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On the Usage of Reliability Methods in Early Design Phases
Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology. Saab Aeronautics, Linköping, Sweden.
Saab Aeronautics, Linköping, Sweden.
Linköping University, Department of Management and Engineering, Machine Design. Linköping University, The Institute of Technology.
2012 (English)In: Proceedings of the 11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012 (PSAM11 ESREL 2012), Curran Associates, Inc., 2012, 769-778 p.Conference paper, Published paper (Refereed)
Abstract [en]

One important challenge in the early phases of product development is to apply reliability methods for estimating the safety and reliability of the system when information about the chosen equipment and components is limited. For systems consisting of units with several degraded states, and not only “up” and “down”, the results from reliability and system safety analysis are often difficult to interpret and use. The main contribution of this paper is to evaluate the applicability of different reliability methods for analyzing an overall system concept in early development stages. Furthermore, the paper constitutes the first step of a methodology intended to address the issues outlined above from a practical point of view. In the paper, two static methods, Reliability Block Diagram and Fault Tree Analysis, and one dynamic method, Markov Analysis, have been applied to conceptual design of an aircraft electrical system. These three methods have been evaluated regarding usefulness, modeling possibilities and applicability in the conceptual design. Each method is, from a practical point of view, dependent on the limitations of the software that is used. In order to overcome this issue the calculations and partly the modeling have been performed in three different software tools.

Two iterations have been performed for Markov Analysis, and the results are used to evaluate the method regarding applicability and possibilities of modeling the system and to find out what results can be gained by extending the model.

Place, publisher, year, edition, pages
Curran Associates, Inc., 2012. 769-778 p.
Keyword [en]
System Reliability, Markov Analysis, Reliability Block Diagram, Fault Tree
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-94350ISBN: 978-1-62276-436-5 (print)OAI: oai:DiVA.org:liu-94350DiVA: diva2:632438
Conference
11th International Probabilistic Safety Assessment and Management Conference and the Annual European Safety and Reliability Conference 2012 (PSAM11 ESREL 2012), 25-29 June, Helsinki, Finland
Available from: 2013-06-25 Created: 2013-06-25 Last updated: 2017-02-20Bibliographically approved
In thesis
1. On System Safety and Reliability in Early Design Phases: Cost Fo cused Optimization Applied on Aircraft Systems
Open this publication in new window or tab >>On System Safety and Reliability in Early Design Phases: Cost Fo cused Optimization Applied on Aircraft Systems
2013 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

System Safety and Reliability are fundamental to system design and involve a quantitative assessment prior to system development. An accurate prediction of reliability and system safety in a new product before it is manufactured and marketed is necessary as it allows us to forecast accurately the support costs, warranty costs, spare parts requirements, etc. On the other hand, it can be argued that an accurate prediction implies knowledge about failures that is rarely there in early design phases. Furthermore, while predictions of system performance can be made with credible precision, within reasonable tolerances, reliability and system safety are seldom predicted with high accuracy and confidence.

How well a product meets its performance requirements depends on various characteristics such as quality, reliability, availability, safety, and efficiency. But to produce a reliable product we may have to incur increased cost of design and manufacturing. Balancing such requirements, that are often contradictory, is also a necessary step in product development. This step can be performed using different optimization techniques.

This thesis is an attempt to develop a methodology for analysis and optimization of system safety and reliability in early design phases. A theoretical framework and context are presented in the first part of the thesis, including system safety and reliability methods and optimization techniques. Each of these topics is presented in its own chapter. The second and third parts are dedicated to contributions and papers. Three papers are included in the third part; the first evaluates the applicability of reliability methods in early design phases, the second is a proposed guideline for how to choose the right reliability method, and the third suggests a method to balance the safety requirements, reliability goals, and costs.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2013. 62 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1600
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-94354 (URN)LIU-TEK-LIC-2013:34 (Local ID)978-91-7519-584-1 (ISBN)LIU-TEK-LIC-2013:34 (Archive number)LIU-TEK-LIC-2013:34 (OAI)
Supervisors
Funder
Vinnova
Available from: 2013-06-25 Created: 2013-06-25 Last updated: 2013-06-25Bibliographically approved
2. Multiobjective Optimization for Safety and Reliability Trade-off: Applications on Early Phases of Aircraft Systems Design
Open this publication in new window or tab >>Multiobjective Optimization for Safety and Reliability Trade-off: Applications on Early Phases of Aircraft Systems Design
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A strategic issue for any industrial company is to conceive safe and reliable systems while performing all systems’ intended functions at a minimum cost. System safety and reliability are fundamental to system design and involve a quantitative assessment prior to system development. Aircraft design is a multifaceted process that involves several different disciplines, system safety and reliability among them, to obtain o holistic approach of a complex product. During the last decades, the idea of trade-off between safety or reliability goals against other characteristics has become more prominent. Furthermore, while predictions of system performance can be made in early design phases with credible precision, within reasonable tolerances, reliability and system safety are seldom predicted with high accuracy and confidence. Making the right design decisions in the early design phase is vital to the success of a project. Nowadays, it is essential within the design of new products, to increase awareness (knowledge) early in the design phases and keep the design decisions (freedom) open as long as possible, and with that also keep down the allocated costs.

This thesis presents MOSART (Multiobjective Optimization for Safety and Reliability Trade-off), a method promoting a systematic approach regarding trade-offs between system safety and reliability goals against other contradictory targets, such as weight and cost, in early design phases.

A theoretical framework and context are presented in the first part of the thesis, including system safety and reliability methods and optimization techniques. The second and third parts are dedicated to contributions and papers, where seven papers are included. These papers approach different aspects of MOSART, from the basic idea to the implementation and usage of the method in the conceptual phase of aircraft systems design. Several aspects regarding the choice of system safety and reliability methods in early design phases are also included in the papers, e.g. evaluation of applicability of reliability methods in early design phases, considerations around the usage of these methods within the MOSART framework and a proposal of a guideline for how to choose the right reliability method. All the examples used in the papers are chosen from basic aircraft sub-systems.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. 89 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1833
National Category
Production Engineering, Human Work Science and Ergonomics Embedded Systems Other Engineering and Technologies not elsewhere specified Computer Systems Design
Identifiers
urn:nbn:se:liu:diva-134592 (URN)9789176855768 (ISBN)
Public defence
2017-03-23, C3, C-huset, Campus Valla, Linköping, 10:15 (English)
Opponent
Supervisors
Funder
VINNOVA
Note

The research project has been financed by the researchprogrammes NFFP5 2009-01316 and NFFP6 2013-01223 funded by Saab Aeronautics and theNational Aviation Engineering Research Program (NFFP), jointly driven by the Swedish ArmedForces, the Swedish Defence Materiel Administration (FMV),

Available from: 2017-02-20 Created: 2017-02-20 Last updated: 2017-02-20Bibliographically approved

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