List of English Publication

@article{nokey,

title = {How Does a Swarm Exhibit Emergent Behavior Through Synchronization?},

author = {Hyungbo Shim},

url = {https://icros.org/publication/sub03_04.asp?sub_param=4},

doi = {https://doi.org/10.5302/J.ICROS.2024.24.0039},

issn = {1976-5622},

year  = {2024},

date = {2024-04-01},

urldate = {2024-04-01},

journal = {Journal of Institute of Control, Robotics and Systems},

volume = {30},

issue = {4},

pages = {352},

abstract = {A swarm of individuals often exhibits behaviors that are not possible for each individual. This phenomenon is called emergence, and this paper mathematically demonstrates that new dynamics can arise in swarm behavior that cannot be explained by the dynamics of individuals. In particular, we argue that emergence occurs when heterogeneity is coupled with synchronization.

These two concepts may seem conflicting, as heterogeneity is the tendency to differ whereas synchronization is the tendency toward sameness. However, we show that emergent behavior arises from the interplay between the two.},

keywords = {Blended dynamics, Multi-agent systems, 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{YunShimAhn19,

title = {Initialization-free Privacy-guaranteed Distributed Algorithm for Economic Dispatch Problem},

author = {Hyeonjun Yun and Hyungbo Shim and Hyo-Sung Ahn},

url = {https://post.cdsl.kr/archives/615

https://arxiv.org/abs/1801.01658},

doi = {10.1016/j.automatica.2018.12.033},

year  = {2019},

date = {2019-04-01},

journal = {Automatica},

volume = {102},

pages = {86-93},

abstract = {This paper considers the economic dispatch problem for a network of power generators and customers. In particular, our aim is to minimize the total generation cost under the power supply-demand balance and the individual generation capacity constraints. This problem is solved in a distributed manner, i.e., a dual gradient-based continuous-time distributed algorithm is proposed in which only a single dual variable is communicated with the neighbors and no private information of the node is disclosed. The proposed algorithm is simple and no specific initialization is necessary, and this in turn allows on-line change of network structure, demand, generation constraints, and even the participating nodes. The algorithm also exhibits a special behavior when the problem becomes infeasible so that each node can detect over-demand or under-demand situation of the power network. Simulation results on IEEE 118 bus system confirm robustness against variations in power grids.},

keywords = {Blended dynamics, Synchronization},

pubstate = {published},

tppubtype = {article}

}

@article{KimYangShimKimSeo16,

title = {Robustness of Synchronization of Heterogeneous Agents by Strong Coupling and a Large Number of Agents},

author = {Jaeyong Kim and Jongwook Yang and Hyungbo Shim and Jung-Su Kim and Jin Heon Seo},

doi = {10.1109/TAC.2015.2498138},

year  = {2016},

date = {2016-10-01},

journal = {IEEE Transactions on Automatic Control},

volume = {61},

number = {10},

pages = {3096-3102},

abstract = {This technical note studies robustness of synchronization against heterogeneity of multi-agent systems. Here, heterogeneity also includes uncertainties and external disturbances in each agent. In order to effectively deal with the heterogeneous agents, we introduce the concept of the averaged dynamics which is the average of all agents’ dynamics, and then claim that two sources enhance the robustness of synchronized behavior against heterogeneity of agents’ dynamics. First, in spite of the heterogeneity of agents’ dynamics, we show that strong coupling among agents makes the trajectories of all agents arbitrarily close to the averaged dynamics. Second, in the averaged dynamics, the effect of variations in each agent gets smaller as the number of agents increases. Simulation results confirm the claim that a large number of agents with strong couplings have robust synchronization.},

keywords = {Blended dynamics, Heterogeneity, Multi-agent system, Synchronization},

pubstate = {published},

tppubtype = {article}

}

@article{KimKimBackShimSeo16,

title = {Design of Stable Parallel Feedforward Compensator and its Application to Synchronization Problem},

author = {Hongkeun Kim and Seongjun Kim and Juhoon Back and Hyungbo Shim and Jin Heon Seo},

doi = {10.1016/j.automatica.2015.11.020},

year  = {2016},

date = {2016-02-01},

journal = {Automatica},

volume = {64},

pages = {208-216},

abstract = {This paper addresses the design problem of a stable parallel feedforward compensator V for a given SISO LTI plant P (possibly being of non-minimum phase and/or having relative degree greater than one). The objective of the problem is that their parallel interconnection P+V becomes minimum phase having relative degree one. Based on the classical results of simultaneous stabilization, a necessary and sufficient condition for solving the problem is presented as well as a design procedure for constructing such a compensator. The proposed feedforward compensator allows the control system to have the three useful features: (1) the ability that assigns the zeros of P+V to a region of complex numbers having arbitrary negative real parts, (2) infinite gain margin property of P+V controlled by a static output feedback, and (3) block diagonal structure of P+V. These features are extensively exploited in the synchronization problem of multi-agent systems to achieve arbitrary fast convergence rate and to have the synchronized trajectory independent of the initial conditions and parameters of the involved dynamic controllers.},

keywords = {Multi-agent system, Non-minimum phase, Parallel feedforward compensator, Synchronization},

pubstate = {published},

tppubtype = {article}

}