Mum proof read for english
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@ -62,8 +62,8 @@ Let us first define a component. This is anything which we use to build a
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product or system with. This could be something quite complicated
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like an integrated microcontroller, or quite simple like the humble resistor.
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We can define a
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component by its name, a manufacturers part number and perhaps
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a vendors reference number.
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component by its name, a manufacturers' part number and perhaps
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a vendors' reference number.
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What these components all have in common is that they can fail, and fail in
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a number of well defined ways. For common components
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there is established literature for the failure modes for the system designer to consider (often with accompanying statistical
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@ -120,7 +120,7 @@ When building from the bottom up, it is more meaningful to call them `derived~co
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%% Paragraph using failure modes to build from bottom up
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%%
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\section{Fault Mode Analysis, top down or bottom up?}
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\section{Fault Mode Analysis, \\ top down or bottom up?}
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Traditional static fault analysis methods work from the top down.
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They identify faults that can occur in a system, and then work down
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@ -167,16 +167,16 @@ all the failure modes of all the components in the group,
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and analysing it is called `symptom abstraction' and
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is dealt with in detail in chapter \ref{symptom_abstraction}.
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In terms of our UML model the symptom abstraction process takes a functional~group,
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and creates a new derived component from it.
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In terms of our UML model, the symptom abstraction process takes a {\fg}
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and creates a new {\dc} from it.
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%To do this it first creates
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%a new set of failure modes, representing the fault behaviour
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%of the functional group. This is a human process and to do this the analyst
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%must consider all the failure modes of the components in the functional
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%group.
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The newly created derived~component requires a set of failure modes of its own.
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These failure modes are the failure mode behaviour of the functional group that it was derived from.
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Because these new failure modes were determined from a derived component we can call
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The newly created {\dc} requires a set of failure modes of its own.
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These failure modes are the failure mode behaviour of the {\fg} that it was derived from.
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Because these new failure modes were derived from a {\fg} we can call
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these `derived~failure~modes'.
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%It then creates a new derived~component object, and associates it to this new set of derived~failure~modes.
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We thus have a `new' component, or system building block, but with a known and traceable
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@ -185,7 +185,7 @@ fault behaviour.
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The UML representation shows a `functional group' having a one to one relationship with a derived~component.
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We can represent this using a UML diagram in figure \ref{fig:cfg}.
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Using the symbol $\bowtie$ to indicate the analysis process that takes a
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The symbol $\bowtie$ is used to indicate the analysis process that takes a
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functional group and converts it into a new component.
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\[ \bowtie ( FG ) \mapsto DerivedComponent \]
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@ -258,7 +258,7 @@ $$ FM ( C ) = F $$
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For FMMD failure mode analysis we need to consider the failure modes
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from all the components in a functional~group as a flat set.
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Consider the components in a functional group to be $C$ indexed by j thus $C_j$.
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Thflat set of failure modes we are after can be found by applying function $FM$ to all the components
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The flat set of failure modes we are after can be found by applying function $FM$ to all the components
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in the functional~group and taking the union of them thus:
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$$ FunctionalGroupAllFailureModes = \bigcup_{j \in \{1...n\}} FM(C_j) $$
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@ -271,12 +271,12 @@ FM : FG \mapsto \mathcal{F}
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\end{equation}
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\section{Unitary State Component Failure Mode sets}
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\section{Unitary State Component \\ Failure Mode sets}
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\paragraph{Design Descision/Constraint}
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An important factor in defining a set of failure modes is that they
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should be as clearly defined as possible.
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It should not be possible for instance for
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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 an additional $2^N-1$ failure mode scenarios.
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@ -329,7 +329,7 @@ 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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Because of this, the failure mode set $F=FM(R)$ is `unitary~state'.
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Thus because both fault modes cannot be active at the same time, the intersection of $ R_{SHORTED} $ and $ R_{OPEN} $ cannot exist.
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@ -365,9 +365,9 @@ Note where there are more than two failure~modes,
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by banning any pairs from being active at the same time,
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we have banned larger combinations as well.
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\section{Handling Simultaneous Component Faults}
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\section{Handling Simultaneous \\ Component Faults}
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For some integrity levels of static analysis there is a need to consider not only single
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For some integrity levels of static analysis, there is a need to consider not only single
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failure modes in isolation, but cases where more then one failure mode may occur
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simultaneously.
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It is an implied requirement of EN298\cite{en298} for instance to consider double simultaneous faults.
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@ -377,7 +377,7 @@ all combinations of failures modes of size $N$ and less.
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The Powerset concept from Set theory is useful to model this.
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The powerset, when applied to a set S is the set of all subsets of S, including the empty set
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\footnote{The empty set ( $\emptyset$ ) is a special case for FMMD analysis, it simply means there
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is no fault active in the functional~group under analysis}
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is no fault active in the functional~group under analysis.}
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and S itself.
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In order to consider combinations for the set S where the number of elements in each sub-set of S is $N$ or less, a concept of the `cardinality constrained powerset'
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is proposed and described in the next section.
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@ -388,7 +388,7 @@ is proposed and described in the next section.
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A Cardinality Constrained powerset is one where sub-sets of a cardinality greater than a threshold
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are not included. This threshold is called the cardinality constraint.
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To indicate this the cardinality constraint $cc$, is subscripted to the powerset symbol thus $\mathcal{P}_{cc}$.
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To indicate this, the cardinality constraint $cc$ is subscripted to the powerset symbol thus $\mathcal{P}_{cc}$.
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Consider the set $S = \{a,b,c\}$.
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The powerset of S:
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@ -537,7 +537,7 @@ associated with the test cases, complete coverage would be verified.
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\pagebreak[1]
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\section{Component Failure Modes and Statistical Sample Space}
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\section{Component Failure Modes \\ and Statistical Sample Space}
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%\paragraph{NOT WRITTEN YET PLEASE IGNORE}
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A sample space is defined as the set of all possible outcomes.
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For a component in FMMD analysis, this set of all possible outcomes is its normal correct
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