Multi-spacecraft System Research Articles

Attitude consensus coordination algorithm for spacecraft formation under compound disturbance

To address the attitude coordination and consensus tracking problem in the multi-spacecraft system, a distributed attitude-coordinated strategy based on the Fixed-time theory is proposed. An observer based on second-order integral sliding mode is designed to accurately estimate the compound disturbance, which consists of external disturbance and inertia uncertainties. On the basis of the observed information, a distributed Fixed-time attitude coordination controller is proposed, which can guarantee the attitude tracking errors converge to zero in a fixed time. System stability is analyzed by using the Lyapunov function. Finally, simulations and comparison analysis demonstrate the effectiveness and superiority of the proposed control scheme.

Stubborn Observer for Leader-Following Consensus of Nonlinear Multiagent Systems With Application to Spacecraft.

In this article, the leader-following consensus problem is investigated for a class of nonlinear multiagent systems with transmission outliers. First, through the relative output information and observer states of neighbor agents, a distributed stubborn reduced-order observer is proposed to estimate the leader-following consensus error which is affected by abnormal and isolated transmission outliers. Moreover, considering that the leader agent in practice is a controllable plant, another distributed stubborn reduced-order observer is designed by using the relative information and inputs of neighbor agents. Sufficient conditions are established in terms of the Laplacian matrix such that two stubborn reduced-order observers are convergent and the studied nonlinear multiagent system could achieve leader-following consensus with directed topology. Finally, an example of the multispacecraft system is provided to illustrate the effectiveness of the proposed methodology.

Attitude control of multi-spacecraft systems on SO(3) with stochastic links failure

In this paper, for Multi-Spacecraft System (MSS) with a directed communication topology link and a static virtual leader, a controller is proposed to realize attitude consensus and attitude stabilization with stochastic links failure and actuator saturation. First, an MSS attitude error model suitable for a directed topology link and with a static virtual leader based on SO(3) is derived, which considers that the attitude error on SO(3) cannot be defined based on algebraic subtraction. Then, we design a controller to realize the MSS on SO(3) with attitude consensus and attitude stabilization under stochastic links failure and actuator saturation. Finally, the simulation results of a multi-spacecraft system with stochastic links failure and a static virtual leader spacecraft are demonstrated to illustrate the efficiency of the attitude controller.

Disturbance observer-based performance guaranteed fault-tolerant control for multi-spacecraft formation reconfiguration with collision avoidance

In this study, the issue of the performance guaranteed fault-tolerant control for formation reconfiguration with collision avoidance in the multi-spacecraft system subjects to space perturbations and thruster faults is investigated. A new nonlinear iterative learning disturbance observer is constructed to accurately reconstruct the synthesized disturbance no matter it is time-varying or not. Then, an exponential artificial potential function with a simple structure and low computation requirement is designed to avoid collision between spacecrafts. A nonsingular terminal sliding mode fault-tolerant control method is explored to accomplish fault-tolerant formation reconfiguration with collision avoidance ability and prescribed robust performance. Finally, numerical simulations and comparisons are performed to validate the effectiveness and superiority of the proposed approaches.

Prescribed Performance Rotating Formation Control of Multi-Spacecraft Systems with Uncertainties

This paper investigates the problem of rotating formation control for multi-spacecraft systems with prescribed performance in the presence of model uncertainties. Firstly, The spacecraft dynamics containing unmodelled parts is described in a polar coordinate system, which is to solve the problem of the controllable angular velocity of rotating formation. Then, the prescribed performance control method is improved by developing new prescribed performance functions. Based on the improved prescribed performance control method, the distributed controller is designed for multi-spacecraft systems to achieve rotating formations with prescribed performance, i.e., the formations error converges to a predefined arbitrarily small residual set, with convergence time no less than a prespecified value. And an RBF neural network is used to fit the unmodelled components of the spacecraft dynamics. Compared with the existing works of literature, this paper not only solves the robust prescribed performance rotating formation control of multi-spacecraft system, but also acheives rotating formation with adjustable angular velocity. Finally, the Lyapunov approach is employed for convergence analysis, and simulation results are provided to illustrate the effectiveness of the theoretical results.

Distributed coordinated attitude tracking control of a multi-spacecraft system with dynamic leader under communication delays

This paper is dedicated to the challenging issue of the cooperative attitude tracking control of a multi-spacecraft system under communication delays. A state estimator using the attitude information of the neighbors is designed for each follower spacecraft to estimate the time-varying attitude information of the leader spacecraft in the case that the leader spacecraft cannot directly communicate with all following spacecraft. By constructing auxiliary variables based on estimated values and proposing a fixed-time control law to ensure that the auxiliary variables of the spacecraft can reach zero in fixed time, which is independent of the initial state, the effects of time-varying reference attitudes on the system can be reduced. The attitude error and the estimation error are proven to converge to the region containing the origin by input-to-state stability theory combined with the Lyapunov–Krasovskii approach. To further illustrate the effectiveness of the proposed control algorithm, numerical simulation results are presented.

Distributed Prescribed-Time Attitude Coordination for Multiple Spacecraft With Actuator Saturation Under Directed Graph

This article studies the distributed prescribed-time coordination problem for the attitude system of multiple spacecraft subject to actuator saturation under the communication topology containing a directed spanning tree. The prescribed-time coordination requires that every spacecraft in a formation reaches an agreement state in a preset time. This preset time is set by the user and independent of any other control parameters and the initial state of spacecraft. To achieve this goal, we first design a distributed prescribed-time observer for every follower spacecraft to estimate the state of leader spacecraft. Next, a prescribed-time attitude control law is proposed by utilizing the estimated state of the leader spacecraft. In the proposed control law, an adaptive compensation law is used to compensate the input saturation. Furthermore, the prescribed-time stability of multispacecraft system subject to input saturation under the proposed scheme is analyzed in theory and simulation. The simulation results show the high reliability and effectiveness of the scheme.

Distributed dynamic event-triggered adaptive attitude consensus control of multiple spacecraft

This paper addresses the issue of distributed attitude consensus control for a group of rigid spacecraft with bounded external disturbances and inter-spacecraft communication bandwidth constraint. By developing a model-based dynamic event-triggered communication mechanism, attitude information of spacecraft is sent to their neighbors only when a defined event is triggered. To suppress the effect of the errors induced by the event-triggered mechanism on the multi-spacecraft system, a model-based state estimator is employed to estimate the attitude of the neighbors during the event-triggered intervals. By using the estimated attitude, a distributed event-triggered adaptive attitude consensus control scheme is proposed to achieve the attitude consensus tracking of a group of spacecraft. Furthermore, only a small subset of spacecraft can obtain the reference attitude, and the other spacecraft that cannot obtain the reference attitude information directly just uses the attitude information of their neighbors to track the reference attitude trajectory. The communication topology among spacecraft is assumed to be undirected. The Lyapunov approach is employed to guarantee the stability of the resulting closed-loop systems, and the Zeno phenomenon is excluded. Finally, the results of numerical simulation illustrate the effectiveness and robustness of the proposed scheme.

Sliding-Mode-Observer-Based Time-Varying Formation Tracking for Multispacecrafts Subjected to Switching Topologies and Time-Delays

In this article, the time-varying practical formation problem is investigated for a group of spacecrafts subjected to switching topologies, and time-delays. First, a sliding mode observer is designed to estimate the derivatives of time-varying delays. In virtue of the self-stable region, the sufficient condition is provided to guarantee that the error dynamics of the super-twisting sliding mode observer is convergent. Then, the sliding-mode-observer-based formation tracking protocol is designed using position, and velocity of the neighboring agents with time-varying delays. Sufficient conditions are established in terms of average dwell time such that the studied multispacecraft system could achieve the goal of time-varying formation with switching topologies. Finally, an example on the multispacecraft system is provided to illustrate effectiveness of the proposed methodology.

Architecture and Strategy of the Intelligent Hybrid Autonomous System for Complex Mixed Spacecraft

For manned spacecraft, constellation and other types of complex mixed spacecraft, in view of the complexity of the system construction and the long-term nature of their on-orbit service including multiple spacecraft building, system multi-module integration, changeable operation and working mode and uncertainty of on-orbit environment, the ability of autonomous operation is essential for long-term reliable flight, automatic emergency disposal and the reduction of ground resource commitment. In this paper, the construction of the intelligent autonomous system of single spacecraft centralized mode and multi-spacecraft networking hybrid mode is researched, in order to realize efficient communication and effective negotiation among multi-agents. Based on mixed method of data, model and expert rules, an intelligent autonomous strategy with combined hierarchical structure is formed at spacecraft, subsystem and equipment levels, which can provide a good reference for autonomous management of highly-integrated single spacecraft system, constellation and complex multi-spacecraft system.

Finite-time leader-following output consensus for multi-agent systems via extended state observer

In this paper, the finite-time leader-following output consensus problem is investigated for a multi-agent system subjected to directed topology and disturbance. Firstly, a distributed finite-time extended state observer (DFTESO) is designed to provide estimate for unmeasured consensus errors and disturbances. The sufficient condition is provided in terms of linear matrix inequality (LMI) to ensure that the error dynamics of the DFTESO is convergent in finite time. Then, based on the designed observer, the leader-following consensus protocol based on dynamic gain method is proposed under the directed topology. Finally, an example on the multi-spacecraft system is provided to illustrate the effectiveness of the proposed methodology.

Event- and self-triggered control of attitude coordination to multi-spacecraft system

PurposeThe purpose of this paper is to investigate the attitude cooperation control of multi-spacecraft with in-continuous communication.Design/methodology/approachA decentralized state-irrelevant event-triggered control policy is proposed to reduce control updating frequency and further achieve in-continuous communication by introducing a self-triggered mechanism.FindingsEach spacecraft transmits data independently, without the requirement for the whole system to communicate simultaneously. The local predictions and self-triggered mechanism avoid continuous monitoring of the triggering condition.Research limitations/implicationsThis investigation is suitable for small Euler angle conditions.Practical implicationsThe control policy based on event-triggered communication can provide potential solutions for saving communication resources.Originality/valueThis investigation uses event- and self-triggered policy to achieve in-communication for the multi-spacecraft system.

Almost Sure Attitude Consensus in Multispacecraft Systems With Stochastic Communication Links

Leaderless attitude consensus problem over multispacecraft systems is studied. The base of convergence analysis of existing results devoted to attitude consensus control of multispacecraft systems is deterministic knowledge on networks communication links. The main contribution of the present study is to design a control strategy guaranteeing almost sure attitude consensus in a multispacecraft system when communication links stochastically fail over time. Moreover, it is assumed that there exist constraints on the spacecraft input torques. To achieve the mentioned objectives, we propose a magnitude-constrained consensus control law for the spacecraft; then, by invoking the generalized invariance principle and the super-martingales convergence theorem, almost sure convergence of quaternion-based consensus errors to zero is concluded. The results are verified via a simulation example.

Attitude Consensusability in Multispacecraft Systems Using Magnetic Actuators

The leaderless attitude consensusability of multispacecraft systems by using magnetic actuators is addressed. By proposing a nonlinear consensus protocol for the actuators magnetic dipoles, it is shown that the multispacecraft system is average controllable under the consensus protocol if it is maneuvering at orbits with persistently exciting magnetic fields in the Earth-centered inertial frame. Then, under some conditions, achieving consensus in the multispacecraft system is studied. Simulation results for a team of spacecraft validate the proposed consensus strategy.

Design of a formation of solar pumped lasers for asteroid deflection

This paper presents the design of a multi-spacecraft system for the deflection of asteroids. Each spacecraft is equipped with a fibre laser and a solar concentrator. The laser induces the sublimation of a portion of the surface of the asteroid, and the resultant jet of gas and debris thrusts the asteroid off its natural course. The main idea is to have a formation of spacecraft flying in the proximity of the asteroid with all the spacecraft beaming to the same location to achieve the required deflection thrust. The paper presents the design of the formation orbits and the multi-objective optimisation of the formation in order to minimise the total mass in space and maximise the deflection of the asteroid. The paper demonstrates how significant deflections can be obtained with relatively small sized, easy-to-control spacecraft.

Extension of the Cucker-Smale Control Law to Space Flight Formations

We designed a spacecraft control law for autonomous formation acquisition and formation keeping. This control law extends the ideas on flight formation for flocks first introduced by Cucker and Smale [Cucker, F., and Smale, S., Emergent Behavior in Flocks, IEEE Transactions on Automatic Control, Vol. 52, 2007, pp. 852-862] by also allowing for particle accelerations, thus incorporating dynamics. When this control law is applied to a multispacecraft system, the resulting formation orbits as a rigid body driven by the natural dynamics of the centroid of the formation. We applied the law to the transfer orbit of a set of spacecraft that, in loose formation, follows a natural trajectory to a libration point orbit, as it is suggested for the Darwin mission. We used two standard metrics to evaluate the performance of this control law: the maximum variation in interspacecraft distance and the integral of the motor thrusts necessary to maintain the formation, or fuel expenditure. For the Darwin case study, the new control law outperforms the zero relative radial acceleration cone control. In particular, we find that the minimum fuel expenditure of the new control law can be 4 orders of magnitude less than the fuel expenditure of zero relative radial acceleration cone control.

Planar dynamics of variable length multi-tethered spacecraft near collinear Lagrangian points

This paper examines the planar dynamics of a wheel-and-spoke configured multi-spacecraft system, connected together by variable length tethers, near the second Sun–Earth Lagrangian point. The closed form solutions of the system under some simple tether length functions are determined and numerical results for the tether pitch librations under more complex tether length functions are obtained, along with the control effort required to maintain the desired tether librations.

Dynamics of Lagrangian Point Multi-Tethered Satellite Systems

This paper examines the dynamics of a tether-connected multi-spacecraft system, arranged in a wheel-spoke configuration, in the vicinity of the L2 Lagrangian point of the Sun-Earth system. Equilibrium configurations of the system are determined and small motions about one of these configurations are analyzed. A simple feedback controller is also developed to stabilize the motion of the system. Numerical simulation of the free and controlled motion of the parent mass and tether librations is carried out for a three-mass case.

Relative navigation for multi-spacecraft system with GPS

A type of multi-spacecraft system with kinematical restraint but no structural restraint and force action is considered. Both the absolute and relative navigation information is required for this multi-spacecraft system, but the relative information is more critical and the accuracy requirements for relative information will be much higher than those for the absolute information. In this paper, the Global Positioning System (GPS)/Differential GPS (DGPS) are introduced and used for relative navigation. Relative motion of space vehicles is modeled. Relative position, relative velocity and relative attitude are represented and solved by GPS/DGPS measurements. Using a type of commercial GPS receiver onboard spacecraft and relative differential GPS technique, the relative navigation of space vehicles can be implemented in real-time.