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This paper proposes an H_/H fault detection observer method by using generalized output for a class of polytopic linear parameter-varying (LPV) systems. As the main contribution, with the aid of the relative degree of output, a new output vector is generated by gathering the original output and its time derivative, and it is feasible to consider H_ actuator fault sensitivity in the entire frequency for the new system. In order to improve actuator and sensor fault sensitivity as well as guarantee robustness against disturbances, simultaneously, an H_/H fault detection observer is designed for the new LPV polytopic system. Besides, the design conditions of the proposed observer are transformed into an optimization problem by solving a set of linear matrix inequalities (LMIs). Numerical simulations are provided to illustrate the effectiveness of the proposed method.

The fault-tolerant control problem of a hydraulic servo actuator in the presence of actuator faults is studied utilizing adaptive dynamic programming. This task is challenging because of unknown system dynamics, uncertain disturbances or unmeasurable system states of such highly nonlinear systems in real applications. The aim is to achieve asymptotic tracking and actuator faults compensation by minimizing some predefined performance index. The discrete-time algebraic Riccati equation is iteratively solved by the adaptive dynamic programming approach. For practical reasons, adaptive dynamic programming techniques and fault compensation are integrated to iteratively compute an approximated optimal fault-tolerant control using real-time input/output data without any a priori knowledge of the system dynamics and unmeasurable states. As a result, a fault-tolerant control of hydraulic servo actuator is then designed based on adaptive dynamic programming via output feedback. Also, the convergence analysis of a data-driven fault-tolerant control is theoretically shown as well. Finally, intensive simulation results are given to prove the validity and merits of the developed data-driven fault-tolerant control strategy.

The article presents an active fault-tolerant control scheme with an integral terminal sliding mode controller for the UAV systems. This scheme effectively addresses saturation issues, disturbances, and sensor and actuator faults. Initially, the quadcopter UAV's model is represented in state space form. Subsequently, an augmented system incorporating auxiliary states from sensor faults is developed. An adaptive sliding mode observer is proposed for estimating the actuator and sensor faults. The integral terminal sliding mode fault-tolerant control, designed for altitude and attitude regulation, relies on fault estimation data. In contrast, a cascade proportional-integral-derivative (PID) controller is employed for position control. Simulation results demonstrate the superiority of the proposed method over existing control algorithms.

The aim of this paper is to study an adaptive neural finite-time resilient dynamic surface control (DSC) strategy for a category of nonlinear fractional-order large-scale systems (FOLSSs). First, a novelty fractional-order Nussbaum function and a coordinate transformation method are formulated to overcome the compound unknown control coefficients induced by the unknown severe faults and false data injection attacks. Then, an enhanced fractional-order DSC technology is employed, which can tactfully surmount the deficiency of explosive calculations exposed in the backstepping framework. Furthermore, the radial basis function neural network is applied to address the unknown items related to the nonlinear FOLSSs. Based on the fractional Lyapunov stability criterion, a decentralized finite-time control approach is developed, which can ensure that all states of the closed-loop system are bounded and that the stabilization errors of each subsystem tend toward a small area in finite time. At last, two simulation examples are given to confirm the put-forward control algorithm’s effectiveness.

The use of Nano Satellite in space missions has generated a lot of interest due to their compact size and relatively low development, launch and operating costs compared to larger satellites. This allows for launches that are more frequent and the ability to replace or upgrade satellites more frequently. The stability of Nano satellite is crucial for its successful operation in space, and designers and engineers must take various measures to ensure that the satellite is able to maintain its orientation and position in space throughout its mission Indeed. The proposed control approach is based on backstepping control theory and uses adaptive control to handle actuator uncertainties and faults. The control system is developed for 3-axis stabilization and its performance is illustrated in numerical simulations. The results show that the proposed control approach can successfully maintain the stability of the Nano satellite under actuator failure compared with classical backstepping control.

In this paper, a composite adaptive fault-tolerant control strategy is proposed for a quadrotor unmanned aerial vehicle (UAV) to simultaneously compensate actuator faults, model uncertainties and external disturbances. By assuming knowledge of the bounds on external disturbances, a baseline sliding mode control is first designed to achieve the desired system tracking performance and retain insensitive to disturbances. Then, regarding actuator faults and model uncertainties of the quadrotor UAV, neural adaptive control schemes are constructed and incorporated into the baseline sliding mode control to deal with them. Moreover, in terms of unknown external disturbances, a disturbance observer is designed and synthesized with the control law to further improve the robustness of the proposed control strategy. Finally, a series of comparative simulation tests are conducted to validate the effectiveness of the proposed control strategy where a quadrotor UAV is subject to inertial moment variations and different level of actuator faults. The capabilities and advantages of the proposed control strategy are confirmed and verified by simulation results.

This paper presents an adaptive fault-tolerant control method for nonstrict-feedback nonlinear systems with unmodeled dynamics and output dead-zone in the presence of actuator faults. A dynamic signal is used to handle the unmodeled dynamics and a multi-dimensional Taylor network (MTN) to approximate unknown functions. The presented adaptive fault-tolerant control method ensures that all signals in closed-loop systems are semi-globally uniformly ultimately bounded (SGUUB) by applying the Lyapunov stability theory. It also guarantees that the tracking error will eventually converge to a bounded region around the origin. Finally, a numerical example and a real-world application of a one-link manipulator system are used to illustrate the effectiveness of the proposed control approach.

This paper presents an adaptive fuzzy fault-tolerant tracking control for a class of unknown multi-variable nonlinear systems, with external disturbances, unknown control sign, and actuator faults. By employing fuzzy logic systems, the unknown nonlinear dynamics and the state-dependent actuator faults are approximated, and by utilizing a Nussbaum-type function, the issue of unknown control sign is solved. The proposed control scheme is based on two forms, an adaptive fuzzy controller along with a robust controller that is equipped with a Nussbaum-type gain function, which guarantees stability with the boundedness of all signals involved in the closed-loop system. To prove the accuracy, and the effectiveness of the proposed control scheme, a simulation example on two-inverted pendulums system is carried out.

In this article, for a class of stochastic pure-feedback nonlinear systems with simultaneous actuator and sensor faults, the problem of adaptive fault-tolerant control is examined. The stochastic pure-feedback nonlinear system is first converted into a strict-feedback by applying the mean value theorem and radial basis function neural networks are used to approximate the unknown functions. Only one adaptive parameter needs to be calculated online rather than the actual weight vector elements by determining the greatest value of the norm of the neural network weight vector. With the help of regrouping and parameter separation methods, the unavailability of state variables caused by sensor faults is addressed. The Lyapunov function methods and the backstepping recursive design technique are used to design an adaptive fault-tolerant controller. It is shown that by choosing proper the design parameters, the tracking errors converge to a small region of the origin, and all the signals in the closed-loop system are bounded in probability. The performance of the proposed controller is illustrated using a numerical example and a real-world example of a rigid robot manipulator system.

For the launch vehicle attitude control problem, traditional methods can seldom accurately identify the fault types, making the control method lack of pertinence, which largely affects the effect of attitude control. This paper proposes an active fault tolerant control strategy, which mainly includes fault diagnosis and fault tolerant control. In the fault diagnosis part, a small deviation attitude dynamics model of the launch vehicle is established, Kalman filters with different structures are designed to detect and isolate faults through residual changes, and the fault quantity of the actuator is further estimated. In the fault tolerant control part, the following control scheme is adopted according to the above diagnostic information: when the sensor fault is detected, the sensor measurement data is reconstructed; when the actuator fault is identified, the control allocation matrix is reconstructed. Simulation results show that the proposed method can effectively diagnose sensor fault and actuator faults, and significantly improve attitude tracking accuracy and control adjustment time.