Distributed Control Protocol Research Articles

Consensus of multi-agent systems with randomly occurring nonlinearities via uncertain pinning control under switching topologies

This paper is focused on the consensus problem of multi-agent systems via uncertain pinning control under switching topologies. The stochastic disturbances and randomly occurring nonlinearities are proposed to describe more realistic systems. The communication topology is modeled by a directed graph and it is divided into two cases, the consensus problem is discussed in these two cases. In addition, there exist some uncertain pinning connections between the followers and leader due to switching topologies, the distributed control protocol is designed to satisfy the follower asymptotically converge to the leader. By constructing suitable multiple Lyapunov functions and utilizing tools of M-matrix theory, some sufficient consensus criteria are deduced to reach this goal. Finally, two examples are given to verify the correctness of the proposed method.

Distributed Fixed-Time Formation Tracking Control for the Multi-Agent System and an Application in Wheeled Mobile Robots

This work addresses the issue of multi-agent system (MAS) formation control under external disturbances and a directed communication topology. Firstly, a new disturbance observer is proposed to effectively reconstruct and compensate for external disturbances within a short period of time. Then, the integral terminal sliding mode technology is introduced to devise a novel distributed formation control protocol, ultimately realizing the stability of the MAS within a fixed time. Moreover, by means of rigorous Lyapunov theory analyses, a faster formation convergence rate and more accurate consensus accuracies are achieved in the proposed fixed-time strategy with variable exponent form. Finally, the formation tracking control scheme is applied to a multi-wheeled mobile robot (WMR) system. The experimental results strongly support the fine effectiveness of the control scheme designed in this work.

Bipartite Formation Control of Nonlinear Multi-Agent Systems with Fixed and Switching Topologies under Aperiodic DoS Attacks

This paper concentrates on bipartite formation control for nonlinear leader-following multi-agent systems (MASs) with fixed and switching topologies under aperiodic Denial-of-Service (DoS) attacks. Firstly, distributed control protocols are proposed under the aperiodic DoS attacks based on fixed and switching topologies. Then, considering control gains, as well as attack frequency and attack length ratio of the aperiodic DoS attacks, using algebraic graph theory and the Lyapunov stability method, some criteria are acquired to ensure that the nonlinear leader-following MASs with either fixed or switching topologies can realize bipartite formation under aperiodic DoS attacks. Finally, numerical simulations are carried out to validate the correctness of the theoretical results.

Event-Triggered-Based Distributed Consensus Tracking for Nonlinear Multiagent Systems With Quantization.

In this article, an observer-based adaptive neural network (NN) event-triggered distributed consensus tracking problem is investigated for nonlinear multiagent systems with quantization. In the first place, the limited capacity of the communication channel between agents is considered. The event-trigger mechanism and dynamic uniform quantizers are set up to reduce information transmission. The next NN is utilized to handle the unknown nonlinear functions. Finally, in order to estimate the unmeasurable states, an NN-based state observer is designed for each agent by using a dynamic gain function. To settle the difficulty caused by the coupling effects of event-triggered conditions and the scaling function in dynamic uniform quantizers and observers, a distributed control protocol with estimated information of its neighbors is designed, which ensures distributed consensus tracking of the nonlinear multiagent systems without incurring the Zeno behavior. The effectiveness of the control protocol is illustrated by a simulation example.

Dual-Event-Triggered Intelligence Security Control for Multiagent Systems Against DoS Attacks With Applications in Mobile Robot Systems

The intelligence security control problem of multiagent systems in the presence of actuator faults is investigated against denial-of-service (DoS) attacks. Noticing that the DoS attacks usually make the actuator signal not available for distributed control protocols, a novel intelligence dual-eventtriggered control strategy is developed to eliminate the impact of DoS attacks. This control strategy includes two related event triggers respectively set on different channels, in which the second event-triggered condition is related to the triggering sequence of the previous event. Through the coordination between two nested event triggers set on different channels, the controller is avoided by being affected by wrong signals caused by DoS attacks. The developed distributed control protocol can not only guarantee the realization of the tracking control task but also ensure that no ‘Zeno behavior” occurs in the process of the event triggering. Moreover, the obtained results are applied to the mobile robot systems. Finally, a numerical simulation example and a mobile robot system application are given to verify the feasibility and effectiveness of the proposed control strategy.

Fixed time containment control of multi-agent system under multi-source mismatched disturbance

Aiming at the cooperative control problem of multi-agent system, the fixed-time containment control of general second-order multi-agent system under mismatched disturbances is studied. Firstly, the problem of multi-agent system fixed-time containment control in ideal state is analyzed, and a distributed control protocol based on variable structure control is proposed. Then, a nonlinear fixed-time disturbance observer is designed, aiming at the mismatched disturbance, and a fixed-time control protocol based on the nonlinear disturbance observer is proposed. Finally, the effectiveness of the proposed control protocol under switching topology and multi-source disturbance is verified by numerical simulation.

Couple-group consensus of heterogeneous nonlinear multi-agent systems with cooperative–competitive interactions and input saturation

Couple-group consensus of multi-agent systems with cooperative–competitive interactions and input saturation is studied under fixed and switching topologies based on pinning control and event-triggered control. First, for heterogeneous multi-agent systems consisting of first- and second-order agents, we propose two new distributed event-triggered control protocols, and the control protocols both enable the groups of agents to achieve the desired consensus state, which can effectively reduce the number of controller updates and save communication resources. Second, based on the Lyapunov stability theory, the sufficient conditions are established for the couple-group consensus of multi-agent systems. Meanwhile, Zeno behavior is excluded. Third, the effectiveness and feasibility of the control methods proposed in this paper are verified via some simulation examples.

Boundary Disturbance Rejection Control for Fractional-order Multi-agent Systems with Reaction-diffusion

This paper focuses on boundary disturbance rejection control (BDRC) for fractional-order multi-agent systems (FMASs) with reaction diffusion terms. Firstly, based on the output information, the corresponding observer is designed to obtain information about all the agents and the unknown external perturbations. Then, a novel distributed boundary control protocol is designed based on the observed values. Thus, the convergence analysis of the closed-loop system is accomplished through the Mittag-Leffler stability theory and the linear matrix inequality condition. Finally, a simulation example is used to verify the correctness of the results.

Distributed Fixed-Time Control for Leader-Steered Rigid Shape Formation With Prescribed Performance.

Resorting to the principle of rigid body kinematics, a novel framework for a multirobot network is proposed to form and maintain an invariant rigid geometric shape. Unlike consensus-based formation, this approach can perform both translational and rotational movements of the formation geometry, ensuring that the entire formation motion remains consistent with the leader. To achieve the target formation shape and motion, a distributed control protocol for multiple Euler-Lagrange robotic vehicles subject to nonholonomic constraints is developed. The proposed protocol includes a novel prescribed performance control (PPC) algorithm that addresses the second-order dynamics of the robotic vehicles by employing a combination of nonsingular sliding manifold and adaptive law. Finally, the effectiveness of the proposed formation framework and control protocol is demonstrated through the numerical simulations and practical experiments with a team of four robotic vehicles.

Adaptive Neural Consensus of Unknown Non-Linear Multi-Agent Systems with Communication Noises under Markov Switching Topologies

In this paper, the adaptive consensus problem of unknown non-linear multi-agent systems (MAs) with communication noises under Markov switching topologies is studied. Based on the adaptive control theory, a novel distributed control protocol for non-linear multi-agent systems is designed. It consists of the local interfered relative information and the estimation of the unknown dynamic. The Radial Basis Function networks (RBFNNs) approximate the nonlinear dynamic, and the estimated weight matrix is updated by utilizing the measurable state information. Then, using the stochastic Lyapunov analysis method, conditions for attaining consensus are derived on the consensus gain and the weight of RBFNNs. The main findings of this paper are as follows: the consensus control of multi-agent systems under more complicated and practical circumstances, including unknown nonlinear dynamic, Markov switching topologies and communication noises, is discussed; the nonlinear dynamic is approximated based on the RBFNNs and the local interfered relative information; the consensus gain k must to be small to guarantee the consensus performance; and the proposed algorithm is validated by the numerical simulations finally.

Practical finite-time and fixed-time containment for second-order nonlinear multi-agent systems with IDAs and Markov switching topology

In this article, the finite-time containment problem and the fixed-time containment problem accompanied by injection and deception attacks (IDAs) and Markov switching topology for second-order nonlinear multi-agent systems (MASs) are investigated, respectively. By introducing a radial basis function neural network (RBFNN), the approximation property of radial basis neural networks is used to solve the unmeasurable difficulties of nonlinear functions and injection attacks. Finite-time and fixed-time distributed control protocols are proposed for switching topologies and attack-induced state deception and control injection, and finite-time and fixed-time containment as well as obtaining their corresponding sufficient conditions are achieved, respectively. Correspondingly, two examples are shown to demonstrate the feasibility of the control protocols.

Particle swarm optimization based leader-follower cooperative control in multi-agent systems

Multi-agent systems (MAS) have attracted significant attention in recent years due to their wide applications in cooperative control, formation control, synchronization of complex networks, and distributed coordination. A fundamental problem in MAS is the leader-follower consensus or cooperative tracking, where the followers are required to track the state trajectory of the leader agent. To solve the leader-follower consensus problem, we propose a novel evolutionary computation approach to design the optimal distributed control protocols for leader-follower MAS. First, we formulate the design of distributed control gains for leader-follower consensus as an optimization problem to minimize tracking errors. Then, we leverage particle swarm optimization as an efficient evolutionary technique for distributed gain optimization in multi-agent networks. Finally, we guarantee stability for the closed-loop dynamics under directed communication topologies based on algebraic graph theory. The simulation results indicate that the proposed method yields a diminished tracking error, expedites the convergence process, and minimizes the requisite control effort while enhancing computational efficiency. Furthermore, these results exemplify the method's versatility when applied to nonlinear dynamic scenarios, directed network topologies, fluctuating disturbances, and optimization across multiple domains.

Distributed time-varying optimization control protocol for multi-agent systems via finite-time consensus approach

This paper addresses a distributed time-varying optimization problem with inequality constraints based on multi-agent systems over switching communication graphs. To reduce the influence of time-varying inequality constraints, an exact penalty method and smoothing technique are employed. Then, a Hessian-based distributed control protocol is presented to seek the time-varying optimal solution of the distributed time-varying optimization problem by virtue of only local information and interaction. It is shown that all agents not only achieve finite-time consensus but also track the time-varying global optimal target eventually. Compared with the existing distributed optimization protocols, the proposed control protocol is suitable for more general distributed time-varying optimization problems and enjoys high-efficiency convergence. Finally, numerical examples and experiment on moving target tracking of Unmanned Aircraft Vehicle (UAV) are performed to illustrate the effectiveness of the proposed control protocol.

Observer-based consensus of multi-agent systems under odd distributed impulsive control protocol

In this paper, for leader-follower Lipschitz nonlinear multi-agent systems (MASs) affected by external disturbances, observer-based distributed controller design problems are discussed in order to realize the MASs consensus. Firstly, to deal with unmeasured system states and the unknown disturbances, for each follower, a joint unknown input observer is proposed. To do so, through an interval observer, a mathematical relationship between the state and the disturbance is set up in advance. Secondarily, by using the estimations of the state and the disturbance, a local feedback controller is designed aiming at stabilizing the linear part of each follower. Thirdly, an odd distributed impulsive control method is proposed which is utilized to deal with the nonlinearity. Then the MASs consensus goal is realized by combining the local feedback controller and the distributed impulsive controller. At last, a simulation is discussed so as to display the effectivity of the raised scheme.

Global Reachability of Heterogeneous Multiagent Systems Under Collaborative Interaction Topology and Unknown Delays

The multi-agent rendezvous problem for single- and double-integrator agents in the presence of unknown constant input and communication delays is investigated in this paper. Existing works address the rendezvous problem by incorporating negative gain(s) into the distributed consensus protocol and showing that negative gain(s) expands the reachable set beyond the initial configuration of the agents' convex hull. On the contrary, the present control protocol ensures global reachability of a network of agents with a directed communication topology having non-negative edge weights. This is accomplished with the help of a dynamic distributed control protocol, where the information exchange among agents occurs in the internal controller states. For homogeneous delays, the analytical expression of the rendezvous point confesses the non-dependency of the point with delays, which in turn signifies that rendezvous can be achieved with unknown and arbitrarily large but bounded delays. The very structure of the control protocol ensures rendezvous at any desired point, even if the input delays are heterogeneous and unknown. However, heterogeneity in communication delays has an effect on the rendezvous point, and hence, global reachability of agents can be established if these delays are exactly known. For heterogeneous multi-agent systems composed of single- and double-integrator agents, tuning of the design parameters gets simplified due to the single-integrator based internal controller structure for all agents. Numerical simulations are provided to validate the robustness of the protocol against delays.

Observer‐based event‐triggered consensus control for multi‐agent systems with nonlinearity and unknown inputs

AbstractThis article investigates observer‐based consensus issues for a class of Lipschitz nonlinear multi‐agent systems (MASs) with unknown input. To address the challenges because of the unmeasurable states and the unknown input of each agent system, an interval observer is utilized to design an unknown input observer (UIO). The UIO possesses the capability of generating asymptotically the estimations of both the system states and unknown input simultaneously. Subsequently, a distributed control protocol scheme is put forwarded. The distributed controller for each agent is designed by using the state estimation and the unknown input reconstruction (UIR). The unknown input is compensated thanks for the introduction of the UIR into the controller, and thus leads to a better control performance. Besides, the event‐triggered strategy is also considered such that agents communicate with each other discontinuously. In this way, an observer‐based event‐triggered distributed control protocol scheme is developed, and under the scheme, the asymptotic convergent MASs consensus is accomplished. Finally, the effectiveness of the proposed methods is verified by a simulation example.

Resilient distributed secure consensus control for uncertain networked agent systems under hybrid DoS attacks

In this paper, the problem of resilient distributed secure consensus control for uncertain networked agent systems under hybrid denial-of-service (DoS) attacks is investigated. The current situation is that there exists a cyber layer connecting the network control units and a physical layer with specific physical links in the networked agent systems. Both the communication networks connecting the two layers and within the cyber layer may be attacked by DoS maliciously. These two attack scenarios have different impacts on the networked system. The former focuses on updating the control inputs timely, while the latter influences the connection weight of the cyber communication topology. Firstly, a distributed security consensus framework is proposed for the case that updates of signals are destroyed by DoS attacks between two layers, in which an acknowledgment (ACK)-based attack detection and a recovery mechanism are introduced, and a self-triggered based distributed control protocol is designed. On the premise of avoiding Zeno behavior, the relationship between trigger intervals and DoS attack characteristics is revealed. Secondly, corresponding asynchronous switching topology method is developed for secure consensus of the networked systems when DoS attacks are launched within the cyber layer. In addition, we found that large signals jump during switching and triggering will generate pulses and affect system stability. Therefore, a saturation function is introduced to constrain the fluctuation range of the signal. Finally, the effectiveness of the design scheme is verified by the simulation results of multi-robot systems.

Distributed adaptive time‐varying formation of multi‐UAV systems under undirected graph

AbstractIn this paper, a fully distributed control protocol is presented based on adaptive technology to solve the time‐varying formation problem of multi‐unmanned aerial vehicle (UAV) systems, where the coupling weights between neighbouring UAVs can be adjusted through adaptive method. Firstly, the proposed control protocol eliminates the need for global information on the interaction topology of multi‐UAV systems, the calculation of Laplacian matrix eigenvalues is avoided and reduces the computational complexity of the system. Secondly, an algorithm with two steps is proposed to determine the distributed adaptive control gain matrices, where the feasibility condition of time‐varying formation of multi‐UAV systems is given. Then, the closed‐loop stability of multi‐UAV systems is proved through Lyapunov theory. Finally, numerical simulation is conducted to verify the effectiveness of the theoretical results.

Strong reciprocal ratio consensus of modified second-order multi-agent systems with periodically time-varying topologies

The strong reciprocal ratio consensus problem of modified second-order discrete-time multi-agent systems (DTMASs) with periodically time-varying topologies is investigated. The strong reciprocal ratio consensus is a new consensus and covers the strong ratio average-consensus as a special case. Modified second-order DTMAS is a variant of second-order DTMAS. A distributed control protocol is designed to achieve the strong reciprocal ratio consensus and it is the first time that ratio strategy is combined with second-order DTMASs. Furthermore, our work covers several cases where dynamically changing topologies are directed or undirected, connected or disconnected, or even mixed patterns of connected and disconnected graphs.

Free-will arbitrary time consensus of heterogeneous nonlinear multi-agent systems

This paper addresses several kinds of free-will arbitrary time (FWAT) consensus problems for heterogeneous nonlinear multi-agent systems (MASs). For first-order MASs, both leaderless and leader-following FWAT consensus are studied. Based on the FWAT control technology, some novel distributed control protocols are proposed, under which FWAT consensus of first-order MASs is achieved within the arbitrary pre-specified time and maintained after then. Then, the backstepping method is employed to design the controller for second-order heterogeneous nonlinear MASs. FWAT consensus of second-order MASs can also be guaranteed by using the proposed controller. Finally, simulation examples are presented to illustrate the effectiveness of theoretical analysis.