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Originally, protocols were designed for multi-agent systems (MAS) using information about the network which might not be available. Recently, there has been a focus on scale-free synchronization where the protocol is designed without any prior information about the network. As long as the network contains a directed spanning tree, a scale-free protocol guarantees that the network achieves synchronization. If there is no directed spanning tree then synchronization cannot be achieved. But what happens when these scale-free protocols are applied to such a network where the directed spanning tree no longer exists? This paper establishes that the network decomposes into a number of basic bicomponents which achieves synchronization among all nodes in this basic bicomponent. On the other hand, nodes which are not part of any basic bicomponent converge to a weighted average of the synchronized trajectories of the basic bicomponents. The weights are independent of the initial conditions and are independent of the designed protocol., Comment: The article was submitted to IEEE Transactions on Automatic Control at March 27th, 2024. Now, this updated version is the one re-submitted at October 7th, 2024 for second-round review

This paper provides necessary and sufficient conditions for the existence of solutions to the state synchronization problem of homogeneous multi-agent systems (MAS) via scale-free linear dynamic non-collaborative protocol for both continuous- and discrete-time. These conditions guarantee for which class of MAS, one can achieve scale-free state synchronization. We investigate protocol design with and without utilizing local bounds on neighborhood. The results show that the availability of local bounds on neighborhoods plays a key role., Comment: This paper was submitted to IJRNC on Aug. 3, 2023 and resubmitted on June 15, 2024. Now, it is under review at the fifth round

This paper aims to achieve scalable exact output and regulated output synchronization for discrete-time multi-agent systems in presence of disturbances and measurement noise with known frequencies. Both homogeneous and heterogeneous multi-agent systems are considered, with parts of agents' states accessible in the latter case. The key contribution of this paper is on the distributed protocol that only uses the information of agent models, rather than the communication network information and the agent number, so as to achieve the scalable exact synchronization under disturbances and measurement noise. The validity of the protocol is verified by numerical simulations with arbitrarily chosen number of agents., Comment: This paper was submitted to International Journal of Robust and Nonlinear Control at Feb. 19, 2023, and obtained the recommendation of "resubmitting" at Aug. 23, 2023. Now, the authors are in the process of revising based on comments from the Referees

In this paper, we study scalable $\delta-$level coherent state synchronization for multi-agent systems (MAS) where the agents are subject to bounded disturbances/noises. We propose a scale-free framework designed solely based on the knowledge of agent models and agnostic to the communication graph and the size of the network. We define the level of coherency for each agent as the norm of the weighted sum of the disagreement dynamics with its neighbors. The objective is to restrict the network's coherency level to $\delta$ without a-priori information about the disturbance., Comment: 25 pages, 15 figures, This is a preprint of the paper "Scalable {\delta}-Level Coherent State Synchronization of Multi-Agent Systems with Adaptive Protocols and Bounded Disturbances" submitted to the International Journal of Adaptive Control & Signal Processing

In this paper, we have focused on identifying a class of continuous- and discrete-time MAS for which a scale-free non-collaborative (i.e., scale-free fully distributed) linear protocol design is developed. We have identified conditions on agent models that enable us to design scalable linear protocols. Moreover, we show that these conditions are necessary if the agents are single input and single output. We also provide a complete design of scalable protocols for this class., Comment: This paper was accepted for publish to IEEE Transactions on Automatic Control at Vol. 69, Issue 5, 2024

This paper studies global regulated state synchronization of discrete-time double-integrator multi-agent systems subject to actuator saturation by utilizing localized information exchange. We propose a scale-free linear protocol that achieves global regulated state synchronization for any network with arbitrary number of agents and arbitrarily directed communication graph that has a path between each agent and exosystem which generates the reference trajectory., Comment: This paper was submitted to 2023 Chinese Control and Decision Conference (CCDC), Yichang, China. arXiv admin note: substantial text overlap with arXiv:2204.02129

This paper studies scalable global state synchronization of discrete-time double integrator multi-agent systems in presence of input saturation based on localized information exchange. A scale-free collaborative linear dynamic protocols design methodology is developed for discrete-time multi-agent systems with both full and partial-state couplings. And the protocol design methodology does not need any knowledge of the directed network topology and the spectrum of the associated Laplacian matrix. Meanwhile, the protocols are parametric based on a parameter set in which the designed protocols can guarantee the global synchronization result. Furthermore, the proposed protocol is scalable and achieves synchronization for any arbitrary number of agents., Comment: This article is the complete version of the paper that was accepted by CCC 2022, Hefei China, July 25th-28th, 2022. arXiv admin note: text overlap with arXiv:1908.06535, arXiv:2004.13479

This paper studies scale-free protocol design for H_\infty almost output and regulated output synchronization of heterogeneous multi-agent systems with linear, right-invertible, and introspective agents in presence of external disturbances. The collaborative linear protocol designs are based on localized information exchange over the same communication network, which do not require any knowledge of the directed network topology and spectrum of the associated Laplacian matrix. Moreover, the proposed scale-free protocols achieve H_\infty almost synchronization with a given arbitrary degree of accuracy for any size of the network., Comment: This paper is the extended version of the paper accepted at 2021 CCC Conference. arXiv admin note: substantial text overlap with arXiv:2006.01890, arXiv:2012.14032

This paper presents a method for controlling the voltage of inverter-based Microgrids by proposing a new scale-free distributed cooperative controller. The communication network is modeled by a general time-varying graph which enhances the resilience of the proposed protocol against communication link failure, data packet loss, and fast plug and play operation in the presence of arbitrarily communication delays. The proposed scale-free distributed cooperative controller is independent of any information about the communication system and the size of the network (i.e., the number of distributed generators). The stability analysis of the proposed protocol is provided. The proposed method is simulated on the CIGRE medium voltage Microgrid test system. The simulation results demonstrate the feasibility of the proposed scale-free distributed nonlinear protocol for regulating the voltage of Microgrids in presence of communication failures, data packet loss, noise, and degradation., Comment: A version of this paper is submitted to IEEE Transactions on Power Systems Journal

In this paper, we study scale-free state synchronization of discrete-time homogeneous multi-agent systems (MAS) subject to unknown, nonuniform, and arbitrarily large communication delays. The scale-free protocol utilizes localized information exchange and is designed solely based on the knowledge of the agents' model and does not require any information about the communication network and the size of the network (i.e. number of agents)., Comment: This is the extended version of the paper submitted to 2021 Chinese Conference on Decision and Control. arXiv admin note: text overlap with arXiv:2007.03478, arXiv:2002.06577

In this paper, we consider scalable output and regulated output synchronization problems for heterogeneous networks of right-invertible linear agents based on localized information exchange where in the case of regulated output synchronization, the reference trajectory is generated by a so-called exosystem. We assume that all the agents are introspective, meaning that they have access to their own local measurements. We propose a scale-free linear protocol for each agent to achieve output and regulated output synchronizations. These protocols are designed solely based on agent models and they need no information about communication graph and the number of agents or other agent models information., Comment: The short version of this paper is presented in 2020 American Control Conference Denver, CO, USA. arXiv admin note: text overlap with arXiv:2007.03478, arXiv:2004.13014, arXiv:2004.09498, arXiv:1908.06535, arXiv:2004.13479

In this paper, we study delayed regulated state/output synchronization for discrete-time homogeneous and heterogeneous networks of multi-agent systems (MAS) subject to unknown, non-uniform and arbitrarily large communication delays. A delay transformation is utilized to transform the original MAS to a new system without delayed states. The proposed scale-free dynamic protocols are developed solely based on agent models and localized information exchange with neighbors such that we do not need any information about the communication networks and the number of agents., Comment: 18 pages, 10 figures, a short version of this paper will be submitted to ACC 2021. arXiv admin note: text overlap with arXiv:2004.09498, arXiv:2004.13014

This paper studies scale-free protocol design for H2 almost state synchronization of homogeneous networks of non-introspective agents in presence of external disturbances. The necessary and sufficient conditions are provided by designing collaborative linear dynamic protocols. The design is based on localized information exchange over the same communication network, which does not need any knowledge of the directed network topology and the spectrum of the associated Laplacian matrix. Moreover, the proposed protocol is scalable and achieves H2 almost synchronization with a given arbitrary degree of accuracy for any arbitrary number of agents.

This paper studies output synchronization problems for heterogeneous networks of continuous- or discrete-time right-invertible linear agents in presence of unknown, non-uniform and arbitrarily large input delay based on localized information exchange. It is assumed that all the agents are introspective, meaning that they have access to their own local measurements. Universal linear protocols are proposed for each agent to achieve output synchronizations. Proposed protocols are designed solely based on the agent models using no information about communication graph and the number of agents or other agent models information. Moreover, the protocols can tolerate arbitrarily large input delays., Comment: 9 pages, 3 figures, short version of this paper will be presented at Chinese Control Conference 2020. arXiv admin note: text overlap with arXiv:2002.06577, arXiv:2001.02117, arXiv:1908.06535, arXiv:2004.09498

This paper studies global regulated state synchronization of homogeneous networks of non-introspective agents in presence of input saturation. We identify three classes of agent models which are neutrally stable, double-integrator, and mixed of double-integrator, single-integrator and neutrally stable dynamics. A \textit{scale-free linear observer-based} protocol design methodology is developed based on localized information exchange among neighbors where the reference trajectory is given by a so-called exosystem which is assumed to be globally reachable. Our protocols do not need any knowledge about the communication network topology and the spectrum of associated Laplacian matrix. Moreover, the proposed protocol is scalable and is designed based on only knowledge of agent models and achieves synchronization for any communication graph with arbitrary number of agents., Comment: arXiv admin note: text overlap with arXiv:2004.09498, arXiv:1908.06535, arXiv:2001.02117, arXiv:2002.06577

This paper studies synchronization of homogeneous and heterogeneous discrete-time multi-agent systems. A class of linear dynamic protocol design methodology is developed based on localized information exchange with neighbors which does not need any knowledge of the directed network topology and the spectrum of the associated Laplacian matrix. The main contribution of this paper is that the proposed protocols are scale-free and achieve synchronization for arbitrary number of agents., Comment: 10 pages, 8 figures, a part of this paper will be presented at 2020 Chinese Control Conference. arXiv admin note: text overlap with arXiv:1908.06535, arXiv:2001.02117, arXiv:2002.06577

This paper studies regulated state synchronization of discrete-time homogeneous networks of non-introspective agents in presence of unknown non-uniform input delays. A scale free protocol is designed based on additional information exchange, which does not need any knowledge of the directed network topology and the spectrum of the associated Laplacian matrix. The proposed protocol is scalable and achieves state synchronization for any arbitrary number of agents. Meanwhile, an upper bound for the input delay tolerance is obtained, which explicitly depends on the agent dynamics., Comment: This article focuses on the synchronization of DISCRETE-TIME multi-agent systems (MAS) in present of unknown non-uniform input delays. It is the discrete-time version of article arXiv:2001.02117. Even though the same problem (the synchronization of MAS) is dealt with in these two papers, the analysis and design tools and the resulting protocols are completely different

This paper studies regulated state synchronization of homogeneous networks of non-introspective agents in presence of unknown nonuniform input delays. A scale-free protocol is designed based on additional information exchange, which does not need any knowledge of the directed network topology and the spectrum of the associated Laplacian matrix. The proposed protocol is scalable and achieves state synchronization for any arbitrary number of agents. Meanwhile, an upper bound for the input delay tolerance is obtained, which explicitly depends on the agent dynamics., Comment: arXiv admin note: text overlap with arXiv:1908.06535