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papers/software_fmea/abs.tex
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%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.
%
%% INTRO %% INTRO
% the problem % the problem
% the solution % the solution
% why you would want to read the paper % why you would want to read the paper
%
The certification process of safety critical products for European and The certification process of safety critical products for European and
other international standards often demand environmental stress, other international standards often demand environmental stress,
endurance and Electro Magnetic Compatibility (EMC) testing. Theoretical, or 'static testing', endurance and Electro Magnetic Compatibility (EMC) testing. Theoretical, or `static~testing',
is often also required. Failure Mode effects Analysis (FMEA) is a tool used 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. 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 generally, software is increasingly being seen as a missing factor in FMEA analysis. 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 takes a simple example of a hardware/software hybrid (an industry standard {\ft} input), analyses it This paper takes a simple example of a hardware/software hybrid (an industry standard {\ft} input), analyses it
using hardware and software FMEA, and then discusses the effectiveness of the using hardware and software FMEA, and then discusses the effectiveness of the
failure modelling from the perspective of the hybrid hardware/software sub-system. failure modelling from the perspective of the hybrid hardware/software sub-system.
This paper demonstrates the pitfalls and benefits of applying HFMEA and SFMEA %
FMEA performed on mechanical and electronic
systems can be termed Hardware FMEA (HFMEA), and on software, SFMEA.
%
This paper highlights the pitfalls and benefits of applying HFMEA and SFMEA
to a hybrid system. to a hybrid system.
% %
%% MIDDLE %% MIDDLE
% some background % some background
% how important software is today % how important software is today, how there is no FMEA to encompass both software and hardware
% %
Failure Mode Effects Analysis (FMEA), is a bottom-up technique that aims to assess the effect all FMEA is a bottom-up technique that aims to assess the effect all
component failure modes on a system. 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. 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. FMEA has been successfully applied to mechanical, electrical and hybrid electro-mechanical systems.
%
Work on software FMEA (SFMEA) is beginning, but Work on SFMEA is beginning, but
at present no technique for SFMEA that at present no technique for SFMEA that
integrates hardware and software models %known to the authors integrates hardware and software models %known to the authors
exists. FMEA performed on mechanical and electronic exists.
systems can be termed Hardware FMEA (HFMEA). %
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.
% %
Software generally, sits on top of most modern safety critical control systems
and defines its most important system wide behaviour and communications.
Currently standards that demand FMEA for hardware (e.g. EN298, EN61508), Currently standards that demand FMEA for hardware (e.g. EN298, EN61508),
do not specify it for Software, but instead specify, good practise, do not specify it for software, but instead specify, computer architecture, good software practise,
review processes and language feature constraints. review processes and language feature constraints.
% %
Where FMEA % scientifically Where FMEA % scientifically
traces component {\fms} traces component {\fms}
to resultant system failures, software has been left in a non-analytical to resultant system failures, software has been left in a non-analytical
limbo of best practises and constraints. limbo of best practises and constraints.
Where software FMEA (SFMEA) has been applied, it is Where SFMEA has been applied---for some automotive and highly safety critical systems---it has always been
performed a separately from the HFMEA. performed separately from HFMEA.
%
The {\ft} input circuitry used in the example and its related software, are accepted practise and in common use, and therefore the failure mode
behaviour is well known and understood.
%
For this reason it is a good example to use for comparing the results from the SFMEA and HFMEA methodologies
with known failure mode behaviour from the field/direct experience of engineers.
%% CONCLUSIONS. %% CONCLUSIONS.
% %
% %
This paper presents an analysis of a simple software/hardware hybrid sub-system, the {\ft} input circuit consisting of
This paper presents an analysis of a simple software/hardware hybrid sub-system (a {\ft} input circuit, MUX, ADC and two software functions a resistive element, multiplexer (MUX), Analogue to Digital Converter (ADC) and two software functions.
that are used to convert the electrical current signal into a value for use in software). The purpose of this sub-system is to convert an electrical current signal into a value for use in software.
HFMEA is applied to the hardware and SFMEA to the software components. %
The two failure models are then compared, and then compared with heuristic HFMEA is applied to the hardware (resistive element, MUX and ADC) and SFMEA to the software components (two `C' functions), producing two separate
knowledge about {\ft} inputs circuitry and software. failure mode models for the {\ft} input.
%
Conclusions are then reached giving a positive and negative aspects The two failure models are then discussed and compared with heuristic
knowledge of {\ft} inputs, circuitry and software.
%
Conclusions are then presented listing the benefits and draw-backs
of analysing the hardware/software hybrid system using HFMEA and SFMEA. of analysing the hardware/software hybrid system using HFMEA and SFMEA.
Authors:
\begin{table}[h]
\center
\begin{tabular}{||p{3cm}|p{6cm}|p{5cm}||}
\hline \hline
{\em Author } & {\em Email} & {\em Institution} \\ \hline
& & \\ \hline
R.P. Clark & r.clark@energytechnologycontrol.com & Energy Technology Control Ltd. \\ \hline
%R.P.Clark@brighton.ac.uk & Energy Technology Control Ltd \\ \hline
A. Fish & Andrew.Fish@brighton.ac.uk & Brighton University, UK \\ \hline
C. Garrett & C.Garrett@brighton.ac.uk & Brighton University, UK \\ \hline
J. Howse & John.Howse@brighton.ac.uk & Brighton University, UK \\ \hline
& & \\ \hline
\hline
\end{tabular}
%\caption{Authors}
\label{tbl:authors}
\end{table}
Presenting Author is R.P. Clark.
\begin{table}[h]
\center
\begin{tabular}{||p{1cm}|p{10cm}|p{1cm}||}
& Short Biography & \\ \hline
& R.P. Clark is an embedded software Engineer, working with
safety critical industrial burner controllers, and the design of safety critical sensors. He is currently
working for a part-time PhD at Brighton University.
& \\ \hline
& & \\ \hline
\end{tabular}
%\caption{Authors}
\label{tbl:bio}
\end{table}

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papers/software_fmea/abs_pre.tex
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\begin{document} \begin{document}
\section*{FMEA applied to a hybrid software and hardware sub-system} \section*{FMEA applied to hybrid software and hardware systems}