From fc89b68499d1c0e8b8e117cebae50d41170fd523 Mon Sep 17 00:00:00 2001 From: Robin Clark Date: Wed, 21 Nov 2012 21:54:49 +0000 Subject: [PATCH] arrrghhhhh..... so muh work.... --- mybib.bib | 13 +++++++++++ submission_thesis/CH2_FMEA/copy.tex | 26 ++++++++++++++++----- submission_thesis/CH5_Examples/copy.tex | 17 +++++++------- submission_thesis/CH5_Examples/software.tex | 6 ++++- 4 files changed, 47 insertions(+), 15 deletions(-) diff --git a/mybib.bib b/mybib.bib index 4163983..7ce65f4 100644 --- a/mybib.bib +++ b/mybib.bib @@ -269,6 +269,19 @@ Database } +@article{sanjeev, +author = {Sanjeev Kumar Appicharla}, +title = {Analysis and modelling of space shuttle challenger accident using management oversight and risk tree(MORT)}, +journal = {7th IET System Safety Conference 2012}, +publisher = {IEEE}, +issn = {}, +url = {}, +doi = {}, +keywords = {System approach to safety, groupthink bias, technology standards, safety critical decision making}, +year = {2012}, +} + + @article{SMR:SMR580, author = {Bachmann, Volker and Messnarz, Richard}, title = {Improving safety and availability of complex systems by using an integrated design approach in development}, diff --git a/submission_thesis/CH2_FMEA/copy.tex b/submission_thesis/CH2_FMEA/copy.tex index ab150fd..f454af6 100644 --- a/submission_thesis/CH2_FMEA/copy.tex +++ b/submission_thesis/CH2_FMEA/copy.tex @@ -1,4 +1,6 @@ +%%% CHAPTER 2 +\label{sec:chap2} The generic and statistical European Safety Standard, EN61508:6\cite{en61508}[B.6.6] describes Failure Mode Effect Analysis (FMEA) as: @@ -141,16 +143,28 @@ approach in looking for system failures. \section{Theoretical Concepts in FMEA} - \paragraph{The unacceptability of a single component failure causing a catastrophe} - -FMEA, due to its inductive bottom-up approach, is very good -at finding potential single component failures that could have catastrophic implications. +% NEED SOME NICE HISTORICAL REFS HERE +FMEA, due to its inductive bottom-up approach, is good +at mapping potential single component failures to system level faults/events. Used in the design phase of a project FMEA is an invaluable tool -for unearthing these failure scenarios. -It is less useful for determining catastrophic events for multiple +for unearthing potential failure scenarios. +FMEA is always performed in the context of the use of the equipment. +This, put in terms of philosophy, is the subjective and the objective. +We can using objective reasoning trace a component level failure to a system level event, +but only in +the subjective sense can we determine its severity. +Failure mode analysis on the leaks possible from the O ring on the space shuttle +did not link this failure to the catastrophic failure of the spacecraft~\cite{challenger,sanjeev}. +It is less useful for determining events for multiple simultaneous\footnote{Multiple simultaneous failures are taken to mean failure that occur within the same detection period.} failures. +\paragraph{Failure modes, dectectable and undetectable} +Often the effects of a failure mode may be easy to detect, and our equipment can react by raising an alarm or compensating for the resulting fault. +Some failure modes may cause undetectable failure, for instance a component that causes +a measured reading to change could have dire consequences yet not be obvious. +In fault diagnosis failures are said to be observable and unobservable. + \paragraph{Impracticality of Field Data for modern systems} Modern electronic components, are generally very reliable, and the systems built from them diff --git a/submission_thesis/CH5_Examples/copy.tex b/submission_thesis/CH5_Examples/copy.tex index ceb9da1..eaf5f72 100644 --- a/submission_thesis/CH5_Examples/copy.tex +++ b/submission_thesis/CH5_Examples/copy.tex @@ -33,29 +33,30 @@ a variety of typical embedded system components including analogue/digital and e % %This is followed by several example FMMD analyses, \begin{itemize} - \item The first example applies FMMD to an operational amplifier inverting amplifier (see section~\ref{sec:invamp}) + \item The first example applies FMMD to an operational amplifier inverting amplifier (see section~\ref{sec:invamp}), %using an op-amp and two resistors; -this demonstrates how the re-use of a potential divider {\dc} from section~\ref{subsec:potdiv}. +this demonstrates re-use of a potential divider {\dc} from section~\ref{subsec:potdiv}. This inverting amplifier is analysed again, but this time with a different composition of {\fgs}. The two approaches, i.e. choice of membership for {\fgs}, are then discussed. \item Section~\ref{sec:diffamp} analyses a circuit where two op-amps are used to create a differencing amplifier. Building on the two approaches from section~\ref{sec:invamp}, re-use of the non-inverting amplifier {\dc} from section~\ref{sec:invamp} -is discussed in the context of this circuit, -where its re-use is appropriate in the first stage and +is examined, +where re-use is appropriate in the first stage and not in the second. \item Section~\ref{sec:fivepolelp} analyses a Sallen-Key based five pole low pass filter. -This demonstrates re-use the first Sallen-Key analysis, %encountered as a {\dc} +It demonstrates re-use the first Sallen-Key analysis, %encountered as a {\dc} increasing test efficiency. This example also serves to show a deep hierarchy of {\dcs}. \item Section~\ref{sec:bubba} shows FMMD applied to a -loop topology---using a `Bubba' oscillator---demonstrating how FMMD id different to fault diagnosis techniques. +loop topology---using a `Bubba' oscillator---demonstrating how FMMD differs from fault diagnosis techniques. %which uses %four op-amp stages with supporting components. Two analysis strategies are employed, one using -initially identified {\fgs} and the second using a more complex hierarchy of {\fgs} and {\dcs}, showing +initially identified {\fgs} and the second using a more complex hierarchy of %{\fgs} and +{\dcs} showing that a finer grained/more de-composed approach offers more re-use possibilities in future analysis tasks. \item Section~\ref{sec:sigmadelta} demonstrates FMMD can be applied to mixed analogue and digital circuitry -using a sigma delta ADC. +by analysing a sigma delta ADC. %shows FMMD analysing the sigma delta %analogue to digital converter---again with a circular signal path---which operates on both %analogue and digital signals. diff --git a/submission_thesis/CH5_Examples/software.tex b/submission_thesis/CH5_Examples/software.tex index 93f1430..e0afc80 100644 --- a/submission_thesis/CH5_Examples/software.tex +++ b/submission_thesis/CH5_Examples/software.tex @@ -1,5 +1,7 @@ +%%% CHAPTER 6 +\label{sec:chap6} \section{Software and Hardware Failure Mode Concepts} \label{sec:elecsw} @@ -798,7 +800,9 @@ $$fm (micro-controller) =\{ PROM\_FAULT, RAM\_FAULT, CPU\_FAULT, ALU\_FAULT, CLO We must start from the bottom-up with the software, and consider the hardware elements used (if any) by each software function. -Starting at the bottom +Starting at the bottom we form a {\fg} with +the function read\_ADC. +