Output Consensus Tracking of Heterogeneous Open Multiagent Systems Under Actuator Attacks

Adaptive output containment control of heterogeneous multi-agent systems with unknown leaders

Purpose This paper proposes an adaptive distributed observer-based optimal control protocol designed to tackle the challenges posed by unavailable state information, without relying on global information, while ensuring optimal system performance in heterogeneous multi-agent systems. The purpose of this paper is to achieve distributed output tracking control under these constraints. Design/methodology/approach An adaptive distributed observer using single adaptive and local static gains estimates leader’s output. A feedback-feedforward control policy is designed for optimal tracking. Unlike conventional methods, this reduces communication load and broadens applications when leader’s state is unmeasurable. Findings A numerical simulation example related to autonomous ground vehicle is given to demonstrate that the proposed control algorithm can ensure output tracking in heterogeneous multi-agent systems. Research limitations/implications Although the proposed algorithm can effectively guarantee output tracking, further research is needed to design an optimal controller for model-free system dynamics in unknown environments. Practical implications The proposed method can be implemented for formation control of multi-robot systems since each robot can measure the relative output information, thereby effectively overcoming the limitation of unavailable system states. Originality/value This paper introduces a novel adaptive distributed observer-based optimal control protocol for heterogeneous multi-agent systems, uniquely relying on a single adaptive gain and local output information, eliminating the need for global network data. This reduces communication overhead and enhances applicability in scenarios where the leader’s state is unmeasurable. Unlike existing methods, it integrates optimal tracking control via the Bellman equation, considering transient performance. Its value lies in practical implementation for multi-robot formation control, though limitations include the need for further research into model-free systems in unknown environments.

In this article, a model-free-adaptive-control-based (MFAC-based) event-triggered (ET) consensus output tracking problem for multiagent systems (MASs) is investigated. The dynamic models of agents are unknown, and only a subset of agents can acquire the reference trajectory. The consensus tracking algorithm is designed by the real-time input/output data and pseudo-partial-derivative (PPD), which is an important parameter of MFAC approach. An output observer is built to design the centralized ET mechanism. Then, the boundedness analysis that the tracking error is uniformly ultimately bounded (UUB) is given. Finally, a simulation experiment is provided to verify the feasibility of the ET consensus output tracking strategy for MASs.

In this paper, the problem of formation control of heterogeneous multi-agent systems is investigated. The heterogeneous multi-agent system is composed of first-order and second-order agents, where the second-order agents cannot obtain the velocity information. Firstly, without considering the input saturation, the distributed formation control protocols are designed for multi-agent systems with static leader and active leader respectively. By using Lyapunov stability theory and LaSalle's invariance principle, the protocols are proved to be effective. Then due to the actor saturation, the formation protocols for multi-agent systems with input saturation based on distributed observers and auxiliary systems are presented. Finally, the simulation results are given to illustrate the effectiveness of the proposed protocols.

SummaryThis paper studies the bipartite output synchronization problem of general linear heterogeneous multiagent systems on signed digraphs. We first show that, for heterogeneous multiagent systems, the bipartite output synchronization over the structurally balanced signed digraphs and the conventional output synchronization over the associated nonnegative digraphs are equivalent. Then, 3 different control protocols, using full‐state feedback, static output feedback, and dynamic output feedback are designed at each agent to solve the bipartite output synchronization problem based on solutions to the corresponding output regulator equations. Explicit local design procedures are proposed for all 3 control protocols. The compensators employed in these protocols incorporate only one copy of the virtual exosystem's dynamics, regardless of the dimensions of the outputs. This results in lower‐dimensional compensators and controllers and, hence, is more computationally tractable compared to the popular internal model principle‐based control protocols. Numerical simulations over 3 different signed communication digraphs validate the proposed control protocols.

A periodic intermittent adaptive control method with saturation is proposed to pin the quasi-consensus of nonlinear heterogeneous multi-agent systems with external disturbances in this paper. A new periodic intermittent adaptive control protocol with saturation is designed to control the internal coupling between the follower agents and the feedback gain between the leader and the follower. In particular, we use the saturation adaptive law: when the quasi-consensus error converges to a certain range, the adaptive coupling edge weight and the adaptive feedback gain will not be updated. Furthermore, we propose three saturated adaptive pinning control protocols. The quasi-consensus is achieved through its own pinning as long as the agents remain connected to each other. Using the Lyapunov function method and inequality technique, the convergence range of the quasi-consensus error of a heterogeneous multi-agent system is obtained. Finally, the rationality of the proposed control protocol is verified through numerical simulation. Theoretical derivation and simulation results show that the novel proposed periodic intermittent adaptive control method with saturation can successfully be used to achieve the pinning of quasi-consensus of nonlinear heterogeneous multi-agent systems.

Scaled consensus control of heterogeneous multi-agent systems with switching topologies

In this paper, we develop an adaptive control algorithm for addressing security for a class of networked vehicles that comprise n human-driven vehicles sharing kinematic data and an autonomous vehicle in the aft of the vehicle formation receiving data from the preceding vehicles by wireless vehicle-to-vehicle communication devices. Specifically, we develop an adaptive controller for mitigating time-invariant, state-dependent adversarial sensor and actuator attacks while guaranteeing uniform ultimate boundedness of the closed-loop networked system. The effectiveness of the proposed approach is demonstrated by an illustrative numerical example involving a platoon of connected vehicles.

In this paper, we develop a novel distributed adaptive control architecture for addressing networked multiagent systems subject to stochastic exogenous disturbances with compromised sensor and actuators. Specifically, for a class of linear leader-follower multiagent systems, we develop a new structure of the neighborhood synchronization error for the control design protocol of each follower. The proposed control algorithm addresses time-varying multiplicative sensor attacks on the leader state measurements. In addition, the framework addresses time-varying multiplicative actuator attacks on the followers that do not have a communication link with the leader and additive actuator attacks on all follower agents in the network. The proposed adaptive controller guarantees uniform ultimate boundedness of the state tracking error for each agent in a mean-square sense.

ABSTRACTIn this paper, we develop a novel distributed adaptive control architecture for addressing networked multiagent systems subject to stochastic exogenous disturbances with compromised sensor and actuators. Specifically, for a class of linear leader–follower multiagent systems, we develop a new structure of the neighbourhood synchronisation error for the control design protocol of each follower. The proposed control algorithm addresses time-varying multiplicative sensor attacks on the leader state measurements. In addition, the framework addresses time-varying multiplicative actuator attacks on the followers that do not have a communication link with the leader and additive actuator attacks on all follower agents in the network. The proposed adaptive controller guarantees uniform ultimate boundedness of the state tracking error for each agent in a mean-square sense.

This article is concerned with achieving resilient consensus for multi-agent systems under cyber attacks. Without loss of generality, we consider a leader-following multi-agent system where each agent is modeled with a Lipschitz nonlinear model, and the actuator attacks are imposed on agents’ states. To begin with, an adaptive observer is constructed to estimate the attacks for each follower based on relative output errors with respect to its neighbors and the leader. The global error system is proved to be asymptotically stable. Moreover, a resilient consensus control protocol is proposed for each follower where the guaranteed-performance is considered. Under this control protocol, the impact of the attack is compensated and the state of each agent is consistent. Different from the existing secure control scheme, the new one can simultaneously resist multiple types of attacks. Finally, simulation results are given to verify the effectiveness of attack estimation and resilient consensus control protocol for multi–unmanned aerial vehicle systems.

In this paper, a model-free reinforcement learning (RL) based distributed control protocol for leader-follower multi-agent systems is presented. Despite successful utilization of RL for learning optimal control protocols in multi-agent systems, the effects of the adversarial inputs are neglected in existing results. The susceptibility of the standard synchronization control protocol against adversarial inputs is shown. Then, a RL-based distributed control framework is developed for multi-agent systems to stop corrupted data of a compromised agent from propagating across the network. To this end, only the leader communicates its actual sensory information and other agents estimate the leader state using a distributed observer and communicate this estimation to their neighbors to reach consensus on the leader state. The observer cannot be physically changed by any adversarial input. Therefore, it guarantees that all intact agents synchronize to the leader trajectory except compromised agent. A distributed control protocol is used to further enhance the resiliency by attenuating the effect of the adversarial inputs on the compromised agent itself. An off-policy RL algorithm is developed to solve the output synchronization control problem online and using only measured data along the system trajectories.

This paper addresses the edge-consensus problem in a directed nodal network, where each edge is described by uncertain fractional-order dynamics subject to positivity constraints. To solve the issues of positivity and consensus in uncertain fractional-order networked systems (UFONSs) with the order 0 < <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> ≤ 1, a distributed control protocol by virtue of state feedback is designed. Some sufficient criteria are established to ensure positive edge-consensus of UFONSs. Subsequently, to handle scenarios with unmeasurable states in practical systems, an observer-based control protocol is proposed to achieve positive edge-consensus for UFONSs. Furthermore, by leveraging the fractional-order stability theory and the properties of positive systems, some sufficient positive edge-consensus conditions that depend only on the number of edges and nodes are formulated instead of the global information of the network. Finally, two simulation examples are shown to verify the feasibility of the proposed protocols.

An observer-based piezoelectric control of flexible Cartesian robot arms: theory and experiment

This paper studies the bipartite consensus of multiagent systems (MASs) with a multi-rate sampling mechanism under detail-balanced antagonistic interactions. A multi-rate sampling mechanism is introduced to sample the system output variables asynchronously. Moreover, a sensor buffer is utilized for storing an agent’s asynchronous output variables and broadcasting its information to the communication network, which is represented by a detail-balanced directed graph. An observer-based distributed control protocol using the information from the corresponding sensor buffer is constructed to guarantee the bipartite consensus of MASs. A numerical simulation is offered to illustrate the validity of the proposed scheme.