Reliability Modeling of Fault Tolerant Control Systems

This paper proposes a novel approach of reliability modeling for Fault Tolerant Control Systems (FTCS). By introducing the reliability function of FTCS based on the control performance and hard deadline, a semi-Markov process model is proposed to describe the system operation for reliability evaluation. The degraded performance of FTCS in the presence of imperfect Fault Detection & Isolation (FDI) is reflected by the states of the semi-Markov process. The semi-Markov kernel, the key parameter of the process, is determined by four probabilistic parameters from the Markovian model of FTCS. The reliability function, computed from the transition probability of the semi-Markov process, gives a suitable quantitative measure of the overall performance because it incorporates the control objectives, performance degradation, hard deadline and effects of imperfect FDI.