Reliability block diagrams

2007

Dependability evaluation is an important, often indispensable, step in design and analyze (critical) systems, acquiring importance with the systems complexity growth. When the complexity of a system is high and/or increases, for example automizing or expanding some parts, dynamic effects, not present or manifested before, could arise or become significant in terms of reliability/availability. The system could be affected by common cause failures, the system components could interfere each other or could become inter/sequencedependent, effects due to load sharing arise and therefore should be considered, and so on. Moreover could be interesting to evaluate redundancy and maintenance policies. In those cases it is not possible to recur to notations as reliability block diagrams (RBD), fault trees (FT) or reliability graphs (RG) to represent the system, since the statistical independence assumption is not satisfied. Also more enhanced formalisms as dynamic FT (DFT) could not result adequate to the objective. To overcome those problems we developed a new formalism derived from RBD: the dynamic RBD (DRBD). In this paper we explain how to use the DRBD notation in system modeling and analysis, coming inside a methodology that, starting from the system structure, drives to the overall system availability evaluation following modeling and analysis phases. To do this we use an example drawn from literature, consisting of a multiprocessor distributed computing system. By this we also compare our approach with the DFT one.

Proceedings of the 9th EAI International Conference on Performance Evaluation Methodologies and Tools, 2016

Reliability block diagram (RBD) models are a commonly used reliability analysis method. For static RBD models, combinatorial solution techniques are easy and efficient. However, static RBDs are limited in their ability to express varying system state, dependent events, and non-series-parallel topologies. A recent extension to RBDs, called Dynamic Reliability Block Diagrams (DRBD), has eliminated those limitations. This tool paper details the RBD implementation in the Möbius modeling framework and provides technical details for using RBDs independently or in composition with other Möbius modeling formalisms. The paper explains how the graphical front-end provides a user-friendly interface for specifying RBD models. The back-end implementation that interfaces with the Möbius AFI to define and generate executable models that the Möbius tool uses to evaluate system metrics is also detailed.

2021

Reliability Block Diagrams (RBDs) are widely used in reliability engineering to model how the system reliability depends on the reliability of components or subsystems. In this paper, we present librbd, a C library providing a generic, efficient and open-source solution for time-dependent reliability evaluation of RBDs. The library has been developed as a part of a project for reliability evaluation of complex systems through a layered approach, combining different modeling formalisms and solution techniques at different system levels. The library achieves accuracy and efficiency comparable to, and mostly better than, those of other well-established tools, and it is well designed so that it can be easily used by other libraries and tools.

2007

Key Words: system reliability, dynamic systems, dynamic fault tree, dynamic reliability block diagrams

Microelectronics Reliability, 1967

2004

The proposed tool, using a novel "compression algorithm" is capable of reducing any complicated series-parallel system to a visible sequence of series and parallel blocks in a reliability block diagram (RBD) by first finding all existing paths, then algorithmically compressing all redundant component duplications and finally calculating an exact reliability and creating an encoding of the topology. A fast algorithm to perform state enumeration in a hybrid form assisted by the polish encoding approach on complex networks to compute the exact s-t reliability is in progress by the authors. The graphical screening ease and convenience of this algorithm is advantageous for planners and designers trying to improve system reliability by allowing a quick and efficient intervention that may be required at a dispatch center to observe routine operations and/or identify solution alternatives in case of a crisis. Note, s denotes the source and t denotes the target.

AIP Conference Proceedings, 2015

Reliability Block Diagrams (RBDs) allow us to model the failure relationships of complex systems and their sub-components and are extensively used for system reliability, availability, dependability and maintainability analyses of many engineering systems. Traditionally, Reliability Block Diagrams (RBD) are analyzed using paper-and-pencil proofs or computer simulations. Recently, formal techniques, including Petri Nets and higher-order-logic theorem proving, have been used for their analysis as well. In this paper, we provide a concise survey of these available RBD analysis techniques and compare them based on their accuracy, user friendliness and computational requirements.

1997

1993

The region of useful redundancy for a k-out-of-n system of identical components is the interval in component reliability for which the reliability of the system is better than that of a single component. A table for the lower boundary of that region is presented for n ( 56. The table is compiled with a high precision and a minimal round-off error by using a highly efficient algorithm for computing the k-out-of-n system reliability. Certain symmetries and limiting values are noted, thereby allowing a cutting of the number of entries actually listed in the table by more than one half. If the component lifetime is assumed to be exponentially distributed, then the table entries can be used to compute the point that divides the tlme axis into intervals of a short mission and a long mission for k-out-of-n redundancy.