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fmmd_concept/System_safety_2011/submission.tex

@@ -98,10 +98,10 @@ support for environmental and operational states.
 
 \subsection{Fault Mode Effects Analysis FMEA)}
 FMEA is used principally in manufacturing. 
-Each defect is assessed by its cost to repair and its frequency.%, using a 
+Each defect is assessed by its cost to repair and its frequency. %, using a 
 %failure mode ratio. 
 A list of failures and their cost is generated. 
-It is easy to identify single component failure to system failure scenarios 
+It is easy to identify single component failure to system failure scenarios, 
 and an estimate of product reliability can be calculated. It cannot focus on 
 component interactions that cause system failure modes or determine potential 
 problems from simultaneous failure modes. It does not consider environmental 
@@ -139,7 +139,7 @@ event, this leads to repeated work, with limited ability for cross checking/mode
 
 \paragraph{State Explosion problem}
 The bottom -up techniques all suffer from a problem of state explosion.
-To perform the analysis rigorously, we need to consider the effect
+To perform the analysis rigorously, we would need to consider the effect
 of a component failure against all other components. Adding environmental
 and operational states further increases this effect.
 
@@ -149,7 +149,7 @@ is $N \times K$. To examine the effect that one failure mode has on all
 the other components\footnote{A %base 
 component failure will typically affect the sub-system
 it is part of, and create a failure effect at the SYSTEM level.}
-will be $(N-1) \times N \times K$.%, in effect a very large set cross product.
+will be $(N-1) \times N \times K$. %, in effect a very large set cross product.
 If $E$ is the number of environmental conditions to consider
 in a system, and $A$ the number of applied/operational states (or modes of the SYSTEM),
 the job of the bottom-up analyst is presented with two
@@ -282,6 +282,24 @@ for its results, such as  error causation trees.%, reliability and safety statis
 % of sub-systems the SYSTEM. 
 
 
+
+\section{The proposed Methodology}
+\label{fmmdproc}
+The proposed methodology is a bottom-up process
+starting with base~components.
+These are collected into functional groups
+and each component failure mode (and optionally combinations) are considered in the 
+context of the {\fg}. These are termed `test~cases'. For each test~case
+there will be a corresponding failure mode, from the perspective of the {\fg}.
+A symptom collection stage is then applied. Here common symptoms are collected
+from the results of the test~cases.Diagram1
+With a collection of the {\fg} failure symptoms, we can now create a {\dc}.
+The failure modes of this new {\dc} are the symptoms of the {\fg} it was derived from.
+
+By using {\dcs} in higher level functional groups, a hierarchy can be built representing
+the failure mode behaviour of a SYSTEM.
+
+ 
 \subsection{Environmental Conditions, Operational States}
 
 Any real world sub-system will exist in a variable environment
@@ -362,24 +380,6 @@ Operational states are conditions that apply to some functional groups, not indi
 %DEVELOP UML MODELS
 
 
-
-\section{The proposed Methodology}
-\label{fmmdproc}
-The proposed methodology is a bottom-up process
-starting with base~components.
-These are collected into functional groups
-and each component failure mode (and optionally combinations) are considered in the 
-context of the {\fg}. These are termed `test~cases'. For each test~case
-there will be a corresponding failure mode, from the perspective of the {\fg}.
-A symptom collection stage is then applied. Here common symptoms are collected
-from the results of the test~cases.Diagram1
-With a collection of the {\fg} failure symptoms, we can now create a {\dc}.
-The failure modes of this new {\dc} are the symptoms of the {\fg} it was derived from.
-
-By using {\dcs} in higher level functional groups, a hierarchy can be built representing
-the failure mode behaviour of a SYSTEM.
-
-
 \subsection{FMMD analysis Example: A Voltage/Potential Divider}
 \begin{figure}
  \centering
@@ -389,7 +389,7 @@ the failure mode behaviour of a SYSTEM.
  \label{fig:pd}
 \end{figure}
 
-We consider here an example functional group, the potential divider
+We consider here an example functional group, the potential divider\footnote{A commonly used configuration in electronics to provide specific voltage levels}
 which consists of two resistors used to provide a voltage
 intermediate of its supply and ground rails.
 %It consists of two resistors.
@@ -440,10 +440,8 @@ $R1$ has failure modes $\{R1\_OPEN, R1\_SHORT\}$ and $R2$ has failure modes $\{R
 
 %\ifthenelse {\boolean{dag}}
 %{
-Modelling the two resistors as a functional group, we present this as a directed graph.
-%failure modes, taken from the components R1 and R2,
-%in the potential divider, shown 
-in figure \ref{fig:fg1dag}.
+Modelling the two resistors as a functional group, we present this as a directed graph
+(see figure \ref{fig:fg1dag}).
 
 \begin{figure}[h+]
  \centering
@@ -507,7 +505,7 @@ on the potential dividers' operation. For instance
 were the resistor $R_1$ to go open, the circuit would not be grounded and the 
 voltage output from it would be the +ve supply rail.
 This would mean the symptom of the failed potential divider, would be that it
-gives an output high voltage reading. We can now consider the {\fg}
+gives an output high voltage. We can now consider the {\fg}
 as a component in its own right, and its symptoms as its failure modes.
 
 From table  \ref{pdfmea} we can see that resistor 
@@ -625,6 +623,10 @@ We avoided the state explosion problem of having to
 check $R1$ and $R2$ against all other components in the system they may belong to.
 Also, by modularising the circuit as a {\dc}, we have reduced the number of errors we need to consider at higher levels
 of analysis.
+
+Using {\dcs} in higher level {\fgs} we can build a hierarchy to represent the failure mode behaviour
+of complete systems.
+
 % \subsection{Re-Factoring the UML Model}
 % 
 % The UML models thus far % in this 

invopamp/paper.tex

@@ -15,10 +15,11 @@
 \setboolean{paper}{true} % boolvar=true or false
 
 \newboolean{pld}
-\setboolean{pld}{false} % boolvar=true or false : draw analysis using propositional logic diagrams
+\setboolean{pld}{true} % boolvar=true or false : draw analysis using propositional logic diagrams
 
 \newboolean{dag}
 \setboolean{dag}{true} % boolvar=true or false : draw analysis using directed acylic graphs
+
 \def\layersep{2.5cm}