List of English Publication

@article{nokey,

title = {A Sliding Mode Approach to Asymptotic Recovery of Nominal Performance for Uncertain Linear Systems},

author = {Hyuntae Kim and Hyungbo Shim and Mohammad Ataei and Nam Hoon Jo and Gyunghoon Park},

doi = {10.1109/TIE.2025.3589423},

issn = {0278-0046},

year  = {2026},

date = {2026-02-01},

urldate = {2026-02-01},

journal = {	IEEE Transactions on Industrial Electronics},

abstract = {This article presents a new structure of a slid

ing mode disturbance observer (SM-DOB) for handling

model uncertainty and unmodeled disturbances. The pro

posed SM-DOB is composed of two key components. First,

a Levant’s differentiator is used to estimate the high-order

time derivatives of the output. To satisfy the conditions

required for the effective operation of Levant’s differentia

tor, we employ an integral SM technique so that on the slid

ing surface, the real plant’s dynamics are substituted with

the nominal dynamics. With this structure, the proposed

SM-DOB can achieve robust disturbance rejection and

recover nominal performance in finite time. The stability

and the finite time convergence of the proposed SM-DOB

are rigorously proved by the Lyapunov stability method.

Finally, to show the superiority and verify the validity of the

proposed SM-DOB, we conduct both numerical simulations

andlaboratory experiments with brushless dc (BLdc) motor

drives. It is observed that the proposedSM-DOBguarantees

satisfactory performance in rejecting both input distur

bance and plant uncertainty while },

keywords = {},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{nokey,

title = {Stability of linear systems with slow and fast time variation and switching: General case},

author = {Hyungbo Shim and Daniel Liberzon},

doi = {10.1016/j.nahs.2025.101626},

issn = {1751-570X},

year  = {2025},

date = {2025-11-01},

urldate = {2025-11-01},

journal = {Nonlinear Analysis: Hybrid Systems},

volume = {58},

pages = {101626},

abstract = {This paper studies exponential stability of linear systems with slow and fast time variation and switching. We use averaging to eliminate the fast dynamics and only retain the slow dynamics. We then use a recent stability criterion for slowly time-varying and switched systems, combined with perturbation analysis, to prove stability of the original system. The analysis involves working with an impulsive system in new coordinates, which enables us to treat a more general class of systems compared to previous work.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Two algorithms for distributed mode computing based on blended dynamics approach},

author = {Chao Huanga and Siliang Yu and Hyungbo Shim and Brian D.O. Anderson},

doi = {https://doi.org/10.1016/j.sysconle.2025.106082},

isbn = { 0167-6911 },

year  = {2025},

date = {2025-08-01},

urldate = {2025-08-01},

journal = {Systems & Control Letters},

volume = {202},

issue = { Systems & Control Letters},

pages = {106082},

abstract = { This paper studies the distributed mode computing problem in a multi-agent system, in which each individual 

agent possesses a certain attribute and the agent group aims to agree upon the mode (the most frequent 

attribute owned by the agents) via distributed computing. Two algorithms are proposed, the first one estimates 

the frequency of all attributes at every agent, and then identifies the most frequent attribute as the mode; the 

second is based on a distributed consensus protocol that renders all the agents agreeing on an attribute whose 

frequency is no less than a given threshold. This protocol is then used as the main building block to compute 

the mode via a branch-and-bound algorithm. Analysis of both algorithms establishes finite time convergence 

and is based on the blended dynamics approach.},

keywords = {Blended dynamics, Consensus, ConsensusMode computingBlended dynamics, Mode computing},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Singularly Perturbed Hybrid Systems for Analysis of Networks With Frequently Switching Graphs},

author = {Aneel Tanwani and Hyungbo Shim and Andrew R. Teel},

doi = {10.1109/TAC.2024.3523242},

issn = {0018-9286},

year  = {2025},

date = {2025-07-01},

urldate = {2025-07-01},

journal = {IEEE Transactions on Automatic Control},

volume = {70},

issue = {7},

pages = {4344-4359},

abstract = {For a class of hybrid systems, where jumps occur frequently, we analyze the stability of system trajectories in view of singularly perturbed dynamics. The specific model we consider comprises an interconnection of two hybrid subsystems, a timer which triggers the jumps, and some discrete variables to determine the index of the jump maps. The flow equations of these variables are singularly perturbed differential equations and, in particular, a smaller value of the singular perturbation parameter leads to an increase in the frequency of the jump instants. For the limiting value of this parameter, we consider a decomposition that comprises a quasi-steady-state system modeled by a differential equation without any jumps and a boundary-layer system described by purely discrete dynamics. Under appropriate assumptions on the quasi-steady-state system and the boundary-layer system, we derive results showing practical stability of a compact attractor when the jumps occur sufficiently often. As an application of our results, we discuss the control design problem in a network of second-order continuous-time coupled oscillators, where each agent communicates the information about its position to some of its neighbors at discrete times. Using the results developed in this article, we show that if the union of the communication graphs being used for information exchange between agents is connected, then the oscillators achieve practical consensus.},

keywords = {Hybrid system, Multi-agent systems, Singular perturbation},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Data-driven displacement-based formation control with range-only measurements},

author = {Soojeong Hyeon and Hyuntae Kim and Hyungbo Shim},

doi = {10.1109/ACCESS.2025.3584829},

issn = {2169-3536},

year  = {2025},

date = {2025-07-01},

journal = {IEEE Access},

volume = {13},

pages = {115167-115177},

abstract = {This paper proposes an algorithm to coordinate a displacement-based formation of a multi-agent system when their local frames are not aligned. Agents can measure neither the relative positions nor orientations, but only the range (distance) to their neighbors. We demonstrate that persistently exciting data exchanged between two agents can be used to infer relative positions and orientations. In the proposed method, we address discrete-time distributed orientation estimation based on an averaging consensus protocol. An asymptotic stability analysis of the desired formation shape is presented and the proposed strategy is validated through simulation results.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {A Distributed Observer Accommodating a Broad Range of Intermittent Communication Scenarios},

author = {Sunghyun Koo and Jin Gyu Lee and Hyungbo Shim},

doi = {https://doi.org/10.1109/LCSYS.2025.3583672},

issn = {2475-1456},

year  = {2025},

date = {2025-06-27},

urldate = {2025-06-27},

journal = {IEEE Control Systems Letters},

volume = {9},

pages = {1682-1687},

abstract = {This paper proposes a distributed observer that utilizes intermittent communication and accommodates a broad range of scenarios, including asynchronous operation, unidirectional communication, packet loss, and communication delays. An analysis over jointly connected switching topology supports this and provides a condition for exponential convergence of the estimation error. This condition can be used to determine a communication rate. The analysis is valid when the unobservable subspace of each agent admits an invariant orthogonal complement. This is a property that is always achievable via a coordinate transformation when the system matrix is diagonalizable over the complex field},

keywords = {distributed observer, Distributed state estimation, Multi-agent systems},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ring-LWE-Based Encrypted Controller With Unlimited Number of Recursive Multiplications and Effect of Error Growth},

author = {Yeongjun Jang and Joowon Lee and Seonhong Min and Hyesun Kwak and Junsoo Kim and Yongsoo Song},

url = {https://ieeexplore.ieee.org/document/11052663},

doi = {10.1109/TCNS.2025.3583610},

isbn = {2325-5870},

year  = {2025},

date = {2025-06-26},

journal = {IEEE Transactions on Control of Network Systems},

volume = {12},

issue = {4},

pages = {2604 - 2616},

abstract = {In this article, we propose an encrypted dynamic controller that executes an unlimited number of recursive homomorphic multiplications on a Ring Learning With Errors (Ring-LWE)-based cryptosystem without bootstrapping. The proposed controller exhibits lower computational complexity compared to existing encrypted controllers implemented on LWE-based schemes due to the polynomial structure of Ring-LWE. However, the structural difference introduces additional difficulties in analyzing the effect of error growth; Ring-LWE-based schemes inject multiple error coefficients when encrypting a single message, which accumulate under recursive homomorphic multiplications. We show that their effect on control performance can be arbitrarily bounded by the closed-loop stability, thus recovering the performance of the unencrypted controller. Furthermore, a novel method to “pack” a vector into a polynomial is presented, which enhances computational and memory efficiency when applied to the proposed encrypted controller. The effectiveness of the proposed design is demonstrated through numerical simulations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Ring-LWE based encrypted controller with unlimited number of recursive multiplications and effect of error growth},

author = {Yeongjun Jang, Joowon Lee, Seonhong Min, Hyesun Kwak, Junsoo Kim, and Yongsoo Song},

url = {https://ieeexplore.ieee.org/abstract/document/11052663/metrics#metrics},

doi = {10.1109/TCNS.2025.3583610},

issn = {2325-5870},

year  = {2025},

date = {2025-06-26},

journal = {IEEE Transactions on Control of Network Systems},

volume = {12},

number = {4},

pages = {2604 - 2616},

abstract = {In this article, we propose an encrypted dynamic controller that executes an unlimited number of recursive homomorphic multiplications on a Ring Learning With Errors (Ring-LWE)-based cryptosystem without bootstrapping. The proposed controller exhibits lower computational complexity compared to existing encrypted controllers implemented on LWE-based schemes due to the polynomial structure of Ring-LWE. However, the structural difference introduces additional difficulties in analyzing the effect of error growth; Ring-LWE-based schemes inject multiple error coefficients when encrypting a single message, which accumulate under recursive homomorphic multiplications. We show that their effect on control performance can be arbitrarily bounded by the closed-loop stability, thus recovering the performance of the unencrypted controller. Furthermore, a novel method to “pack” a vector into a polynomial is presented, which enhances computational and memory efficiency when applied to the proposed encrypted controller. The effectiveness of the proposed design is demonstrated through numerical simulations.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Relative entropy regularized reinforcement learning for efficient encrypted policy synthesis},

author = {Jihoon Suh and Yeongjun Jang and Kaoru Teranishi and Takashi Tanaka},

doi = {10.1109/LCSYS.2025.3578573},

issn = {2475-1456},

year  = {2025},

date = {2025-06-01},

journal = {IEEE Control Systems Letters},

volume = {9},

abstract = {We propose an efficient encrypted policy synthesis to develop privacy-preserving model-based reinforcement learning. We first demonstrate that the relative-entropy-regularized reinforcement learning framework offers a computationally convenient linear and “min-free” structure for value iteration, enabling a direct and efficient integration of fully homomorphic encryption with bootstrapping into policy synthesis. Convergence and error bounds are analyzed as encrypted policy synthesis propagates errors under the presence of encryption-induced errors including quantization and bootstrapping. Theoretical analysis is validated by numerical simulations. Results demonstrate the effectiveness of the RERL framework in integrating FHE for encrypted policy synthesis.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Robust disturbance rejection for uncertain linear system with time-varying exo-system: A disturbance observer approach},

author = {Hyuntae Kim and Gyunghoon Park and Hyungbo Shim},

url = {https://www.sciencedirect.com/science/article/pii/S0005109824005934?dgcid=author},

doi = {10.1016/j.automatica.2024.112100},

issn = { 0005-1098},

year  = {2025},

date = {2025-04-01},

urldate = {2025-04-01},

journal = {Automatica},

issue = {174},

pages = {112100},

abstract = {This paper addresses the problem of completely eliminating modeled disturbance that enters linear minimum-phase systems having parametric uncertainty and is generated by a linear time-varying exo-system. Motivated by the internal model principle (IMP), the core is to append a filter in front of the plant, such that (a) the disturbance model is embedded into the filter dynamics and (b) the filter is of minimum phase. Then the cascade connection of the plant and the filter is robustly stabilized by employing a disturbance observer (DOB)-based controller. In addition to simplicity in the design over the existing IMP-based approaches, the proposed controller also enjoys benefits of the DOB techniques, such as robustness against large parametric uncertainty and additional unmodeled disturbance, and guaranteeing a pre-defined nominal tracking performance in both transient and steady-state. Stability and performance of the controller are analyzed by the singular perturbation theory.},

howpublished = {Automatica},

keywords = {Disturbance observer, Internal model principle, Linear Systems},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Documentation on Encrypted Dynamic Control Simulation Code Using Ring-LWE Based Cryptosystems},

author = {Yeongjun Jang and Joowon Lee and Junsoo Kim},

doi = {https://doi.org/10.11499/sicejl.64.248},

year  = {2025},

date = {2025-04-01},

journal = {Journal of The Society of Instrument and Control Engineers},

volume = {64},

issue = {4},

pages = {248~254},

abstract = {This paper provides example codes with instruc-tions on implementing Ring-LWE based encrypted controllers 13), 14) for a four-tank system using Lattigo

The codes can be easily customized by readers for application to different systems or approaches. It is demonstrated that the methods of Ref. 13) and Ref. 14) enable fast implementations of encrypted controllers, taking less than 17 ms on average at each time step for computing the control input of a fourthorder controller.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Complexity Reduction for Resilient State Estimation of Uniformly Observable Nonlinear Systems},

author = {Junsoo Kim and Jin Gyu Lee and Henrik Sandberg and Karl H. Johansson},

doi = {10.1109/TAC.2024.3459413},

issn = {0018-9286},

year  = {2025},

date = {2025-02-01},

journal = {IEEE TRANSACTIONS ON AUTOMATIC CONTROL},

volume = {70},

issue = {2},

pages = {1267-1272},

abstract = {A resilient state estimation scheme for uniformly observable nonlinear systems, based on a method for local identification of sensor attacks, is presented. The estimation problem is combinatorial in nature, and so many methods require substantial computational and storage resources as the number of sensors increases. To reduce the complexity, the proposed method performs the attack identification with local subsets of the measurements, not with the set of all measurements. A condition for nonlinear attack identification is introduced as a relaxed version of existing redundant observability condition. It is shown that an attack identification can be performed even when the entire state cannot be recovered from the measurements. As a result, although a portion of measurements are compromised, they can be locally identified and excluded from the state estimation, and thus, the true state can be recovered. Simulation results demonstrate the effectiveness of the proposed scheme.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Encrypted Dynamic Control Exploiting Limited Number of Multiplications and a Method Using RLWE-based Cryptosystem},

author = {Joowon Lee and Donggil Lee and Junsoo Kim and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/document/10730788},

doi = {10.1109/TSMC.2024.3452007},

issn = {2168-2216},

year  = {2025},

date = {2025-01-01},

urldate = {2024-10-23},

journal = {IEEE Transactions on Systems, Man, and Cybernetics: Systems},

volume = {55},

issue = {1},

pages = {158-169},

abstract = {In this article, we present a method to encrypt dynamic controllers that can be implemented through most homomorphic encryption schemes, including somewhat, leveled fully, and fully homomorphic encryption. To this end, we represent the output of the given controller as a linear combination of a fixed number of previous inputs and outputs. As a result, the encrypted controller involves only a limited number of homomorphic multiplications on every encrypted data, assuming that the output is re-encrypted and transmitted back from the actuator. A guidance for parameter choice is also provided, ensuring that the encrypted controller achieves predefined performance for an infinite time horizon. Furthermore, we propose a customization of the method for ring learning with errors (RLWE)-based cryptosystems, where a vector of messages can be encrypted into a single ciphertext and operated simultaneously, thus reducing computation and communication loads. Unlike previous results, the proposed customization does not require extra algorithms, such as rotation, other than basic addition and multiplication. Simulation results demonstrate the effectiveness of the proposed method.},

keywords = {Controller encryption, Homomorphic encryption},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = { Robust Stability Condition and Simplified Design of Filter-embedded Disturbance Observer},

author = {Hamin Chang and Donghyeon Song and Chanhwa Lee and Hyungbo Shim},

url = {https://link.springer.com/article/10.1007/s12555-024-0503-2},

doi = {10.1007/s12555-024-0503-2},

issn = { 1598-6446},

year  = {2024},

date = {2024-12-09},

urldate = {2024-12-09},

journal = {International Journal of Control, Automation, and Systems},

volume = {22},

pages = {3584-3594},

publisher = {International Journal of Control, Automation and Systems},

abstract = {Embedding a filter is one of the simplest ways to enhance the disturbance attenuation performance of

feedback control systems. In this paper, we introduce the filter-embedded disturbance observer (FDOB) and present

a rigorous stability analysis of the FDOB. The proposed robust stability condition for the closed-loop system with

the FDOB shows that if the filter to be embedded is stable and has zero relative degree with unity high-frequency

gain, then the FDOB can be designed by simply adding the filter to a well-designed conventional disturbance

observer (DOB) that guarantees closed-loop robust stability, and by adjusting the time constant of the Q-filter of the

conventional DOB. It is also highlighted that the FDOB can be implemented by integrating the filter into the Q-filter

of the conventional DOB, maintaining the add-on structure of the conventional DOB. In addition, it is shown that

internal models of disturbances can be directly embedded into the filter of FDOB, which does not affect the design

of the Q-filter. Simulation results on a motor control system are provided to validate the theoretical results.

},

keywords = {Disturbance observer},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {A Lyapunov Characterization of Prescribed Performance Control Systems},

author = {Yutian Wang and Tengfei Liu and Hyungbo Shim and George A. Rovithakis and Zhong-Ping Jiang},

doi = {10.1109/TAC.2024.3399090},

issn = {0018-9286},

year  = {2024},

date = {2024-11-01},

urldate = {2024-11-01},

journal = {IEEE Transactions on Automatic Control},

volume = {69},

issue = {11},

pages = {7917 - 7924},

abstract = {This paper contributes a Lyapunov formulation for prescribed performance controller designs. In particular, we first show that the closed-loop system of a typical class of prescribed performance control systems can be transformed into an interconnection of input-to-state practically stable (ISpS) subsystems characterized by ISpS-Lyapunov functions. Then, we take advantage of the gain-interconnections between the subsystems and construct a Lyapunov function for the closed-loop system. The proposed approach is validated through prescribed performance control for both SISO and MIMO plants, as well as systems not necessarily in the lower-triangular form and systems with dynamic uncertainty.},

keywords = {Input-to-state practical stability, Lyapunov function, Prescribed performance control},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Evaluating MR-GPR and MR-NN: An Exploration of Data-driven Control Methods for Nonlinear Systems},

author = {Hyuntae Kim and Hamin Chang and Hyungbo Shim},

url = {https://rdcu.be/d04xd},

doi = {/10.1007/s12555-023-0695-x},

issn = {1598-6446},

year  = {2024},

date = {2024-08-01},

urldate = {2024-08-01},

journal = {International Journal of Control, Automation, and Systems},

volume = {22},

pages = {2934–2941},

abstract = {This paper addresses the challenge of data-driven control of nonlinear systems, focusing on the limi-tations and capabilities of model reference Gaussian process regression (MR-GPR) and its evolved counterpart,model reference neural networks (MR-NN). MR-GPR, based on Gaussian processes renowned for their adaptabil-ity to diverse data structures, encounters scalability issues especially when handling large datasets. To address theselimitations, this paper introduces MR-NN, an extension of MR-GPR, leveraging neural networks (NN) to managelarge datasets and capture complex nonlinear dynamics effectively. We present a comprehensive evaluation of bothmethods through a classical control problem of the inverted pendulum, a system well-recognized for its nonlinearbehavior. Numerical experiments are conducted to compare the methods in terms of control performance, compu-tational efficiency, and reliability.},

keywords = {Data-driven control, Gaussian process, Neural Network, nonlinear systems, Stability, System identification},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {On Existence of Uniformly Marginally Stable Zeros of Linear Sampled-data Systems and its Application to Stable Inversion-based Control},

author = {Gyunghoon Park and Hyungbo Shim and Tomomichi Hagiwara},

url = {https://ieeexplore.ieee.org/document/10488419},

doi = {10.1109/ACCESS.2024.3384396},

issn = {2169-3536},

year  = {2024},

date = {2024-07-01},

urldate = {2024-07-01},

booktitle = {IEEE Access},

journal = {IEEE Access},

volume = {12},

pages = {49826 - 49836},

publisher = {IEEE Access},

abstract = {This paper investigates a class of sampled-data systems in which at least one of the discretetime zeros remains on the unit circle regardless of the sampling period. This type of zero is referred to as an

‘‘uniformly marginally stable’’ (UMS) zero. Utilizing this novel concept, we present necessary conditions

as well as sufficient conditions for the continuous-time plant whose sampled-data model has an UMS

zero. The significance of the symmetry regarding the zeros and the poles of the continuous-time plant is

highlighted as it plays a vital role in enforcing a discrete-time zero of the sampled-data system to be UMS,

for both discretization zeros and intrinsic zeros. We develop the theory for sampled-data systems employing

a conventional sampler and a zero-order hold together with a single-input single-output continuous-time

plant, and then observe that certain results can be extended to the generalized holds. As an application, we

establish a condition for sampled-data systems that allow for discrete-time stable inversion-based control

where the absence of such an UMS zero is crucial in the design of such control systems.},

keywords = {Linear Systems, marginal stability, Sampled data system},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Maintaining and steering a formation in an unknown dynamic environment via a consistent distributed dynamic map},

author = {Miao Guo and Bayu Jayawardhana and Jin Gyu Lee and Hyungbo Shim},

doi = {/10.1002/rnc.7414},

issn = { 1049-8923},

year  = {2024},

date = {2024-05-22},

urldate = {2024-05-22},

journal = {International Journal of Robust and Nonlinear Control},

volume = {34},

issue = {13},

pages = {8785-8801},

abstract = {In this paper, we study the problem of maintaining a stable mobile robot formation, steering and localizing all robots in an unknown dynamic environment consisting of multiple periodically moving objects, without the presence of a global positioning system or a robot tracking system. We propose a distributed observer such that each agent can estimate global positions of all mobile robots and that of moving landmarks in an unknown environment. By combining the proposed distributed observer with the distributed formation control and centroid tracking control law, we show that the formation shape can be maintained by utilizing its available relative measurements and the estimated relative measurements to its neighbors, and the group's centroid follows a desired trajectory. We present 

 stability analysis of the closed-loop system. Finally, we validate the proposed methods in a simulation result where a group of mobile robots can maintain a robust formation and maneuver in an unknown dynamic environment.},

keywords = {Formation control, Localization, simultaneous localization and mapping},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Path Generating Inverse Gaussian Process Regression for Data-Driven Ultimate Boundedness Control of Nonlinear Systems},

author = {Yeongjun Jang and Hamin Chang and Heein Park and Hyungbo Shim},

doi = {10.1109/LCSYS.2024.3403525},

issn = {2475-1456},

year  = {2024},

date = {2024-05-20},

urldate = {2024-05-20},

journal = {IEEE Control Systems Letters},

volume = {8},

pages = {748 - 753},

abstract = {A data-driven ultimate boundedness controller for a nonlinear system is proposed. The controller is designed based on the inverse model of the system identified by Gaussian process regression with state/input measurement data to track a reference trajectory suitable for achieving a desired ultimate bound. In particular, a suitable reference trajectory is actively generated based on the data that have been used for the identification. For this reason, the controller is named the path generating inverse Gaussian process regression (PGIGP) controller. We provide a sufficient condition on the data under which the PGIGP controller guarantees ultimate boundedness with a desired ultimate bound. It is shown that the condition can serve as a practical guideline for data acquisition and, conversely, be employed to determine the baseline of the control performance achievable from a given dataset. The effectiveness of the PGIGP controller is demonstrated through numerical simulations.},

keywords = {Data-driven control, Gaussian process, nonlinear systems},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Decentralized Design and Plug-and-Play Distributed Control for Linear Multi-Channel Systems},

author = {Taekyoo Kim and Donggil Lee and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/document/10174243},

doi = {10.1109/TAC.2023.3293036},

issn = {0018-9286},

year  = {2024},

date = {2024-05-01},

urldate = {2023-07-06},

journal = {IEEE Transactions on Automatic Control},

volume = {69},

issue = {5},

pages = {2807 - 2822},

abstract = {We propose a distributed control, in which many identical control agents are deployed for controlling a linear time-invariant plant that has multiple input-output channels. Each control agent can join or leave the control loop during the operation of stabilization without particular initialization over the whole networked agents. Once new control agents join the loop, they self-organize their control dynamics, which does not interfere the control by other active agents, which is achieved by local communication with the neighboring agents. The key idea enabling these features is the use of Bass' algorithm, which allows the distributed computation of stabilizing gains by solving a Lyapunov equation in a distributed manner.},

keywords = {Distributed algorithm, Multi-channel system, Plug-and-play},

pubstate = {published},

tppubtype = {article}

}

@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 = {Node-Wise Monotone Barrier Coupling Law for Formation Control},

author = {Jin Gyu Lee and Cyrus Mostajeran and Graham Van Goffrier},

url = {https://www.mdpi.com/1099-4300/26/2/134},

doi = {https://doi.org/10.3390/e26020134},

issn = {1099-4300},

year  = {2024},

date = {2024-01-31},

urldate = {2024-01-31},

journal = {Entropy},

volume = {26},

issue = {2},

pages = {134},

abstract = {We study a node-wise monotone barrier coupling law, motivated by the synaptic coupling of neural central pattern generators. It is illustrated that this coupling imitates the desirable properties of neural central pattern generators. In particular, the coupling law (1) allows us to assign multiple central patterns on the circle and (2) allows for rapid switching between different patterns via simple ‘kicks’. In the end, we achieve full control by partitioning the state space by utilizing a barrier effect and assigning a unique steady-state behavior to each element of the resulting partition. We analyze the global behavior and study the viability of the design.},

keywords = {Consensus, Formation control, Nonlinear space, Positivity},

pubstate = {published},

tppubtype = {article}

}

@article{noneb,

title = {Asymptotic output tracking in a class of non-minimum phase nonlinear systems via learning-based inversion},

author = {Namguk Kim and Hyungbo Shim},

doi = {https://doi.org/10.1002/rnc.6969},

issn = {1049-8923},

year  = {2024},

date = {2024-01-10},

urldate = {2024-01-10},

journal = {International Journal of Robust and Nonlinear Control},

volume = {34},

issue = {1},

pages = {240-269},

abstract = {Asymptotic output tracking of non-minimum phase (NMP) nonlinear systems has been a popular topic in control theory and applications. Many approaches have focused on finding solutions under minimal assumptions either in the target system or desired trajectories, as there is no general solution available. In this article, we propose a practical and simple solution for cases where the reference trajectory is periodic in time. Our approach employs a learning-based scheme to iteratively determine the desired feedforward input. Unlike previous learning-based frameworks, our method only requires the output tracking error to update the feedforward input iteratively and can be applicable to NMP systems. Our method retains the key advantages of the learning-based framework, including robustness to parameter uncertainties and periodic disturbances. We evaluate the effectiveness of our algorithm using simulation results with an inverted pendulum on a cart, a typical NMP nonlinear system.},

keywords = {asymptotic output tracking, iterative learning, Non-minimum phase, stable inversion},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Spectral Trade-off for Measurement Sparsification of Pose-graph SLAM},

author = {Jiyeon Nam and Soojeong Hyeon and Youngjun Joo and DongKi Noh and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/document/10333265},

doi = {10.1109/LRA.2023.3337590},

issn = {2377-3766},

year  = {2024},

date = {2024-01-02},

urldate = {2024-01-02},

journal = {IEEE Robotics and Automation Letters},

volume = {9},

issue = {1},

pages = {723 - 730},

abstract = {In this paper, we propose a trade-off optimization algorithm to compute an appropriate number of edges for measurement (edge) sparsification in pose-graph SLAM. The greater the amount of measurement data, the larger is the computational burden. To reduce computational burden, one can remove a portion of measurements. However, reliable data, such as odometric measurements, can be lost if measurements are removed without any principle. To remove measurements which is redundant, we propose a trade-off optimization algorithm between maximization of the Fiedler value and minimization of the largest eigenvalue of adjacency matrix for measurement graph. This problem formulation gives virtues twofold. First, it is scalable. For any dataset, when a weight for trade-off is given, this algorithm determines the appropriate number of edges since this is a trade-off optimization problem. Second, the edges of the measurement graph can be distributed evenly. The algorithm considers the minimization of the largest eigenvalue of the adjacency matrix, so it suppresses the upper bound of the maximum degree of the measurement graph. It removes the redundant information concentrated on a few nodes, and improves the estimation accuracy of the sparsified graph. To validate the performance of the proposed trade-off optimization algorithm, we apply our approach to CSAIL, Intel, and Manhattan datasets.},

keywords = {optimal control, simultaneous localization and mapping},

pubstate = {published},

tppubtype = {article}

}

@article{Discrete-timeheterogeneousmulti-agentsystemMulti-stepcouplingBlendeddynamics,

title = {A design method of distributed algorithms via discrete-time blended dynamics theorem},

author = {Jeong Woo Kim and Jin Gyu Lee and Donggil Lee and Hyungbo Shim},

editor = {Automatica},

doi = {https://doi.org/10.1016/j.automatica.2023.111371},

issn = {0005-1098},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

booktitle = {Automatica},

journal = {Automatica},

volume = {159},

pages = {111371},

abstract = {We develop a discrete-time version of the blended dynamics theorem for the use of designing distributed computation algorithms. The blended dynamics theorem enables to predict the behavior of heterogeneous multi-agent systems. Therefore, once we get a blended dynamics for a particular computational task, design idea of node dynamics for individual heterogeneous agents can easily occur. In the continuous-time case, prediction by blended dynamics was enabled by high coupling gain among neighboring agents. In the discrete-time case, we propose an equivalent action, which we call multi-step coupling in this paper. Compared to the continuous-time case, the blended dynamics can have more variety depending on the coupling matrix. This benefit is demonstrated with three applications; distributed estimation of network size, distributed computation of the PageRank, and distributed computation of the degree sequence of a graph, which correspond to the coupling by doubly-stochastic, column-stochastic, and row-stochastic matrices, respectively.},

key = {Discrete-time heterogeneous multi-agent systemMulti-step couplingBlended dynamics},

keywords = {Blended dynamics, Discrete-time blended dynamics, Discrete-time heterogeneous multi-agent system, Multi-step coupling},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Model Reference Gaussian Process Regression: Data-Driven State Feedback Controller},

author = {Hyuntae Kim and Hamin Chang},

doi = {10.1109/ACCESS.2023.3336421},

issn = {2169-3536},

year  = {2023},

date = {2023-11-01},

journal = {IEEE Access},

volume = {11},

pages = {134374},

abstract = {This paper proposes a data-driven state feedback controller that enables reference tracking for nonlinear discrete-time systems. The controller is designed based on the identified inverse model of the system and a given reference model, assuming that the identification of the inverse model is carried out using only the system’s state/input measurements. When its results are provided, we present conditions that guarantee a certain level of reference tracking performance, regardless of the identification method employed for the inverse model. Specifically, when Gaussian process regression (GPR) is used as the identification method, we propose sufficient conditions for the required data by applying some lemmas related to identification errors to the aforementioned conditions, ensuring that the Model Reference-GPR (MR-GPR) controller can guarantee a certain level of reference tracking performance. Finally, an example is provided to demonstrate the effectiveness of the MR-GPR controller.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@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 = {A Toolkit for Globally Robust Observer-Based Feedback with Relaxed Characterization of iISS/ISS},

author = {Hiroshi Ito and Hyungbo Shim},

url = {https://ieeexplore.ieee.org/abstract/document/9837417},

doi = {10.1109/TAC.2022.3193270},

issn = {0018-9286},

year  = {2023},

date = {2023-07-01},

urldate = {2022-07-22},

journal = {IEEE Transactions on Automatic Control},

volume = {68},

issue = {7},

pages = {3858-3871},

abstract = {This paper elaborates on flexibility in dealing with the interconnection of integral input-to-state stable (iISS) and input-to-state stable (ISS) systems. The undecoupled characterizations introduced separately for iISS and ISS in the literature are linked to build a framework enabling global analysis without settling for local and semi-global properties. Feedback control design in the presence of measurement noise can benefit from the framework immediately if plants are nonlinear, irrespective of application areas. This paper proposes a toolkit for providing robustness guarantees in observer-based output feedback control subject to measurement noise. For a nonlinear plant, the couplings among the plant state, the estimation error, and the measurement noise arising in the closed-loop equations often hinder global analysis such as ISS with respect to the measurement noise. In the formalism of iISS, this paper demonstrates that the flexibility in dealing with the couplings allows one to establish the robustness globally. Moreover, it gives a condition under which the closed-loop system can possess ISS and strong iISS which are stronger than iISS.},

keywords = {Integral input-to-state stability, Lyapunov function, Output feedback, Small gain theorem},

pubstate = {published},

tppubtype = {article}

}