IFM target 2.0: an innovative method to define reliability target for prototype systems

The success of a mission, in general terms of functionality of a complex system, is based on the probability that failure events do not happen during the mission. Therefore, a preliminary reliability analysis and consequently the definition of the reliability target are required. The reliability target of the whole system can be an input or output data of the reliability study; consequently, the reliability values of components are respectively output or input data. If we start from the definition of the target of the system (input data), considering similar ones (if available, especially for innovative ones!), we can allocate the reliability of each component (output data). The choice of the most suitable allocation technique is not a simple task, advantages and disadvantages are discussed in literature. Instead, if we start from the characteristics of the units available (input data), studying the structure (links in series and parallel), it is possible to calculate the reliability target of the whole system. However, these values could be not completely available (innovative systems) or refer to units with not comparable levels in terms of technology, complexity, safety and so on. In the manuscript, a new method is proposed to define the reliability target: Integrated Factors Method 2.0 (IFM 2.0). The purpose will be to combine the advantages of both above approaches. IFM 2.0 is an upgrade of IFM that was developed in 2002 by Falcone et al. The new methodology combines the old IFM method with new maintenance factors. Thanks to IFM 2.0, it is possible to estimate the reliability target of a system in a more confident way: “IFM Target 2.0.” The proposed method has been validated and applied to two complex systems. The obtained results show the effectiveness of the new method and its capability to overcome the problems of other previous methods.