From e4988e2fb33188d5c4beeb91fd4814feb992a3f8 Mon Sep 17 00:00:00 2001 From: "Robin P. Clark" Date: Thu, 12 Sep 2013 09:10:15 +0100 Subject: [PATCH] tidy up of CH4 after WE removal, CH5 and CH6 next, better check App A too --- submission_thesis/CH4_FMMD/copy.tex | 66 ++++++++++++++--------------- 1 file changed, 31 insertions(+), 35 deletions(-) diff --git a/submission_thesis/CH4_FMMD/copy.tex b/submission_thesis/CH4_FMMD/copy.tex index 0505366..1ae3b59 100644 --- a/submission_thesis/CH4_FMMD/copy.tex +++ b/submission_thesis/CH4_FMMD/copy.tex @@ -26,7 +26,7 @@ FMMD is in essence a modularised variant of traditional FMEA~\cite{sccs}[pp.34- % In order to analyse from the bottom-up and apply a modular methodology, small groups of components that naturally -work together to perform a simple function are chosen: these groups are termed `{\fgs}'. +work together to perform simple functions are chosen: these groups are termed `{\fgs}'. % \fmmdglossFG % @@ -60,34 +60,31 @@ All the failure modes of all the components within a {\fg} are collected. %A flat set is a set containing just the failure modes and not sets of failure modes~\cite{joyofsets}[p.8]. % Each component failure mode can considered as a `failure~scenario' or 'test~case' -applied to a {\fg}. +to be applied applied to the {\fg}. % Each of these failure modes, and optionally combinations of them, are formed into test~cases which -are analysed for their effect on the failure mode behaviour of the `{\fg}'. +are analysed for their effect on the failure mode behaviour of the {\fg}. % Once the failure mode behaviour of the {\fg} is obtained, its symptoms of failure can be determined. %, %or the failure modes of the {\dc}. %for the {\fg}. % -These symptoms are treated as failure modes of the {\fg}. +These symptoms are then treated as failure modes of the {\fg}. % \fmmdglossFG \fmmdglossSYMPTOM %Or in other words That is, how the {\fg} can fail has been determined. % -As a set of failure modes has been defined for the {\fg} it can be treated as a component. +As a set of failure modes has been defined for the {\fg} it can be treated as a component in its own right. % The {\fg} can be considered as a `{\dc}' % sort of super component with its own set of failure modes. % \fmmdglossDC % -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% -% UP TO HERE IN WE REMOVAL 11SEP2013 -%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % %This {\dc} has a set of failure modes: we can thus treat it as a `higher~level' component. % @@ -125,7 +122,7 @@ thus avoiding state explosion). %% GARK BEGIN The principles of FMMD are demonstrated, by using it to analyse a -commonly used circuit, a non-inverting amplifier built from an op amp~\cite{aoe}[p.234] and +common circuit, the non-inverting amplifier built from an op amp~\cite{aoe}[p.234] and two resistors; a circuit schematic for this is shown in figure \ref{fig:noninvamp}. % \begin{figure}[h+] @@ -201,7 +198,7 @@ a failure in the potential~dividers' operation. % For instance -if resistor $R_1$ were to become open, then the potential~divider would not be grounded and the +if resistor $R_1$ were to go open, then the potential~divider would not be grounded and the voltage output from it would float high (+ve). % This would mean the resulting failure of the potential~divider would be voltage high output. @@ -352,8 +349,8 @@ This {\dc} will have two failure modes, $HighPD$ and $LowPD$. % The derived component is defined by its failure modes and % the functional group used to derive it. % %piss can consider this an an orthogonal WHAT???? Group ???? Collection ???? -With this {\dc} model for a generic potential divider, it can be used -as a building block for other {\fgs} in the same way the base components $R1$ and $R2$ were. +This {\dc} model for a generic potential divider can be used +as a building block for other {\fgs} in the same way that the base components $R1$ and $R2$ were. % %\clearpage % @@ -411,7 +408,7 @@ These op-amp failure modes are represented on the DAG in figure~\ref{fig:op1dag} %\clearpage %\paragraph{Modelling the OP amp with the potential divider.} The op-amp and the {\dc} {\em PD} now % andrew heavily critised this sentence but it made sense to Chris and I -form a {\fg} to model the failure mode behaviour of the non-inverting amplifier. +formed into a {\fg} to model the failure mode behaviour of the non-inverting amplifier. % %piss have the failure modes of the {\dc} for the potential divider, %so we do not need to go back and consider the individual resistor failure modes that defined its behaviour. @@ -419,7 +416,7 @@ form a {\fg} to model the failure mode behaviour of the non-inverting amplifier. %piss can now create a {\fg} for the non-inverting amplifier %by bringing together the failure modes from \textbf{opamp} and \textbf{PD}. % -The two components in this new {\fg}, the op-amp and the {\dc} {\em PD} have failure modes, which are used +The two components in this new {\fg}, the op-amp and the {\dc} {\em PD} have failure modes which are used as {\fcs} in table~\ref{tbl:ampfmea1}. %Each of these failure modes will be given a {\fc} for analysis, %and this is represented in table \ref{tbl:ampfmea1}. @@ -601,7 +598,7 @@ as {\fcs} in table~\ref{tbl:ampfmea1}. % For this amplifier configuration there are three {\dc} failure modes; {\em AMP\_High, AMP\_Low, LowPass}. % see figure~\ref{fig:fgampb}. % HTR 05SEP2012 -This model now has two stages of analysis, as represented in figure~\ref{fig:eulerfmmd}. +This model now has two stages of analysis. %, as represented in figure~\ref{fig:eulerfmmd}. % From the analysis in table \ref{tbl:ampfmea1} the {\dc} {\em NONINVAMP} can be created, which represents the failure mode behaviour of the non-inverting amplifier. @@ -639,7 +636,7 @@ It is possible to traverse this DAG, tracing the top level % symptoms failure modes down to the base component failure modes, %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 {\dc} {\em INVAMP}. +the three high level symptoms, i.e. the {\bc} failure~modes of the non-inverting amplifier {\dc} {\em INVAMP}. % Knowing all possible causes for a top level event/failure~mode is extremely useful; @@ -669,7 +666,7 @@ A component is anything used to build a %a product or system. It could be something quite complicated like an %integrated -micro-controller/servo motor, or quite simple like the resistor. +micro-controller/servo motor, or quite simple like a resistor. % A component is usually identified by its name, a manufacturer's part number and perhaps @@ -691,7 +688,7 @@ in the chip would be considered to be a separate {\bc}. % CAN WE FIND SUPPORT FOR THIS IN LITERATURE??? \fmmdglossBC % -The above definition of a part, needs further refinement, and to be defined as % defining +The above definition of a part, needs further refinement, i.e. to be defined as % defining an atomic entity. % used as a building block. %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. @@ -726,7 +723,7 @@ A component can be viewed as a sub-system that is a part of some larger system. % A modular system common to many homes is the sound separates audio system or stereo hi-fi. % -This is used as an example to describe the concepts {\fg} and {\dc} found in FMMD. +This is used as an example to describe the concepts of {\fg} and {\dc} used by FMMD. % For instance a stereo amplifier separate/slave is a component. %The @@ -739,7 +736,7 @@ CD-player, tuner, amplifier~separate, loudspeakers and ipod~interface. %and is the way in which FTA\cite{nucfta} analyses a System %and breaks it down. \paragraph{Functional Groupings and Components.} % {\fgs} and components.} -Components can be composed of components, recursively down to +Components can be composed of components, recursively on down to the {\bcs}. % \fmmdglossFG @@ -823,16 +820,18 @@ failure rates)~\cite{mil1991,en298,fmd91}. For instance, a simple resistor is generally considered to fail in two ways, it can go open circuit or it can short. % -Electrical components have data-sheets associated with them. The data sheets -supply detailed information on the component as supplied by the manufacturer. +Electrical components have data-sheets associated with them. +% +Data sheets, supplied by the manufacturer, +are a detailed source of information on the component. % \fmodegloss % Because they are written for system designers, and to an extent advertise the product, -they rarely give %show %clearly detail the -failure modes of the component. +they rarely list %show %clearly detail the +failure modes. % of the component. % -For FMEA purposes, ideally failure modes along with +For FMEA purposes, ideally, failure modes along with with environmental factors and MTTF~\cite{sccs}[p.165] statistics would be presented. % Given the growing usage of FMEA/FMEDA and the emergence of SIL as a safety benchmark in industry, this may change. @@ -885,11 +884,9 @@ it is common to term the modules identified as sub-systems. \fmmdglossFG % When modularising failure mode behaviour from the bottom up, -it is more meaningful to call them `{\dcs}'. -% -This is because they have been derived from the bottom-up according to functional +it is more meaningful to call them `{\dcs}' (i.e. they have been derived from the bottom-up according to functional criteria, rather than with the top down approach, de-composed from -a system into 'sub-systems'. +a system into 'sub-systems'). % \fmodegloss \fmmdglossDC @@ -907,7 +904,7 @@ of the component. The FMEA analyst is not usually concerned with how the component has failed internally. % -What the analyst need to know are the symptoms of failure. +What the analyst needs to know are the symptoms of failure. % \fmmdglossSYMPTOM % @@ -961,7 +958,7 @@ An advantage of working from the bottom up is that it can be ensured that all component failure modes must be considered. % A top down approach (such as FTA) -can miss individual failure modes of components~\cite{faa}[Ch.~9], +can miss~\cite{faa}[Ch.~9] individual failure modes of components, especially where there are non-obvious top-level faults. % \fmmdglossFTA @@ -1065,7 +1062,7 @@ in a {\fg} higher in the hierarchy. The {\em PD} derived component is now placed into a {\fg} with the op-amp. % -This {\fg} is now analysed and a {\dc} created to represent the failure mode behaviour +This {\fg} is analysed and a {\dc} created to represent the failure mode behaviour of the {\em INVAMP}\footnote{The results of this analysis are placed into the analysis~report. This will contain mapping relationships between the component {\fms} and the {\dc} {\fms} and ideally, descriptions that would aid auditors to understand the reasoning behind each analysis test~case.}. @@ -1182,7 +1179,7 @@ Ensuring this condition is described in section~\ref{sec:completetest}. \paragraph{Mutual exclusivity of {\dc} failure modes.} % It is a desirable feature of a component that its failure modes -are mutually exclusive. +are naturally mutually exclusive. % This also applies to {\dcs} produced in the FMMD process. % @@ -1209,8 +1206,7 @@ has to be made for each component {\fm} in the system. \paragraph{State explosion problem of FMEA solved by FMMD.} % Because FMMD considers failure modes within functional groups; -the traditional state explosion problem in FMEA where the ideal of exhaustive FMEA (XFMEA)---where each failure -mode could be considered in the context of all other components in the system---disappears. +the traditional state explosion problem in FMEA--which lead to the ideal of XFMEA---disappears. % With FMMD, because the {\fgs} have small numbers of components in them, XFMEA can be easily applied within the {\fgs}. %