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added a sw_hw_hierarchy diagram and description

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Robin P. Clark 2015-04-02 10:17:46 +01:00
parent e6d8965b7e
commit 148bc7cba9
3 changed files with 32 additions and 3 deletions
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8
papers/JOURNAL_fmea_sw_hw/Makefile
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@ -1,11 +1,15 @@
PNG = fmmdh.png ct1.png hd.png ftcontext.png # dia PNG is broken, text mangled // PNG = fmmdh.png ct1.png hd.png ftcontext.png
JPG = fmmdh.jpg ct1.jpg hd.jpg ftcontext.jpg sw_hw_hierarchy.jpg
%.png:%.dia %.png:%.dia
dia -t png $< dia -t png $<
%.jpg:%.dia
dia -t jpg $<
all: ${PNG}
all: ${JPG}
pdflatex sw_hw_fmea pdflatex sw_hw_fmea
pdflatex sw_hw_fmea pdflatex sw_hw_fmea
acroread sw_hw_fmea.pdf || okular sw_hw_fmea.pdf || xpdf sw_hw_fmea.pdf acroread sw_hw_fmea.pdf || okular sw_hw_fmea.pdf || xpdf sw_hw_fmea.pdf

27
papers/JOURNAL_fmea_sw_hw/sw_hw_fmea.tex
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@ -225,7 +225,7 @@ examining all known failure modes in the context of the system that it is part o
Various handbooks and international standards list common components and Various handbooks and international standards list common components and
their know failure modes, often with accompanying statistics~\cite{en298, fmd91, mil1991}. their know failure modes, often with accompanying statistics~\cite{en298, fmd91, mil1991}.
\subsection{Origins of FMEA tecniques} \subsection{Origins of FMEA techniques}
%FMEA methodologies trace from the 1940's and were designed to %FMEA methodologies trace from the 1940's and were designed to
%model simple electro-mechanical systems. %model simple electro-mechanical systems.
% %
@ -243,8 +243,33 @@ software elements.
%This paper explores the historical reasons why FMEA is performed in the way it is currently and %This paper explores the historical reasons why FMEA is performed in the way it is currently and
%the new factors placing higher demands upon it. %the new factors placing higher demands upon it.
% %
A control system designed up to the mid 1960's would typically have had no
programmatic/software elements.
Software generally sits on top of most modern safety critical control systems Software generally sits on top of most modern safety critical control systems
and defines its most important system wide behaviour and communications. and defines its most important system wide behaviour and communications.
%
A typical control system, be in in a car or a microwave oven in the kitchen
will generally combine a micro-controller with electronics.
It will form a hierarchy where low level electronics
is implemented at the bottom, which prepares input/output (IO)
signals for/from the micro controller.
The micro controller will have software to read/send signals to the electronics
and on top of that a functional software layer where the control algorithms will
reside. On the top of this hierarchy are the \cf{main} and \cf{monitor} functions.
This hierarchy is represented in figure~\ref{fig:sw_hw_hierarchy}.
\begin{figure}[h]+
\centering
\includegraphics[width=300pt]{./sw_hw_hierarchy.jpg}
% sw_hw_hierarchy.jpg: 814x412 pixel, 72dpi, 28.72x14.53 cm, bb=0 0 814 412
\caption{Software and hardware hierarchy of a typical modern embedded control system.}
\label{fig:sw_hw_hierarchy}
\end{figure}
% %
Currently standards that demand FMEA investigations for hardware FMEA (HFMEA) (e.g. EN298, EN61508), Currently standards that demand FMEA investigations for hardware FMEA (HFMEA) (e.g. EN298, EN61508),
do not specify FMEA for software but instead essentially just specify good practise, do not specify FMEA for software but instead essentially just specify good practise,

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papers/JOURNAL_fmea_sw_hw/sw_hw_hierarchy.dia Normal file
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