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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
dia -t png $<
%.jpg:%.dia
dia -t jpg $<
all: ${PNG}
all: ${JPG}
pdflatex sw_hw_fmea
pdflatex sw_hw_fmea
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
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
%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
%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
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),
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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