ABSTRACT: In this paper the problem of active fault tolerant control (FTC) in noisy systems is studied. The proposed FTC strategy is based on the known of the fault estimate and the error between the faulty system state and a reference system state. A proportional integral observer is used in order to estimate the state and the actuator faults. The obtained results are then extended to nonlinear systems described by nonlinear Takagi-Sugeno models. The problem of conception of the proportional integral observer and the FTC strategy is formulated in linear matrix inequalities (LMI) which can be solved easily. Simulation examples are given to illustrate the proposed method for the linear and nonlinear systems.