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This article presents a single‐hidden‐layer feedforward network (SLFN) aided fault‐tolerant control (FTC) scheme for a class of nonlinear systems subject to actuator faults. First, the upper bounds of the norms of the unknown functions, which cover information of actuator faults and amplitude saturation degrees, are deployed. The upper bounds are approximated by SLFNs with adaptive techniques. Subsequently, a sliding mode control approach is presented to allow for prompt corrective reactions, with explicit consideration of multivariable conditions and control input constraints. Finally, simulation results based on a nonlinear Boeing 747 aircraft model are presented to demonstrate the effectiveness of the proposed FTC scheme. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid anti-disturbance composite control scheme is presented to address the problem subject to systems remarkably affected by external disturbances and discrete dynamics of actuators. By explicitly considering the hybrid feature resulting from discrete actuation signals acted on a continuous system, the hybrid disturbance observer is designed to estimate the effect of external disturbance. Meanwhile, H∞ technique is used to mitigate the effect of continuous command executing error caused by discontinuous operation, which cannot be modeled in priori. Within the proposed composite control scheme, the combination of the disturbance estimation information and the H∞ technique enables the entire hybrid system precisely performing. The stability of the whole continuous–discrete control system is analyzed. Finally, based on the Mars lander dynamics, comparative simulation studies illustrate that the developed control scheme can preserve a satisfactory level of performance, even in the presence of external disturbances and actuator quantization errors. [ABSTRACT FROM AUTHOR]

This paper is devoted to attitude tracking control of fractionated spacecraft with wireless communication. We consider the practical case that the spacecraft suffers from uncertain inertia parameters, external disturbances, and even unknown and time-varying actuator faults. Within the framework of the backstepping method, a novel event-triggered adaptive fault-tolerant control scheme is proposed. In our design, an event-triggering mechanism is introduced to determine the time instants for communication, which successfully avoids continuous communication and Zeno phenomenon. Then, with the aid of a bound estimation approach and a smooth function, the impacts of the actuator faults, as well as the network-induced error, are effectively compensated for. Moreover, by employing the prescribed performance control technique, it is shown that the attitude tracking errors can converge to predefined arbitrarily small residual sets with prescribed convergence rate and maximum overshoot, no matter if there exist unknown actuator faults. Compared with conventional adaptive attitude control schemes, the proposed scheme significantly reduces the communication burden, while providing high reliability and stable, rapid, and accurate response for attitude maneuvers. Simulation results are presented to illustrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this article, a novel spacecraft composite attitude stabilization scheme based on dual disturbances observers (DDOs) and high-precision nonsingular terminal sliding mode control is presented, with explicit consideration of reaction wheel dynamics and multiple disturbances. First, spacecraft attitude coupling dynamics model is constructed covering reaction wheel dynamics and multiple disturbances. These disturbances include matched disturbances caused by motor counter electromotive force and equivalent mismatched disturbance caused by reaction wheel friction and environment disturbances. DDOs are designed to estimate both equivalent matched and mismatched disturbances, respectively. Subsequently, the high-precision control scheme is designed to compensate the estimated disturbances and attenuate the influence of estimated errors via composite nonsingular terminal sliding mode attitude controller. The closed-loop stability and convergence are proved based on the Lyapunov stability theory. Finally, hardware-in-the-loop experiments are conducted to verify the effectiveness of proposed spacecraft attitude stabilization scheme. [ABSTRACT FROM AUTHOR]

This brief investigates the high-precision trajectory tracking control of space manipulator after capturing an unknown target. The neutral uncertainty induced by parameter variation poses great challenges to the controller design. Moreover, the existence of actuator deadzone nonlinearity makes the situation more complicated. In order to address the aforementioned difficulties, a novel control scheme is proposed in this brief. First, to reduce the conservativeness in the descriptions of uncertainties, the dynamic of space manipulator is described by an uncertain system with neutral uncertainty, state-dependent uncertainty, and norm-bounded uncertainty for the first time. Then, by incorporating a novel deadzone compensation control effort, a composite controller is proposed to attenuate these uncertainties and compensate the deadzone nonlinearity. Finally, stability and robustness analyses are carried out, and simulation results are given to demonstrate the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Abstract Precise and fast attitude maneuvers are a requirement in many future space missions. However, the actuator deviation fault of micro satellite is inevitable, which affects the precision of spacecraft pointing. To overcome this difficulty, this paper presents a novel attitude control scheme to compensate the actuator deviation fault and achieve the finite-time attitude maneuver. Moreover, the proposed control scheme is constituted by an outer attitude tracking loop and an inner angular velocity tracking loop according to dynamic features of micro satellite. In the outer loop, a novel virtual control law, namely a desired angular velocity command, is developed, under which the finite-time attitude tracking can be achieved. Furthermore, in the inner loop, an effective composite controller which consists of a terminal sliding mode controller and a finite-time disturbance observer (FTDO) is proposed. The aim of composite controller is to ensure that the angular velocity can track the virtual control law in finite time, where the FTDO is designed to estimate and compensate the actuator deviation fault in the feed-forward channel. Finally, simulation results are conducted to demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Reusable launch vehicles (RLVs) offer advantages such as low cost and high efficiency, yet they still face challenges related to real-time precise control and reliability enhancement. To address these issues, this paper presents a fixed-time attitude control method designed for RLVs, incorporating a reliability-based control allocation scheme. Initially, a fixed-time radial basis function neural network (RBFNN) disturbance observer is introduced to estimate disturbances rapidly and accurately. Subsequently, a control method integrating non-singular terminal sliding mode control (NTSMC) with a saturation compensator is proposed to achieve real-time and precise angle tracking. Furthermore, a reliability-based control allocation scheme is employed to enhance the reliability of the attitude control system. Finally, simulation analysis is conducted to validate the effectiveness of the proposed control scheme. • A reliability model for RLVs actuators is established. • A fixed-time RBFNN observer for disturbance estimation is proposed. • A fixed-time control using NTSMC and anti-windup compensator is developed. • A reliability-based control allocation is introduced to enhance reliability. [ABSTRACT FROM AUTHOR]