Leader-following Consensus Protocol Research Articles

Optimal rejection of bounded perturbations in linear leader-following consensus protocol: invariant ellipsoid method

Optimal rejection of bounded perturbations in linear leader-following consensus protocol: invariant ellipsoid method

Output Feedback-Based Consensus for Nonlinear Multiagent Systems: The Event-Triggered Communication Strategy.

The current investigation explores the leader-following consensus problem for nonlinear multiagent systems under the output feedback control mechanism and the event-triggered communication mechanism. Owing to the physical instrument constraints, a significant portion of the state variables is not readily available. Therefore, this article put forward a distributed event-based leader-following consensus protocol only using agents' relative output measurements and underlying neighbors. Furthermore, this article develops two event-triggered mechanisms simultaneously, one is the event-triggered communication mechanism in the sensor-to-controller channel, and another is the event-triggered controller update in the controller-to-actuator track. Besides that, it is proven that the developed event-triggered control protocol can settle the leader-following consensus problem of the nonlinear multiagent systems, and the Zeno behavior is excluded in both the channels. Finally, we perform two simulation examples to illustrate the efficacy of the obtained results.

Distributed Nash Equilibrium Seeking Strategies Under Quantized Communication

This paper is concerned with distributed Nash equilibrium seeking strategies under quantized communication. In the proposed seeking strategy, a projection operator is synthesized with a gradient search method to achieve the optimization of players' objective functions while restricting their actions within required non-empty, convex and compact domains. In addition, a leader-following consensus protocol, in which quantized information flows are utilized, is employed for information sharing among players. More specifically, logarithmic quantizers and uniform quantizers are investigated under both undirected and connected communication graphs and strongly connected digraphs, respectively. Through Lyapunov stability analysis, it is shown that players' actions can be steered to a neighborhood of the Nash equilibrium with logarithmic and uniform quantizers, and the quantified convergence error depends on the parameter of the quantizer for both undirected and directed cases. A numerical example is given to verify the theoretical results.

Distributed Observer-Based Leader-Follower Consensus of Multiple Euler-Lagrange Systems.

This article investigates the leader-follower consensus problem of multiple Euler-Lagrange (EL) systems, where each agent suffers uncertain external disturbances, and the communication links among agents experience faults. Besides, we consider a more general case that only a portion of followers can measure partial components of leader's output and access the dynamic information of leader. The main idea of solving the consensus problem in this article is proceeded in two steps. First, we design an adaptive distributed observer to estimate the full state information of leader in real time with resilience to communication link faults. Second, based on the proposed distributed observer, we propose a proportional-integral (PI) control protocol for each agent to track the trajectory of leader, which is model-independent and robust to uncertain external disturbances. Distinct from the existing leader-follower consensus protocols of multiple EL systems, the proposed distributed observer-based PI consensus protocol in this article is model-independent, which is irrelevant to the structures or features of EL system model. Finally, we present a simulation example to show the resilience of the above adaptive distributed observer and the robustness of the distributed observer-based consensus protocol.

Fixed-time consensus-based distributed Nash equilibrium seeking for noncooperative game with second-order players

This paper aims to study the Nash equilibrium (NE) seeking algorithm of noncooperative game with second-order system under strongly connected digraph. In the algorithm, velocity information is not directly accessible to players, in order to avoid the need for additional velocity observers. Meanwhile, for position information, the position estimation of all the other players under local communication is completed in fixed time. To address the aforementioned concern, a NE seeking algorithm with a two-time-scale structure is designed. (1) For reduced system, a second-order velocity estimation model based on state observer is introduced to avoid direct acquisition of velocity information; (2) For fast compensation mechanism, each player uses leader-following consensus protocol to estimate the position of all the other players. The fixed-time consensus protocol is utilized to ensure that the position is estimated in fixed time. Then, aiming to reduce the communication costs and communication burden among players, the event-triggered mechanism is introduced into the above algorithm, and Zeno behavior is excluded. Lastly, a self-organized network problem involving autonomous vehicles is presented to validate the efficacy of the proposed theoretical results.

Distributed Nash Equilibrium Seeking for Multicluster Game Under Switching Communication Topologies

In this article, we investigate the distributed Nash equilibrium (NE) seeking problem for the multi-cluster game under switching communication topologies. Specifically, the communication topology switches between a group of jointly connected digraphs. First, a new distributed NE seeking algorithm for the multi-cluster games is designed by the consensus protocol and gradient play rule under the switching communication topologies. Furthermore, in order to make the algorithm still applicable when the agent only knows part of the decision information, the leader-following consensus protocol is used to generate the estimates for all agents action in the cluster under the assumption that the switching topology between clusters is directed and strongly connected. A more general NE seeking algorithm for the multi-cluster games is designed. For these two algorithms, the results of local convergence and non-local convergence are given, respectively. Two examples verify the validity of the theoretical results.

Robust Formation Control Based on Leader-Following Consensus in Multi-Agent Systems With Faults in the Information Exchange: Application in a Fleet of Unmanned Aerial Vehicles

In this paper, a robust leader-following consensus protocol for multi-agent systems (MASs) subject to faults in the information exchange and disturbance is presented. The problem under consideration is to guarantee the convergence of the agent trajectories to a leader agent when all the agent followers are under faults in the information exchange as smooth time-varying delays and disturbances. The main contribution in this paper is the design of a robust leader-following control through the Lyapunov approach and an optimal \mathscr H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> criterion such that all agents follow a virtual leader agent despite faults in the information exchange and disturbances. Linear matrix inequalities (LMIs)-based conditions are obtained whose solution allows computing the robust controller gain. In order to show the effectiveness of the proposed approach, numerical examples are carried out comparing a state-of-the-art approach and the proposed strategy in a fleet of unmanned aerial vehicles (UAVs) subject to wind turbulence which are shown to achieve the formation control.

Event/Self-Triggered Consensus Control of Multiagent Systems With Undesirable Sensor Signals.

This article focuses on event-triggered consensus control for multiagent systems subject to sensor faults or noises. First, a descriptor state observer with a low-pass filtering characteristic being developed for each agent using output information. The convergence regions of estimation errors can be reduced by a nonsingular suppression matrix. Leader-follower event-triggered consensus protocols with continuous-time communication are designed for multiagent systems based on the estimated states. By virtue of the Jordan form of the Laplacian matrix, the stability conditions are derived by using the Lyapunov analysis. Then, new self-triggered consensus protocols are designed for the multiagent systems to remove the requirement of the continuous monitoring triggering condition and continuous communication simultaneously. The triggering interval is proved greater than 0, and the Zeno behavior is excluded for all agents. Finally, numerical simulations are conducted to demonstrate the effectiveness of the proposed design.

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.

Distributed Nash equilibrium seeking for networked games of multiple high-order systems with disturbance rejection and communication delay

This paper investigates distributed Nash equilibrium seeking problems for networked games played by multiple high-order systems with disturbance rejection and communication delay, where each player’ payoff function is determined by all players’ actions. To be specific, a fixed-time disturbance observer is used to enhance the capacity of disturbance rejection. In virtue of the observed values, the backstepping technique is performed to design a seeking strategy on the basis of a synthesis of a leader–follower consensus protocol and the gradient play technique, where a fixed-time differentiator is used to overcome the problem of ‘explosion of terms.’ Detailed stability analysis is conducted via the Lyapunov–Krasovskii method to show the convergence of the players’ actions to the Nash equilibrium under both constant and time-varying delays. Moreover, the relationship between the allowed upper bound of the communication delay and the controller parameters is also obtained analytically. Finally, numerical simulations are presented to demonstrate the effectiveness of the proposed seeking algorithms.

Non-fragile guaranteed-performance [formula omitted] leader-following consensus of Lipschitz nonlinear multi-agent systems with switching topologies

In this paper, the problem of non-fragile guaranteed-performance H∞ leader-following consensus protocol design for high-order multi-agent systems with Lipschitz nonlinearities and switching topologies is investigated. The communication interactions among all agents are described by a set of switching directed graphs, whose union contains a directed spanning tree rooting at the leader node. By constructing a nonsingular transformation, leader-following consensus of the concerned multi-agent system is transformed into the problem of asymptotic stability analysis for some consensus error systems. Taking into account the existences of exogenous disturbances in practical agent systems and gain perturbations in physical controller implementations, the non-fragile H∞ criterion is introduced not only to design the consensus protocol which is capable of tolerating some level of parametric uncertainties, but also to make the consensus error system asymptotically stable with a prescribed H∞ disturbance attenuation level. To regulate the consensus performance, a quadratic function collecting consensus errors among in-neighboring agents is proposed. By employing tools from algebraic graph theory and Lyapunov functional technique, sufficient conditions on the desired consensus protocol design are derived in terms of linear matrix inequalities. Simulation illustrates the effectiveness of the theoretical results.

Distributed fixed time super-twisting sliding mode leader–follower tracking protocol design for nonlinear networked flexible joint robots

A fixed time super-twisting sliding mode controller is proposed for the leader–follower consensus protocol of a canonical high order affine nonlinear multi-agent system (MAS), in this paper. The proposed methodology is designated to reach the leader–follower consensus in determined convergence time independent of any initial conditions. The focal features of the proposed methodology are as: (1) the robustness of the MAS in presence of both the uncertainties and the external disturbances, (2) the stability of the closed loop MAS in sense of Lyapunov, (3) the finite time tracking of the leader by the followers, (4) the convergence of the sliding surface to zero in finite time, and (5) the chattering reduction. Simulation results perform to authenticate the efficiency of the presented approach.

Predictor-Based Extended-State-Observer Design for Consensus of MASs With Delays and Disturbances

In this paper, we study output feedback leader-follower consensus problem for multiagent systems subject to external disturbances and time delays in both input and output. First, we consider the linear case and a novel predictor-based extended state observer is designed for each follower with relative output information of the neighboring agents. Then, leader-follower consensus protocols are proposed which can compensate the delays and disturbances efficiently. In particular, the proposed observer and controller do not contain any integral term of the past control input and hence are easy to implement. Consensus analysis is put in the framework of Lyapunov-Krasovskii functionals and sufficient conditions are derived to guarantee that the consensus errors converge to zero asymptotically. Then, the results are extended to nonlinear multiagent systems with nonlinear disturbances. Finally, the validity of the proposed design is demonstrated through a numerical example of network-connected unmanned aerial vehicles.

A novel hierarchical control strategy combined with sliding mode control and consensus control for islanded micro‐grid

In order to improve the control effect on voltage and frequency of each distributed energy resource (DER) and improve the stability of the islanded micro-grid, a novel hierarchical control strategy combined sliding mode control (SMC) and consensus control is proposed in this study. The control structure is divided into two layers: the physical layer and the cyber layer. In the physical layer, in order to improve the dynamic control effect, an improved droop control based on consensus theory with considering packet loss is proposed in this study. And the control can be completed in finite time by selecting the approximate parameters in the controller; in order to improve the stability of voltage loop and current loop, an improved double closed-loop structure based on the SMC is proposed. Moreover, the control can also be completed in the finite time. In the cyber layer, an event-triggered SMC-virtual leader-following consensus protocol is proposed in this study to solve the problem of channel noise (disturbance). For improving the control effect, the protocol is used to complete the secondary control on voltage and frequency of each DER. Finally, the effectiveness of the novel control strategy is verified by simulation results.

Third-order leader-following consensus protocol of traffic flow formed by cooperative vehicular platoons by considering time delay: constant spacing strategy

In this article, the problem of third-order consensus of homogeneous traffic flow formed by cooperative vehicular platoons is studied. This article is presented in two main parts. Inter-platoon sta...

A new virtual leader-following consensus protocol to internal and string stability analysis of longitudinal platoon of vehicles with generic network topology under communication and parasitic delays

In this paper, a new virtual leader following consensus protocol is introduced to perform the internal and string stability analysis of longitudinal platoon of vehicles under generic network topology. In all previous studies on multi-agent systems with generic network topology, the control parameters are strictly dependent on eigenvalues of network matrices (adjacency or Laplacian). Since some of these eigenvalues are complex, the stability analysis with the presented methods is very hard or even impossible for large scale or time-varying networks. A new approach is introduced in this paper to decouple the large dimension closed-loop dynamics to individual third-order linear differential equations. A new spacing policy function assuring safety and increasing the traffic capacity is introduced to adjust the inter-vehicle spacing. The stable regions of communication and parasitic delays are calculated by employing the cluster treatment characteristic roots (CTCR) method. In addition to internal stability, it will be shown that the presented approach guarantees the string stability of generic vehicular networks. The most important privilege of the presented method compared with the previous approaches, is that the control gains are independent on network structure. This new finding, simplifies the stability analysis and control design specially for large scale platoons and time-varying networks. Several simulation results are provided to show the effectiveness of the proposed approaches.

Distributed Nash Equilibrium Seeking in Multiagent Games Under Switching Communication Topologies.

This paper investigates distributed Nash equilibrium seeking in multiagent games under switching communication topologies. To be specific, the communication topology is supposed to be switching among a set of strongly connected digraphs, which might suffer from occasional loss of communication due to sensor failure, packet loss, etc. The synthesis of the leader-following consensus protocol and the gradient play is exploited to achieve the distributed Nash equilibrium seeking under the switching communication topologies. Switching topology without loss of communication is firstly considered, followed by switching topology subject to missing communication within some time slots. For both situations, nonquadratic and quadratic games are addressed separately. Local convergence results are presented for nonquadratic games and nonlocal convergence results are provided for quadratic games. The theoretical results are verified by numerical examples.

Distributed Torque Control of Deloaded Wind DFIGs for Wind Farm Power Output Regulation

In this work, we propose a distributed control methodology that solves the problem of dispatching and regulating the power outputs of a group of deloaded wind double-fed induction generators (DFIGs) to attain fast, dynamic, and efficient wind farm power output regulation, with fair load-sharing among the DFIGs. In this context, fair load-sharing means that the ratio defined by the mechanical power over the maximum power from the wind, i.e., the utilization level, of all DFIGs, is the same in the steady state. Dynamic distributed dispatch and control of the power outputs of DFIGs refers to their ability to self-dispatch and regulate their power outputs under dynamical conditions and through peer-to-peer information exchange. Initially, we propose a leader-follower consensus protocol that DFIGs can adopt into their control system to attain: 1) asymptotic consensus on their utilization levels (i.e., fair load-sharing), and 2) total power output regulation. Then, we perform compositional stability analysis and prove that the protocol asymptotically converges under sufficient conditions. Finally, we design a distributed control-Lyapunov-function-based torque controller for the rotor-side converter that realizes the protocol in practice. The performance of the distributed control methodology is evaluated through numerical simulations on the modified IEEE 24-bus RT system.

Modified leader-following consensus of time-delay multi-agent systems via sampled control and smart leader

In this paper, the consensus problems of multiple agents with continuous-time single-integrator dynamics are studied, where each agent can obtain the position data of its neighboring agents at discrete-time points by using the periodic sampling technology and zero-order hold circuit. The smart leader is introduced, which can adjust the interaction strength between itself and the target point according to the state errors between itself and its neighboring followers. The modified leader-following consensus problem is defined as the leader-following consensus problem when the smart leader is adopted. Different leader-following consensus protocols are obtained for the multi-agent systems with or without sampling delays. The theoretical results, which are analysed with Lyapunov stability theory, can decrease the tracking error of the system, especially for the multi-agent systems with disturbance generated by actuator faults. Some simulation examples and real experiments are presented for illustration.

Distributed Nash Equilibrium Seeking by a Consensus Based Approach

In this paper, Nash equilibrium seeking among a network of players is considered. Different from many existing works on Nash equilibrium seeking in non-cooperative games, the players considered in this paper cannot directly observe the actions of the players who are not their neighbors. Instead, the players are supposed to be capable of communicating with each other via an undirected and connected communication graph. By a synthesis of a leader-following consensus protocol and the gradient play, a distributed Nash equilibrium seeking strategy is proposed for the non-cooperative games. Analytical analysis on the convergence of the players' actions to the Nash equilibrium is conducted via Lyapunov stability analysis. For games with non-quadratic payoffs, where multiple isolated Nash equilibria may coexist in the game, a local convergence result is derived under certain conditions. Then, a stronger condition is provided to derive a non-local convergence result for the non-quadratic games. For quadratic games, it is shown that the proposed seeking strategy enables the players' actions to converge to the Nash equilibrium globally under the given conditions. Numerical examples are provided to verify the effectiveness of the proposed seeking strategy.