Robust fault detection of turbofan engines subject to adaptive controllers via a ToMFIR technique

This paper provides a new design of robust fault detection for turbofan engines with adaptive controllers. The critical issue is that the adaptive controllers can depress the faulty effects such that the actual system outputs remain the pre-specified values, making the fault detection difficult. In addition, observer-based fault-detection strategies are not always reliable because the observer gain may be selected large due to the consideration of stability, robustness or performance, leading to the size of output estimation errors, which are used as fault-detection residuals, small. To solve this problem, the Total Measurable Fault Information Residual (ToMFIR) technique is adopted to detect faults in turbofan engines with adaptive controllers. To this end, a bank of systems, each corresponding to a particular fault, is formulated by reorganizing the considered uncertain engine model. Each system in the bank is first transformed into two subsystems. Then, a ToMFIR is designed for the disturbance-free subsystem to generate a fault-detection residual. In this manner, a bank of ToMFIR´s is constructed to detect a specific fault source. The advantage of such a design is that all of ToMFIR´s in the bank will together declare the occurrence of a single fault. This design is a ToMFIR-redundancy-based robust fault detection. Detailed design process of the ToMFIR´s is presented and a turbofan engine model is simulated to verify the effectiveness of the proposed ToMFIR-based fault-detection strategy.