. %for the {\fg}.
% %
We could term these symptoms the derived failure modes of the `{\fg}'. We view these symptoms as derived failure modes of the {\fg}.
% %
Or in other words we can determine how the `{\fg}' can fail. Or in other words we can determine how the `{\fg}' can fail.
We can now consider the {\fg} as a {\dc} % sort of super component We can now consider the {\fg} as a {\dc} % sort of super component
@ -1337,8 +1343,7 @@ The process for taking a {\fg}, analysing its failure mode behaviour, considerin
all the failure modes of all the components in the group all the failure modes of all the components in the group
and collecting symptoms of failure, is termed `symptom abstraction'. and collecting symptoms of failure, is termed `symptom abstraction'.
% %
This This is dealt with in detail using an algorithmic description, in appendix \ref{sec:algorithmfmmd}.
is dealt with in detail using an algorithmic description, in appendix \ref{sec:algorithmfmmd}.
% % define difference between a \fg and a \dc % % define difference between a \fg and a \dc

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