Class Of High-order Multi-agent Systems Research Articles

Fully Distributed Hierarchical ET Intrusion-and Fault-Tolerant Group Control for MASs With Application to Robotic Manipulators

This paper studies group synchronization tracking problem for a class of high-order multi-agent systems (MASs) with nonidentical and unknown direction faults (NUDFs) under multiple cyber attacks (i.e., denial-of-service (DoS) attacks and false data injection attacks (FDIAs)). Be motivated by this, a fully distributed hierarchical (cyber layer and physical layer) Zeno-free event-triggered (ET) intrusion-and fault-tolerant controller is presented based on Nussbaum-type gain technique, where a positive inter-event time exists in the state-dependent asynchronous ET mechanism (ETM). The constructed virtual cyber layer realizes the interaction among different agents so as to avoid the interaction in physical processes and thus reduce the error propagation. This two layer controller greatly increase the flexibility of the controller design compared with single-layer control strategies. In addition, a novel Nussbaum function stability lemma (Lemma lem4lem4) is developed for the first time. Based on this lemma, the fully distributed adaptive controller can adjust the direction of the input to match the fault direction with the help of Nussbaum function. Finally, a robotic manipulator example demonstrates the effectiveness and merit of the proposed control scheme. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Note to Practitioners</i> —In industrial processes, NUDFs and cyber attacks often occur in many different systems, which usually lead to performance degradation or even serious accidents. Typically, NUDFs affect the performance of chemical and industrial processes, circuits, and sensors. Meanwhile, in driverless vehicle platoon, attackers change the control signal through the wireless network, and then issue emergency braking commands, etc. Therefore, this paper designs a fully distributed hierarchical ET intrusion-and fault-tolerant scheme for high-order MASs that are usually used to model ship dynamics, robotic manipulators, and quarter-car active suspension. The control scheme gives solutions to the problem of NUDFs, multiple cyber attacks, and network bandwidth limitations at different layers, and effectively integrates the physical and cyber layers to achieve group synchronization. Meanwhile, a new event-triggered mechanism under the framework of group synchronization is developed to save communication resources. Robotic manipulator simulation studies verify the validity of the proposed scheme.

Nash Equilibrium Seeking for High-Order Multiagent Systems With Unknown Dynamics

In this article, we consider a Nash equilibrium seeking problem for a class of high-order multiagent systems with unknown dynamics. Different from existing results for single integrators, we aim to steer the outputs of this class of uncertain high-order agents to the Nash equilibrium of some noncooperative game in a distributed manner. To overcome the difficulties brought by the high-order structure, unknown nonlinearities, and the regulation requirement, we first introduce a virtual player for each agent and solve an auxiliary noncooperative game for them. Then, we develop a distributed adaptive protocol by embedding this auxiliary game dynamics into some proper tracking controller for the original agent to resolve this problem. We also discuss the parameter convergence issue under certain persistence of excitation conditions. The efficacy of our algorithms is verified by numerical examples.

Distributed Coordination for a Class of High-Order Multiagent Systems Subject to Actuator Saturations by Iterative Learning Control

This paper investigates a distributed coordination control for a class of high-order uncertain multiagent systems. Under the framework of iterative learning control, a novel fully distributed learning protocol is devised for the coordination problem of MASs including time-varying parameter uncertainties as well as actuator saturations. Meanwhile, the learning updating laws of various parameters are proposed. Utilizing Lyapunov theory and combining with Graph theory, the proposed algorithm can make each follower track a leader completely over a limited time interval even though each follower is without knowing the dynamics of the leader. Moreover, the extension to formation control is made. The validity and feasibility of the algorithm are verified conclusively by two examples.

Robust Leader-Following Consensus of High-Order Multi-Agent Systems in Prescribed Time

This article addresses the distributed prescribed-time leader-following consensus problem for a class of high-order multi-agent systems (MASs) with perturbed nonlinear agents dynamics and where the topology of the network contains a directed spanning tree, with the leader as the root. Prescribed-time consensus means that an agreement state of the MAS is achieved in a preset time, introduced as a parameter of the control law, and this constant settling time is achieved independently of the agents' initial state. The proposed control method exhibits three main advantages: first, to our best knowledge, it is the first time that prescribed-time convergence in a consensus problem is achieved for agents with high-order nonlinear dynamics, using a robust leader-following protocol, which allows an effective rejection of matched disturbances in the agents' model. Second, the proposed controller provides control signals of lower magnitude than existing approaches. Third, the proposed consensus protocol does not have parameters to be adjusted depending on the connectivity of the considered communication graph.

Distributed Consensus Algorithms for a Class of High-Order Multi-Agent Systems on Directed Graphs

We consider the consensus problem of high-order multi-agent systems, described by multiple integrator dynamics, under general directed graphs. In contrast to the existing results, we propose a fully-distributed consensus algorithm, albeit employing static state feedback. Specifically, it is shown that, with a suitably designed similarity transformation, consensus is reached under only the necessary and sufficient condition of an interconnection graph having a spanning tree. The proposed approach relaxes some restrictive assumptions commonly considered in the available literature, such as imposing global gains in the network and/or exploiting additional information from neighboring agents other than their position-like states. In addition, the proposed approach enables the explicit determination of the final consensus state even in the presence of constant communication delays. Simulation results are provided to illustrate the effectiveness of the proposed approach.

Distributed adaptive control and stability verification for linear multiagent systems with heterogeneous actuator dynamics and system uncertainties

ABSTRACTThe contribution of this paper is a control synthesis and stability verification framework for linear time-invariant multiagent systems with heterogeneous actuator dynamics and system uncertainties. In particular, we first propose a distributed adaptive control architecture in a leader-follower setting for this class of high-order multiagent systems. The proposed architecture uses a hedging method, which alters the ideal reference model dynamics of each agent in order to ensure correct adaptation in the presence of heterogeneous actuator dynamics of these agents. We then use Lyapunov stability theory and linear matrix inequalities to analyse the proposed architecture. This analysis reveals a stability condition, where evaluation of this condition with respect to a given graph topology allows stability verification of the controlled multiagent system. From a practical point of view, this condition also shows a fundamental tradeoff between heterogeneous agent actuation capabilities and unknown parameters in agent dynamics. Several illustrative numerical examples are also provided to demonstrate the efficacy of the proposed architecture.

Consensus Problem in High-Order Multiagent Systems With Lipschitz Nonlinearities and Jointly Connected Topologies

The leaderless consensus problem in a class of high-order multiagent systems with Lipschitz nonlinearities is studied in this paper. Despite existing leaderless consensus protocols devoted to high-order multiagent systems with Lipschitz nonlinearities, the proposed protocol in this paper guarantees achieving consensus in networks of agents with jointly connected topologies. To achieve this goal, first a consensus protocol for high-order multiagent systems with general linear models is proposed. By introducing a common Lyapunov candidate for the set of switching topologies and based on the Cauchy convergence criterion, achieving consensus under the proposed protocol is studied. Then, sufficient conditions are derived under which the results are extended to the case of Lipschitz nonlinearities in agents models. Numerical examples validate the proposed consensus protocol.

Leader-following consensus for a class of high-order nonlinear multi-agent systems

The finite-time leader-following consensus problem is addressed for a class of high-order multi-agent systems with uncertain nonlinear dynamics. Each follower node is modeled by lower-triangular system. By using recursive method, we develop the finite-time consensus control design scheme. Based on finite-time Lyapunov stability theorem and matrix theory, we prove that the finite-time consensus of high-order uncertain nonlinear multi-agent systems is guaranteed by non-lipschitz continuous control laws. Simulation results are given to illustrate the effectiveness of the theoretical results.

Decentralized H∞ consensus protocol for a class of high-order multiagent systems

Summary This paper proposes a consensus protocol for a class of high-order multiagent systems under directed networks. It is supposed that each agent is exposed to an external disturbance additive to its control input. Based on the H∞ optimization theory, the consensus protocol gains are designed in order to attenuate the effects of the external disturbances on the performance of the multiagent system. The main problem of existing H∞ high-order consensus protocols in the literature is the dependency of the design on the information of coupling matrices associated with networks topologies. Despite existing H∞ high-order consensus protocols in the literature, the proposed consensus protocol can be designed in a fully decentralized manner based on no global information. The main idea of the design is to propose an H∞ control formulation in which the coupling information of the agents is considered as exogenous signals, while the coupling effects of these signals lead to achieving consensus in the multiagent system. Numerical examples verify the effectiveness of the proposed consensus protocol. Copyright © 2016 John Wiley & Sons, Ltd.

Distributed fault-tolerant control for a class of cooperative uncertain systems with actuator failures and switching topologies

This paper studies the distributed fault-tolerant control (DFTC) problem for a class of high-order multi-agent systems (MASs) with switching undirected topologies, heterogeneous matching uncertainties, disturbances and actuator faults including loss of effectiveness, bias, outage and stuck. In this frame work, the communication network of dynamic agents may switch among several undirected connected graphs. It is assumed that the actuator efficiency factors, the lower and upper bounds of the time-varying failures and heterogeneous uncertainties, disturbances and the leader’s control input signal, are unknown. Based on the relative information of neighbors, a novel fault-tolerant consensus tracking protocol is designed for each follower node via distributed adaptive mechanism. By utilizing the multiple Lyapunov functions method and algebraic graph theory, a sufficient condition for consensus tracking is established. Furthermore, it is proved that if the topology dwell time is larger than a positive threshold, the state of each follower node synchronizes to that of the leader with a bounded residual error in the presence of actuator faults, heterogeneous matching uncertainties and disturbances. Finally, two numerical examples are given to show the effectiveness of the proposed control scheme.

High-order multi-agent consensus with dynamically changing topologies and time-delays

This study is concerned with consensus problems of a class of high-order multi-agent systems with dynamically changing topologies and time-delays. A nearest-neighbour rule is introduced for these high-order discrete-time agents with the consideration of communication time-delays. It is shown that consensus can be reached, even when the communication topologies are dynamically changing and the corresponding communication graphs have no spanning trees. It is also shown that the communication time-delays do not affect the stability of the multi-agent systems. Finally, a numerical example is included to illustrate the obtained results.

H∞ consensus control of a class of high-order multi-agent systems

This study is devoted to the consensus problems for high-order multi-agent systems with external disturbances. A dynamic neighbour-based protocol is adopted for the agents with the consideration of communication time delay and external disturbances. Sufficient conditions are derived to make all agents reach consensus with H∞ performance. Finally, simulation results are provided for demonstrating the effectiveness of the results presented.

On consensus protocols for high-order multiagent systems

In this paper, the static consensus problem and the dynamic consensus problem are considered for a class of high-order multiagent systems. With the proposed consensus protocols, necessary and sufficient conditions for the consensus problems are obtained. For the static consensus protocol, the desired consensus speed can be achieved by adjusting feedback gains. Simulations show the effectiveness of the proposed consensus protocols.

Dynamic feedback consensus control of a class of high-order multi-agent systems

This study investigates consensus of high-order multi-agent systems. A new dynamic neighbour-based protocol is proposed that only uses the relative information of the first states of agents, extending second-order protocols from the literature. Sufficient conditions are derived to make all agents reach consensus. Finally, simulation results are included to show the effectiveness of the obtained results.