A nonlinear UIO scheme for the FDI on a small commercial aircraft

In this paper we consider the problem of detecting and isolating sensor faults on a small commercial aircraft in the presence of external disturbances and uncertainties. A nonlinear observer based approach is proposed which makes use of the complete nonlinear model of the aircraft. This approach is based on the so-called unknown input observers (UIO) theory and guarantees disturbance decoupling, H-infinity performance, and an assigned rate of convergence for the estimation errors. A comparison between the application of the standard UIO based fault diagnosis and isolation (FDI) scheme, and the proposed nonlinear scheme shows the benefits of this technique. Some numerical simulations are carried out on the model of the small commercial aircraft under consideration in the Brite Euram ADFCS-III project.