Fixed-time fault-tolerant control for virtually coupled train set with actuator faults and saturation

Investigating the design of the controller stabilizing the wing flutter system, which is robust against actuator faults, actuator saturation, time delay, parameter uncertainties and external disturbances. The model of the wing flutter system that considered the effects of actuator faults and saturation, time delay, parameter uncertainties and external disturbances is constructed by the Lagrange method. Then the finite-time fault-tolerant controller is derived, the stability of which is proved by the Lyapunov function. The simulation results elucidate that, the proposed fault-tolerant controller can handle the actuator faults effectively, meanwhile the wing flutter of the reentry vehicle can be suppressed instantly. The robustness of the actuator against actuator saturation, time delay, parameter uncertainties and external disturbances is also demonstrated.

Many control methods are used in attitude control of reentry vehicle, such as optimal control and classical control methods. However, those control laws may not work effectively if the attitude system is confronted with actuator faults and saturation. This paper proposes an adaptive fault tolerant attitude control method for the reentry vehicle's attitude control system, by combining the radial basis function network technology with adaptive fault tolerant control method. We simultaneously considered actuator fault, actuator saturation, time varying unknown disturbances and uncertainties when designing the control method. First, we set up the reentry attitude dynamic model concerning actuator fault; second, a finite-time H∞ adaptive fault-tolerant attitude controller is introduced to deal with the actuator fault, saturation, unknown disturbances and uncertainties of the reentry vehicle system; we proved the stability of our proposed adaptive attitude fault-tolerant controller through the Lyapunov function and the linear matrix inequality method. Finally, the effectiveness of such adaptive fault-tolerant control method has been identified by numerous simulation results. The simulation results show that our proposed method can not only effectively deal with actuator fault in the attitude control system, but also has very good robustness for actuator saturation, time varying unknown disturbances and uncertainties.

In this paper, an adaptive sliding mode fault-tolerant control scheme based on prescribed performance control and neural networks is developed for an Unmanned Aerial Vehicle (UAV) quadrotor carrying a load to deal with actuator faults. First, a nonsingular fast terminal sliding mode (NFTSM) control strategy is presented. In virtue of the proposed strategy, fast convergence and high robustness can be guaranteed without stimulating chattering. Secondly, to obtain correct fault magnitudes and compensate the failures actively, a radial basis function neural network-based fault estimation scheme is proposed. By combining the proposed fault estimation strategy and the NFTSM controller, an active fault-tolerant control algorithm is established. Then, the uncertainties caused by load variation are explicitly considered and compensated by the presented adaptive laws. Moreover, by synthesizing the proposed sliding mode control and prescribed performance control (PPC), an output error transformation is defined to deal with state constraints and provide better tracking performance. From the Lyapunov stability analysis, the overall system is proven to be uniformly asymptotically stable. Finally, numerical simulation based on a quadrotor helicopter is carried out to validate the effectiveness and superiority of the proposed algorithm.

This study proposes an integrated fault estimation (FE) and fault‐tolerant control design for a rigid spacecraft attitude system with inertia uncertainties, external disturbances, input saturation, and different type multiple actuator faults. A barrier function is first introduced to eliminate the effects of inertia uncertainties and disturbances in the design of the sliding mode FE observer. By using the non‐singular fast terminal sliding mode control technology, a finite‐time fault‐tolerant attitude stabilisation controller and a finite‐time fault‐tolerant attitude tracking controller are designed to guarantee that the closed‐loop attitude system has a good fault‐tolerant performance under actuator faults. Furthermore, when considering actuator saturation, an auxiliary system is utilised to compensate for the saturation. The stability of the closed‐loop system is analysed by Lyapunov theory. Finally, the effectiveness of the proposed control approach is demonstrated via simulation results.

This paper proposes a fault-tolerant control (FTC) scheme for unmanned aerial vehicles (UAVs) with state constraints, actuator saturation, and faults. Firstly, a nonlinear mapping function is designed to transform the limited states into new unlimited states. Furthermore, based on the transformed system, neural network (NN) is used to approximate the unknown nonlinear function caused by the parametric uncertainties, external disturbances, and actuator faults. Then, dynamic surface control (DSC) technique is used to solve the problem of "explosion of complexity". Moreover, an auxiliary system is designed to avoid actuator saturation and a Nussbaum function is used to simplify solving the inverse of the matrix in the auxiliary system. Finally, the Lyapunov method is used to prove the correctness of the FTC scheme, and simulation results show the effectiveness of this scheme.

Distributed adaptive finite-time fault-tolerant formation-containment control for networked Euler–Lagrange systems under directed communication interactions

Learning‐based robust control methodologies under information constraints

A dual-loop fault-tolerant control scheme is investigated for UAV attitude control systems subject to actuator faults, input saturation, and external disturbances in this paper. In the outer loop of attitude angles, a nonlinear dynamic inversion controller is developed as baseline controller for fast response and is augmented by a neural network disturbance observer to enhance the adaptability and robustness. Considering input saturation, actuator faults, and external disturbances in the inner loop of attitude angle velocities, the unbalanced input saturation is first converted into a time-varying system with unknown parameters and disturbances using a nonlinear function approximation method. An L1 adaptive fault-tolerant controller is then introduced to compensate for the effects of lumped uncertainties including system uncertainties, actuator faults, external disturbances, and approximation errors, and the stability and performance boundaries are verified by Lyapunov theorem and L1 reference system. Some simulation examples are carried out to demonstrate its effectiveness.

In this paper, an adaptive fault-tolerant control (FTC) strategy is proposed for a class of nonlinear systems in the presence of actuator fault, actuator saturation, and unknown external disturbance. The mathematical model of a second-order nonlinear system with actuator fault is first given, and a fault estimation observer is designed to estimate the occurred time-varying actuator fault. On this basis, the adaptive FTC strategy is proposed using both nonsingular fast terminal sliding mode (NFTSM) and radial basis function neural networks (RBFNNs) techniques to compensate for the negative effects caused by time-varying actuator fault and external disturbance. Another adaptive FTC scheme is further presented under actuator saturation case, and the Lyapunov stability analysis demonstrates that the designed FTC approach could guarantee that the trajectory of sliding mode dynamics could converge to a small neighborhood of the origin within a finite time. Compared with some existing results, the FTC approach proposed in this paper has better fault acceptability. Finally, the proposed adaptive FTC approach is applied to the attitude control of rigid spacecraft, and the simulation results illustrate the advantages of the designed control scheme.

This paper proposes a passive fault-tolerant control strategy for a multi-caliper disc elevator brake system subject to unknown external disturbances and multiple actuator faults. Initially, a detailed analysis of the dynamic equations of the actuator in a multi-caliper disc elevator brake system with actuator faults is conducted. Subsequently, a nonsingular terminal sliding mode fault-tolerant control scheme with rapid fixed-time convergence is proposed, where the settling time is independent of the system’s initial state and can be preset through design parameters. The upper bound of the convergence time is derived using Lyapunov theory, ensuring that the faulty elevator brake control system converges within a predetermined fixed time. Ultimately, theoretical analysis and numerical simulation results confirm that the proposed controller can effectively handle the effects of actuator faults, parametric uncertainties, and external disturbances, ensuring satisfactory tracking accuracy.

Anti-disturbance control for HVs system subject to nonlinear actuator characteristics with extended state observer

Robust fault-tolerant control for wing flutter under actuator failure

Underwater vehicle system, as a kind of special machine capable of underwater resource exploration, submarine pipeline maintenance, marine environment reconnaissance and submarine rescue, is a common tool in modern marine exploitation. Underwater vehicles play an important role in the survey and exploration of marine resource. The fault tolerant control for underwater vehicle system with external disturbance and actuator faults is studied in this paper. The fault observer can estimate the fault in the existence of disturbance environment. A sufficient condition for the existence of fault observer is proposed which guarantees the stability of the closed-loop system under actuator faults. Moreover, a fault-tolerant controller is developed to compensate for the failure effects on the system by updating the design feedback matrices online. For the fault-tolerant controller, Lyapunov function is used to obtain the stability for underwater vehicle system about actuator saturation. Finally, an example is included to show the effectiveness of the presented theory.

Adaptive sliding mode and RBF neural network based fault tolerant attitude control for spacecraft with unknown uncertainties and disturbances

This paper focuses on the potential actuator failures of spacecraft in practical engineering applications. Aiming at the shortcomings and deficiencies in the existing attitude fault-tolerant control system design, combined with the current research status of attitude fault-tolerant control technology, we carry out high-precision, fast-convergent attitude tracking algorithms. Based on the adaptive nonsingular terminal sliding mode control theory, we design a kind of fixed-time convergence control method. This method solves the problems of actuator faults, actuator saturation, external disturbances, and inertia uncertainties. The control method includes control law design and controller design. The designed fixed-time adaptive nonsingular terminal sliding mode control law is applicable to the development of fixed-time fault-tolerant attitude tracking controller with multiple constraints. The designed controller considers the saturation of the actuator output torque so that the spacecraft can operate within the saturation magnitude without on-line fault estimation. Lyapunov stability analysis shows that under multiple constraints such as actuator saturation, external disturbances, and inertia uncertainties, the controller has fast convergence and has good fault tolerance to actuator fault. The numerical simulation shows that the controller has good performance and low-energy consumption in attitude tracking control.