Reliability Indices
Modern complex systems are expected to be reliable and to provide certain levels of performance during operation. Hence definition and evaluation of reliability and performability indices become necessary. State-space models, such as continuous time Markov chains, are often used because of their capacity of handling different failure/repair behaviors, such as imperfect coverage, correlated failures, and repair dependencies. However time-dependent rates associated to events and particular repair strategies make computation of indices harder. In such cases, nonhomogeneous continuous time Markov chains, semi-Markov processes, Markov regenerative processes (MRGPs), or phase-type approximation can be used. In this article, by means of a simple example, we show how to compute the reliability of such systems with three techniques: piecewise constant approximation, phase type expansion, and simulation.
