Multiple Flexible Spacecraft Research Articles

PDE-based distributed adaptive fault-tolerant attitude consensus of multiple flexible spacecraft

In this article, a distributed adaptive fault-tolerant control scheme is presented for the attitude consensus of multiple flexible spacecraft formulated by partial differential equations (PDEs). Each spacecraft is supposed to be actuated by a control torque on the rigid hub and a control force on the tip payload. First, a finite-time distributed observer is constructed to estimate the virtual leader's state for each follower spacecraft under local communication. Then, an individual controller is exploited for each follower spacecraft, which consists of an adaptive boundary control torque law to track the recovered attitude and velocity and an adaptive boundary control force law to eliminate the elastic deformation. Particularly, the parametric adaptation laws are incorporated to compensate the actuator faults and perturbations. The attitude synchronization errors, velocity synchronization errors, and elastic deformations can asymptotically stabilize to zero under the introduced controller. This work owns the following two major novelties. One is introducing a unified distributed control framework for the PDE-based attitude consensus of multiple flexible spacecraft. Another is developing a novel parametric adaptation strategy to accommodate the actuator faults. Lastly, comparative simulations verify and highlight the main results.

Fault-tolerant attitude coordination control for multiple flexible spacecraft using vector measurements

This paper addresses the control problems of distributed attitude coordination for multiple flexible spacecraft based on the feedback of inertial vector measurements. It is assumed that the angular velocity information is not available, and the modal variable cannot be measured. The orientation error model with vector measurements is introduced. And then the distributed attitude synchronization control scheme is presented without actuator faults or disturbances. It is guaranteed that the desired equilibrium is locally asymptotically stable and the undesired equilibrium is unstable. Meanwhile, the domain of attraction is given by inequality constraints. In the case that there exist actuator faults and external disturbances, a robust fault-tolerant control strategy is developed to realize attitude synchronization. The hyperbolic tangent function in place of sign function is adopted to eliminate external disturbances. Meanwhile, the adaptive laws are proposed to estimate actuator faults. The salient feature of these control approaches is that no modal variable observers are utilized and the control schemes are robust to the inertia uncertainty of spacecraft. Finally, numerical simulations are implemented to manifest the validity of the presented control schemes.

Autonomous assembly of multiple flexible spacecraft using RRT* algorithm and input shaping technique

Autonomous assembly of multiple flexible spacecraft using RRT* algorithm and input shaping technique

Distributed spacecraft attitude tracking and synchronization under directed graphs

Distributed adaptive controllers are developed for attitude tracking and synchronization on SO(3) of multiple flexible spacecraft under a directed graph. Since not all spacecraft can receive the virtual leader's information, a finite-time observer is designed for each follower spacecraft to estimate the moving virtual leader's information. An adaptive controller is then proposed to realize the distributed attitude tracking synchronously and achieve the bounded flexible vibration. A rigorous theoretical proof is presented based on the separation principle. Furthermore, an adaptive controller with a modal variable observer is designed for the case without the measurements of the modal variables. Finally, numerical and experimental verifications are presented.

Continuous constrained attitude regulation of multiple spacecraft on SO(3)

In this paper, both the centralized and distributed attitude regulation of multiple flexible spacecraft are studied on SO(3) with attitude constraints in the absence of the measurements of the angular velocities and modal coordinates. For centralized regulation, each spacecraft knows the desired attitude. A repulsive potential function is constructed to handle attitude constraints. Then a continuous controller is designed without the measurements of angular velocities. With the assumption that only some spacecraft know the desired attitude, a finite-time observer is introduced to estimate the leader's information under fixed or switching communication graphs. A continuous control law is proposed for the distributed attitude regulation with the estimate of the leader as the reference signal.

Distributed passivity-based control for multiple flexible spacecraft with attitude-only measurements

Abstract This paper focuses on the leader-follower attitude consensus of multiple under-actuated flexible spacecraft without system damping based on attitude measurements only. By constructing two different kinds of auxiliary Euler-Lagrange systems, passivity-based controllers are designed under undirected or directed communication graphs to achieve the distributed attitude tracking and vibration suppression simultaneously. For the leader-follower consensus under directed graphs, only the controller's generalized coordinates and the spacecraft attitudes are exchanged among the followers with the help of an extended state observer. The Lyapunov theory is adopted for the stability analysis of the overall system. Finally, numerical simulations are conducted to verify the effectiveness of the proposed controllers.

Distributed attitude tracking for multiple flexible spacecraft described by partial differential equations

In this study, two distributed control strategies without or with a Partial Differential Equation (PDE) observer are proposed for a team of flexible spacecraft to track the attitude of a virtual leader under an undirected and connected graph. The PDE is used to describe the dynamics of each spacecraft with an appendage, which is simplified as a hub-beam system. It is assumed that both the hub and the free tip of the beam are actuated directly. The desired attitude angle, i.e., the state of the virtual leader, is only available for one spacecraft in the team. A distributed controller with the state measurements of the hub and the free tip of the beam is proposed first. Then a PDE observer is presented to estimate the states of the whole beam from the information of the hub only. A novel distributed controller with such a PDE observer is developed to drive the team to track the virtual leader. It is indicated by rigorous proof that the two controllers can actuate the team to the desired attitude without any residual vibration asymptotically. Finally, two numerical examples are given to demonstrate the effectiveness of the proposed controllers.

Distributed adaptive fault-tolerant attitude tracking of multiple flexible spacecraft on $$\textit{SO}(3)$$SO(3)

This paper presents distributed adaptive fault-tolerant control for the attitude tracking of multiple flexible spacecraft on \(\textit{SO}(3)\) without modal variable measurement. Assume that the communication graph among the followers is undirected and connected and there exists at least one follower linked to the leader. To deal with the distributed tracking on \(\textit{SO}(3)\), a finite-time observer is designed to estimate the leader’s information for the followers. A distributed adaptive fault-tolerant controller is proposed to achieve the attitude tracking based on the estimation of the unmeasurable modal variables. The separation principle between the finite-time observer and the proposed controller is adopted to prove the controller convergence. Since the controllers are developed on \(\textit{SO}(3)\) directly, the singularity and ambiguity associated with other attitude representations can be avoided. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed control protocols.

Distributed attitude synchronization control for multiple flexible spacecraft without modal variable measurement

SummaryThis paper solves the attitude synchronization and tracking problem for a group of flexible spacecraft without flexible‐mode variable measurement. The spacecraft formation is studied in a leader‐following synchronization scheme with a dynamic virtual leader. With the application of adaptive sliding‐mode control technique, a distributed modified Rodriguez parameters‐based dynamic controller is proposed for flexible spacecraft without requiring modal variable measurement. It is proved that the attitude synchronization and tracking can be achieved asymptotically under the control strategy through the Lyapunov's stability analysis. Furthermore, a distributed robust continuous control algorithm is designed to guarantee the ultimate boundedness of both the attitude tracking error and the modal variable observation error when bounded external disturbances exist. Some numerical simulation examples for multiple flexible spacecraft formation are given to demonstrate the effectiveness of the proposed method.

Distributed adaptive tracking control of multiple flexible spacecraft under various actuator and measurement limitations

This paper investigates the distributed leader–follower tracking problem for a team of flexible spacecraft over an undirected communication network with uncertain parameters subject to various actuator and measurement limitations. Assuming that at least one team member can receive information from the virtual leader, three scenarios are considered: (i) all the states of the flexible spacecraft can be completely measured and driven, (ii) only the rigid part of the flexible spacecraft can be driven with full state feedback and (iii) only the rigid part of the flexible spacecraft can be measured and driven. In the first case, a continuous adaptive control law is designed by building a unified architecture based on the linear-in-parameter property. In the second case, a distributed adaptive control algorithm is developed with a discontinuous parameter update law by treating the team of flexible spacecraft as two cascading subsystems. In the third case, a distributed adaptive control law is established with feedback from the generalized coordinates, generalized velocities and generalized accelerations of the rigid part of the spacecraft. It is theoretically proved that the closed-loop systems under the three designed adaptive control laws are all convergent to the target states. Finally, three numerical examples are presented to illustrate the effectiveness of the three proposed control laws.

Distributed attitude control for multiple flexible spacecraft under actuator failures and saturation

This paper solves the problem of attitude consensus for flexible spacecraft formation under actuator failures and saturation constraints. Three insightful distributed consensus control laws are designed based on the Lyapunov’s stability theory and graph theory. The induced oscillations of the spacecraft’s flexible appendages are compensated online with adaptive update parameters. Attitude consensus for the multiple spacecraft system can be achieved with limited information transfer. The modal variables of the flexible appendages are avoided in the distributed controllers in order to reduce the payload of the spacecraft. In addition, the issue of actuator saturation is rejected by applying a switching control scheme. Numerical simulations are performed to demonstrate that the proposed controller can guarantee attitude consensus despite the presence of modeling uncertainties, external disturbances, and simultaneous loss of actuator effectiveness faults and additive faults.

Attitude synchronization for multiple flexible spacecraft based on non-smooth control

This paper considers the problem of attitude synchronization for a group of flexible spacecraft based on distributed attitude cooperative control strategy. Based on the backstepping design, non-smooth control, and the neighbor-based design rule, a distributed attitude control law is constructed step by step. Under the proposed control law, it is shown that the attitude synchronization is achieved asymptotically and the induced vibration by flexible appendages is simultaneously suppressed.