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For a practical engineering system, disturbances usually have a negative impact on system performance. Especially, when the system physical constraints (e.g., actuator amplitude saturation and input channel constraint) are present, the study for antidisturbance controllability (ADC) is of paramount importance. This article presents the concepts of disturbance estimability, disturbance compensability, and an enhanced antidisturbance control (EADC). From the viewpoint of control system design, an example of spacecraft attitude control is given. The control constraints and multiple disturbances are explicitly analyzed for the sake of attitude control system design of flexible spacecraft. Subsequently, an EADC approach with integration of the disturbance observer-based control (DOBC) and active disturbance rejection control (ADRC) is proposed, based on the characteristics of disturbances exposed. Moreover, prescribed performance approach is incorporated into the spacecraft attitude tracking control. In consequence, the presented control can not only achieve superior antidisturbance capability than DOBC or ADRC, but also quantify the control performances. Numerical simulations and hardware-in-the-loop tests exemplify the applicability of the proposed scheme. [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]

A novel composite anti‐disturbance control scheme is proposed for attitude control system (ACS) of flexible spacecraft with the reaction wheel friction. The proposed control scheme can overcome the performance degradation of controller under the condition of reaction wheel friction and flexible appendage vibration. First, the dynamic model of the flexible spacecraft is modelled, including disturbance torque of the reaction wheel. A sliding mode friction observer is designed to estimate the reaction wheel friction torque for feed‐forward compensation. Then, a flexible appendage vibration observer is constructed to estimate and compensate for the flexible appendage vibration. Finally, an H∞ controller is adopted to attenuate the estimation error and other bounded disturbances, such as the environment disturbance. Simulations on the ACS of a flexible spacecraft demonstrate the robustness and effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The attitude control problem is much more complicated due to the existence of faults and multiple disturbances simultaneously in satellites. In this paper, an adaptive fault tolerant attitude control method is presented for satellites with both time-varying actuator faults and multiple disturbances. Differing from previous results, the first part of the multiple disturbance is the uncertain modelled disturbance and the second part represents an uncertain variable bounded by a given function. A composite observer is designed to estimate the uncertain modelled disturbance and the time-varying fault simultaneously. Then, a new fault tolerant control strategy consisting of disturbance observer based control, fault accommodation and an adaptive controller is constructed to reconfigure the concerned systems and so as to achieve the anti-disturbance performance. In the proposed method, the modelled disturbance can be rejected by its estimation and the uncertain bounded disturbance can be compensated by the adaptive compensation term. The simulation results are given to show the efficiency of the proposed approach. [ABSTRACT FROM AUTHOR]