This paper considers the problem of Fault Tolerant Tracking Control (FTTC) strategy design for nonlinear systems using Takagi-Sugeno (T-S) fuzzy models with measurable premise variables affected by actuator faults subject to unknown bounded disturbances (UBD). Firstly, the Adaptive Fuzzy Observer (AFO) is proposed to estimate the faults. Based on the information provided by this observer, an active fault tolerant tracking controller described by an adaptive Proportional-Integral-Derivative (PID) structure has been developed to compensate for the actuator fault effects and to guarantee the trajectory tracking of desired outputs to the reference model despite the presence of actuator faults. The stability and the trajectory tracking performances of the proposed approach are analyzed based on the Lyapunov theory. Sufficient conditions can be obtained and solved for the design of the controller, and the observer gains using Linear Matrix Inequalities (LMIs). Finally, the effectiveness of the proposed technique is illustrated by using a single-link flexible joint robot.

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The present paper aims to design an integrated state/fault estimation and fault tolerant control issues for switched systems affected by actuator fault and external disturbances. A switched adaptive state/fault estimation observer is proposed to simultaneously estimate the system state and actuator fault. Based on this observer, we develop a fault tolerant control law not only to stabilize the closed-loop system, but also to compensate the faults effects. Then, by using the switched Lyapunov function and Average Dwell Time (ADT) concept, some sufficient conditions are derived and applied to build the switched adaptive observer-based state feedback controller. The observer and controller gain matrices are also obtained by solving an optimization problem with Linear Matrix Inequality (LMI) constraints. Finally, simulation results of a switched electrical system are presented to illustrate the effectiveness of the proposed design methods.