Maintenance modelling and scheduling in fault-tolerant control

The present paper studies the modelling and scheduling problem of maintenance strategies in fault-tolerant control systems (FTCSs) using a stochastic modelling method. In FTCSs, the controller reconfigures itself to accommodate the occurrence of critical faults based on the information obtained from a fault detection and identification (FDI) scheme. Discrete semi-Markov chains are constructed to describe the operation of FTCSs with their unique characteristics incorporated. Two different maintenance strategies are discussed: FDI-dependent and FDI-independent periodic strategies, classified based on the use of FDI information in maintenance decision making. For each strategy, methods are presented for calculating the stationary availability and determining the optimal maintenance strategy to achieve the best availability. Two examples are given to demonstrate the proposed methods for both FDI-dependent and -independent cases.