Robust Consensus Tracking Research Articles

Adaptive consensus tracking for linear multi‐agent systems with heterogeneous unknown nonlinear dynamics

SummaryThis paper considers the consensus tracking control problem for general linear multi‐agent systems with unknown dynamics in both the leader and all followers. Based on parameterizations of the unknown dynamics of all agents, two decentralized adaptive consensus tracking protocols, respectively, with dynamic and static coupling gains, are proposed to guarantee that the states of all followers converge to the state of the leader. Furthermore, this result is extended to the robust adaptive consensus tracking problem in which there exist parameter uncertainties and Lipschitz‐type disturbances in the network. It is also shown that the parameter estimation errors converge to zero based on contradiction method and Lyapunov function approach. Finally, a simulation example is provided to illustrate the theoretical results. Copyright © 2015 John Wiley & Sons, Ltd.

Robust consensus tracking for a class of heterogeneous second‐order nonlinear multi‐agent systems

SummaryThis paper deals with the robust consensus tracking problem for a class of heterogeneous second‐order nonlinear multi‐agent systems with bounded external disturbances. First, a distributed adaptive control law is proposed based on the relative position and velocity information. It is shown that for any connected undirected communication graph, the proposed control law solves the robust consensus tracking problem. Then, by introducing a novel distributed observer and employing backstepping design techniques, a distributed adaptive control law is constructed based only on the relative position information. Compared with the existing results, the proposed adaptive consensus protocols are in a distributed fashion, and the nonlinear functions are not required to satisfy any globally Lipschitz or Lipschitz‐like condition. Numerical examples are given to verify our proposed protocols. Copyright © 2014 John Wiley & Sons, Ltd.

Adaptive NN consensus tracking control of a class of nonlinear multi-agent systems

This paper proposes a novel robust adaptive consensus tracking control approach for a class of nonlinear multi-agent systems with modeling uncertainties and external disturbances. Radial Basis Function Neural Networks (RBFNNs) are used to approximate the unknown nonlinear function of agent׳s dynamic. Compared with existing NN consensus algorithms of nonlinear multi-agent systems, the proposed consensus control method only needs a small number of adjustable parameters, thus the online computation burden is greatly alleviated. In addition, by online updating the estimation of the NN approximation errors, the proposed consensus control approach can enhance the system robustness against modeling uncertainties. It is proven that all the signals of the multi-agent system are uniformly bounded and the consensus tracking errors converge to a small neighborhood of zero. A simulation is carried out to demonstrate the effectiveness of the proposed control method.

Robust semi-global coordinated tracking of linear multi-agent systems with input saturation

SUMMARY This paper investigates the problem of coordinated tracking of a linear multi-agent system subject to actuator magnitude saturation and dead zone characteristic with input additive uncertainties and disturbances. Distributed consensus and swarm tracking protocols are developed from a low-and-high gain feedback approach. Under the assumption that each agent is asymptotically null controllable with bounded controls, it is shown that robust semi-global consensus tracking and swarm tracking of the multi-agent system can always be reached provided that the networks are connected. Numerical examples are provided to illustrate the theoretical results. Copyright © 2014 John Wiley & Sons, Ltd.

Distributed Tracking Control for Multi-Agent Systems Under Two Types of Attacks

This paper studies a distributed consensus tracking control problem for a class of stochastic linear multi-agent systems subject to two types of attacks. The problem boils down to how to achieve robust consensus tracking of multi-agent systems with switching connected and disconnected directed topologies under attacks. The attacks on the edges instead of nodes lead to the loss of consensus tracking security. Based on a multi-step design procedure for designing a distributed secure algorithm, sufficient conditions on robust mean-square exponential consensus tracking are derived via the idea of average dwell time switching between some stable and unstable subsystems obtained from graph theory analysis. An applicaton to a practical power system is considered. It is proved that each distributed generator (DG) modeled as an agent in a microgrid can successfully synchronize their terminal voltage amplitude to a prespecified reference value under these two types of attacks.

Distributed consensus tracking of multi-agent systems with nonlinear dynamics under a reference leader

This paper investigates the distributed consensus tracking problem for multi-agent systems with Lipschitz-type dynamics under a reference leader. It is assumed that the leader state information is only available to a subset of followers, while the bounded reference input of the leader’s is unavailable to any follower. To achieve consensus tracking, a class of discontinuous protocols based on the relative information between the neighbouring agents are proposed. Furthermore, as extensions of the former result, the robust and adaptive consensus tracking problems are studied for the case where there exist parameter uncertainties and external disturbances in the network. Finally, the effectiveness of the theoretical result is demonstrated through a network of single-link manipulators.

Robust consensus tracking of multi‐agent systems with uncertain Lur'e‐type non‐linear dynamics

This study addresses the robust consensus tracking problem of multi-agent systems with uncertain Lur'e-type non-linear dynamics under a fixed topology. To achieve consensus tracking, a class of discontinuous control protocols are first proposed, which rely on the relative information among the neighbouring agents. Theoretical analysis indicates that the robust consensus tracking of uncertain Lur'e network can be achieved if the coupling strength and the control gain are both larger than the thresholds depending on some global information of the network. Then, an adaptive consensus tracking protocol is further designed to solve the robust consensus tracking problem as a modification of a fully distributed version without the need of any global information of the multi-agent systems. Furthermore, as an expansion of the discontinuous protocols, a new class of continuous control laws are developed based on the boundary layer concept. Finally, a couple of examples are given to illustrate the effectiveness of the theoretical results.

Robust Consensus Tracking Control of A Second-order Leader-follower Multi-agent System

In this paper, a robust consensus tracking control problem is considered for a second-order multi-agent system with an active leader. The acceleration of the leader is assumed to be time-varying and partially unknown. Then a distributed “observer”-based control is designed for every follower, based on a novel relative-velocity estimation technique. Additionally, an event-triggered strategy is applied to the system and the ultimate boundedness stability of the tracking error is ensured by Lyapunov stability theory.

Robust consensus tracking of a class of second-order multi-agent dynamic systems

In this paper, we study the problem of robust consensus tracking for a class of second-order multi-agent dynamic systems with disturbances and unmodeled agent dynamics. Contrary to previous approaches, we design continuous distributed consensus protocols to enable global asymptotic consensus tracking. Our focus is on consensus protocol design and stability analysis which also leads to the derivation of sufficient conditions for consensus tracking. We first consider the case of undirected information exchange with a symmetric and positive definite information-exchange matrix. We develop an identifier for each agent to estimate the unknown disturbances and unmodeled agent dynamics. Based on the identifier, we develop a consensus tracking protocol to enable global asymptotic consensus tracking using local information obtained from neighboring agents. The closed-loop stability is proven using Lyapunov analysis theory and an invariance-like theorem. We then extend the approach to the case of directed information exchange, whose information-exchange matrix is only of full rank so that the approach for undirected graphs cannot be directly applied. We show that global asymptotic consensus tracking can still be enabled under the new derived sufficient conditions by designing a new identifier, which utilizes the estimated information exchanged from neighboring agents, and constructing a new Lyapunov function. Examples and numerical simulations are provided to validate the effectiveness of the proposed robust consensus tracking method.

Robust consensus tracking for an integrator-type multi-agent system with disturbances and unmodelled dynamics

In this article, a robust consensus tracking problem for a multi-agent system with integrator-type dynamics has been addressed in the presence of disturbances and unmodelled dynamics. The desired trajectory to be tracked is only provided to a small group of team members. An identifier is developed to estimate the unknown disturbances and unmodelled dynamics. A consensus controller is developed based on this identifier to achieve asymptotic consensus tracking using the local information obtained from neighbouring agents. The closed-loop stability is proved using the Lyapunov-based analysis and an invariance-like theorem. Numerical simulations are provided to demonstrate the effectiveness of the developed robust consensus controller.