New results on fault reconstruction using a finite-time converging unknown input observer

This study presents a fault reconstruction scheme that converges in a pre-assigned finite time, which is chosen as the parameter of the finite-time converging unknown input observer (FT_UIO). After the convergence time, the actuator faults can be detected and diagnosed promptly and accurately by the simple threshold test on the fault estimates, provided by the fault reconstruction scheme, which are free from the transient observation error because of the initial condition mismatch and the intermittent output disturbance. The fault reconstruction scheme consists of the FT_UIO and the fault reconstruction algorithm. The FT_UIO, designed with two distinct reduced-order unknown input observers that converge asymptotically, provides a disturbance and fault-free state estimate that converges in the pre-assigned finite time. The state estimate obtained from FT_UIO is applied to reconstruct the faults of interest. The proposed scheme is compared with the design previously reported in the simulation.