In this article, a new fault-tolerant control (FTC) method is presented for the Lipschitz nonlinear systems that is capable of handling the actuator faults, sensor faults, unknown external disturbances, and system uncertainties. An augmented system is first constructed by treating the sensor fault as an auxiliary state. An adaptive fault estimation scheme with an H ∞ performance criterion is then developed to simultaneously estimate the actuator and sensor faults. To achieve the tracking control, a nonlinear sliding mode-based state feedback control law is proposed depending on the estimated states and information about fault from the fault estimating unit. The efficacy of the suggested technique is evaluated using a nonlinear model of the multirotor unmanned aerial vehicle (UAV) system with six degrees-of-freedom (DoF) motion. The proposed method is implemented in the inner loop subsystem in order to obtain the attitude and altitude tracking while the outer-loop control is simply a PID controller. Several simulations on the nonlinear system are performed to prove the effectiveness of the proposed method compared with the existing methods.

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A disturbance observer-based control scheme is proposed in this paper to deal with the attitude stabilization problems of spacecraft subjected to external disturbances, parameter uncertainties, and input nonlinearities. Particularly, the proposed approach addresses the dead-zone issue, a non-smooth nonlinearity affiliated with control input that significantly increases controller design difficulties. A novel nonlinear disturbance observer (NDO) is developed, which relaxes the strong assumption in conventional NDO design that disturbances should be constants or varying with slow rates. After that, a special integral sliding mode controller (ISMC) is combined with the NDO to achieve asymptotic convergence of system states. Simulations are performed in the presence of time-varying disturbances, parameter uncertainties, and dead-zone nonlinearity to justify the effectiveness of the proposed control scheme.

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This article introduced fault-tolerant control (FTC) schemes for over-actuated affine non-linear uncertain systems. The proposed methodologies incorporate two different control allocation (CA) units with high-level nonlinear adaptive sliding mode control (NLASMC) strategy. The first FTC strategy is active that utilizes an online CA unit to effectively manage the redundant actuators towards the chosen flight path in faulty conditions. On the other hand, the second FTC scheme is passive based on the idea of a fixed CA scheme and does not require control-input reconfiguration during the faulty condition. A robust NLASMC law is selected to enforce the state trajectories converges to the sliding manifold despite the uncertainty in the model dynamics and external disturbance effect. The proposed schemes are then applied to the nonlinear F16 aircraft detailed model equipped with thrust vectoring (TV) control. The nonlinear simulations on 6-degree-of-freedom (6-DOF) F16 aircraft are performed under the failure of the aileron, rudder, and elevator. It can be visualized that both schemes performed well, but online CA scheme can cope with more faults and failures combinations in comparison to fixed CA schemes. Furthermore, both FTC approaches performed well when compared to existing methods in the literature.