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This paper proposes a class of velocity-free attitude stable controller using a novel finite-time observer for spacecraft attitude tracking, which explicitly takes into account control input saturation to assure fast and accurate response and to achieve effective compensation to the effect of external disturbance as well. First, a novel semiglobal finite-time convergent observer is proposed to estimate the angular velocity in a finite-time under external disturbance. Then, a simple global output feedback controller is proposed by adoption of the designed finite-time observer. Rigorous proofs show that the proposed observer can achieve the finite-time stability and the controller rigorously enforces actuator magnitude constraints. Numerical simulations illustrate the spacecraft performance obtained using the proposed controller. [ABSTRACT FROM AUTHOR]

In this paper, finite-time attitude coordinated control for spacecraft formation flying (SFF) subjected to input saturation is investigated. More specifically, a bounded finitetime state feedback control law is first developed with the assumption that both attitude and angular velocity signals can be measured and transmitted between formation members. Then, a bounded finite-time output feedback controller is designed with the addition of a filter, which removes the requirement of the angular velocity measurements. In both cases, actuator saturation is explicitly taken into account, and the homogeneous system method is employed to demonstrate the finite-time stability of the closed-loop system. Numerical simulation results are presented to illustrate the efficiency of the proposed control schemes. [ABSTRACT FROM AUTHOR]

This paper investigates the design of spacecraft attitude stabilization controllers that are robust against actuator faults and external disturbances. A nominal controller is developed initially, using the adaptive backstepping technique, to stabilize asymptotically the spacecraft attitude when the actuators are fault-free. Additive faults and the partial loss of actuator effectiveness are considered simultaneously and an auxiliary controller is designed in addition to the nominal controller to compensate for the system faults. This auxiliary controller does not use any fault detection and isolation mechanism to detect, separate, and identify the actuator faults online. The attitude orientation and angular velocity of the closed-loop system asymptotically converge to zero despite actuator faults providing the nominal attitude system is asymptotically stable. Numerical simulation results are presented that demonstrate the closed-loop performance benefits of the proposed control law and illustrate its robustness to external disturbances and actuator faults. [ABSTRACT FROM AUTHOR]

This paper presents a dual-stage control system design method for flexible spacecraft attitude tracking control and active vibration suppression by an embedded smart material as sensors/actuators. More specifically, a conventional sliding mode controller with the assumption of knowing system parameters is first designed that ensures asymptotical convergence of attitude tracking error described by error quaternion and its derivative in the presence of bounded parameter variation/disturbance. Then it is redesigned, such that the need for knowing the system parameters in advance is eliminated by using an adaptive updating law. For the synthesis of the controller, to achieve the prescribed L2-gain performance criterion, the control gains are designed by solving a linear matrix inequality problem. Indeed, external torque disturbances/parametric error attenuations with respect to the performance measurement along with the control input penalty are ensured in the L2-gain sense. Even if this controller has the ability to reject the disturbance and deal with actuator constraint, it excites the elastic modes of flexible appendages, which will deteriorate the pointing performance. Then the undesirable vibration is actively suppressed by applying feedback control voltages to the piezoceramic actuator, in which the modal velocity feedback control method is employed for determining the control voltages. Numerical simulations are performed to show that attitude tracking and vibration suppression are accomplished, in spite of the presence of disturbances/parameter uncertainties and even control input constraint. [ABSTRACT FROM AUTHOR]