Control Of Heterogeneous Multi-agent Systems Research Articles

Distributed bipartite output containment control of heterogeneous multi-agent systems with directed signed graphs

This paper investigates the bipartite output containment control problem by utilising distributed control protocols for heterogeneous multi-agent systems over directed signed graphs. A fully distributed dynamic compensator is proposed to estimate the convex hull and symmetric convex hull spanned by states of leaders. Then, a distributed observer based on neighbour information is presented for estimating the state of each follower. An output feedback control protocol is further given based on the fully distributed dynamic compensator and neighbour-based observer to cope with the bipartite containment control problem of the linear heterogeneous multi-agent systems. Different from the related works, a neighbour-based observer is presented for heterogeneous multi-agent systems, in which the analysis method used in the Luenburger observer cannot be applied directly, because of the heterogeneity. Besides, the dynamics of the agents are allowed to not only have nonidentical coefficient matrices but also have different dimensions. A simulation example is shown to verify the effectiveness of the proposed theoretical results.

Dynamic Event-Triggered Bipartite Output Consensus for Heterogeneous Multi-Agent Systems Under Signed Digraphs

In this brief, the bipartite output consensus (BOC) problem is studied by dynamic event-triggered control for heterogeneous multi-agent systems under signed digraphs. A novel fully distributed control protocol, containing an observer-based adaptive controller and a Zeno-free dynamic event-triggered mechanism (ETM), is provided to guarantee the asymptotic convergence of BOC errors. Notably, an internal dynamic variable is introduced in the ETM to prolong interevent time intervals, which further reduces consumption on transmission. In addition, it is worth pointing out that the provided protocol remains valid even if global information about signed digraphs is unavailable. Finally, a numerical example is taken to demonstrate the effectiveness of protocol.

Continuous Fixed-Time Fault-Tolerant Formation Control for Heterogeneous Multiagent Systems Under Fixed and Switching Topologies

This article proposes a novel continuous fixed-time fault-tolerant formation control framework for heterogeneous multiagent systems (HMASs) involving unmanned aerial vehicles (UAVs) and unmanned ground vehicles (UGVs) with actuator faults and model uncertainties under fixed and switching topologies. Firstly, to estimate the information of actuator faults and uncertainties for each follower, a fixed-time observer is constructed. Then, an integral fixed-time sliding mode surface is designed such that the merits of high robustness, exact transient response and fixed-time convergence can be achieved. Subsequently, based on the integration of disturbance observer, high-order sliding mode and backstepping technologies, distributed and decentralized continuous fixed-time formation tracking control schemes under actuator faults are developed of the HMASs in the X-Y axis and Z axis, respectively. The proposed algorithm can not only handle time-varying formation in a timely manner, but also provide continuous control action under fixed and switching topologies. It is theoretically proved that the designed protocol can realize the expected fixed-time formation missions by employing the Lyapunov stability theorem. Finally, simulation results verify the effectiveness of the designed fixed-time control algorithm.

Sliding mode fault-tolerant consensus control for heterogeneous multi-agent systems based on finite-time observer and controller

This paper mainly investigates the fault-tolerant consensus problem for leader-following heterogeneous multi-agent systems with actuator faults. The model of multi-agent systems is reconstructed and the lumped faults, including external disturbances and actuator faults, are constructed. A new adaptive super-twisting sliding mode observer (ASTSMO) is constructed to estimate the undetectable lumped faults. The time-varying gain is introduced to solve the initial error problem and peak value problem. Then, based on the estimated results, an integral terminal sliding mode controller (ITSMC) is designed by integrating the fixed-time stability theory, which can effectively eliminate the nonlinear term and lumped faults. Finally, simulations are provided to illustrate the effectiveness and benefits of the proposed theoretical results.

Fixed-Time and Prescribed-Time Fault-Tolerant Optimal Tracking Control for Heterogeneous Multiagent Systems

Fixed-Time and Prescribed-Time Fault-Tolerant Optimal Tracking Control for Heterogeneous Multiagent Systems

Fully Distributed Dynamic Event-Triggered Pinning Cluster Consensus Control for Heterogeneous Multiagent Systems With Cooperative–Competitive Interactions

In this article, the cluster consensus of heterogeneous multiagent systems is investigated via dynamic event-triggered and pining control strategies. Comprehensively considering the cooperative and competitive interactions among the agents, a novel cluster consensus control protocol is designed, and a class of fully distributed dynamic event-triggered laws that do not depend on the global information is proposed. Being distinct from the traditional static threshold value, a time-varying threshold value is introduced which can effectively reduce the trigger time. Meanwhile, some sufficient conditions are obtained theoretically by using Lyapunov stability theory and the pinning control strategy is addressed as well. Furthermore, it has also been shown that each agent can exclude Zeno behavior. Finally, two simulated examples are given to illustrate the correctness and validity of the proposed methods and our findings.

Multi-Agent Formation Control under Switching Network and Input Constraints

This work discusses formation control of heterogeneous Multi-Agent Systems (MASs) under discrete time setting where its formation size is scalable by a scaling factor. The case with and without input constraints are discussed. The communication network is assumed to be jointly connected and the leader-follower network is assumed for the unconstrained case. Compared to the previous work on distributed scalable formation control for heterogeneous agents, this work considers input constraints in the formulation. The proposed algorithm is based on the discrete time version of the internal model principle and the constraint is handled by the command governor. Numerical examples are shown to illustrate the proposed method.

Prescribed-Time Fault-Tolerant Control for Fully Actuated Heterogeneous Multiagent Systems: A Hierarchical Design Approach

The formation control of heterogeneous multi-agent systems that are subjected to actuator faults is addressed in this work. To prevent the spread of faults among agents, a hierarchical design approach is utilized. In the upper layer, distributed prescribed-time observers are presented to estimate the leader's trajectory for followers on directed graphs. In the lower layer, adaptive fault-tolerant controllers are provided for the heterogeneous multi-agent systems subjected to partial effectiveness loss faults based on the fully actuated system model. Contrary to the results of fault-tolerant control that are already in use, the proposed method enables formation errors to zero within a predetermined time that can be set freely. What's more, the estimated errors of efficiency factors are bounded. Finally, simulation results are provided to show the suggested protocol's availability.

Adaptive fault tolerant tracking control of heterogeneous multi-agent systems with non-cooperative target

In this paper, the problem of tracking a non-cooperative target by heterogeneous multi-agent systems(MASs) with actuator faults is studied. Since the target is non-cooperative, the system matrix of the target is unavailable. Hence, the existing results dealing with consensus problem of heterogeneous multi-agent based on known exosystem matrix are inapplicable. A neural-network-based adaptive observer is designed for estimating the output of the non-cooperative target. Then, a finite-time adaptive fault tolerant controller is developed to resolve the heterogeneous target tracking problem in the presence of actuator faults. The tracking errors can converge within finite time. The proposed controller is fully distributed, thereby no longer requiring the system matrix of the target and actuator fault rates of the tracking agents. Finally, the effectiveness of the developed strategies and the correctness of achieved stability conditions are verified by some numerical examples.

Distributed adaptive fixed-time formation control for UAV-USV heterogeneous multi-agent systems

This paper investigates formation trajectory tracking control for heterogeneous multi-agent systems with external disturbances, model uncertainties and input saturation. The system that is considered comprises one unmanned aerial vehicle (UAV) and multiple unmanned surface vessels (USVs). First, based on directed graph theory, a distributed formation control protocol is proposed for the UAV-USV heterogeneous multi-agent system. Second, combining the advantages of the adaptive technique and radial basis function (RBF) neural networks, a global fixed-time adaptive neural network nonsingular fast terminal sliding formation control protocol is designed to ensure tracking of the desired trajectory and form the predetermined formation configuration within a fixed time in the presence of various uncertainties. Through the proposed adaptive neural network (NN) control technology, the lumped uncertainty can be estimated, and the number of update parameters can be reduced, thereby relieving the calculation burden of the controllers. In addition, a dynamic event-triggered mechanism is incorporated into the controllers, which can reduce the update frequency of controllers, thereby decreasing the communication number of controllers. A saturation function is introduced simultaneously to solve the problem of input saturation. Finally, the simulation results are given to indicate the feasibility of the proposed formation control protocol.

Guest Editorial: Learning, optimisation and control of cyber‐physical systems

Guest Editorial: Learning, optimisation and control of cyber‐physical systems

Research on fault-tolerant consensus of heterogeneous multi-agent systems based on adaptive robust sliding mode observer

Abstract The fault-tolerant consensus control for heterogeneous multi-agent systems with actuator faults and external disturbances is studied in this paper. Firstly, considering the unknown actuator fault information and the influence of external disturbance on the observer, a robust sliding mode observer with adaptive laws modification was proposed to realize the actuator fault reconstruction. Secondly, a fault-tolerant controller is designed based on the reconstructed values obtained from the adaptive robust sliding mode observer, and the original heterogeneous complex dynamic high-dimensional system is converted into two low-dimensional closed-loop error systems by decoupling method. Furthermore, Lyapunov and Ricatti theories are used to obtain the controller gain solution method. Finally, a simulation experiment of fault-tolerant consensus control for heterogeneous multi-agent systems is carried out with one leading agent and four following agents, and the effectiveness and feasibility of the proposed method are verified.

Distributed Antiwindup Consensus Control of Heterogeneous Multiagent Systems Over Markovian Randomly Switching Topologies

The consensus control of multiagent systems (MASs) over randomly switching communication topologies has drawn increasing attention from researchers, since the mean square consensus or the most surely consensus is significant and practical. This manuscript focuses on the output consensus problem for heterogeneous MASs with input saturation constraints over the Markovian randomly switching topologies. The main challenge of solving the concerned problem lies in the interplay among the heterogeneous dynamics, input saturation constraints and the Markovian randomly switching topologies. To overcome such a challenge, a class of distributed adaptive observers is first designed for all agents to deal with the uncertainty caused by the randomly switching topologies. Then, a class of local state observers is presented for estimating each agent’s state information. Based on the above steps, a class of antiwindup controllers is constructed and the control gain matrices are selected using only the dynamics information of each node. Finally, the effectiveness of the consensus protocol is demonstrated.

Finite-time group consensus via pinning control for heterogeneous multi-agent systems with disturbances by integral sliding mode

In this paper, the finite-time group consensus for a class of heterogeneous multi-agent systems (HMASs) with bounded disturbances is studied by designing a pinning control scheme with an integral sliding mode. For an HMAS without disturbance, a continuous finite-time consensus protocol with a pinning and grouping strategy is proposed. Under the designed control protocol, the HMAS achieves consensus according to the given grouping requirement in a finite time and the final states converge to the desired consistency values. The detailed theoretical proof is given on the strength of Lyapunov theory, LaSalle’s invariance principle and homogeneity with dilation principle. On this basis, this paper further introduces an integral sliding mode into finite-time group consensus protocol designed above such that the HMAS with one or more pinning agents can achieve accurate finite-time group consensus even if there exist uncertain bounded disturbances. It is noted that the control input is chattering-free. Two simulation examples are presented to illustrate the effectiveness of the proposed control schemes.

Collaborative Optimal Formation Control for Heterogeneous Multi-Agent Systems

In this paper, the distributed optimal control method is used to study the cooperative formation of heterogeneous multi-agents in the air–ground environment. The considered system consists of an unmanned aerial vehicle (UAV) and an unmanned ground vehicle (UGV). The optimal control theory is introduced into the formation control protocol, the distributed optimal formation control protocol is designed, and the stability is verified by graph theory. Furthermore, the cooperative optimal formation control protocol is designed, and the stability is analyzed using a block Kronecker product and matrix transformation theory. Through the comparison of simulation results, the introduction of optimal control theory shortens the formation time of the system and accelerates the convergence speed of the system.

Approximate Output Regulation of Discrete-Time Stochastic Multiagent Systems Subject to Heterogeneous and Unknown Dynamics

The output regulation approach has been extensively applied for the cooperative control of heterogeneous multiagent systems (MASs) with known dynamics, but rarely for MASs subject to stochastic and unknown dynamics. One challenging problem is that it is still unclear how to construct the regulator equations of stochastic MASs with unknown dynamics for dynamic exosystem compensation. Toward this end, this article develops a novel distributed control scheme for the approximate output regulation of discrete-time stochastic MASs subject to heterogeneous and unknown nonlinear dynamics. A distributed observer is designed for the exosystem-state estimation of agents, based upon which nonlinear regulator equations are constructed for the feedforward control design, thereby achieving distributed exosystem compensation. A high-order neural network is deployed to approximately solve the nonlinear regulator equations with unknown nonlinearity, and an adaptive control law is developed for the approximate output regulation of discrete-time stochastic MASs. Stability analysis shows that the closed-loop system is semiglobally uniformly ultimately bounded. Simulation results demonstrate the effectiveness and efficiency of the proposed control law.

Consensus Problem and Formation Control for Heterogeneous Multi-Agent Systems with Switching Topologies

The cooperative control problem of discrete-time multi-agent systems (MASs) is discussed, and bounded uncertain time-delays and directed switching topologies are considered. By applying model transformations and matrix theory, an augmented system method is introduced to handle a heterogeneous time-delay MAS. Then, the consensus problem of the system is turned to the convergence issue of the product of innumerable row stochastic matrices. Sufficient conditions for asymptotic consensus of the system under directed switching topologies are obtained. Moreover, a novel consensus-based formation control strategy is designed to gain sufficient and necessary conditions for the formation control of a second-order differential robot system. Finally, the effectiveness of the obtained results is verified through simulations.

Adaptive Fault-Tolerant Formation Control of Heterogeneous Multi-Agent Systems under Directed Communication Topology.

This paper investigates the adaptive fault-tolerant formation control scheme for heterogeneous multi-agent systems consisting of unmanned aerial vehicles (UAVs) and unmanned surface vehicles (USVs) with actuator faults, parameter uncertainties and external disturbances under directed communication topology. Firstly, the dynamic models of UAVs and USVs are introduced, and a unified heterogeneous multi-agent system model with actuator faults is established. Then, a distributed fault-tolerant formation controller is proposed for the unified model of UAVs and USVs in the plane by using adaptive updating laws and radial basis function neural network. After that, a decentralized formation-tracking controller is designed for the altitude control system of UAVs. Based on the Lyapunov stability theory, it can be proved that the formation errors and tracking errors are uniformly ultimately bounded which means that the expected time-varying formation is achieved. Finally, a simulation study is given to demonstrate the effectiveness of the proposed scheme.

Heterogeneous Multiagent Systems With Different Fractional Order: An Experience-Based Fusion Controller

Cooperation control of heterogeneous multi-agent systems (MASs) with different fractional order subject to intermittent sampled-data transmission is investigated in this brief. Existing works considering MASs with multiple fractional order mainly focus on continuous input with frequency domain analysis and their results are thus based on sophisticated characteristic equations. Instead, inspired by the memory retention property of Caputo fractional derivative, heterogeneous experience-based fusion controllers are devised to handle the hereditary effect based on time domain analysis. The devised fusion controllers are composed of intermittent sampled data, which not only incorporate current available samplings but also include earlier experience of agents. In addition, the fusion controllers can successfully transform MASs with different fractional order into general discrete-time plants at sampling instants, and at the same time, ensure the asymptotical stability of sampling errors as well as controllers besides those sampling instants. Thereby, the achievement of consensus only relates to the connectivity of communication graph. Effectiveness of theoretical results is substantiated finally by numerical examples.

Adaptive fully distributed anti-disturbance containment control for heterogeneous multi-agent systems

This paper studies the output containment control problem for heterogeneous multi-agent systems subject to unknown time-varying disturbances by designing fully distributed anti-disturbance control protocols. Fully distributed observers are designed to estimate convex combination of leader states, which are independent of any global information including global leaders' dynamics and global graph. There are external disturbances to contaminate the control inputs of the followers, which may damage the cooperation of the systems. Then adaptive anti-disturbance compensators are designed to eliminate the adverse effects of the external disturbances. Based on the proposed fully distributed observers and adaptive anti-disturbance compensators, adaptive anti-disturbance containment control protocols are provided to ensure that the output trajectories of each follower can converge to the dynamic convex hull spanned by the leader outputs. Finally, a numerical example and a practical example of heterogeneous mobile vehicles are given to demonstrate the effectiveness of the proposed method.