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.

This paper proposes an active fault‐tolerant control (FTC) strategy for a class of non‐linear Lipschitz systems. The proposed FTC approach employs the integral sliding mode control (ISMC) technique due to its inherent capability of dealing with system uncertainties. First, under the nominal fault‐free condition, the linear matrix inequality technique is introduced to design the primary controller for the non‐linear Lipschitz system. To accommodate the actuator faults/failures, the ISMC law is combined with a control allocation scheme that distributes the control signals to the redundant actuators. A non‐linear octorotor system is then used as a test bench to validate the tolerance performance of the proposed FTC strategy. In particular, the proposed FTC strategy is applied for the inner‐loop control, while in the outer loop, a fractional‐order control approach is used to achieve the precise longitude and latitude control. Finally, various simulations are performed to justify the effectiveness of the proposed control scheme.

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The paper proposes the application of fractional order controller in position tracking control of 2-link nonlinear robotic arm. The nonlinear system dynamics is linearized using inverse dynamics of the model and fractional order PID controller is designed to deal with remaining tracking errors. The optimal values of controller parameters are calculated using Nelder-Mead optimization technique based on desired design criteria. The objective function is designed using weighted sum approach on each performance specification based on transient domain parameters. It can be seen from simulation results that fractional order controller together with computed torque controller improved tracking performance of proposed system as compared to PID controller used in the outer loop. Moreover, the robustness of proposed scheme is checked by applying the disturbance signal at control input channels of 2-link nonlinear robotic arm links.

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