Saturated fault tolerant control based on partially decoupled unknown-input observer: a new integrated design strategy

This study presents a fault tolerant control (FTC) scheme based on fault estimation (FE) for a system subject to input saturation, uncertainty, L₂-bounded disturbance and additive faults. In this study, the saturation is represented in polytopic form, and the disturbance is partitioned into matched and unmatched parts. For the FE scheme, a partially-decoupled unknown input observer is introduced to completely compensate for the matched part and only the unmatched part affects the FE performance. The FE and FTC schemes are integrated to ensure that the resulting closed-loop system is stable with L₂-gain performance. Furthermore, all sufficient conditions for robust performance are derived and cast as linear matrix inequalities (LMIs). Usage of the Young relation removes equality constraints, and thus all LMIs are solvable in a single step. Numerical simulations are provided to verify the effectiveness of the proposed scheme.