Attitude Tracking Of Flexible Spacecraft Research Articles

Prescribed performance fault‐tolerant attitude control for flexible spacecraft under limited communication network

AbstractThis paper investigates the prescribed performance fault‐tolerant attitude tracking control for flexible spacecraft under limited communication network, where the controller and the actuator are connected via wireless network. The hysteresis quantizer is employed to quantize the control signal, which can reduce the communication burden of the network onboard. First, a novel iterative learning observer is developed by combining with neural‐network approximation method to reconstruct the actuator faults and estimate the unmeasurable nonlinear rigid‐flexible dynamics simultaneously. Then, the signal quantization technique is introduced for control command quantization, and the concerned parametric quantization error is given. Based on the learning observer output, prescribed performance design procedure, and a quantization error compensation method, an active fault‐tolerant control strategy is developed for flexible spacecraft attitude tracking to deal with actuator faults, unmeasurable system nonlinearity, quantization errors, and external disturbances. The stability analysis of the closed‐loop system proves that the quantization errors, modal vibrations, disturbances can be effectively rejected, moreover, the convergence of the transformed performance states and angular velocity states can be guaranteed, which achieves the tracking problem with predetermined transient‐state and steady‐state performance requirements. Finally, a numerical simulation is conducted to illustrate the validness of the proposed control strategy.

Adaptive quantized sliding mode attitude tracking control for flexible spacecraft with input dead-zone via Takagi-Sugeno fuzzy approach

This paper addresses the sliding mode control design problem for the flexible spacecraft attitude tracking control system with Takagi-Sugeno fuzzy model based method. In this design, the external disturbance and actuator input dead-zone are considered simultaneously, and the signals between sensors and controller are quantized before transmission over digital communication channels. A quantized adaptive integral sliding mode control law is proposed to ensure that the sliding motion is globally asymptotically stable, and the effects of unknown external disturbances, actuator nonlinearity and quantization errors are compensated via the online adaptive mechanism simultaneously. Moreover, under the proposed digital control law the finite-time reachability of the designed sliding surface can be guaranteed strictly. Finally, simulation results are presented to illustrate the feasibility and effectiveness of the developed quantized spacecraft attitude control method.

Adaptive Fault-Tolerant Control for Attitude Tracking of Flexible Spacecraft With Limited Data Transmission

This article investigates the fault-tolerant control for attitude tracking problem of flexible spacecraft in the presence of actuator degradation, external disturbance, and signal quantization, where a logarithmic encoder-decoder scheme is employed for input quantization. A quantized adaptive terminal sliding mode control law is proposed to solve the attitude tracking problem. In this design, the quantizer parameters are injected to the controller gains to reject quantization errors, and the designed controller can compensate the effects of the unknown information, including actuator efficiency factors, external disturbance, and bounds of rigid-flexible coupled nonlinearity. It is shown that the attitude of the spacecraft can track the desired objective under the developed attitude controller. Finally, a simulation example is provided to verify the validness of the proposed attitude tracking control law.

Finite‐time attitude tracking control and vibration suppression for flexible spacecraft

AbstractIn this paper, an adaptive multivariable continuous terminal sliding mode (CTSM) controller with robust input shaper (RIS) is proposed for flexible spacecraft under model uncertainty and external disturbance. Firstly, for the problem of flexible vibration introduced by flexible appendage, the RIS based on disturbance observer is designed. The proposed input shaper can eliminate the flexible vibration effectively even if there are some disturbances in flight. Then, an adaptive multivariable CTSM controller is proposed for attitude tracking of flexible spacecraft, using only information about the output and its first derivative. The features of the developed methods are that it is continuous multivariable controller which attenuates the chattering effectively and the attitude tracking can be achieved in finite time. The stability and robustness properties of the system are proven using Lyapunov function. Finally, some numerical simulations are performed to validate the efficiency of the developed algorithm.

Neural adaptive integral sliding mode control for attitude tracking of flexible spacecraft with signal quantisation and actuator nonlinearity

This study investigates the neural adaptive integral sliding mode control for attitude tracking of flexible spacecraft, where unknown actuator nonlinearity, input quantisation and external disturbances are considered simultaneously. In this design, the hysteresis encoder–decoder scheme is employed between the controller and actuator side for signal quantisation. A quantised adaptive integral sliding mode control strategy is developed, where the neural network scheme is applied to approximate the unmeasurable rigid-flexible coupled nonlinear dynamics. The proposed control strategy can compensate for quantisation error, actuator faults, actuator dead-zone as well as external disturbances effectively, and guarantee the trajectory of the attitude tracking error converge to the equilibrium point along the designed sliding surface. Finally, a simulation example is conducted to demonstrate the validness of the developed quantised control strategy for flexible spacecraft attitude tracking problem.

Model-Free Prescribed Performance Control for Spacecraft Attitude Tracking

The problem of flexible spacecraft attitude tracking control with guaranteeing the prescribed performance is investigated. First, the Lagrangian model of the flexible spacecraft is derived. Then, a model-free control law is proposed, in which information of spacecraft and flexible appendage is not required. The proposed control law is able to guarantee the prescribed transient and steady-state behavior for both attitude and angular velocity errors in the presence of bounded external disturbances. The stability of the resulting closed-loop system is guaranteed by the Lyapunov approach. Two special forms of the proposed control law are subsequently obtained. The effectiveness of both complete form and special forms of the proposed control law is verified by numerical simulations. Since the modal information of spacecraft is not involved in the control design, the proposed control law can also be used for rigid spacecraft.

Adaptive fast nonsingular terminal sliding mode control for attitude tracking of flexible spacecraft with rotating appendage

This paper investigates the attitude tracking problem for the flexible spacecraft composed of a rigid platform with a rotating appendage. Two robust attitude controllers, each matched to the platform and the appendage, are constructed simultaneously. First, the relative kinematic models are presented, and the dynamic model describing the translation, rotation, and vibration of the spacecraft is proposed using the Lagrange Method. Then, a novel fast nonsingular terminal sliding mode surface is designed, and control strategies are proposed by integrating the aforementioned sliding manifold with the adaptive methodology. The adaptive update laws are employed to estimate the boundaries of various uncertainties, which do not require a priori disturbance information. Finally, illustrative numerical simulations are conducted to demonstrate the performance of the proposed control technique in terms of fast convergence and robustness compared to existing control schemes.

Adaptive tracking and command shaped vibration control of flexible spacecraft

An adaptive multivariable continuous non-singular terminal sliding mode (NTSM) control scheme with fast and robust input shaper (FRIS) is developed for flexible spacecraft which is subject to external disturbances. Firstly, the FRIS is proposed to suppress residual vibration of flexible spacecraft. It is shown that the FRIS decreases the duration of the impulse sequence at the meanwhile it is robust to parameter uncertainties. Then the adaptive multivariable continuous NTSM control is proposed to the attitude tracking of flexible spacecraft and the supression of residual vibration in finite time. The remarkable feature of the developed algorithm is to eliminate the overestimation of the control gains, and the tracking errors can be driven into a small region around zero in finite time even in the presence of bounded but unknown disturbances. Finally, some numerical simulations are performed to validate the efficiency of the developed algorithm.

Robust dynamic surface sliding mode control for attitude tracking of flexible spacecraft with an extended state observer

The nonlinear attitude motion equations of flexible spacecraft described by the Euler angles are expressed in the vector form. Based on dynamic surface control, a new robust dynamic surface sliding mode controller is proposed for the attitude tracking and active vibration suppression of flexible spacecraft in the presence of parameter uncertainty and external disturbances. Then, a novel robust dynamic surface finite time sliding mode controller is proposed with an extended state observer such that the uncertainties can be estimated. Lyapunov stability analyses show that the two controllers can guarantee the asymptotical stability of the attitude control system. The undesirable vibration of flexible spacecraft is also actively suppressed by the modal velocity feedback approach. Finally, simulation results verified the effectiveness of the presented control algorithms.

Uncertainty decomposition-based fault-tolerant adaptive control of flexible spacecraft

A fault-tolerant adaptive control scheme is developed for attitude tracking of flexible spacecraft with unknown inertia parameters, external disturbance, and actuator faults. The uncertainties of flexibility and dynamics are parameterized, and the control gain matrix uncertainty is handled using an uncertainty decomposition. The control scheme, with adaptive laws of the overall system uncertain parameter estimates, guarantees the system stability and asymptotic attitude tracking properties. Simulation results illustrate the effectiveness of the proposed control scheme.

Adaptive-Gain Second-Order Sliding Mode Control of Attitude Tracking of Flexible Spacecraft

This paper investigates the robust finite-time control problem for flexible spacecraft attitude tracking maneuver in the presence of model uncertainties and external disturbances. Two robust attitude tracking controllers based on finite-time second-order sliding mode control algorithms are presented to solve this problem. For the first controller, a novel second-order sliding mode control scheme is developed to achieve high-precision tracking performance. For the second control law, an adaptive-gain second-order sliding mode control algorithm combing an adaptive law with second-order sliding mode control strategy is designed to relax the requirement of prior knowledge of the bound of the system uncertainties. The rigorous proofs show that the proposed controllers provide finite-time convergence of the attitude and angular velocity tracking errors. Numerical simulations on attitude tracking control are presented to demonstrate the performance of the developed controllers.

Finite-Time Anti-Disturbance Inverse Optimal Attitude Tracking Control of Flexible Spacecraft

We propose a new robust optimal control strategy for flexible spacecraft attitude tracking maneuvers in the presence of external disturbances. An inverse optimal control law is designed based on a Sontag-type formula and a control Lyapunov function. An adapted extended state observer is used to compensate for the total disturbances. The proposed controller can be expressed as the sum of an inverse optimal control and an adapted extended state observer. It is shown that the developed controller can minimize a cost functional and ensure the finite-time stability of a closed-loop system without solving the associated Hamilton-Jacobi-Bellman equation directly. For an adapted extended state observer, the finite-time convergence of estimation error dynamics is proven using a strict Lyapunov function. An example of multiaxial attitude tracking maneuvers is presented and simulation results are included to show the performance of the developed controller.

Fault tolerant control with H∞ performance for attitude tracking of flexible spacecraft

A fault-tolerant control scheme with thruster redundancy is developed and applied to perform attitude tracking manoeuvres for an orbiting flexible spacecraft. Based on the assumption of bounded elastic vibrations, an adaptive sliding mode controller is proposed to guarantee that all the signals of the resulting closed-loop attitude system are uniformly ultimately bounded in the presence of an unknown inertia matrix, bounded disturbances and unknown faults. An H ∞ performance index is introduced to describe the disturbance attenuation performance of the closed-loop system. This approach is then extended to the problem of elastic vibration without knowledge of the bounds a priori. The presented approach addresses thruster saturation limits and the desired thruster force is guaranteed to stay within the limit of each thruster. Extensive simulation studies have been conducted to demonstrate the closed-loop performance benefits compared to conventional control schemes.

Fault-Tolerant Attitude Control for Flexible Spacecraft Without Angular Velocity Magnitude Measurement

S INCE some catastrophic faults or failures may be induced due to the aging or damage of actuators and sensors during the mission of a spacecraft, those faults would lead to performance degradation of the spacecraft attitude control system or even result in the specified aerospacemission failure. Therefore, fault tolerance of the spacecraft attitude control system is one of the key issues that needs to be addressed. With a view to tackle such a challenge, fault-tolerant control (FTC) has received considerable attention in order to enhance the spacecraft reliability and to guarantee the attitude control performance [1–5]. In [5], an adaptive FTC is developed for the flexible spacecraft attitude tracking system where the persistent bounded disturbances, unknown inertia parameter, and even two types of reaction wheel faults are successfully accommodated. Indeed, the aforementioned approaches offer many attractive conceptual features, but at the same time they are derived based on the availability of direct and exact measurements of both the angular velocity and the attitude orientation. It is important to note, however, that when it comes to practical implementation, the angular velocity measurements are not always available because of either cost limitations or implementation constraints. Motivated from such a practical consideration, it is therefore highly desirable to develop partial state feedback attitude control strategies with spacecraft angular velocity measurements eliminated. The issue has been addressed in the literature by using observer-based control [6,7], Lyapunov-based control [8,9], and variable structure control [10] under normal operation of spacecraft. In this work, we provide solutions to two different problems of the flexible spacecraft attitude control system. The first problem consists of developing a control law to perform a attitude stabilization maneuver without angular velocity magnitude. In contrast with the velocity-free control schemes available in the literature, the presented approach can guarantee the attitude control performance be greatly robust to external disturbances and unknown inertia parameters. The second problem solved is the casewhere both loss of control effectiveness and additive fault occur in actuators simultaneously, but the attitude still requires stabilization with high resolution. To the best knowledge of the authors, this study is the first attempt to deal with fault-tolerant attitude stabilization control for flexible spacecraft with the angular velocity magnitude eliminated. The Note is organized as follows. Section II presents the mathematical model and attitude control problems formation of a flexible spacecraft under normal and faulty actuator conditions. Section III presents the proposed fault-tolerant attitude stabilization controller without velocity magnitude in the presence of two types of actuator faults. Simulation results to demonstrate various features of the proposed scheme are given in Sec. IV followed by conclusions in Sec. V.

Fault-Tolerant Attitude Control for Spacecraft Under Loss of Actuator Effectiveness

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.

Adaptive quaternion-based output feedback control for flexible spacecraft attitude tracking with input constraints

This work mainly explores a quaternion-based output feedback control scheme for the flexible spacecraft attitude tracking problem in which not only the unavailability of the body angular velocity measurements is considered, but also external disturbances and uncertain inertia parameters as well as input constraints are explicitly taken into account. The proposed controller incorporates a pseudo velocity filter to account for the unmeasured angular velocity, and the neural network technique is implemented to approximate the system uncertainties of the flexible spacecraft in the synthesis of the control algorithms. It is shown that this developed control method ensures the uniformly ultimate boundedness of the attitude tracking error and the control input can rigorously enforce actuator magnitude constraints. Numerical simulation results are also presented which not only highlight ensuring closed-loop performance benefits from the control law derived here, but also illustrate its robustness in the face of external disturbances when compared with conventional approaches for spacecraft attitude tracking control.

Robust Adaptive Attitude Tracking Control With L2-Gain Performance and Vibration Reduction of an Orbiting Flexible Spacecraft

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.

Robust adaptive sliding-mode fault-tolerant control with L2-gain performance for flexible spacecraft using redundant reaction wheels

A robust adaptive fault-tolerant control approach for attitude tracking of flexible spacecraft is proposed for use in situations when there are reaction wheels/actuator failures, external disturbances and time-varying inertia-parameter uncertainties. More specifically, a robust controller based on sliding-mode control scheme is first designed to ensure that the equilibrium point in the closed-loop system is uniform ultimate bounded stability, incorporating constraints on actuator failures, whose failure time instants, patterns and values are unknown, as motivated from a practical spacecraft control application. Then, this controller is redesigned such that an assumption on a bound required of the unknown and time-varying inertia matrix is released by using online estimation for this bound. The prescribed robust performance is also evaluated by L2-gain less than a given small level for the penalty output signal. Complete stability and performance analysis are presented, and illustrative simulation results of an application to flexible spacecraft show that the high precise attitudes control and vibration suppression are successfully achieved using various scenarios of control effect failures.

Adaptive sliding mode backstepping control for attitude tracking of flexible spacecraft under input saturation and singularity

This article presents non-linear and adaptive sliding mode control (SMC) design for attitude tracking of flexible spacecraft in situations when there exist uncertainties, external disturbances, and input saturation constraints. In this approach, the function approximation technique is employed to represent the disturbances and uncertainties with finite combinations of some basis functions. Based on the backstepping technique, an adaptive SMC law for attitude tracking is first derived. In the closed-loop system, the roll angle, angle of pitch, and yaw angle trajectories asymptotically follow the reference output trajectories. To cope with the limitations of control saturation, a modified control design is given, and the stability of the closed-loop system is also verified. An additional updating law is employed for the derivative of singularity-free attitude tracking law as well, in which the possible singularity problem of the estimated control gains in the existing adaptive control schemes can be removed. Numerical simulation is conducted for the attitude tracking of a flexible spacecraft, and the results demonstrate the effectiveness and feasibility of the control strategy.

Active Vibration Suppression in Flexible Spacecraft Attitude Tracking

The active suppression of vibrations of spacecraft  exible appendages during attitude tracking or large-angle maneuvers is discussed.On thebasisof amodelobtainedusingtheLagrangianapproachand theunitaryquaternion parameterization, piezoelectric actuators are used to damp the vibration of  exible booms induced during the maneuvers. The results of simulation reveal the interest and the practical feasibility of such a control scheme. The control law requires only the measure of the attitude and the angular velocity. The absence of  exible displacement and velocity sensors is compensated for by the presence of appropriate dynamics in the controller.