Design for Availability

Abstract of the contribution to the First European Conference of the Prognostics and Health Management Society on July 3-7 2012 in Dresden, Germany.  *)


Design for Availability – Flexible System Evaluation with a Model Library of Generic RAMST Blocks

Tailoring a complex system to meet given availability require­ments is a challenging task in the design process. Besides compiling the applicable mtbf and mttr figures of the required components, the specific set of algebraic rules has to be identified and applied to compute the overall pre­dicted availability of the designated system functions for the in­dividual architecture and for individual usage profiles.

Design for Availability - a new way to analyse the availability of a system, Poster presented at PHM Europe 2012While on the other hand model based methods have mean­while become established in the system development pro­cess, such time- and effort-saving simulation-based ap­proaches are by far not so common in the field of RAMST-analyses.

This contribution reports about an approach of amending a reusa­ble library of functional component models – originally designed to explore the effect of assumed failures in com­plex networks by simulation – and applying it to compute the availability of a generic launcher system. Here the design engineer is faced with the complex task to find an architecture to guarantee a specified availability of the firing function with the given resource items onboard.

Developed within the tool environment RODON, the developed prototypical library enables a quick evalua­tion of structural design alternatives of the selected launcher application. On top it sup­ports the full range of RAMST-analyses – like computation of cause-effect-relationships for FMEA, automatic drawing of FTAs for hazards of loosing designated system functions or systematic evaluation of the Diagnostic Coverage resp. potentially monitor or reconfiguration strategies – based on the same single model. Further generalization activities are going on.

Since the model is composed of generic qualitative building blocks, it took much less time to develop than full quantitative or physical model descriptions usually need. Although this qualitative representation implies certain limitations, as the authors experienced this is compensated by the advantage of an easier understanding by the modeler and quick adaption and to new principal architectures, while still providing sufficient system insight and result.

Driven by requirements from the industrial application, ideas for further library extension are being discussed to support also questions regarding repair procedures and time, resource allocation or cover even economical aspects.

The paper sections focus on the description of the launcher design task, a short introduction to the applied tool, the library development and application and finally the results and outlook.


*) by Dipl.-Ing. Dieter Fasol (MBDA Deutschland GmbH) and Dr.-Ing. Burkhard Münker (icomod – munker consulting)

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