diff --git a/submission_thesis/colophon/copy.tex b/submission_thesis/colophon/copy.tex index fb84f74..4ba7e1c 100644 --- a/submission_thesis/colophon/copy.tex +++ b/submission_thesis/colophon/copy.tex @@ -118,7 +118,7 @@ Typeset in \LaTeX \today. \renewcommand{\baselinestretch}{1.5} - +\clearpage \chapter*{Declaration} @@ -136,3 +136,128 @@ Signed \\ Dated \clearpage + + +\section*{Abstract} + +\subsection*{Failure Mode Modular De-Composition} + +% +% This should be a three hundred word summary of the work and findings +% Supervisors did not warn me this was required. +% I found out by reading the OU ``how to get a PhD'' book in the bath, and then wading through the Brighton University +% regulations where it is stated on page 14 of a 30+ page document filled with mostly n/a regulations to me. +% Ho HUM. No wonder these shits have trouble working in the real world. +% +% + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% BEGINING --- Introduce the field +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +The certification process of safety critical products for European and other international +standards typically demand environmental stress, endurance and electro magnetic compatibility testing. +% +Theoretical, or `static~testing' also a requirement. +% +Failure Mode effects Analysis (FMEA) is a tool used for static testing. +FMEA is a bottom-up technique that aims to assess the effects +of all component failure modes in a system. +% +Its use is traditionally limited to hardware systems. % only. +% +With the growing complexity of modern electronics traditional FMEA +is suffering from state explosion and re-use of analysis problems. +% +Also with the now ubiquitous use of micro-controllers in smart~instruments and control systems, +software is increasingly being seen as a `missing~factor' for FMEA. % analysis. + + +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% Middle work and findings +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +This thesis presents a new modular variant of FMEA, Failure Mode Modular Decomposition (FMMD). +% +FMMD has been designed to integrate mechanical/electronic and software +failure models, by treating them all as components in terms of their failure modes. +% +For instance, software functions, +electronic and mechanical components +can all be assigned sets of failure modes. +% +FMMD builds failure mode models from the bottom-up by incrementally analysing +{\fgs} of components, using the results of analysis to create higher level {\dcs}, +which in turn can be used to build {\fgs}. +% +In this way a hierarchical failure mode model +is built. +% +Software functions are treated as components by FMMD and can thus be incorporated seamlessly into +the failure mode hierarchical model. +% +A selection of examples, electronic circuits and hardware/software hybrids are analysed using +this new methodology. +% +The results of these analyses are then discussed from the perspective of safety critical application. +% +Performance in terms of test efficiency is greatly improved by FMMD and +the examples analysed and theoretical models are used to demonstrate this. +% + +%Because FMMD is modular and hierarchical, and deals with all its objects in +%terms of their failure mode behaviour, it is ideally suited to creating integrated software and hardware models. +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% +% End what has been achieved ---- all in 300ish word OK here we go. +%Conclusions are presented listing the +%and FMMD is compared with traditional HFMEA and SFMEA. +This thesis presents a methodology that solves the state explosion problems of FMEA; +provides integrated hardware and software failure mode models; +facilitates multiple failure mode analysis; +encourages re-use of analysis work +and can be used to produce traditional format FMEA reports. +%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% + + +% The certification process of safety critical products for European and other international +% standards often demand environmental stress, endurance and Electro Magnetic Compatibility (EMC) testing. +% Theoretical, or `static testing',is often also required. Failure Mode effects Analysis (FMEA) is a tool used for static testing. +% Its use is traditionally applied to hardware (electrical and mechanical) systems. +% With the increasing use of micro-controllers in smart~instruments and control systems, +% software is increasingly being seen as the `missing factor' in FMEA analysis. +% This paper presents a new modular variant of FMEA, Failure Mode Modular Decomposition (FMMD). +% Because FMMD is modular and hierarchical, and deals with all its objects in +% % terms of their failure mode behaviour, it is ideally suited to creating integrated software and hardware models. +% FMEA is a bottom-up technique that aims to assess the effects +% of all component failure modes on a system. It is used both as a design tool (to determine weaknesses), +% and is a requirement of certification of safety critical products. FMEA has been successfully applied to +% mechanical, electrical and hybrid electro-mechanical systems. Work on software FMEA (SFMEA) is beginning, +% but at present no technique for SFMEA that integrates hardware and software models exists. +% Software in current embedded systems practise sits on top of most modern safety critical control systems +% [and inside many data collection/actuator modules (smart~instruments)], and defines their most important +% system wide behaviour, interfaces and communications. Currently standards that demand FMEA for hardware +% (e.g. EN298, EN61508), do not specify it for software, but instead specify, computer architecture, good software practise, +% review processes and language feature constraints. Where FMEA traces component failure modes to resultant system failures, +% software has been left in a non-analytical limbo of best practises and constraints. Where SFMEA has been applied---for some +% automotive and highly safety critical systems---it has always been performed separately from hardware FMEA (HFMEA). +% % +% At present the hardware/software interface is a source for confusion and misunderstanding, and in many organisations, +% the actual design teams for software and hardware work in separate departments. Subtle errors of electronic systems for instance, +% may not be picked up by software specialists, and vice versa. It would be desirable to have a methodology that provides seamless +% software and hardware integration in its failure modelling. FMMD has been designed to integrate mechanical/electronic and software +% failure models, by treating all modular components in terms of their failure modes. For instance, a software function, +% or an electronic or a mechanical component can be assigned a known set of failure modes. +% This paper presents an overview of the FMMD methodology and then an FMMD analysis of a simple software/hardware hybrid sub-system. +% +% +% The example system chosen is a 4->20mA input circuit consisting of a resistive element, multiplexer (MUX), +% Analogue to Digital Converter (ADC) and two software functions. The purpose of this system is to convert an +% electrical current signal into a value for use in software. FMMD is applied to the hardware (resistive element, MUX and ADC) +% and to the software components (two `C' functions), producing one integrated failure mode model. +% The 4->20mA input circuitry used in the example and its related software, are accepted practise and in +% common use, and therefore its failure mode behaviour is well known and understood. For this reason it is a +% good example to use for comparing the results from FMMD analysis with known failure mode behaviour +% from the field/direct experience of engineers. The failure model is then discussed and compared with +% heuristic knowledge of 4->20mA inputs, circuitry and software. +% Conclusions are then presented listing the benefits and draw-backs of analysing the +% hardware/software hybrid system using FMMD, and FMMD is compared with traditional HFMEA and SFMEA. + +