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In this study, the authors study the distributed finite-time attitude dynamic tracking control problem for multiple rigid spacecraft systems with a single dynamic leader under directed graphs. By constructing a sliding-mode estimator for each follower, they remove the requirement of the angular acceleration information. Based upon a sliding-mode observation vector, the distributed input torques are designed to guarantee that not only the attitude but also the angular velocity of the followers will converge to the leader's. Necessary and sufficient criteria are established for the proposed protocol. Finally, the theoretical result is illustrated by a numerical simulation.

This paper provides an overview of attitude coordination problems of multi-rigid-body with the goal of promoting research in this area. Theoretical results regarding consensus seeking with different system models, different communication topologies, different control goals and different techniques are summarized. And applications of consensus protocols to multirigid- body coordination are investigated. Finally, some future research directions and open problems are also proposed.

In this paper, we investigate the finite-time regulation problem for heterogeneous multi-agent system composed of linear first-order, second-order integrator agents and nonlinear Euler-Lagrange (EL) dynamical agents. Based on homogeneity approach, a continuous finite-time controller is designed. A distinctive feature of this work is to address the finite-time consensus problem of first-order, second-order integrator agents and nonlinear EL agents in a unified theoretical framework. Simulation results are also provided to illustrate the effectiveness of the controller.

Real-time and accurate fault detection is essential to enhance the aircraft navigation system’s reliability and safety. The existent detection methods based on analytical model draws back at simultaneously detecting gradual and sudden faults. On account of this reason, we propose an online detection solution based on non-analytical model. In this article, the navigation system fault detection model is established based on belief rule base (BRB), where the system measuring residual and its changing rate are used as the inputs of BRB model and the fault detection function as the output. To overcome the drawbacks of current parameter optimization algorithms for BRB and achieve online update, a parameter recursive estimation algorithm is presented for online BRB detection model based on expectation maximization (EM) algorithm. Furthermore, the proposed method is verified by navigation experiment. Experimental results show that the proposed method is able to effectively realize online parameter evaluation in navigation system fault detection model. The output of the detection model can track the fault state very well, and the faults can be diagnosed in real time and accurately. In addition, the detection ability, especially in the probability of false detection, is superior to offline optimization method, and thus the system reliability has great improvement.

This paper studies the state consensus for a class of networked nonlinear mechanical systems with coupling time delay. In particular, robust consensus protocols for both deterministic and uncertain systems with time delay are investigated. For deterministic systems, we develop a P-like protocol which allows for variable coupling time delay. We show that it is sufficient to have only the relative position information together with a damping control term, whereas the relative velocity information is not needed for state consensus. Then, an adaptive robust control protocol is proposed for uncertain systems with unknown parameters in the system dynamics and arbitrary constant coupling time delays. By introducing the passivity-based framework, we demonstrate that state consensus is still reachable in this case. Finally, a numerical example is included to illustrate the obtained results.

SUMMARY This paper presents the novel approaches of designing robust fuzzy static output feedback H ∞ controller for a class of nonlinear singularly perturbed systems. Specifically, the considered system is approximated by a fuzzy singularly perturbed model. With the use of linear matrix inequality (LMI) methods, two methods are provided to design fuzzy static output feedback H ∞ controllers. The resulted controllers can guarantee that the closed-loop systems are asymptotically stable and satisfy H ∞ performances for sufficiently small ϵ. In contrast to the existing results, the proposed approaches have two advantages: (i) the gains of controller are solved directly by a set of ϵ-independent LMIs, and therefore, the problem of selecting the initial values in iterative LMIs algorithm can be avoided, and (ii) the smaller control input efforts are needed. The given methods are easy to implement and can be applied to both standard and nonstandard nonlinear singularly perturbed systems. Two numerical examples are provided to illustrate the effectiveness of the developed methods. Copyright © 2012 John Wiley & Sons, Ltd.

This work studies distributed six degree-of-freedom spacecraft formation control with possible switching topology. By rearranging the combined translational and rotational dynamics into a unified Euler–Lagrange formulation, the developed controllers can be applied directly to maintain formation as well as desired relative attitudes. Based on a novel adaptive control architecture, distributed controllers are developed, which allow for parameter uncertainties and unknown external disturbances. By using the Lyapunov theory and a non-linear switching system theory, it is proved that arbitrary desired formation and relative attitudes among spacecrafts can be obtained with either fixed or switching communication topology. Simulations are provided that demonstrate the effectiveness of our theoretical results.

In this paper, the spacecraft formation control and its stability problems are studied on the basis of the energy concept. The formation systems are viewed as a multi-mass point system with both generalized elastic deformation and rigid body movement, and certain potential fields interact with each other within the formation. Consequently, the stability of formation and coordination and the controller design problems are studied from the perspectives of energy. The symmetry in formation motion is studied, and the definition of formation stability and its corresponding criteria are presented based upon the notion of relative equilibrium. Then, the artificial potential method is explored to design the formation control law, and the stability of which is followed by utilizing the former criterions. The effectiveness of the proposed formation control approach is also demonstrated by numerical results.

Formation-based space net capture is a novel mode for spacecraft capturing and docking. After the object is successfully captured by space net, the relative movement model is firstly established based on the orbit elements after the target has been captured. Then, main disturbance elements for the spacecraft in the process of space net dragging are analyzed in detail. Besides, numerical simulations are carried out, whose results show that the formation mode is an effective means for investigating the complex compounded body movement. Moreover, the movement law between spacecraft and its capture target is derived via simulation. It turns out that the target will surround the spacecraft around its orbit.

Due to the ability to handle control and state constraints, MPC has become quite popular recently. In order to guarantee the stability of MPC, a terminal constraint and a terminal cost are added to the on-line optimization problem such that the terminal region is a positively invariant set for the system and the terminal cost is an associated Lyapunov function [1, 9]. As we know, the domain of attraction of MPC can be enlarged by increasing the prediction horizon, but it is at the expense of a greater computational burden. In [2], a prediction horizon larger than the control horizon was considered and the domain of attraction was enlarged. On the other hand, the domain of attraction can be enlarged by enlarging the terminal region. In [3], an ellipsoidal set included in the stabilizable region of using linear feedback controller served as the terminal region. In [4], a polytopic set was adopted. In [5], a saturated local control law was used to enlarge the terminal region. In [6], SVM was employed to estimate the stabilizable region of using linear feedback controller and the estimated stabilizable region was used as the terminal region. The method in [6] enlarged the terminal region dramatically. In [7], it was proved that, for the MPC without terminal constraint, the terminal region can be enlarged by weighting the terminal cost. In [8], the enlargement of the domain of attraction was obtained by employing a contractive terminal constraint. In [9], the domain of attraction was enlarged by the inclusion of an appropriate set of slacked terminal constraints into the control problem. In this paper, the domain of attraction is enlarged by enlarging the terminal region. A novel method is proposed to achive a large terminal region. First, the sufficient conditions to guarantee the stability of MPC are presented and the maximal terminal region satisfying these conditions is defined. Then, given the terminal cost and an initial subset of the maximal terminal region, a subsets sequence is obtained by using one-step set expansion iteratively. It is proved that, when the iteration time goes to infinity, this subsets sequence will converge to the maximal terminal region. Finally, the subsets in this sequence are separated from the state space one by one by exploiting SVM classifier (see [10,11] for details of SVM).

We address the problem of tracking relative translation in a leader-follower spacecraft formation architecture using Robust Integral of the Sign Error (RISE) based Neural Network (NN) technique. Based on the relative translational dynamic model of the spacecraft formation, RISE is introduced to approximate the dynamics of the follower as well as various practical disturbances. It is shown that the errors of the entire formation closed-loop are asymptotical stability (AS), which takes significant advantage over the typical Uniformly Upper Bounded (UUB) property of most NN controllers in high-precision formation tasks. Finally, numerical simulation is provided to verify the effectiveness of the proposed algorithm.

We consider the problem of formation flight for a set of Unmanned Air Vehicles (UAV) in a possible obstacle laden environment. A novel decentralized control design procedure is developed which guarantees collision and obstacle avoidance. The control design is based on a modified virtual leader-follower structure and a simple consensus protocol. Vehicle collision and obstacle avoidance is ensured by comprehensively utilizing artificial potential function and the gyroscopic force approach. By introducing gyroscopic force, a smoother formation trajectory is obtained which makes the UAV maneuver behavior more reasonable and it also tackles the local minimal problem caused by artificial potential function method. Numerical simulations are provided to demonstrate the correctness of the algorithm.

For the sake of enlarging the domain of attraction of model predictive control (MPC), a novel method of computing a large terminal region was proposed. Given the terminal cost, a subset sequence of the maximal terminal region was constructed by employing one-step set expansion iteratively. It was proved that, when the iteration time goes to infinity, this subsets sequence will converge to the maximal terminal region. Each subset in the sequence was extracted from the state space by exploiting support vector machine classifier.

Most consensus protocols developed in the past are for linear-integrator systems or deterministic non-linear systems. Here, the authors study the state consensus for non-point, non-linear networked Euler-Lagrange systems with unknown parameters. Specifically, state consensus problems with both coupling time delay and switching topology are investigated. By establishing a unified architecture based on the passivity property, adaptive consensus protocols are developed. It is shown that state consensus is reachable despite the unknown parameters, and the estimation errors of these parameters converge to zero. Furthermore, by introducing the leader-follower architecture, the authors show that each agent will converge its origin. Finally, a numerical example is given to illustrate the effectiveness of the proposed algorithms.