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Robin P. Clark 2015-03-30 08:57:02 +01:00
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papers/JOURNAL_fmea_sw_hw/sw_hw_fmea.tex
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@ -657,15 +657,17 @@ out of one program and place it in another if it used some of the global variabl
Newer computer languages were invented where modularity was encouraged. Newer computer languages were invented where modularity was encouraged.
Instead of FORTRANs global scope for variables, individual functions in a newer language like `C' Instead of FORTRANs global scope for variables, individual functions in a newer languages like `C'
started to have `local' variables. This meant that started to have `local' variables. This meant that
a programmer could take a function from a `C' program and a programmer could take a function from a `C' program and
use it in another one without complication. use it in another one without complication.
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Later languages implemented object orientation Later languages implemented object orientation
which grouped functions and data together into modules called classes, where which grouped functions and data together into modules called classes, where
even the internal local variables could be hidden from the even the internal local variables of a class could be hidden from the
programmer using the class. programmer using the class. For instance the internal workings of a binary~tree or linked~list do no need to be
accessed if you simply want to use a class in your program to store data: in this case
your would pick a ready written and well de-bugged data store class and simply use it.
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Software expanded in complexity faster than electronics, Software expanded in complexity faster than electronics,
and to cope with this software languages developed modularity (function call trees, classes and finally distributed processing mechanisms). and to cope with this software languages developed modularity (function call trees, classes and finally distributed processing mechanisms).
@ -897,10 +899,10 @@ The basic concept behind FMMD is to from the bottom-up, modularise the problem.
FMEA cannot easily be modularised from the top-down, because FMEA cannot easily be modularised from the top-down, because
it has to deal with component failure modes. it has to deal with component failure modes.
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It may seem bit counter intuitive, but this means that if FMEA is to be modularised It may seem bit counter intuitive, but this means that if FMEA is to be modularised
it must be done from the bottom up. it must be done from the bottom up.
This may seem like a stange idea, but consider how an engineer would look This may seem like a strange idea, but consider how an engineer would look
at an electronic circuit/schematic. at an electronic circuit/schematic.
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The Engineer might, for instance, trace an input signal The Engineer might, for instance, trace an input signal
@ -911,12 +913,15 @@ those components did.
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For instance were it an amplifier, the engineer would For instance were it an amplifier, the engineer would
recognise the electronic configuration, recognise the electronic configuration,
and maybe get his calculator out and calculate its gain and maybe get a calculator out and determine its gain
or some other feature, by looking at the other components connected to it. or some other property, by looking at the other components connected to it.
% %
This is a form of modularisation from the bottom-up. This is a form of modularisation from the bottom-up.
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The Engineer has identified a module, an input amplifier. The Engineer has identified a module, an input amplifier.
By identifying other modules at component level
in the circuit, these modules can then be merged to form
bigger modules until there is a hierarchy and one final module representing the whole system.
\paragraph{Broadly FMMD is modularisation from the bottom-up of FMEA} \paragraph{Broadly FMMD is modularisation from the bottom-up of FMEA}
@ -924,10 +929,12 @@ The Engineer has identified a module, an input amplifier.
Firstly modules are identified (for instance common circuitry formations such as amplifiers or digital outputs) and Firstly modules are identified (for instance common circuitry formations such as amplifiers or digital outputs) and
then failure mode analysis is performed on them. then failure mode analysis is performed on them.
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By analysing this small group of components as a module By analysing a small group of components as a module
the ways in which the module can fail can be listed. the ways in which the module can fail can be listed.
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This will give a set of symptoms of failure for the module. This gives a set of symptoms of failure for the module.
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This in effect allows the module to be treated as a component, or {\dc}.
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When the lower levels have been analysed, modules can be brought When the lower levels have been analysed, modules can be brought
together to form larger modules using the lower ones as through they were together to form larger modules using the lower ones as through they were