SUMMARYThe paper presents a robust fault estimation approach for a class of non-linear discrete-time systems. In particular, two sources of uncertainty are present in the considered class of systems, i.e., an unknown input and an exogenous external disturbance. Thus, apart from simultaneous state and fault estimation, the objective is to decouple the effect of an unknown input while minimizing the influence of the exogenous external disturbance within the H∞ framework. The resulting design procedure guarantees that a prescribed disturbance attenuation level is achieved with respect to the state and fault estimation error while assuring the convergence of the observer. The core advantage of the proposed approach is its simplicity by reducing the fault estimation problem to matrix inequalities formulation. In addition, the design conditions ensure the convergence of the observer with guaranteed H∞ performance. The effectiveness of the proposed approach is demonstrated by its application to a Twin Rotor MIMO System.
This paper proposes an approach for the joint state and fault estimation for a class of uncertain nonlinear systems with simultaneous unknown input and actuator faults. This is achieved by designing an unknown input observer combined with a set-membership estimation in the presence of disturbances and measurement noise. The observer is designed using quadratic boundedness approach that is used to overbound the estimation error. Sufficient conditions for the existence and stability of the proposed state and actuator fault estimator are expressed in the form of linear matrix inequalities (LMIs). Simulation results for a quadruple-tank system show the effectiveness of the proposed approach.
The paper is devoted to the issue of a robust predictive fault-tolerant control for linear discrete-time systems with an application of an ellipsoidal inner bounding of a robust invariant set. The crucial issue is to maintain the state of the system inside the robust invariant feasible set, which is a set of states guaranteeing the stability of the proposed control strategy. The approach begins with fault estimation, and then the fault is compensated along with a robust controller. In a case when robust fault compensation does not provide expected results, which means that the current state does not belong to the robust invariant set, then a suitable predictive control action is performed in order to enhance the ellipsoidal invariant set. This appealing phenomenon makes it possible to enlarge the domain of attraction of the possibly faulty system that makes the proposed approach an efficient solution to the fault-tolerant control problem. The final part of the paper shows an illustrative example regarding a two-tank system.
The paper deals with the problem of designing sensor-fault tolerant control for a class of non-linear systems. The scheme is composed of a robust state and fault estimator as well as a controller. The estimator aims at recovering the real system state irrespective of sensor faults. Subsequently, the fault-free state is used for control purposes. Also, the robust sensor fault estimator is developed in a such a way that a level of disturbances attenuation can be reached pertaining to the fault estimation error. Fault-tolerant control is designed using similar criteria. Moreover, a separation principle is proposed, which makes it possible to design the fault estimator and control separately. The final part of the paper is devoted to the comprehensive experimental study related to the application of the proposed approach to a non-linear twin-rotor system, which clearly exhibits the performance of the new strategy.
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