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This paper has proposed a robust control for the spacecraft rendezvous system by considering the parameter uncertainties and actuator unsymmetrical saturation based on the discrete gain scheduling approach. By changing of variables, we transform the actuator unsymmetrical saturation control problem into a symmetrical one. The main advantage of the proposed method is improving the dynamic performance of the closed-loop system with a region of attraction as large as possible. By the Lyapunov approach and the scheduling technology, the existence conditions for the admissible controller are formulated in the form of linear matrix inequalities. The numerical simulation illustrates the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

A rotary single inverted pendulum (RSIP) typically represents a space booster rocket, Segway and similar systems with unstable equilibrium. This paper proposes a novel two degree of freedom (2-DOF) fractional control strategy based on 2-loop topology for RSIP system which can be extended to control the systems with unstable equilibrium. It comprises feedback and feed-forward paths. Primary controller relates the perturbation attenuation while the secondary controller is accountable for set point tracking. To tune the parameters of proposed fractional controller a simple graphical tuning method based on frequency response is used. The study will serve the outstanding experimental results for both, stabilization and trajectory tracking tasks. The study will also serve to present a comparison of the performance of the proposed controller with the 1-DOF FOPID controller and sliding mode controller (SMC) for the RSIP system. Further to confirm the usability of the proposed controller and to avoid the random perturbations sensitivity, robustness, and stability analysis through fractional root-locus and Bode-plot is investigated. [ABSTRACT FROM AUTHOR]

In this paper, a robust inertia-free attitude takeover control scheme with guaranteed prescribed performance is investigated for postcapture combined spacecraft with consideration of unmeasurable states, unknown inertial property and external disturbance torque. Firstly, to estimate the unavailable angular velocity of combination accurately, a novel finite-time-convergent tracking differentiator is developed with a quite computationally achievable structure free from the unknown nonlinear dynamics of combined spacecraft. Then, a robust inertia-free prescribed performance control scheme is proposed, wherein, the transient and steady-state performance of combined spacecraft is first quantitatively studied by stabilizing the filtered attitude tracking errors. Compared with the existing works, the prominent advantage is that no parameter identifications and no neural or fuzzy nonlinear approximations are needed, which decreases the complexity of robust controller design dramatically. Moreover, the prescribed performance of combined spacecraft is guaranteed a priori without resorting to repeated regulations of the controller parameters. Finally, four illustrative examples are employed to validate the effectiveness of the proposed control scheme and tracking differentiator. [ABSTRACT FROM AUTHOR]

This paper presents a robust fuzzy tracking controller for position and attitude control, and for vibration suppression in a flexible spacecraft. The robust fuzzy controller guarantees H\infty tracking control performance while satisfying the actuators’ amplitude constraints. The design problem of the fuzzy tracking controller is formulated in terms of linear matrix inequalities. The stability, performance, and robustness of the proposed fuzzy controller are examined and compared with a baseline nonlinear controller such as the model-reference adaptive controller with $\sigma$-modification via numerical simulations. [ABSTRACT FROM AUTHOR]

Based on the inherent coupling of system states, backstepping controllers are designed for underactuated spacecraft hovering without either the radial or in-track thrust and in the presence of input saturation and unmatched disturbances. Feasible hovering positions for either saturated underactuated case are derived. A Lyapunov-based approach is used to prove the asymptotical convergence of state errors and system robustness against unmatched disturbances. The validity of theoretical analysis is verified by simulations in a J2 -perturbed environment. [ABSTRACT FROM AUTHOR]

The problem of spacecraft attitude tracking using hybrid actuators with uncertainties is addressed in this paper. A hybrid actuators configuration that combines reaction wheels for fine pointing and single gimbal control moment gyros for rapid maneuvering is employed for agile spacecraft. A robust control algorithm for the spacecraft attitude tracking problem when the torque axis direction and/or input scaling of the actuators are uncertain is developed. Furthermore, a torque allocation method is proposed for the hybrid actuator configuration to allow a smooth switch between single gimbal control moment gyros and reaction wheels. With this method, single gimbal control moment gyros are used for the phase of rapid maneuvering, while reaction wheels are used for the phase of fine pointing. Simulation results demonstrate the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

The robust adaptive learning control for spacecraft autonomous proximity is investigated in this paper. The relative motion dynamics is firstly proposed and transformed into the state space representation. An adaptive learning controller that allows performing autonomous proximity maneuvers in the presence of uncertain orbital parameters is then developed. The unknown disturbances are considered, and a modified adaptive learning controller is therefore designed in the presence of uncertain parameters and unknown disturbances. The asymptotic stability of the proposed controllers for the closed-loop systems is proven based on the Lyapunov theory. Different numerical results are finally provided and compared to illustrate the performance of the proposed adaptive learning controllers. [ABSTRACT FROM AUTHOR]

In impulsive orbital maneuvers, thrust vector misalignment from the center of mass (C.M) results in a large disturbance torque. In this paper a thrusting maneuver system is proposed and studied which is based on the combination of a one degree of freedom (1DoF) gimbaled-thruster, two reaction wheels (RWs) and spin-stabilization. The main goals are disturbance rejection and thrust vector stabilization without using reaction control systems (RCS). The nonlinear two-body dynamics of the proposed system is formulated. The controller design is formulated as a multi-objective optimization problem where the peak-value of the control input and H ∞ performance are the cost functions. Based on the peak-to-peak gain minimization, the accuracy of the linearized model can be guaranteed. The optimization results give many optimal controllers which are acceptable for a thrusting maneuver. The simulation results illustrate the applicability of the proposed method in presence of the sampling effects of the control inputs. [ABSTRACT FROM AUTHOR]

In this paper, the problem of robust dissipative control is investigated for uncertain flexible spacecraft based on Takagi–Sugeno (T–S) fuzzy model with saturated time-delay input. Different from most existing strategies, T–S fuzzy approximation approach is used to model the nonlinear dynamics of flexible spacecraft. Simultaneously, the physical constraints of system, like input delay, input saturation, and parameter uncertainties, are also taken care of in the fuzzy model. By employing Lyapunov–Krasovskii method and convex optimization technique, a novel robust controller is proposed to implement rest-to-rest attitude maneuver for flexible spacecraft, and the guaranteed dissipative performance enables the uncertain closed-loop system to reject the influence of elastic vibrations and external disturbances. Finally, an illustrative design example integrated with simulation results are provided to confirm the applicability and merits of the developed control strategy. [ABSTRACT FROM AUTHOR]

The problem of relative motion control of spacecraft rendezvous process on elliptical orbit is considered in this paper. Due to the presence of nonlinear dynamics and external disturbances, two robust controllers are developed based on sliding mode control theory. The first one is an optimal sliding mode controller; in which optimal control theory is used to reduce the tracking error and fuel cost, and then integral sliding mode control technique is applied to robustify optimal controller. The other controller is a backstepping sliding mode one that is developed based on nonlinear dynamics of spacecraft rendezvous; having applied the backstepping method to synthesis the tracking errors and Lyapunov functions, a sliding mode controller is developed to guarantee the Lyapunov stability, handling of all nonlinearities, robustness against uncertainties as well as tracking the desired position. It is assumed that the chaser and target spacecraft are in a low Earth orbit and subject to the perturbing effects of J2 and atmospheric drag. In addition, two fault tolerant scenarios, i.e. thruster degradation and short thruster failure are also considered to verify the robustness and efficacy of the control approaches. Simulation results confirm the effectiveness of the proposed controllers in reaching to the desired position in case of actuator fault-free and fault tolerant situations. [ABSTRACT FROM AUTHOR]

Purpose This paper aims to present a three-axis attitude tracking control law to solve the attitude maneuver of a flexible satellite in the presence of parameter uncertainties and external disturbance.Design/methodology/approach Based on the relative dynamic equation where the relative attitude is described by quaternion, a robust control law composed of a proportional derivative (PD) part plus a signum function is designed and only requires the measurement of attitude and angular velocity. Furthermore, the stability analysis of the proposed control law is given through a two-step proof technique.Findings Numerical simulation results demonstrate that fine convergence of the attitude and angular velocity error and low-level vibration of flexible appendages are obtained by the proposed controllers.Practical implications The controller with the structure of a PD term plus a switching function about a sliding variable has low computational complexity and does not need to measure the modal variables of elastic appendages, so it can be used in orbit without modification.Originality/value The globally asymptotic stability of the controller in the presence of model uncertainties and external disturbances is proven rigorously through a two-step proof technique. [ABSTRACT FROM AUTHOR]

Contemporary space engineering advanced new problem before theoretical mechanics and motion control theory: a spacecraft directed respinup by the weak restricted control internal forces. The paper presents some results on this problem, which is very actual for energy supply of information mini-satellites (for communication, geodesy, radio- and opto-electronic observation of the Earth et al.) with electro-reaction plasma thrusters and gyro moment cluster based on the reaction wheels or the control moment gyros. The solution achieved is based on the methods for synthesis of nonlinear robust control and on rigorous analytical proof for the required spacecraft rotation stability by Lyapunov function method. These results were verified by a computer simulation of strongly nonlinear oscillatory processes at respinuping of a flexible spacecraft. [ABSTRACT FROM AUTHOR]

This paper proposes an observer-based robust guaranteed cost control method for thrust-limited rendezvous in near-circular orbits. Treating the noncircularity of the target orbit as a parametric uncertainty, a linearized motion model derived from the two-body problem is adopted as the controlled plant. Based on this model, a robust guaranteed cost observer-controller is synthesized with a less conservative saturation control law, and sufficient condition for the existence of this observer-based rendezvous controller is derived. Finally, an illustrative example with immeasurable velocity states is presented to demonstrate the advantages and effectiveness of the control scheme. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a novel inverse optimal and robust nonlinear attitude control law using the attitude quaternion feedback for regulation of rigid spacecraft. The attitude control law proposed in this paper has optimality with respect to a performance index incorporating a positive penalty on both the angular position and velocity and the control torque. Also, it has robustness with respect to control input uncertainties described as the output of a state strictly passive system and belonging to a sector. The result of the paper is illustrated by numerical simulations. [Copyright &y& Elsevier]

Robust finite-time control for spacecraft with coupled translation and attitude dynamics is investigated in the paper. An error-based spacecraft motion model in six-degree-of-freedomis firstly developed. Then a finite-time controller based on nonsingular terminal sliding mode control technique is proposed to achieve translation and attitude maneuvers in the presence of model uncertainties and environmental perturbations. A finite-time observer is designed and a modified controller is then proposed to deal with uncertainties and perturbations and alleviate chattering. Numerical simulations are finally provided to illustrate the performance of the proposed controllers. [ABSTRACT FROM AUTHOR]

For spacecraft attitude tracking system, there exists the chattering phenomenon. In this paper, the spacecraft motion is decomposed into three-channel subsystems, and a second-order sliding mode control is proposed. This method has been proved to have good convergence and robustness. Combined with the proposed sliding surface, the three-channel controllers are designed. The control performance is confirmed by the simulation results, the approaching process is improved effectively, and a smooth transition is achieved without overshoot and buffeting. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the spacecraft attitude tracking control problem. Two robust sliding mode controllers based on the quaternion and Lagrange-like model are proposed to solve this problem both in the absence of model uncertainties and external disturbances as well as in the presence of these. The controllers can guarantee the convergence of attitude tracking errors in finite time rather than in the asymptotic sense, where time tends to infinity. By constructing a particular Lyapunov function, the convergences of the proposed controllers for the closed-loop systems are proven theoretically. To alleviate the chattering phenomenon while at the same time guaranteeing the finite convergence during the process of attitude tracking, a new function is introduced into the controller. Numerical simulations are finally provided to illustrate the performance of the proposed controllers. [Copyright &y& Elsevier]

Abstract: This paper investigates the formation keeping problem for multiple spacecraft in the framework of networked control systems (NCSs). A continuous-time representation of the NCS is considered for the tracking control of relative translational motion between two spacecraft in a leader–follower formation in the presence of communication constraints and system uncertainties. Model-based control schemes are presented, which employ state feedback (when the relative position and velocity vectors are directly measurable) and output feedback (when velocity measurements are not available), respectively, to guarantee input-to-state stability (ISS) of the system. The stability conditions on network transfer intervals are derived as simple eigenvalue tests of a well-structured test matrix. The results are then extended to include network communication delay. Numerical simulations are presented to demonstrate the effectiveness of the control scheme ensuring high formation keeping precision and robustness to nonlinearities and system uncertainties. The proposed controllers are robust not only to structured uncertainties such as system parameter perturbations but also to unstructured uncertainties such as external disturbances and measurement noises. [Copyright &y& Elsevier]

This study investigates the robust fault-tolerant attitude control of an orbiting spacecraft with a combination of unknown actuator failure, input saturation and external disturbances. A fault-tolerant control scheme based on variable structure control is developed that is robust to the partial loss of actuator effectiveness, where the actuators experience a reduced actuation but are still active. The results are then extended to the case in which some of the actuators fail completely, although some redundancy in actuation is assumed. In contrast to traditional fault-tolerant control methods, the proposed controller does not require knowledge of the actuator faults and is implemented without explicit fault detection, separation and accommodation processes. Moreover, the designed controller rigorously enforces actuator saturation constraints. The associated stability proof is constructive and develops a candidate Lyapunov function that shows the attitude and the angular velocities converge asymptotically to zero. Simulation studies are used to evaluate the closed-loop performance of the proposed control solution and illustrate its robustness to external disturbances, unknown actuator faults and even input saturation. [ABSTRACT FROM AUTHOR]

Abstract: An adaptive control technique can be applicable to reorient spacecraft with uncertain properties such as mass, inertial and various misalignments. A nonlinear quaternion feedback controller is chosen as a baseline attitude controller. A linearly added adaptive input supported by neural networks to the baseline controller can estimate and eliminate the uncertain spacecraft property adaptively. The normalized input neural networks (NINNs) are examined for reliable computation of the adaptive input. The newly defined learning rules of the neural networks are established appropriately for a spacecraft. To prove the stability of the closed-loop dynamics with the control law, Lyapunov stability theory is considered. As a result, the proposed approach results in the uniform ultimate boundedness in tracking error and robustness of the chattering and the singularity problems. [Copyright &y& Elsevier]

This paper deals with the applicability of Robust Adaptive Control to the attitude motion control of large spacecraft. Large spacecraft and space structures, such as large communication satellites and the ISS (International Space Station), have been constructed on orbit. However dynamic characteristics of these structures can not be fully verified on the ground because of their size, mass and flexibility. Therefore, some unmodelled dynamics, for example, truncated vibration modes, and/or unknown elements should be taken into account for the precise and stable control of attitude motion. Based on the above consideration the applicability of the Robust Adaptive Control was carefully examined and the results of numerical simulations are given. These showed good performance of the attitude control system. We also refer to the basic idea about the modal truncation. [ABSTRACT FROM AUTHOR]

In Part 1 (see Ref. 2), a multiple-subarc gradient-restoration algorithm (MSGRA) was developed with the intent of enhancing the robustness of gradient-restoration algorithms and also enlarging the field of applications. Indeed, MSGRA can be applied to optimal control problems involving multiple subsystems as well as discontinuities in the state and control variables at the interface between contiguous subsystems. In Part 2 (this paper), MSGRA is applied to compute the optimal trajectory for a multistage launch vehicle design, specifically, a rocket-powered spacecraft ascending from the Earth surface to a low Earth orbit (LEO). Single-stage, double-stage, and triple-stage configurations are considered. For multistage configurations, discontinuities in the mass occur at the interfaces between consecutive stages. The numerical results show that, given the current levels of the engine specific impulse and spacecraft structural factor, the single-stage version is not feasible at this time, while the double-stage and triple-stage versions are feasible. Further increases in the specific impulse and decreases in the structural factor are needed if the single-stage configuration has to become feasible. Also, the numerical results show that the optimal trajectory requires initially maximum thrust, followed by modulated thrust so as to satisfy the maximum acceleration constraint, followed by nearly zero thrust for coasting flight, followed by a final burst with moderate thrust so as to increase the spacecraft velocity to the circular velocity needed for LEO insertion. The above properties of the optimal thrust time history are useful for developing the guidance scheme approximating in real time the optimal trajectory for a launch vehicle design. [ABSTRACT FROM AUTHOR]

Abstract: In a recent paper by Jin Erdong and Sun Zhaowei [Robust controllers design with finite time convergence for rigid spacecraft attitude tracking control, Aerospace Science and Technology 12 (2008) 324–330], a terminal sliding mode control technique has been applied to the attitude control problem of rigid spacecraft. Unfortunately, the controller has singularity problem which will cause the instability of the closed-loop system of attitude tracking errors. In this article, a nonsingular terminal sliding mode controller is presented to overcome this problem. [Copyright &y& Elsevier]