Search

This paper is devoted to real-time optimal attitude reorientation control of rigid spacecraft control. Particularly, two typical practical problems - actuator misalignment and forbidden pointing constraints are considered. Within the framework of adaptive dynamic programming (ADP), a novel constrained optimal attitude control scheme is proposed. In this design, a special reward function is developed to characterize the environment feedback and deal with the pointing constraints. Notably, a novel argument term is introduced to the reward function for overcoming the inevitable difficulty in actuator misalignment. By virtue of the Lyapunov stability theory, the ultimate boundedness of state error and the optimality of the proposed method can be guaranteed. Finally, the effectiveness and performance of the developed ADP-based controller are evaluated by not only numerical simulations but also experimental tests with a hardware-in-loop platform.

In this article, a novel pose (i.e., concurrent position-attitude) tracking control framework is proposed for spacecraft proximity operations with a freely tumbling target, employing the prescribed performance control (PPC) methodology. Especially, the whole operations involved are divided into two synchronously occurring maneuvers: relative position tracking and boresight pointing adjustment. For the former, a new relative translational dynamics is established to facilitate its problem formulation and solving, while, for the latter, the desired attitude is extracted to align the boresight of the pursuer’s onboard vision sensor toward the target. Given this, a noncertainty-equivalence adaptive pose controller is designed based on the PPC design approach integrating a class of appointed-time performance functions. It is shown that the designed controller is able to achieve prescribed performance guarantees for the pose tracking errors and, meanwhile, guarantee asymptotic convergence of both the velocity and angular velocity errors, regardless of mass and inertia uncertainties. The salient feature of the proposed method is that, by judiciously imposing the performance specifications on the pose tracking errors, it can: 1) enable the pursuer to accomplish the proximity operations in a designer-appointed time and 2) ensure compliance with spatial motion constraints and avoid singularity of the attitude extraction algorithm. Finally, simulation results are presented to illustrate the effectiveness of the proposed method.

This article investigates the attitude control problem of a rigid body subject to attitude and angular rate constraints (double-level state constraints), and inertia uncertainties. A data-driven immersion and invariance (I&I) adaptive control scheme is proposed to tackle this technically challenging problem. As a stepping stone, a novel dynamically scaled I&I adaptive controller is designed to bypass the realizability condition that may not hold in the Lyapunov sense when considering angular rate constraints. Lyapunov stability analysis shows that this controller can enable the attitude errors and angular rates to converge asymptotically to zero for most initial conditions in the accessible space, while strictly obeying double-level state constraints with the help of two judiciously constructed potential functions. After that, to further relax the dependence of parameter convergence on the persistent excitation (PE) condition, the I&I adaptive law is extended to a data-driven counterpart through adding a learning term that is acquired by adopting the regressor filtering in conjunction with the dynamic regressor extension and mixing (DREM) procedure. The extended adaptive controller can not only preserve all the results obtained by the earlier proposed I&I adaptive controller, but also ensure asymptotic parameter convergence under a finite excitation condition much weaker than PE. In addition, benefiting from the DREM method and some special designs, the parameter convergence rates across all the parameter vector components can be flexibly tuned in an explicit way, and moreover, they are independent of the excitation level. Finally, simulation results are given to show the effectiveness of the proposed method.

This brief presents a new class of adaptive controllers for attitude-tracking control problems of rigid bodies. The most important feature of the proposed method is that both instantaneous state data and past measurements (historical data) are introduced into the parameter-adaptation process. Filtered regressor matrices and states are employed in the control formulation, which lay an important foundation for the precision acquirement of historical data and render the resulting parameter-adaptation dynamics to reside within a stable and attracting manifold. A specially designed information matrix is further introduced to encode the composite information into the adaptive law. Under this formulation, state-tracking errors, as well as parameter estimation errors, are guaranteed to converge asymptotically to zero subject to the satisfaction of a finite excitation condition, which is a significant relaxation when compared with the persistent excitation condition that is typically required for these classes of problems. A noncertainty-equivalence term is also used in the adaptation process to ensure the regulation of the tracking error in the absence of finite excitation conditions. Numerical simulations and hardware-in-loop experimental results are illustrated to evaluate the various features of the proposed method.

This paper proposes a novel dynamic near-optimal control allocation scheme with combination of a saturated baseline controller for spacecraft attitude control using single-gimbal control moment gyros (CMGs) and reaction wheels. First, a saturated controller is proposed to stabilize the nominal system in the presence of actuation mismatch. Aided by a state-dependent variable, a dynamic control allocator is then proposed that allows for smooth switching between two actuation sets. Unlike the previous static constraint optimization formulations, the control allocation augments its performance function with penalty terms in order to enforce individual input constraints and configuration singularity avoidance. Moreover, this dynamic control allocation is implemented with an online update law, which has a modest computational complexity compared to its numerical optimization counterpart. The closed-loop boundedness is guaranteed by a constructive Lyapunov-design method. Simulation results demonstrate that during the attitude maneuvers, the input saturation constraint and the active avoidance of CMG singularities are enforced with a relatively small computational cost.

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...

This brief examines the problem of attitude tracking control with prescribed performance guarantees for a spacecraft subjected to actuator faults and input saturation. To pursue this, the open-loop tracking error dynamics with certain designer-specified performance constraints is first transformed into an equivalent “state-constrained” one, via an error transformation; furthermore, the resulting dynamics is augmented with a dynamic system, which is tactfully constructed to ensure that the control input satisfies the magnitude limits. Subsequently, a robust fault-tolerant controller is developed by using a low-pass filter and an auxiliary system in conjunction with adaptive backstepping design. It is shown that the control algorithm developed not only achieves the stable attitude tracking with prescribed behavioral metrics but also guarantees the boundedness of all the closed-loop signals. Finally, simulation results are given to evaluate the efficacy of the proposed scheme.

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. This work was supported in part by the National Natural Science Foundation of China under Grant 61673036, Grant 61661136007, and Grant 61603021, in part by the Beijing Natural Science Foundation under Grant 4182036, and in part by the Program for Changjiang Scholars and Innovative Research Team under Grant IRT_16R03.

This paper investigates the six-degrees-of-freedom (6-DOF) rendezvous and docking issue with an uncontrolled target for a servicing spacecraft under thruster misalignment and external disturbances. Initially, a 6-DOF relative motion dynamic model is established to depict the relative position–attitude between the servicing spacecraft and uncontrolled object (freely tumbling spacecraft). Then, an adaptive fixed-time control scheme with a novel sliding manifold is employed to accomplish the 6-DOF rendezvous (close-range) and docking mission for the servicing spacecraft. Unlike existing methods, the sliding-mode surface is designed by using the new sufficient condition to achieve the system's fixed-time convergence, and this condition reduces the conservativeness of the traditional ones with less dominated terms. Moreover, the settling time of relative translation-rotation tracking errors is guaranteed irrespective of initial motion conditions. Accordingly, the fixed-time stability of the closed-loop system is guaranteed by the rigorous Lyapunov theory analysis. Finally, numerical simulation results with various cases are implemented to verify the superiority of the presented sliding-mode control strategy.

The problem of boresight alignment control is studied when multiple dynamic pointing constraints and angular velocity constraints exist during the maneuver. The tracking errors and dynamic pointing constraints are defined using the reduced attitude, which has only two degrees of freedom and avoids the singularity and redundancy description. An artificial potential function and a barrier Lyapunov function are employed to derive the feedback control law for attitude tracking scenario with no violation of the constraints and limitations. The stability analysis shows that the proposed control law guarantees the asymptotical convergence of the tracking errors. Numerical simulations are conducted to demonstrate the efficacy and performance of the presented control design under several different scenarios.

Reaction wheels as the main actuators for attitude control of spacecraft are very prone to malfunction, which may significantly degrade the performance of the spacecraft attitude control system. In this paper a novel active fault-tolerant control scheme is proposed to react the reaction wheel faults actively. A combined observer is first designed to detect the reaction wheel faults, by combining a traditional adaptive Luenberger observer and a newly designed neural network (NN) observer. It inherits the advantages of the low computational cost of the Luenberger observer and the high performance of the NN observer. Then, a fault isolation scheme is given to locate faults. Subsequently, an adaptive fault-tolerant controller is designed to achieve graceful performance degradation under reaction wheel faults, based on the diagnosis results of the combined observer and the judgment results of the fault isolation scheme. Finally, simulation results show that the proposed scheme is able to achieve precise fault diagnosis and fault-tolerant control of spacecraft in the presence of external interference and limited computation.

A continuous saturated attitude control scheme is proposed that meets the control object of reorientation and attitude forbidden zone avoidance. Constructed from the classical potential-function-based control methodology, the derived controller can achieve uniformly ultimate boundedness without the obstruction of local minima or saddle points of the potential function. Specifically, the properties of derived potential are analyzed meticulously. Moreover, an explicit controllable domain is integrated into certain inequalities featuring initial states and control parameters to describe the capability of avoidance. The control performance can be also estimated and adjusted by tuning control parameters. A Lyapunov-based analysis is provided to show the convergence of the potential function, the gradient of the potential function and the closed-loop system. Furthermore, simulations are performed to demonstrate the effectiveness and features of the control law.

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...

This brief investigates the problem of finite-time output feedback control for spacecraft attitude stabilization without angular velocity measurement. First, two new sufficient conditions for finite-time ultimate boundedness and local finite-time stability are derived, which reduce the conservativeness of the traditional conditions. Then, based on the two new sufficient conditions of the finite-time stability, a finite-time observer is proposed to estimate the unknown angular velocity by using the quadratic Lyapunov function method. Next, a finite-time attitude controller is designed based on the estimate of the angular velocity. The finite-time stability of the entire closed-loop system is analyzed through the Lyapunov approach. The rigorous proof shows that the observation errors and the spacecraft attitude will converge to a residual set of zero in finite time. Numerical simulation results illustrate the effectiveness of the proposed strategy.

This work investigates the challenging problem of fast robust fault tolerant attitude control for spacecraft to handle external disturbances, actuator failures and misalignments. More specially, a novel nonsingular terminal sliding mode based finite-time extended state observer is first designed to estimate and compensate for the lumped system faults or uncertainties. And the proposed extended state observer is analysed and proved to be stable in the sense of fast finite-time uniformly ultimately bounded stability. Then, utilizing the techniques of super-twisting and terminal sliding mode control synthetically, a novel continuous attitude control algorithm is developed. The finite-time stability of the closed-loop attitude control system is proved by using a continuously-differentiable, homogeneous and strict Lyapunov function. And also the proposed control scheme is continuous with the property of chattering restraining. Finally, some numerical simulation results are shown to verify the effectiveness and superior performances of the spacecraft attitude stabilization control system driven by the proposed fast robust fault tolerant attitude control scheme.

This work develops a novel disturbance observer and integral sliding mode technique based fault tolerant attitude control scheme for spacecraft, which is subject to external disturbance torques and actuator failures. More specifically, a simple and novel finite-time disturbance observer is first designed to reconstruct the synthetic uncertainty deriving from actuator failures and disturbances, by which the synthetic uncertainty is also compensated or restricted. Then, an integral sliding mode based finite-time fault tolerant attitude stabilisation controller incorporating with an adjusting law is investigated to ensure the closed-loop attitude control system converge to the stable region in finite time. And also the finite-time stability of the closed-loop attitude control system driven by the proposed attitude control scheme is analysed and proved utilising Lyapunov methodology. Finally, a simulation example for a rigid spacecraft model is carried out to verify the effectiveness and superiority of the proposed attitude control approach.

Attitude control of a rigid spacecraft has attracted tremendous attention for the capability of achieving operational services, such as remote sensing, communication and variety of space-related research.

The six degrees of freedom (6DOF) control problem for spacecraft proximity operations is addressed in this work. During the docking process, the field-of-view constraint of the chaser is required to be satisfied, and both the position and attitude of chaser are required to track with the target simultaneously. More specifically, the integrated translational and rotational error dynamics are developed first, and a novel artificial potential function (APF) is designed involving the motion constraint information. Based on this, a feedback control law is proposed to ensure the chaser can reach the desired docking position and attitude with no violation of the constraint. The analysis for the proposed APF and the stability of the system are given based on Lyapunov theorem. Finally, numerical simulations are conducted to illustrate the effectiveness of the proposed control scheme.

The attitude control issue for hypersonic vehicles (HSV) with coupling analysis is presented in this paper. An auxiliary variable is introduced to identify the effects of coupling terms that are negative or beneficial for the attitude stabilization. To handle the environmental uncertainties and aerodynamic perturbations involved in the hypersonic vehicles flight control system, a modified gain adaptation strategy is presented to tackle these terms that are limited but with unknow bounds. Then, a robust control scheme containing the coupling effect identified terms is constructed to deal with the robustness and coupling issues. It is proved that the utilized control scheme can enforce the tracking errors to a small vicinity of the origin in finite time. Finally, numerical simulations are conducted to demonstrate the provided controller.

This paper studies the rest-to-rest attitude reorientation problem of a three-axis stabilized satellite subject to inertia uncertainties, external disturbances, actuator faults and input saturation. An arc tangent function is first adopted to model the constrained control input, and meanwhile an augmented plant is constructed to facilitate the control law derivation. Then, a novel adaptive fault-tolerant control scheme is proposed by incorporating the prescribed performance control and adaptive estimation techniques into backstepping design. Exploiting the dynamic surface control method, the complexity problem residing in traditional backstepping approaches is effectively averted. It is shown that the control algorithm developed is not only robust against environmental disturbances and adaptive to unknown time-varying inertia properties caused by the mass displacement of large-scale deployable appendages, but also able to steer the attitude reorientation errors along prescribed transient and steady-state behavioral bounds, despite the presence of actuator faults and input saturation. Based on standard Lyapunov synthesis, all signals in the closed-loop system are proved to be semi-globally uniformly ultimately bounded. Finally, simulation experiments carried out on a miniature satellite testify the effectiveness of the proposed control approach.

This paper addresses the problem of designing an angular velocity observer and an output feedback attitude controller with finite-time convergence and disturbances for spacecraft. First, two new concepts of finite-time stability are proposed and defined as the local fast-finite-time stability and the fast-finite-time uniformly ultimately boundness, which can be seen as the extensions of the traditional fast-finite-time stability. Then, based on these two concepts of stability, a fast-finite-time observer is designed to estimate the unknown angular velocity. Next, based on the estimation of the angular velocity, a nonsingular and continuous attitude control algorithm is proposed to achieve the finite-time stability or finite-time boundness. With consideration of the observation errors and disturbances in the closed-loop system, a rigorous analysis of the proposed strategy is provided through Lyapunov approach. It shows that the observation errors and the spacecraft attitude will converge to a region of zero in finite time. Numerical simulation studies are presented to illustrate the effectiveness of the proposed observer-based attitude control scheme.

The science objectives of a spacecraft mission place stringent performance requirements on the spacecraft attitude control system. However, it remains an open problem how to guarantee consistent control performance necessary to meet these requirements, especially in the event of actuator faults and input saturation. Motivated by this fact, in this paper, we address the problem of attitude tracking control with prescribed performance guarantees for a rigid spacecraft subject to unknown but constant inertia parameters, unexpected disturbances, actuator faults, and input saturation. First, certain performance functions specified a priori by the designer are adopted to impose desired performance metrics on the attitude tracking errors. Then, the original attitude tracking error dynamics with performance constraints is transformed into an equivalent “state-constrained” one whose robust stabilization is shown to be sufficient to solve the stated problem via a novel error transformation. Subsequently, based on the transformed system, an adaptive fault-tolerant controller is derived by incorporating backstepping control, the barrier Lyapunov function, and Nussbaum gains. It is proved that the designed controller is able to guarantee the satisfaction of the prespecified constraints on the transformed errors, as well as the boundedness of all other closed-loop signals, without resorting to a judicious selection of the control parameters. Finally, the effectiveness of the proposed control scheme is evaluated by means of simulation experiments carried out on a microsatellite.

This paper addresses the problem of robust fault-tolerant control of spacecraft attitude stabilization in the presence of model uncertainties, actuator failures, and external disturbances simultaneously. Utilizing the fast nonsingular terminal sliding mode control technique, a novel finite-time extended state observer is first proposed to estimate and compensate for the specified synthetic uncertainties derived from actuator failures and/or model deviations. And also the detailed derivations of the observer are provided, along with a thorough analysis for the associated ultimately bounded stability and estimation error convergence property in the sense of finite-time control. Then, with the reconstructed information achieving from the finite-time observer, an adaptive robust sliding mode based fault-tolerant control approach is developed to ensure that the closed-loop attitude control system reach the real sliding mode surface in finite time. Meanwhile, the chattering problem has been restrained via the modified gain adjusting law. The key feature of the proposed strategies is that the whole closed-loop fault-tolerant control system can be guaranteed theoretically to be finite-time stable by the development of Lyapunov methodology. Finally, numerical simulation results are presented to illustrate and highlight the fine performance benefits obtained using the proposed schemes.

The main problem addressed is the quaternion-based attitude stabilization control of rigid spacecraft without angular velocity measurements in the presence of external disturbances and reaction wheel friction as well. As a stepping stone, an angular velocity observer is proposed for the attitude control of a rigid body in the absence of angular velocity measurements. The observer design ensures finite-time convergence of angular velocity state estimation errors irrespective of the control torque or the initial attitude state of the spacecraft. Then, a novel finite-time control law is employed as the controller in which the estimate of the angular velocity is used directly. It is then shown that the observer and the controlled system form a cascaded structure, which allows the application of the finite-time stability theory of cascaded systems to prove the finite-time stability of the closed-loop system. A rigorous analysis of the proposed formulation is provided and numerical simulation studies are presented to help illustrate the effectiveness of the angular-velocity observer for rigid spacecraft attitude control.

A novel smooth attitude algorithm is presented for rigid spacecraft in the presence of assigned sensor and actuator saturations, as well as external disturbances. More specifically, an analog of variable structure control law is first developed by explicitly taking into account the velocity and control constraints simultaneously. In the proposed controller, behavior of the adaptive parameter is investigated to ensure the close-loop convergence and disturbance rejection. The straightforward relationship between the constraints given and parameters tuning is further analyzed. In addition, to avoid the unwinding phenomenon problem caused by quaternion attitude representation, a class of definition of attitude error vector is proposed to ensure that both two equilibria are locally asymptotically stable. Numerical simulations illustrate the performance of proposed attitude controller and the improvement of the anti-unwinding technic.

In this paper, attitude coordinated tracking control algorithms for multiple spacecraft formation are investigated with consideration of parametric uncertainties, external disturbances, communication delays and actuator saturation. Initially, a sliding mode delay-dependent attitude coordinated controller is proposed under bounded external disturbances. However, neither inertia uncertainty nor actuator constraint has been taken into account. Then, a robust saturated delay-dependent attitude coordinated control law is further derived, where uncertainties and external disturbances are handled by Chebyshev neural networks (CNN). In addition, command filter technique is introduced to facilitate the backstepping design procedure, through which actuator saturation problem is solved. Thus the spacecraft in the formation are able to track the reference attitude trajectory even in the presence of time-varying communication delays. Rigorous analysis is presented by using Lyapunov-Krasovskii approach to demonstrate the stability of the closed-loop system under both control algorithms. Finally, the numerical examples are carried out to illustrate the efficiency of the theoretical results. Published version

This paper investigates a velocity-free finite-time attitude control scheme for a rigid spacecraft with actuator saturation and external disturbances. Initially, a finite-time observer is designed to compensate the unknown angular velocity information. With the estimated values, a finite-time controller is further developed under which the time-varying reference attitude trajectory can be tracked precisely. Moreover, input saturation problem is solved by adaptive method. Rigorous Lyapunov-based analysis shows that the states of the closed-loop system converge to a small neighborhood of the origin in finite time. Finally, the dynamic performance of attitude control system is presented by numerical simulation examples and the superiority of the finite-time control scheme is verified.

This paper proposes a model predictive controller for power-limited spacecraft attitude maneuver considering the actuators’ power limitation and the torque and angular momentum saturation. In the space exploration mission, the power provided by the solar panels is limited, and the performance of the reaction wheels is related to the available power. Therefore, the available power for reaction wheels is taken into account in controller design. Besides, the control torque and angular momentum constraints of reaction wheels are also described as inequalities herein. Then, the constrained discrete-time spacecraft attitude dynamics actuated by redundant reaction wheels is derived and the model predictive control is implemented to calculate the control torque while minimizing the special performance index. The validity and effectiveness of the proposed scheme are illustrated through numerical simulations.

This paper addresses the attitude synchronization problem for multiple flexible spacecraft subject to directed communication topology. Taking the time delays of communication network into account, a distributed attitude coordination control scheme is proposed only through local information exchange. It is shown that the control law can not only guarantee that all spacecraft within a formation can track a common reference attitude synchronously, but also ensure the undesirable vibration induced by flexible attachments are perfectly suppressed even when only a subset of formation members have access to the reference attitude. The result is rigorously proved by resorting to the Lyapunov stability analysis and algebraic graph theory. Finally, simulation examples for attitude synchronization among three flexible spacecraft are provided to demonstrate the effectiveness of the proposed control algorithm.

This paper addresses the problem of finite-time output feedback decentralized control of double tethered satellite system (2-TSS) attitude tracking in the presence of external disturbances in deep space. More specifically, the finite-time attitude tracking control law with the reconstructed information achieving from the pseudo-angular velocity filter is proposed in this paper. The significant feature of proposed strategy is that the whole closed-loop control system can be guaranteed theoretically to be finite-time stable by the development of adding a power integrator method, which indicates that the tracking errors for 2-TSS are confronted into a small residual region around origin within finite time. Finally, numerical simulation analysis is presented to validate the effectiveness and feasibility of proposed scheme.

This paper addresses the attitude stabilization problem with the optimization objective regarding system performance and energy consumption for rigid spacecraft. Novel state-dependent coefficient (SDC) parameterizations are developed to reduce the optimization problem to solving the state-dependent Riccati equation (SDRE). To be explicit, a proper SDC parameterization is selected for the stabilization mission among infinite feasible SDC representations by utilizing an improved guideline. Subsequently, a novel analytical SDC reconstruction is evoked alternatively at the mission breakdown region in which the derived SDC parameterization fails to operate. Behind the scenes, the anti-unwinding behavior is supported by the explicit sampling SDC forms derived for the scalar part of the unit quaternion. The novelty of two developed SDC parameterizations lies in that they not only render the maximal pointwise controllable space to facilitate the control mission, but also cover the whole maneuvering domain without any breakdowns. Moreover, the computational burdens for online SDRE solvability checking and numerical SDC reconstruction are alleviated significantly. Finally, comparative numerical simulations are implemented to highlight the superior performance of the presented scheme.

This paper investigates the fixed-time fault-tolerant control problem of spacecraft rendezvous and docking with a freely tumbling target in the presence of external disturbance and thruster faults. More specifically, based on the attitude of the target spacecraft, a line-of-sight coordinate frame is defined first, and the dynamical equations relative to the tumbling target are derived to describe the relative position (not six degrees of freedom). Then two fixed-time position controllers are proposed to guarantee that the closed-loop system is stable in finite time in the sense of a fixed-time concept, even in the presence of simultaneous external disturbance and thruster faults. Numerical simulations illustrate that the chaser spacecraft can successfully perform the rendezvous using the proposed controllers.

This paper addresses the problem of robust optimal control of spacecraft attitude stabilization in the presence of parametric uncertainties, external disturbances and actuator saturation simultaneously. As a stepping stone, an Extended State Observer (ESO) is developed to estimate and compensate the specified uncertainties including actuators' misalignments and parametric uncertainties while ensuring uniformly ultimately bounded estimation error in the sense of finite-time stability. Then, with the reconstructed information, an inverse optimal Control Lyapunov Function (CLF) approach is developed to guarantee asymptotic stability of the closed-loop system, such that an optimal/minimum performance index can be achieved. The associated stability proof is constructive and accomplished by the development of a novel Lyapunov function candidate. Furthermore, with the concept of input–output linearization of dynamics transverse to zero dynamic manifold, a rapid exponential stabilization CLF based optimal control scheme is investigated by utilizing the quadratic programming technique to restrain the actuator saturation. Simulation results are presented to illustrate the performance of the proposed schemes.

A novel pointing control law is presented to the problem of the spacecraft pointing with the presence of the constraints in space configuration. With the pointing constraint expressed by the reduced attitude, a potential function with global minimum located at the desired attitude is presented. Then, a PD-like control law is given with the synthesis of the proposed potential function. To prove the asymptotic stability of the closed-loop system, a Lyapunov-based analysis is performed. Simulation results are conducted to illustrate the effectiveness of the control scheme.

An anti-unwinding attitude controller is presented under angular velocity constraint. As a stepping stone, a novel attitude error function is introduced to eliminate the detrimental unwinding phenomenon of the unit quaternion. Then, the angular velocity constraint is considered, and a new form of barrier Lyapunov function is used to achieve this constraint. Furthermore, a controller aiming at solving the preceding two issues simultaneously is presented, and system's asymptotical stability is guaranteed due to Lyapunov analysis. Numerical simulations are employed to demonstrate the effectiveness and merit of the provided controller.

A finite-time attitude tracking control scheme is presented for rigid spacecraft subject to constant but unknown inertia and external disturbances. The controller, developed using sliding mode control technique, has great fault-tolerant capability to accommodate four types of actuator faults. Different from most of the existing works on attitude fault-tolerant control (FTC), the developed controller guarantees the desired attitude to be followed in finite time, which is critical for FTC systems. Moreover, the convergence time is an explicit parameter for designer’s choice. Thus, the controller design simply meets the finite-time requirement. The attitude-tracking performance is evaluated through a numerical example.

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.

A novel finite-time controller integrated with disturbance observer is investigated for a rigid spacecraft in the presence of disturbance, actuator saturation and misalignment. As a stepping-stone, a second-order disturbance observer is designed firstly such that the reconstruction of lumped disturbances is accomplished in finite time with zero error. Then, with the reconstructed information, a finite-time controller is synthesized even under actuator input saturation and misalignment, and the closed-loop system/state is proved to be finite-time stable and converges to the specified time-varying sliding mode surface. Moreover, the input saturation constraint is overcome via introducing an auxiliary variable to compensate for the overshooting. Numerical simulation results for the in-orbit rigid spacecraft show good performances, which validate the effectiveness and feasibility of the proposed schemes.

An observer-based fault-tolerant control scheme is developed for the attitude stabilization control of the rigid spacecraft in the presence of constants and time-varying actuator faults as well as external disturbances. The proposed iterative learning observer employs a learning mechanism to estimate the fault torque values combined with external disturbances, furthermore, the sign function and the revise term of angular velocity estimation error used in observer decrease the computing complexity and improve the estimation precision, respectively. The convergence of estimation error of composite disturbance signal consisting of actuator faults torque and external disturbances is guaranteed irrespective of the control torque or the initial attitude of the spacecraft. Some analyses of the proposed scheme are provided and numerical simulation studies are performed to verify the rapid and accurate convergence of estimation error and good robustness to external disturbances.

In this paper, we concentrate on the problem of attitude tracking control with guaranteed transient performance for a rigid spacecraft subject to unknown inertia properties and exogenous disturbances. A promising solution to the problem under consideration is presented. Specifically, certain performance functions specified a priori by the designer are first introduced to impose desired transient and steady state performance specifications on the attitude tracking errors. Subsequently, by using an error transformation, the original attitude tracking dynamics with performance constraints are transformed into an equivalent unconstrained one whose robust stabilization is shown to be sufficient to achieve prescribed performance guarantees. Then, based on the transformed system, an adaptive controller is designed by incorporating the backstepping control and the adaptive technique. It is proven that the control algorithm developed can guarantee the stabilization of the transformed errors, and hence the achievement of the desired performance metrics, as well as the boundedness of all other closed-loop signals, without resorting to an exact knowledge of the inertia matrix and despite the presence of external disturbances. Besides detailed control design and rigorous closed-loop stability analysis, numerical simulations are finally performed on a microsatellite to testify the effectiveness of the proposed control scheme.

Results are presented for a study of dual-quaternion-based fault-tolerant control for spacecraft tracking. First, a six-degrees-of-freedom dynamic model under a dual-quaternion-based description is employed to describe the relative coupled motion of a target-pursuer spacecraft tracking system. Then, a novel fault-tolerant control method is proposed to enable the pursuer to track the attitude and the position of the target even though its actuators have multiple faults. Furthermore, based on a novel time-varying sliding manifold, finite-time stability of the closed-loop system is theoretically guaranteed, and the convergence time of the system can be given explicitly. Multiple-task capability of the proposed control law is further demonstrated in the presence of disturbances and parametric uncertainties. Finally, numerical simulations are presented to demonstrate the effectiveness and advantages of the proposed control method.

A novel saturated proportional-derivative control incorporated with null-space-based optimal control reallocation is proposed for spacecraft attitude stabilization in the presence of disturbance and input saturation. More specifically, a saturated proportional-derivative based baseline nonlinear controller is firstly developed to guarantee the globally asymptotic stability under input constraints and external disturbance. This is achieved with inexpensive online computations by dynamically adjusting a single parameter to ensure the desired performance. Then, a novel null-space-based optimal control reallocation method is employed to map the specified virtual control command to the redundant actuators. The optimal control solution is obtained by penalizing the control allocation errors at a lower power/energy cost using quadratic programming algorithm. The benefits of the proposed control method are analytically authenticated and also validated via simulation study.

Adaptive-based integral sliding mode control scheme is developed to solve the actuator fault-tolerant compensation problem for linear time-invariant system in the presence of unknown actuator faults and external disturbances. A nonlinear integral-type sliding manifold is first presented that incorporates a virtual nominal control to achieve prescribed specifications of the perturbed system, and an adaptive sliding mode controller is constructed to automatically compensate for external disturbances and unknown time-invariant faults. It is shown that the proposed controller has the capability to guarantee that the resulting closed-loop system is asymptotically stable. Control design methodology is then extended to tackle with the unknown time-varying actuator faults. It is proved that any given level of gain attenuation from external disturbance/parametric estimation error to system output is achieved with the developed control law. The closed-loop performance of the new control solution derived here is evaluated extensively through numerical simulations in which the flexible spacecraft attitude control under both the external disturbances and actuator faults are considered.

A control scheme is developed to address the attitude tracking problem of a rigid spacecraft. A sufficient condition to accommodate actuator misalignment is presented. The controller asymptotically stabilizes the closed-loop attitude tracking system. The desired attitude trajectories can be tracked in finite time, even in the presence of uncertain inertia tensor, external disturbances, actuator fault, and actuator misalignment. The attitude tracking performance of the controller is evaluated through an illustrative example.