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This paper addresses the attitude-maneuver control problem for a rigid-body spacecraft in the presence of attitude-constrained zones as well as input saturation. More specifically, attitude-constra...

A novel adaptive control solution for pose tracking problems of spacecraft proximity operations subject to not only motion constraints but also parameter uncertainties is proposed in this paper. Sp...

A new algorithm is proposed for rigid spacecraft attitude reorientation guidance under forbidden pointing constraints. Specifically, in view of the parameterized forbidden orientations using the un...

In this paper, two kinds of sliding-mode guidance laws with impact time constraint are proposed for intercepting various target motions, including nonmaneuvering and maneuvering targets. To achieve...

In this paper, a new guidance strategy is proposed for intercepting stationary and constant-velocity moving targets with desired impact time and angle via a virtual target approach, subject to nonl...

This paper addresses the integrated attitude and position control problem for the final phase proximity operations of spacecraft autonomous rendezvous and docking, in which important motion constra...

During the aerospace missions for the on-orbiting spacecraft, actuator faults are frequently encountered such that the control system performance may be degraded, even the unstable ACS may result in the completely collapse, immeasurable losses or catastrophic consequences. Thus, the spacecraft ACS should be capable of dealing with or tolerating possible actuator faults, while at the same time guaranteeing an acceptable performance in the presence of actuator faults. There exist some main approaches to improve the stability and reliability of the spacecraft ACS, such as high reliable control system design with redundant devices, FDD based FTC system design, CA based FTC system design and so on. Recently, CA techniques have drawn significant interests in the aircraft and spacecraft control [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13], especially in the FTC system design. Gui et al. [14] introduced an adaptive SMC law to dynamically compensate the perturbations due to actuator faults and other uncertainties, in which the real time CA algorithm delivers the control command to actuators. In [15], a novel dynamic near-optimal CA scheme with combination of a saturated baseline controller for spacecraft attitude control using single-gimbal control moment gyros. This dynamic control allocation is implemented with online update law, which has a modest computational complexity. All these methods can primarily generate commands to control effectors to achieve some demand moment or acceleration. Some of them take in account the position and rate limits, while some also allow for satisfying a secondary objective. Generally speaking, all the aforementioned CA can be implemented practically to address the concerned constraints and objectives. However, the authors in [16] illustrated that different CA algorithms can lead to different closed-loop maneuver performances owing to the CA errors between the designed signal and actual input. Usually, this CA error is treated as small and neglectable in the control design, which, in fact, may lead to a degraded performance or even potential closed-loop instability. In all the aforementioned references, it is assumed that the system state trajectories are governed by the baseline controller, and CA algorithms have no/little effect on the closed-loop performance.

A smooth attitude-stabilizing controller is proposed for rigid spacecraft actuated by thrusters that achieves finite-time stability in the presence of external disturbance, input saturation, and in...

This paper addresses the translational control problem for the final phase of spacecraft rendezvous and docking. For safety concerns, during the approach process, the pursuer spacecraft is required...

A LTHOUGH the past three decades have witnessed several important developments in attitude stabilization control [1,2], there still remain certain open problems that are of great theoretical and practical interests, such as actuator constraint. Because of physical limitations, typical control actuators (e.g., reaction wheels and thrusters) for attitude control have an upper bound on the torque they can generate. If this issue is not solved during attitude maneuvering, then the attitude system will continue issuing its commands that may no longer be achievable by the satellite, and the required control will quickly saturate actuators. This will subsequently destabilize and even lead to loss of control of the satellite. Therefore, actuator constraint is one key issue that needs to be addressed. At present, a great deal of attention has been focused on the stability analysis and the attitude control design with saturated actuators [3–6]. Another problem that needs to be addressed is fault tolerant control for the attitude system. Any component or system fault can potentially cause a host of economic and safety problems. As a result, online and real-time fault tolerant control (FTC) design for satellites has received considerable attention [7]. Generally speaking, FTC can be classified into two types: passive and active [8]. The passive FTC is designed to be robust to a class of possible faults. It does not require fault detection and diagnosis (FDD) schemes. In an attempt to develop attitude controllers that can accommodate faults, extensive studies on the passive FTC control system for satellites have been performed [9–11]. The active FTC can react to fault events by using a reconfigurationmechanism. The active FTC relies on the availability of an FDD mechanism that gives, in real time, information about the nature and the intensity of the fault. The design of active FTC, especially the fault detection and diagnosis scheme for satellite attitude, has attracted considerable interest [12–14]. Although the methodologies including FDD and control law reconfiguration for the control-type faults of satellite attitude system have been studied extensively (as seen in the preceding references), the problem that is not solved yet is the effective and practical strategies for handling severe failure cases combining with actuators constraint. Lack of such effective FTC strategies may lead to substantial performance deterioration and even the loss of a satellite. The clear knowledge of the link between control reconfiguration and the actuator input constraint is still lacking. Because the control reconfiguration at different time instants with different types of faults has greatly different effects on control actuators saturation, there is no explicit and simple relationship between them, which makes this problem even more difficult. This leads to an important practical problem: how tomake use of the control reconfiguration on available control redundancy. Motivated by this problem, a novel attitude control approach is presented in this paper; an observer-based FDD scheme combining a sliding mode controller by using the estimated information is designed in a framework of active FTC system. The main contribution of this study, relative to otherworks, is that actuator faults, actuator constraints, and external disturbances are simultaneously addressed in an attitude FTC system design.

This paper investigates the velocity-measurement-free feedback control problem associated with attitude tracking for a rigid spacecraft in the presence of both actuator failures and actuator saturation. The decreased reaction torque fault and the increased bias torque fault in the reaction wheel are handled. By using only the measurable attitude, a terminal sliding-mode-based observer is developed to reconstruct all the states of the attitude system in finite time. With the reconstructed information, a novel attitude tracking controller is developed. A Lyapunov analysis shows that the desired attitude trajectories are followed even in the presence of external disturbances. The key features of the proposed control approach are that it is independent from the knowledge of actuator faults and fault-tolerant control is achieved without the need of angular velocity. The attitude tracking performance using the proposed strategy is evaluated through a numerical example.

A novel saturated proportional-derivative control law incorporated with closed-loop control allocation is proposed for spacecraft attitude stabilization in this paper. More specifically, a saturated proportional-derivative-based baseline nonlinear controller is designed to guarantee the globally asymptotic stability under control input/signal constraints. Then, a closed-loop constrained optimal control allocation scheme is employed to distribute the moments synthesized by the baseline controller over the redundant actuators in the presence of constraints due to actuator amplitude and rate constraints. The optimal control solution is to be found by penalizing the control allocation errors and rates using optimal quadratic programming algorithms. A significant feature of this work is that the asymptotic stability with the closed-loop control allocation is guaranteed theoretically. Simulation results are presented to illustrate the performance of the proposed scheme.

A novel attitude tracking control scheme is proposed for rigid spacecraft to simultaneously compensate for reaction wheel faults and reject external disturbances. The reconstruction of the reaction wheel faults and disturbances is treated as a problem of observing the state of a linear system with unknown inputs. A terminal sliding mode observer is proposed to reconstruct the reaction wheel faults and disturbances. A Lyapunov-based analysis shows that the observer asymptotically converges to the actual faults and disturbances with a finite time convergence. Then, with the reconstructed faults and disturbance information, a compensation control law is developed to guarantee that the desired attitude trajectories are followed in finite time. The key feature of the proposed control strategy is that it globally asymptotically stabilizes the system, even in the presence of reaction wheel faults and external disturbances. The attitude tracking performance using the proposed compensation control is evaluated thr...

A LTHOUGH safe-mode transition is a technique widely applied to handle component faults of spacecraft, it is not an option during critical phases. To increase onboard autonomy in fault management fault-tolerant-control (FTC) design without ground intervention has attracted increasing attention [1,2]. Feedback linearization control was developed for automated attitude recovery of spacecraft [3]. An FTC attitude control was presented in [4] to accommodate reaction-wheel faults. In particular, sliding mode control (SMC) is becoming an effective approach to tackle with uncertainty and external disturbance. SMC is successfully applied to design FTC for spacecraft. In [5] an SMC-based lawwas synthesized to stabilize attitudewith actuator outage fault. In [6] an adaptive SMC scheme was proposed to tolerate thruster failures. Accommodating partial loss of actuator effectiveness without angular-velocity measurements was discussed in [7]. In [8] rapid reorientation was studied in the absence of control along either roll or yaw axes. The preceding FTC schemes assume that actuators are free of misalignments. However, finite manufacturing tolerance or warping of structure may introduce actuator alignment errors. This issue may cause performance degradation of the attitude-control system. To address this problem an adaptive-control law was developed to handle small gimbals’ alignment error of variable speed-control moment gyros [9]. In [10] a model reference adaptive controller was tested with alignment errors up to 15 deg. An extended Kalman filter was used for on-orbit alignment calibration [11]. Unknown inertia parameters and actuator uncertainty were investigated in [12]. In [13] an adaptive-control law was presented to compensate for thrustmagnitude error and misalignment. This study investigates attitude stabilization with external disturbance, unknown inertia parameters, and actuator uncertainties including fault and misalignment. An adaptive control is proposed to render the closed-loop system input-to-state stable and is organized as follows: Sec. II presents a mathematical model of a rigid spacecraft, Sec. III presents main results, and simulation results are given in Sec. IV followed by the conclusions in Sec. V.

This paper investigates a quaternion-based finite time attitude synchronization and stabilization problem for satellite formation flying. Sufficient conditions are presented for finite time boundness and stability of this distributed consensus problem. More specifically, a nonlinear control law based on a finite time control technique is developed such that the attitude of the rigid spacecraft will coordinate and converge to the attitude of the leader, while the angular velocity will converge to zero in finite time. The associated stability proof is constructive and accomplished by adding a power integrator term in the Lyapunov function. Furthermore, to reduce the heavy communication burden, a modified control law is then designed by introducing a finite time sliding-mode estimator such that only one satellite has to communicate with the leader. Simulation results are presented to demonstrate the effectiveness of the designed scheme, especially the potential advantages derived through the inclusion of the...

ATPRESENT, a large number of engineers have assorted to faulttolerant control (FTC) to enhance the system reliability and to guarantee the control performance (see, e.g., [1–4] and references therein), and several investigations on the application of FTC to spacecraft attitude maneuvers have also been considered. For instance, based on the dynamics inversion and time-delay control, a passive fault-tolerant controller was developed in [5] to achieve attitude tracking of a rigid satellite. Cai et al. [6] proposed an indirect adaptive fault scheme for spacecraft attitude tracking problem under thruster faults. In [7], a control augmentation method, similar to adaptive fault-tolerant control, was adopted for the flexible spacecraft attitude tracking. However, all the preceding FTC results can only tolerate limited predetermined faults and have great conservativeness due to its implementing a fixed controller only. In this work, the attitude stabilization of rigid spacecraft in the presence of partial loss of actuator effectiveness is investigated. Based on adaptive backstepping technique, a nominal attitude controller is derived first for the normal spacecraft system in the face of external disturbances. Then the case of the partial loss of reactionwheel-effectiveness fault is considered, and the faulty attitude system with time-varying gain is ultimately decoupled into three auxiliary systems by appropriate transformation. Moreover, for each auxiliary system, an implicit estimation filter is proposed to estimate the actuator fault correspondingly, and in the meantime, a new adaptive fault-tolerant controller is synthesized according to the estimated fault to guarantee that outputs of the auxiliary system can follow the normal attitude control command signals. By viewing the tracking error as another disturbance entering the system dynamics, with the robustness of the nominal controller to external disturbances, the online fault tolerance can be achieved. In contrast to preceding FTC results, the main contributions of this study include the following: 1) The proposed strategy can react to the fault online and in real time, and thus the conservativeness of the controller can be reduced largely. 2) Although three implicit estimation filters are developed in the fault-tolerant-controller design, it does not require the precise reconstruction of the faults. Thus, large computation power can be saved and also the response time can be reduced effectively. This Note is organized as follows: Sec. II briefly presents the spacecraft attitude model and control problems. In Secs. III and IV, adaptive backstepping attitude controllers are derived, respectively, with and without partial loss of actuator effectiveness fault. Simulation results of a rigid spacecraft are given in Sec. V, followed by conclusions in Sec. VI.