List of English Publication

@article{nokey,

title = {Edge-wise funnel output synchronization of heterogeneous agents with relative degree one},

author = {Jin Gyu Lee and Thomas Berger and Stephan Trenn and Hyungbo Shim},

url = {https://www.sciencedirect.com/science/article/pii/S0005109823003655},

doi = {https://doi.org/10.1016/j.automatica.2023.111204},

issn = {0005-1098},

year  = {2023},

date = {2023-10-01},

urldate = {2023-10-01},

journal = {Automatica},

volume = {156},

pages = {111204},

abstract = {When a group of heterogeneous node dynamics are diffusively coupled with a high coupling gain, the

group exhibits a collective emergent behavior which is governed by a simple algebraic average of the

node dynamics called the blended dynamics. This finding has been utilized for designing heterogeneous

multi-agent systems by building the desired blended dynamics first and then splitting it into the node

dynamics. However, to compute the magnitude of the coupling gain, each agent needs to know global

information such as the number of participating nodes, the graph structure, and so on, which prevents

a fully decentralized design of the node dynamics in conjunction with the coupling laws. To resolve this

issue, the idea of funnel control, which is a method for adaptive gain selection, can be exploited for a

node-wise coupling, but the price to pay is that the collective emergent behavior is no longer governed

by a simple average of the node dynamics. Our analysis reveals that this drawback can be avoided by an

edge-wise design premise, which is the idea that we present in this paper. After all, we gain benefits

such as a fully decentralized design without global information, collective emergent behavior being

governed by the blended dynamics, and the plug-and-play operation based on edge-wise handshaking

between two nodes},

keywords = {Blended dynamics, Funnel control, Heterogeneous multi-agents, output synchronization},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Synchronization with prescribed transient behavior: Heterogeneous multi-agent systems under funnel coupling},

author = {Jin Gyu Lee and Stephan Trenn and Hyungbo Shim},

url = {https://www.sciencedirect.com/science/article/pii/S0005109822001224},

doi = {https://doi.org/10.1016/j.automatica.2022.110276},

issn = {0005-1098},

year  = {2022},

date = {2022-07-01},

urldate = {2022-07-01},

journal = {Automatica},

volume = {141},

pages = {110276},

abstract = {In this paper, we introduce a nonlinear time-varying coupling law, which can be designed in a fully decentralized manner and achieves approximate synchronization with arbitrary precision, under only mild assumptions on the individual vector fields and the underlying (undirected) graph structure. The proposed coupling law is motivated by the so-called funnel control method studied in adaptive control under the observation that arbitrary precision synchronization can be achieved for heterogeneous multi-agent systems by a high-gain coupling; consequently we call our novel synchronization method ‘(node-wise) funnel coupling.’ By adjusting the conventional proof technique in the funnel control study, we are even able to obtain asymptotic synchronization with the same funnel coupling law. Moreover, the emergent collective behavior that arises for a heterogeneous multi-agent system when enforcing arbitrary precision synchronization by the proposed funnel coupling law, is analyzed in this paper. In particular, we introduce a single scalar dynamics called ‘emergent dynamics’ which describes the emergent synchronized behavior of the multi-agent system under funnel coupling. Characterization of the emergent dynamics is important because, for instance, one can design the emergent dynamics first such that the solution trajectory behaves as desired, and then, provide a design guideline to each agent so that the constructed vector fields yield the desired emergent dynamics. We illustrate this idea via the example of a distributed median solver based on funnel coupling.},

keywords = {Funnel control, Heterogeneous multi-agents, Multi-agent systems, Synchronization},

pubstate = {published},

tppubtype = {article}

}

@article{Lee20,

title = {A Tool for Analysis and Synthesis of Heterogeneous Multi-agent Systems under Rank-deficient Coupling},

author = {Jin Gyu Lee/ Hyungbo Shim},

doi = {https://doi.org/10.1016/j.automatica.2020.108952},

issn = {0005-1098},

year  = {2020},

date = {2020-07-01},

urldate = {2020-07-01},

journal = {Automatica},

volume = {117},

pages = {108952},

abstract = {The behavior of heterogeneous multi-agent systems is studied when the coupling matrices are possibly all different and/or singular, that is, its rank is less than the system dimension. Rank-deficient coupling allows exchange of limited state information, which is suitable for the study of multi-agent systems under output coupling. We present a coordinate change that transforms the heterogeneous multi-agent system into a singularly perturbed form. The slow dynamics is still a reduced-order multi-agent system consisting of a weighted average of the vector fields of all agents, and some sub-dynamics of agents. The weighted average is an emergent dynamics, which we call a blended dynamics. By analyzing or synthesizing the blended dynamics, one can predict or design the behavior of a heterogeneous multi-agent system when the coupling gain is sufficiently large. For this result, stability of the blended dynamics is required. Since stability of the individual agent is not asked, the stability of the blended dynamics is the outcome of trading off the stability among the agents. It can be seen that, under the stability of the blended dynamics, the initial conditions of the individual agents are forgotten as time goes on, and thus, the behavior of the synthesized multi-agent system is initialization-free and is suitable for plug-and-play operation. As a showcase, we apply the proposed tool to four application problems; distributed state estimation for linear systems, practical synchronization of heterogeneous van der Pol oscillators, estimation of the number of nodes in a network, and a problem of distributed optimization.},

keywords = {Blended dynamics, Heterogeneous multi-agents, Singular perturbation, Synchronization},

pubstate = {published},

tppubtype = {article}

}

@article{Lee20b,

title = {Fully distributed resilient state estimation based on distributed median solver},

author = {Jin Gyu Lee and Junsoo Kim and Hyungbo Shim},

doi = {https://doi.org/10.1109/TAC.2020.2989275},

issn = {0018-9286},

year  = {2020},

date = {2020-04-01},

journal = {IEEE Transactions on Automatic Control},

volume = {65},

number = {9},

pages = {3935-3942},

abstract = {In this article, we present a scheme of fully distributed resilient state estimation for linear dynamical systems under sensor attacks. The proposed state observer consists of a network of local observers, where each of them utilizes local measurements and information transmitted from the neighbors. As a fully distributed scheme, it does not necessarily collect a majority of sensing data for the sake of attack identification, whereas the compromised sensors are eventually identified by the distributed network and excluded from the observers. For this, the overall network (not the individual local observer) is assumed to have redundant sensors and assumed to be connected. The proposed scheme is based on a novel design of a distributed median solver, which approximately recovers the median value of local estimates.},

keywords = {Analytical redundancy, Attack detection, Attack resilience, Blended dynamics, Cyber-physical systems, Heterogeneous multi-agents, Resilient state estimation, Strong coupling},

pubstate = {published},

tppubtype = {article}

}