A LMI-based strategy for ℋ∞ fault estimation of non-linear systems: Application to the multi-tank system

The paper is concerned with the task of robust fault estimation of non-linear discrete-time systems. The general unknown input observer strategy and the ℋ_∞ framework are utilised to design a robust fault estimation scheme. The resulting design procedure guaranties that a prescribed disturbance attenuation level is achieved with respect to the fault estimation error while guaranteeing the convergence of the observer. The core advantage of the proposed approach is characterized by its simplicity. Indeed, it is shown that it reduces to solving a set of linear matrix inequalities, which can be efficiently solved with modern computational packages. The final part of the paper presents an illustrative example regarding the multi-tank system which exhibits the performance of the proposed approach.