diff --git a/fmmd_concept/fmmd_concept.tex b/fmmd_concept/fmmd_concept.tex index 5a24b96..6cbb8e7 100644 --- a/fmmd_concept/fmmd_concept.tex +++ b/fmmd_concept/fmmd_concept.tex @@ -19,8 +19,8 @@ modular.} \section{Introduction} -There are three methodologies in common use for failure mode modelling. -These are FTA, FMEA +There are four methodologies in common use for failure mode modelling. +These are FTA, FMEA, FMECA and FMEDA (a form of statistical analysis). These methodologies have several draw backs. @@ -221,10 +221,13 @@ to smaller and smaller functional modules \cite{maikowski}. \end{itemize} -\section{Proposed Methodology} +\section{Proposed Methodology \\ Failure Mode Modular De-Composition (FMMD)} -The proposed methodology will be bottom-up. to fulfill the logical de-composition requirement -it must build {\fg}s from the bottom-up. These are minimal collections of components +The proposed methodology will be bottom-up. +Thiure that all component failure modes are handled. +The bottom-up approach also fulfills the logical de-composition requirement. +FMMD builds {\fg}s of components from the bottom-up. +Thus the {\fg}s are minimal collections of components that work together to perform a simple function. We can perform a failure mode effects analysis on each of the component failure modes within the {\fg}. We can thus ensure that all component failure modes @@ -236,9 +239,24 @@ When we have out set of symptoms, we can now create a {\dc}. The {\dc} will have as its set of failures modes, the collected symptoms of the {\fg}. -Because we can now have a {\dc} we can use these to form +Because we can now have a {\dcs} we can use these to form new {\fg}s and we can build a hierarchical model of the system failure modes. +Advantages + +\begin{itemize} +\item It can be checked, automatically that, all component failure modes have been considered in the model. +\item Because we are modelling with {\fgs} and {\dcs} these can be generic, i.e. mechanical, electronic or software components. +\item The {\dcs} are re-usable, in that commonly used modules can be re-used in other designs/projects. +\item It will have a formal basis, that is to say, it should be able to produce mathematical proofs +for its results (MTTF and the causes for SYSTEM level faults). +\item Overall reliability and danger evaluation statistics can be computed. +\item A graphical representation based on Euler diagrams is proposed. +\item From the top down the failure mode model should will a logical de-composition of the functionality, by +chosing {\fg}s this happens as a natural consequence. + +\end{itemize} + %%- \section{building blocks of a safety critical systen}