edits from printout. added derived component class to uml diagram
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@ -13,5 +13,5 @@ paper: paper.tex component_failure_modes_definition_paper.tex
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# Remove the need for referncing graphics in subdirectories
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#
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component_failure_modes_definition_paper.tex: component_failure_modes_definition.tex
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component_failure_modes_definition_paper.tex: component_failure_modes_definition.tex paper.tex
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cat component_failure_modes_definition.tex | sed 's/component_failure_modes_definition\///' > component_failure_modes_definition_paper.tex
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@ -10,14 +10,16 @@ Mathematical constraints and definitions are made using set theory.
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\section{Introduction}
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This chapter describes the data types and concepts for the Failure Mode Modular De-composition (FMMD) method.
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When analysing a safety critical system using the
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FMMD technique, we need clearly defined failure modes for
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this technique, we need clearly defined failure modes for
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all the components that are used to model the system.
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These failure modes have a constraint such that
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the compoent failure modes must be mutually exclusive.
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This and the definition of a component are
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described in this chapter.
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the component failure modes must be mutually exclusive.
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When this constraint is complied with we can use the FMMD process to
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build hierarchical bottom-up models of failure mode behaviour.
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%This and the definition of a component are
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%described in this chapter.
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%When building a system from components,
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%we should be able to find all known failure modes for each component.
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%For most common electrical and mechanical components, the failure modes
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@ -104,8 +106,8 @@ We can term this a `Functional~Group'. When we have a
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`Functional~Group' we can look at the failure modes of all the components
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in it and decide how these will affect the Group.
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Or in other words we can determine the failure modes of the functional
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group. These failure modes are derived from the functional group, as so we can call
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them `derived failure modes'.
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group. These failure modes are derived from the functional group, we can therefore call
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these `derived failure modes'.
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We now have something very useful, because
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we can now treat this functional group as a component with a known set of failure modes.
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This newly derived component can be used as a higher level
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@ -115,7 +117,7 @@ to form higher level functional groups.
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This process can continue until have build a hierarcy that converges to a failure model of the entire system.
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To differentiate the components derived from functional groups, we can
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add a new attribute to the class `Component', that of analysis
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level.
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level. The UML representation shows a `functional group' having a one to one relationship with a derived component.
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We can represet this in a UML diagram see figure \ref{fig:cfg}
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\begin{figure}[h]
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@ -125,8 +127,8 @@ We can represet this in a UML diagram see figure \ref{fig:cfg}
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\caption{Components Derived from Functional Groups}
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\label{fig:cfg}
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\end{figure}
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\section{Set theory description}
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\clearpage
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\section{Set Theory Description}
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$$ System \stackrel{has}{\longrightarrow} PartsList $$
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@ -312,7 +314,7 @@ It should not be possible for instance for
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a component to have two or more failure modes active at once.
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Having a set of failure modes where $N$ modes could be active simultaneously
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would mean having to consider $2^N$ failure mode scenarios.
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would mean having to consider $2^N-1$ failure mode scenarios.
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%
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Should a component be analysed and simultaneous failure mode cases exit,
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the combinations could be represented by new failure modes, or
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@ -348,10 +350,10 @@ A component with simple ``unitary~state'' failure modes is the electrical resist
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Electrical resistors can fail by going OPEN or SHORTED.
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For a given resistor R we can assign it the failure mode by applying
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the function $FM$ thus $ FM(R) = \{R_{SHORTED},R_{OPEN}\} $.
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Nothing can fail with both conditions open and short active at the same time ! The conditions
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OPEN and SHORT are mutually exclusive.
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For a given resistor R we can apply the
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the function $FM$ to find its set of failure modes thus $ FM(R) = \{R_{SHORTED},R_{OPEN}\} $.
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A resistor cannot fail with both conditions open and short active at the same time ! The conditions
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OPEN and SHORT are thus mutually exclusive.
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Because of this the failure mode set $F=FM(R)$ is `unitary~state'.
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@ -370,7 +372,7 @@ $$ c1 \cap c2 \neq \emptyset | c1 \neq c2 \wedge c1,c2 \in C \wedge C \not\in U
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That is to say that it is impossible that any pair of failure modes can be active at the same time
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for the failure mode set $C$ to exists in the family of sets $U$
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Note where that are more than two failure~modes, by banning pairs from happening at the same time
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Note where that are more than two failure~modes, by banning pairs from being active at the same time
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we have banned larger combinations as well.
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