morning edit, not breakfast!

This commit is contained in:
Robin P. Clark 2014-08-11 09:13:50 +01:00
parent 4266232aa3
commit 2b5a98ea35
2 changed files with 42 additions and 18 deletions

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@ -910,7 +910,7 @@ strength of materials, the causes of boiler explosions",
@BOOK{faa,
AUTHOR = "Federal~Aviation~Administration FAA",
TITLE = "System Safety Handbook",
PUBLISHER = "http://www.faa.gov/library/manuals/aviation/risk\_management/ss\_handbook/",
PUBLISHER = "http://www.faa.gov/ library/manuals/aviation/risk\_management/ss\_handbook/",
YEAR = "2008"
}
@ -973,6 +973,13 @@ doi={10.1109/HASE.2011.10},
ISSN={1530-2059},}
@PHDTHESIS{clark,
AUTHOR = "Robin Clark",
TITLE = "Failure mode modular de-composition",
SCHOOL = "Brighton University, School of Computing, Engineering and Mathematics http://eprints.brighton.ac.uk/12183/",
URL = "http://eprints.brighton.ac.uk/12183/",
YEAR = "2013"
}
@PHDTHESIS{garrett,
AUTHOR = "Chris Garrett",
@ -1291,6 +1298,25 @@ OPTissn = {},
@Manual{mcp2515,
title = {MCP2515 Can Protocol IC Datasheet},
OPTkey = {},
author = {Microchip},
OPTorganization = {},
address = {http://www.microchip.com/ wwwproducts/Devices.aspx?product=MCP2515},
OPTedition = {},
OPTmonth = {},
year = {2012},
OPTnote = {},
OPTannote = {},
OPTurl = {},
OPTdoi = {},
OPTissn = {},
OPTlocalfile = {},
OPTabstract = {},
}
@Manual{pic18f2523,
title = {PIC18F2523 Datasheet},
OPTkey = {},

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@ -198,7 +198,7 @@ the known failure mode behaviour.
%
%Presently FMEA, stops at the glass ceiling of the computer program: FMMD seeks to address
%this, and offers additional test efficiency benefits.
}
This paper is a condensed version of the PhD thesis entitled `failure Mode Modular De-compositon'~\cite{clark}.
%\today
\nocite{en298}
\nocite{en61508}
@ -424,7 +424,7 @@ on anything but a small hypothetical system.
%\item \textbf{PFMEA - Production} Emphasis on cost reduction and product improvement;
\item \textbf{FMECA - Criticality} Emphasis on minimising the effect of critical systems failing~\cite{fmeca}; % Military/Space
\item \textbf{FMEDA - Statistical Safety} Statistical analysis giving Safety Integrity Levels~\cite{en61508};
\item \textbf{DFMEA - Design or Static/Theoretical} Approval of safety critical systems using FMEA and single or double failure prevention~\cite{fmea};% EN298/EN230/UL1998
\item \textbf{DFMEA - Design or Static/Theoretical} Approval of safety critical systems using FMEA and single or double failure prevention~\cite{en298};% EN298/EN230/UL1998
\item \textbf{SFMEA - Software FMEA} --- Usage not enforced by most current standards~\cite{en298,en230,en61508}. %only used in highly critical systems at present.
\end{itemize}
@ -435,10 +435,10 @@ on anything but a small hypothetical system.
Because modern electronics has become more complex the number
of basic components has risen dramatically.
To add to this components used to fulfil common functions are often Integrated Circuits (ICs)..
Typical examples include voltage regulators, op-amps, micro-controller~\cite{pic18f25k80}, memory modules and
Typical examples include voltage regulators, op-amps, micro-controller~\cite{pic18f2523}, memory modules and
protocol handlers~\cite{mcp2515}. To build any of these component from scratch would be very expensive and time consuming,
but these IC `components' have very high internal transistor counts, and each have their own
failure mode behaviours.
but these IC `components' have very high internal transistor counts, and each have their own unique
failure mode behaviour.
Modern electronics has already jumped the gun of the basic component failure mode mapped to
a system failure paradigm.
@ -609,7 +609,7 @@ in an improved FMEA methodology,
\item avoid state explosion (i.e. XFMEA is impractical by hand~\cite{cbds}),
\item encourage exhaustive checking within each modular, %(total failure coverage within {\fgs} all interacting component and failure modes checked),
\item traceable reasoning inherent in system failure models,% to aid repeatability and checking,
\item re-usable i.e. it should be possible to re-use analysis,
\item re-usable i.e. it should be possible to re-use analysis~\cite{rudov2009language},
\item possibility to analyse simultaneous/multiple failures,
\item one to one mapping from {\bc} {\fms} to system level failures (see section~\ref{sec:onetoone}),
\item modular --- i.e. usable in a distributed system.
@ -631,24 +631,16 @@ in an improved FMEA methodology,
\paragraph{A more-complete Failure Mode Model}
% HFMEA
% SFMEA
% VARIABLE CURRUPTION
% MICRO PROCESSOR FAULTS
% INTERFACE ANALYSIS
%
% add them all together --- a load of bollocks, lots of impressive inches of reports that no one will be bothered to read....
%
In order to obtain a more complete failure mode model of
a hybrid electronic/software system we need to analyse
the hardware, the software, the hardware the software runs on (i.e. the software's medium),
and the software/hardware interface.
%
HFMEA is a well established technique and needs no further description in this paper.
%
\section{Example for analysis} % : How can we apply FMEA}
%
For the purpose of example, we chose a simple common safety critical industrial circuit
that is nearly always used in conjunction with a programmatic element.
A common method for delivering a quantitative value in analogue electronics is
@ -676,7 +668,7 @@ current signal into a voltage that we can read with an ADC.%
\begin{figure}[h]
\centering
\includegraphics[width=250pt]{./ftcontext.png}
\includegraphics[width=230pt]{./ftcontext.png}
% ftcontext.png: 767x385 pixel, 72dpi, 27.06x13.58 cm, bb=0 0 767 385
\caption{Context Diagram for {\ft} loop}
\label{fig:ftcontext}
@ -697,6 +689,12 @@ Consider a software function that reads a {\ft} input, and returns a value betwe
representing the value intended by the current detected, with an additional error indication flag to indicate the validity
of the value returned.
%
This example straddles the hardware software interface, but is not overly complex, which allows
the FMEA seamless failure modelling of FMMD to be demonstrated.
%
A complete
PID based temperature controller is modelled in~\cite{clark}[6.3].
%
Let us assume the {\ft} detection is via a \ohms{220} resistor, and that we read a voltage
from an ADC into the software.
Let us define any value outside the 4mA to 20mA range as an error condition.