Design of an unknown input observer for fault diagnosis of non-linear systems with state constraints

Abstract

The paper deals with the problem of designing observers for a class of discrete-time nonlinear systems with an unknown input. In particular, with the use of the Lyapunov method, a design procedure of an asymptotically convergent observer is proposed. Moreover, the effect of decoupling an unknown input is investigated in the light of an undesirable decoupling of possible faults. As a result, a condition for checking an undesirable fault decoupling is provided. Subsequently, it is shown how to employ the proposed robust fault diagnosis observer for the non-linear systems with state constraints. The final part of the paper shows experimental results that confirm the effectiveness of the proposed approach and the potential profits that can be achieved while applying the proposed approach in the fault diagnosis scheme. Copyright©2012 IFAC