2024 |
Hyungbo Shim How Does a Swarm Exhibit Emergent Behavior Through Synchronization? Journal Article In: Journal of Institute of Control, Robotics and Systems, vol. 30, iss. 4, pp. 352, 2024, ISSN: 1976-5622. Abstract | Links | BibTeX | Tags: Blended dynamics, Multi-agent systems, Synchronization @article{nokey, 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. |
2022 |
Jin Gyu Lee / Stephan Trenn / Hyungbo Shim Synchronization with prescribed transient behavior: Heterogeneous multi-agent systems under funnel coupling Journal Article In: Automatica, vol. 141, pp. 110276, 2022, ISSN: 0005-1098. Abstract | Links | BibTeX | Tags: Funnel control, Heterogeneous multi-agents, Multi-agent systems, Synchronization @article{nokey, 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. |
2020 |
Seungjoon Lee / Hongkeun Kim Synchronization of Lur'e-type Nonlinear Systems using Incremental Output-feedback Passivity with Shortage of Passivity Proceedings Article In: Proc. of 20th International Conference on Control, Automation and Systems (ICCAS), IEEE, Busan, Korea, 2020. Abstract | Links | BibTeX | Tags: Multi-agent systems, Passivity, Synchronization @inproceedings{LeeKim20, This paper studies the synchronization problem of Lur’e-type nonlinear systems. For the analysis, the concept of incremental output-feedback passivity (iOFP) is introduced and generalized using the shortage of passivity. It is shown that Lur’e-type nonlinear system is iOFP and examples are presented. Using iOFP, a sufficient condition (which is in form of sector condition) is proposed for the Lur’e-type nonlinear systems to achieve the synchronization using static output diffusive couplings. Results are further extended to nonlinear coupling under fully connected network. Numerical simulations are given to demonstrate the proposed results. |
Seungjoon Lee / Hyungbo Shim Blended dynamics approach for analysis and construction of distributed optimization algorithms Proceedings Article In: Proc. of 20th International Conference on Control, Automation and Systems (ICCAS), IEEE, Busan, Korea, 2020. Abstract | Links | BibTeX | Tags: Distributed optimization, Multi-agent systems @inproceedings{LeeShim20, In this paper, the recently proposed concept of blended dynamics of a heterogeneous multi-agent system is introduced. Although the blended dynamics is originally proposed for the analysis of heterogeneous multi-agent system, it is argued that the same approach provides a flexible framework for the analysis and construction of the distributed algorithms. The utility of the proposed approach is first illustrated by systematically constructing the distributed gradient descent algorithm from the centralized gradient descent method. The proposed approach is further extended to derive two variants of distributed algorithms utilizing the heavy-ball method. Finally, drawback of the proposed approach is identified and integral action is employed to resolve the issue. |
Miao Guo / Bayu Jayawardhana / Jin Gyu Lee / Hyungbo Shim Simultaneous distributed localization, mapping and formation control of mobile robots based on local relative measurements Journal Article In: IFAC-PapersOnLine, vol. 53, iss. 2, pp. 9614-9620, 2020, ISSN: 2405-8963. Abstract | Links | BibTeX | Tags: Distributed algorithm, Formation control, Multi-agent systems @article{nokey, This paper investigates the problem of localizing a team of robots in an indoor environment while simultaneously keeping a robust formation and performing group motion. A distributed observer is proposed to estimate the positions of mobile robots as well as the landmarks under a common global frame. Every robot uses its available local relative measurements, as well as the estimated relative measurements to its neighbors in order to keep a robust formation. Simultaneously, each robot estimates the positions of all the landmarks based on the available on-board relative measurements but also based on the estimated positions from its neighbors. We provide the L2-stability analysis of the closed-loop system where the group is also allowed to maneuver in the unknown environment. Simulation results are also given to show the efficacy of the method. |
Jin Gyu Lee / Thomas Berger / Stephan Trenn / Hyungbo Shim Utility of Edge-wise Funnel Coupling for Asymptotically Solving Distributed Consensus Optimization Proceedings Article In: Proc. of 2020 European Control Conference (ECC), pp. 911-916, IEEE, St. Petersburg, Russia, 2020, ISBN: 978-3-90714-402-2. Abstract | Links | BibTeX | Tags: Distributed optimization, Funnel control, Multi-agent systems @inproceedings{nokey, A new approach to distributed consensus optimization is studied in this paper. The cost function to be minimized is a sum of local cost functions which are not necessarily convex as long as their sum is convex. This benefit is obtained from a recent observation that, with a large gain in the diffusive coupling, heterogeneous multi-agent systems behave like a single dynamical system whose vector field is simply the average of all agents' vector fields. However, design of the large coupling gain requires global information such as network structure and individual agent dynamics. In this paper, we employ a nonlinear time-varying coupling of diffusive type, which we call `edge-wise funnel coupling.' This idea is borrowed from adaptive control, which enables decentralized design of distributed optimizers without knowledge of global information. Remarkably, without a common internal model, each agent achieves asymptotic consensus to the optimal solution of the global cost. We illustrate this result by a network that asymptotically finds the least-squares solution of a linear equation in a distributed manner. |
2009 |
Jin Heon Seo / Hyungbo Shim / Juhoon Back Consensus of High-order Linear Systems using Dynamic Output Feedback Compensator: Low Gain Approach Journal Article In: Automatica, vol. 45, no. 11, pp. 2659-2664, 2009, ISSN: 0005-1098. Abstract | Links | BibTeX | Tags: Multi-agent systems @article{SeoShimBack09, In this paper, we study the consensus (and synchronization) problem for multi-agent linear dynamic systems. All the agents have identical MIMO linear dynamics which can be of any order, and only the output information of each agents is delivered throughout the communication network. It is shown that consensus is reached if there exists a stable compensator which simultaneously stabilizes systems in a special form, where is the number of agents. We show that there exists such a compensator under a very general condition. Finally, the consensus value is characterized as a function of initial conditions with stable compensators in place. |
List of English Publication
2024 |
How Does a Swarm Exhibit Emergent Behavior Through Synchronization? Journal Article In: Journal of Institute of Control, Robotics and Systems, vol. 30, iss. 4, pp. 352, 2024, ISSN: 1976-5622. |
2022 |
Synchronization with prescribed transient behavior: Heterogeneous multi-agent systems under funnel coupling Journal Article In: Automatica, vol. 141, pp. 110276, 2022, ISSN: 0005-1098. |
2020 |
Synchronization of Lur'e-type Nonlinear Systems using Incremental Output-feedback Passivity with Shortage of Passivity Proceedings Article In: Proc. of 20th International Conference on Control, Automation and Systems (ICCAS), IEEE, Busan, Korea, 2020. |
Blended dynamics approach for analysis and construction of distributed optimization algorithms Proceedings Article In: Proc. of 20th International Conference on Control, Automation and Systems (ICCAS), IEEE, Busan, Korea, 2020. |
Simultaneous distributed localization, mapping and formation control of mobile robots based on local relative measurements Journal Article In: IFAC-PapersOnLine, vol. 53, iss. 2, pp. 9614-9620, 2020, ISSN: 2405-8963. |
Utility of Edge-wise Funnel Coupling for Asymptotically Solving Distributed Consensus Optimization Proceedings Article In: Proc. of 2020 European Control Conference (ECC), pp. 911-916, IEEE, St. Petersburg, Russia, 2020, ISBN: 978-3-90714-402-2. |
2009 |
Consensus of High-order Linear Systems using Dynamic Output Feedback Compensator: Low Gain Approach Journal Article In: Automatica, vol. 45, no. 11, pp. 2659-2664, 2009, ISSN: 0005-1098. |