From 56521c4b7bb4cfece5dbe597d3e81412c1b13271 Mon Sep 17 00:00:00 2001 From: Robin Date: Wed, 7 Jul 2010 18:23:25 +0100 Subject: [PATCH] arrrgghhh --- symptom_ex_process/symptom_ex_process.tex | 76 +++++++++++++---------- 1 file changed, 43 insertions(+), 33 deletions(-) diff --git a/symptom_ex_process/symptom_ex_process.tex b/symptom_ex_process/symptom_ex_process.tex index 58b79e0..029cd70 100644 --- a/symptom_ex_process/symptom_ex_process.tex +++ b/symptom_ex_process/symptom_ex_process.tex @@ -14,8 +14,8 @@ and then determining how that functional group can fail. % With this information, we can treat the functional group as a component in its own right. -This new component is a derived component. -For a top down technique this would correspond to a low~level sub-system. +This new component is a derived from the functional~group. +In the field of safety engineering this derived component correspond to a low~level sub-system. %The technique uses a graphical notation, based on Euler\cite{eulerviz} and Constraint diagrams\cite{constraint} to model failure modes and failure mode common symptom collection. The technique is designed for making building blocks for a hierarchical fault model. Once the failure modes have been determined for a sub-system/derived~component, @@ -56,8 +56,8 @@ and then determining how that functional group can fail. % With this information, we can treat the functional group as a component in its own right. -This new component is a derived component. -For a top down technique this would correspond to a low~level sub-system. +This new component is a derived from the functional~group. +In the field of safety engineering this derived component correspond to a low~level sub-system. %The technique uses a graphical notation, based on Euler\cite{eulerviz} and Constraint diagrams\cite{constraint} to model failure modes and failure mode common symptom collection. The technique is designed for making building blocks for a hierarchical fault model. % Once the failure modes have been determined for a sub-system/derived~component, @@ -90,6 +90,24 @@ This chapter focuses on the process of building the blocks, the symptom extracti \section{Fault Finding and Failure Mode Analysis} +\subsection{Static Analysis} + +In the field of safety critical engineering; to comply with +European Law a product must be certified under the approriate `EN' standard. +Typically environmental stress, EMC, electrical stressing, endurance tests, +software~inspections and project~management quality reviews are applied\cite{sccs}. + +Static testing is also applied. This is theoretical analysis of the design of the product from the safety +perspective. +Three main techniques are currently used, +Statistical failure models, FMEA (Failure mode Effects Analysis) and FTA (Fault Tree Analysis). +The FMMD technique is aimed primarily as design verification for +safety critical systems. +However, FMMD also provides the mathematical frame work +to assist in the production of these three results of static analysis. +From the model created by the FMMD technique, the three above failure mode +descriptions can be derived. + \subsection{Top Down or natural trouble shooting} It is interesting here to look at the `natural' trouble shooting process. Fault finding is intinctively performed from the top-down. @@ -103,6 +121,7 @@ Specific measurements and checks will be made, and finally a component or a low level sub-system will be found to be faulty. A natural fault finding process is thus top~down. +Top down fault isolation/finding techniques are described in \ref{NETWORKDECOMPOSITION}. \subsection{FMMD - Bottom~up Analysis} The FMMD technique does not follow the `natural fault finding' or top down approach, it instead works from the bottom up. @@ -121,33 +140,18 @@ This also means that we can obtain statistical estimates based on the known reli of the components. %It also means that every component failure mode must at the very least be considered. -\subsection{Static Analysis} - -In the field of safety critical engineering; to comply with -European Law a product must be certified under the approriate `EN' standard. -Typically environmental stress, EMC, electrical stressing, endurance tests, -software~inspections and project~management quality reviews are applied\cite{sccs}. - -Static testing is also applied. This is theoretical analysis of the design of the product from the safety -perspective. -Three main techniques are currently used, -Statistical failure models, FMEA (Failure mode Effects Analysis) and FTA (Fault Tree Analysis). -The technique outlined here aims to provide a mathematical frame work -to assist in the production of these three results of static analysis. -From the model created by the FMMD technique, the three above failure mode -descriptions can be derived. - -{ -The aims are -\begin{itemize} - \item To automate the process where possible - \item To apply a documented trail for each analysis phase (determination of functional groups, and analysis of component failure modes on those groups) - \item To use a modular approach so that analysed sub-systems can be re-used - \item Automatically ensure no failure mode is unhandled - \item To produce a data model from which FTA, FMEA and statistical failure models may be obtained automatically -\end{itemize} -} +%{ +%The aims are +%\begin{itemize} +% \item To automate the process where possible +% \item To apply a documented trail for each analysis phase (determination of functional groups, and analysis of component failure modes on those groups) +% \item To use a modular approach so that analysed sub-systems can be re-used +% \item Automatically ensure no failure mode is unhandled +% \item To produce a data model from which FTA, FMEA and statistical failure models may be obtained automatically +%\end{itemize} +%} +% \subsection{Systems, functional groups, sub-systems and failure modes} @@ -168,7 +172,8 @@ A sub-system will be composed of components, which may themselves be sub-systems. However each `component' will have a fault/failure behaviour and it should always be possible to obtain a set of failure modes -for each `component'. In FMMD terms a sub-system is a derived component. +for each `component'. +%In FMMD terms a sub-system is a derived component. If we look at the sound system example, the CD~player could fail in several distinct ways, @@ -196,8 +201,13 @@ We can define a functional~group as a set of components that interact to perform a specific function. When we have analysed the fault behaviour of a functional group, we can treat it as a `black box'. -We can now call our functional~group a sub-system or a derived~component. -The goal here is to know how it will behave under fault conditions ! +The fault behaviour will consist of a set of `symptoms' caused by combinations +of the component failure modes. +We can make a new `component' derived from the functional~group. +The symptoms are the failure modes of this new `derived component'. + +%We can now call our functional~group a sub-system or a derived~component. +%The goal here is to know how it will behave under fault conditions ! %Imagine buying one such `sub~system' from a very honest vendor. %One of those sir, yes but be warned it may fail in these distinct ways, here %in the honest data sheet the set of failure modes is listed!