List of English Publication

@article{LeeKimShim12,

title = {Disc Margins of the Discrete-time LQR and its Application to Consensus Problem},

author = {Jinyoung Lee and Jung-Su Kim and Hyungbo Shim},

doi = {10.1080/00207721.2011.555012},

year  = {2012},

date = {2012-10-01},

journal = {International Journal of Systems Science },

volume = {43},

number = {10},

pages = {1891-1900},

abstract = {This article presents a complex gain margin of discrete-time linear quadratic regulator (DLQR) and its application to a consensus problem of multi-agent higher order linear systems. Since the consensus problem can be converted into a robust control problem with perturbation expressed by complex numbers, and since the classical gain and phase margins are not enough to handle the current case, we study the so-called ‘disc margin’ which is somehow a combination of gain and phase margins. We first compute the disc margin of DLQR controller based on a Lyapunov argument, which is simple but yields a relaxed result over those previously reported in the literature. Then, it is shown that the disc margin can be enlarged arbitrarily when the system is asymptotically null controllable with bounded controls and when a low-gain feedback is employed. Based on this fact, the discrete-time consensus problem is solved by a DLQR-based consensus controller. Simulation study shows that the DLQR-based consensus controller has better robustness property against model uncertainties in the input channel.},

keywords = {Consensus},

pubstate = {published},

tppubtype = {article}

}

@article{KimKimShimBack12,

title = {Graph Connectivity-free Consensus Algorithm for State-coupled Linear Multi-agent Systems: Adaptive Approach},

author = {Jisu Kim and Hongkeun Kim and Hyungbo Shim and Juhoon Back},

doi = {10.5302/J.ICROS.2012.18.7.617},

year  = {2012},

date = {2012-07-01},

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

volume = {18},

number = {7},

pages = {617-621},

abstract = {This paper studies asymptotic consensus problem for linear multi-agent systems. We propose a distributed state feedback control algorithm for solving the problem under fixed and undirected network communication. In contrast with the conventional algorithms that use global information (e.g., graph connectivity), the proposed algorithm only uses local information from neighbors. The principle for achieving asymptotic consensus is that, for each agent, a distributed update law gradually increases the coupling gain of LQR-type feedback and thus, the overall stability of the multi-agent system is recovered by the gain margin of LQR. 



Graph Connectivity-free Consensus Algorithm for State-coupled.... Available from: https://www.researchgate.net/publication/290775474_Graph_Connectivity-free_Consensus_Algorithm_for_State-coupled_Linear_Multi-agent_Systems_Adaptive_Approach [accessed May 28 2018].},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{KimYangShimKim12,

title = {Synchronization of Linear Time-Varying Multi-Agent Systems with Heterogeneous Time-Varying Disturbances Using Integral Controller},

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

doi = {10.5302/J.ICROS.2012.18.7.622},

year  = {2012},

date = {2012-07-01},

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

volume = {18},

number = {7},

pages = {622-626},

abstract = {This paper presents synchronization of LTV (Linear Time-Varying) MAS (Multi-Agent Systems) with heterogeneous time-varying disturbances under a fixed, connected, and undirected communication network. All the agents can collect only relative state information from their neighborhoods. To achieve synchronization of the MAS, an integral control scheme is proposed based on relative state information between agents.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{SeoBacKimShim12,

title = {Output Feedback Consensus for High-order Linear Systems Having Uniform Ranks Under Switching Topology},

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

doi = {10.1049/iet-cta.2011.0197},

year  = {2012},

date = {2012-05-17},

journal = {IET Control Theory and Applications},

volume = {6},

number = {8},

pages = {1118-1124},

abstract = {This study addresses a challenging problem on the consensus of multi-agent systems, that is, simultaneously deals with the high-order linear multi-agent systems (including single and double integrators, and harmonic oscillators) and time-varying interaction topology. The interaction topology is assumed to switch among a finite number of connected undirected graphs having a non-vanishing dwell time. It is also constrained that each agent can use only the system outputs of its neighbouring agents for the purpose of feedback. Under these conditions, the authors propose two high-gain dynamic consensus protocols, one with multiple time-scale based and the other single time-scale, for the uniform rank systems without finite zeros. An example is provided to validate the proposed protocols.},

keywords = {Time-varying system},

pubstate = {published},

tppubtype = {article}

}

@article{JonnBack12,

title = {Power Regulation of Variable Speed Wind Turbines using Pitch Control based on Disturbance Observer},

author = {Youngjun Joo and Juhoon Back},

doi = {10.5370/JEET.2012.7.2.273},

year  = {2012},

date = {2012-03-01},

journal = {Journal of Electrical Engineering and Technology},

volume = {7},

number = {2},

pages = {273-280},

abstract = {Most variable speed wind turbines have pitch control mechanisms and one of their objectives is to protect turbines when the wind speed is too high. By adjusting pitch angles of wind turbine, the inlet power and the torque developed by the turbine are regulated. In this paper, the difference between the real wind speed and its rated value is regarded as a disturbance, and a component called disturbance observer (DOB) is added to the pre-designed control loop. The additional DOB based controller estimates the disturbance and generates a compensating signal to suppress the effect of disturbance on the system. As a result, the stability and the performance of the closed loop system guaranteed by an outer-loop controller (designed for a nominal system without taking into account of disturbances) are approximately recovered in the steady state. Simulation results are presented to verify the performance of the proposed control scheme.},

keywords = {Disturbance observer, Power regulation},

pubstate = {published},

tppubtype = {article}

}

@article{LeeKimShim11,

title = {Disc margins of the discrete-time LQR and its application to consensus problem},

author = {Jinyoung Lee and Jung-Su Kim and Hyungbo Shim},

doi = {10.1080/00207721.2011.555012},

isbn = {0020-7721},

year  = {2012},

date = {2012-02-10},

journal = {International Journal of Systems Science},

volume = {43},

number = {10},

pages = {1891-1900},

abstract = {This article presents a complex gain margin of discrete-time linear quadratic regulator (DLQR) and its application to a consensus problem of multi-agent higher order linear systems. Since the consensus problem can be converted into a robust control problem with perturbation expressed by complex numbers, and since the classical gain and phase margins are not enough to handle the current case, we study the so-called ‘disc margin’ which is somehow a combination of gain and phase margins. We first compute the disc margin of DLQR controller based on a Lyapunov argument, which is simple but yields a relaxed result over those previously reported in the literature. Then, it is shown that the disc margin can be enlarged arbitrarily when the system is asymptotically null controllable with bounded controls and when a low-gain feedback is employed. Based on this fact, the discrete-time consensus problem is solved by a DLQR-based consensus controller. Simulation study shows that the DLQR-based consensus controller has better robustness property against model uncertainties in the input channel.},

keywords = {discrete-time LQR},

pubstate = {published},

tppubtype = {article}

}

@article{LeeKimSongShim11,

title = {A constrained consensus problem using MPC},

author = {Jinyoung Lee and Jung-Su Kim and Hwachang Song and Hyungbo Shim},

doi = {10.1007/s12555-011-0516-5},

issn = {1598-6446},

year  = {2011},

date = {2011-10-01},

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

volume = {9},

number = {952},

pages = {952 - 957},

abstract = {This paper presents an MPC (Model Predictive Control) based consensus algorithm which solves a consensus problem in which constraints are imposed on the increment of the state of each agent. After making an artificial consensus trajectory using a previously designed consensus algorithm, the MPC is used to make the agent track the consensus trajectory. Simulation results demonstrate the effectiveness of the proposed algorithm.},

keywords = {Consensus problem},

pubstate = {published},

tppubtype = {article}

}

@article{SongAstofiShim11,

title = {A Control Theoretic Approach to Malaria Immunotherapy with State Jumps},

author = {Hwachang Song and A. Astolfi and Hyungbo Shim},

doi = {10.1016/j.automatica.2011.03.009},

issn = {0005-1098},

year  = {2011},

date = {2011-06-01},

journal = {Automatica},

volume = {47},

number = {6},

pages = {1271-1277},

abstract = {We investigate a control method for malaria dynamics to boost the immune response using a model-based approach. The idea of state jump is introduced and discussed using a hybrid model. To implement the state jumps we use a physiologically feasible method for the biological system, whereby the introduction of a pathogen into the system steers it to a desirable status. It is noted that we take advantage of a pathogen to implement state jumps in the system. The study is supported by recently reported experimental results.},

keywords = {Malaria},

pubstate = {published},

tppubtype = {article}

}

@article{KimShimSep11,

title = {Output Consensus of Heterogeneous Uncertain Linear Multi-Agent Systems},

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

doi = {10.1109/TAC.2010.2088710},

issn = {0018-9286},

year  = {2011},

date = {2011-01-01},

journal = {IEEE Transactions on Automatic Control },

volume = {56},

number = {1},

pages = {200-206},

abstract = {This technical note studies the output consensus problem for a class of heterogeneous uncertain linear multi-agent systems. All the agents can be of any order (which might widely differ among the agents) and possess parametric uncertainties that range over an arbitrarily large compact set. The controller uses only the output information of the plant; moreover, the delivered information throughout the communication network is also restricted to the output of each agent. Based on the output regulation theory, it is shown that the output consensus is reached if the (state) consensus is achieved within the internal models among the agent's controllers (even though the plant's outputs, rather than the internal model's outputs, are communicated). The internal models can be designed and embedded into the controller, which provides considerable flexibility to designers in terms of the type of signals that are agreed on among the agents.},

keywords = {Laplace equations},

pubstate = {published},

tppubtype = {article}

}

@article{SeoShimBack10,

title = {Reduced-order Consensus Controllers for Output-coupled SISO Linear Systems},

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

doi = {10.1007/s12555-010-0623-8},

isbn = {1598-6446},

year  = {2010},

date = {2010-12-01},

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

volume = {8},

number = {6},

pages = {1356-1363},

abstract = {In this paper, we continue the study of the consensus problem for multi-agent linear dynamic systems. All the agents have identical linear dynamics which can be of any order, and only the output information of each agents is delivered throughout the communication network. Under these settings, we show that the first-order and the second-order consensus problems can be solved by a first-order and a second-order dynamic filter, respectively. This holds even for high order dynamics, and therefore, the high order system does not have to use a high order consensus controller.},

keywords = {Consensus},

pubstate = {published},

tppubtype = {article}

}

@article{JoShimSon10,

title = {Disturbance observer for non-minimum phase linear systems},

author = {Nam Hoon Jo and Hyungbo Shim and Young Ik Son},

doi = {10.1007/s12555-010-0508-x},

issn = {1598-6446},

year  = {2010},

date = {2010-10-01},

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

volume = {8},

number = {5},

pages = {994-1002},

abstract = {Disturbance observer (DOB) approach has been widely employed in the industry thanks to its powerful ability to attenuate disturbances and compensate plant uncertainties. Motivated by the fact that the application of the DOB approach has been limited to minimum phase systems, we propose a new DOB configuration for non-minimum phase systems. Rigorous analysis for robust stability and performance recovery is presented in terms of a new filter Θ (s). By restricting the plant uncertainty to a multiplicative perturbation, we also present a systematic design methodology for the filter Θ(s) by virtue of the H∞ synthesis technique. An illustrative example of autopilot design is presented to show the effectiveness of the proposed method for which it is not easy to design H∞ controller to achieve some control goals. The simulation results show that the response of the perturbed system in the presence of disturbance can be recovered to the nominal system response in the absence of disturbance.},

keywords = {Disturbance observer},

pubstate = {published},

tppubtype = {article}

}

@article{BangShimParkSeo10,

title = {Robust Tracking and Vibration Suppression for a Two-Inertia System by Combining Backstepping Approach With Disturbance Observer},

author = {Jae Sung Bang and Hyungbo Shim and Sang Kyun Park and Jin H. Seo},

doi = {10.1109/TIE.2009.2038398},

issn = {0278-0046},

year  = {2010},

date = {2010-09-01},

journal = {IEEE Transactions on Industrial Electronics},

volume = {57},

number = {9},

pages = {3197-3206},

abstract = {In this paper, we consider the problem of designing a robust controller for a two-inertia system which contains arbitrarily large (but bounded) model uncertainties and disturbances. The research is motivated by the fact that a two-inertia system represents most of an industrial robot arm system that has a flexible joint, for which vibration suppression and robust control against model uncertainties and external disturbances are very important. The proposed controller consists of two parts: the outer-loop controller designed by the backstepping approach and the inner-loop controller by the new partial disturbance observer (DOB). The DOB is responsible for compensating the input-matched uncertainties and disturbances, while the backstepping controller is designed for dealing with the rest. The proposed controller makes tracking error and vibration of the system suppressed within an arbitrarily small bound during operation time when full states are measured. The results are verified by simulations and experiments with a Luenberger observer.},

keywords = {Robustness},

pubstate = {published},

tppubtype = {article}

}

@article{ShimKimKimBack10,

title = {A note on the differential regulator equation for non-minimum phase linear systems with time-varying exosystems},

author = {Hyungbo Shim and Jung-Su Kim and Hongkeun Kim and Juhoon Back},

doi = {10.1016/j.automatica.2009.12.007},

issn = {0005-1098},

year  = {2010},

date = {2010-03-01},

journal = {Automatica},

volume = {46},

number = {3},

pages = {605-609},

abstract = {Some control problems in practice are often formulated as a linear output regulation problem with time-varying exosystems. Although this problem has been studied recently, an explicit and constructive solution has been given only for minimum phase systems. This paper presents a solution for non-minimum phase systems whose zero dynamics is hyperbolic (or has an exponentially dichotomic split in the case of time-varying zero dynamics). The idea is inspired by the non-causal stable inversion.},

keywords = {Output regulation},

pubstate = {published},

tppubtype = {article}

}

@article{ShimJo10,

title = {Output Consensus of Heterogeneous Uncertain Linear Multi-Agent Systems”},

author = {Hyungbo Shim and Nam Hoon Jo},

url = {https://www.semanticscholar.org/paper/FURTHER-EXTENSIONS-ON-A-STABILITY-PROPERTY-WITH-Shim-Jo/7525f1f67b5bded0de3c23b27bc4d0b655df40b3},

year  = {2010},

date = {2010-01-01},

journal = {Dynamics of Continuous, Discrete and Impulsive Systems Series B},

volume = {17},

number = {6},

pages = {979-1000},

abstract = {In this paper we present three extended results on the stability property with slowly varying inputs that has been studied in, e.g., Khalil and Kokotovi´c (1991). The stability property has played an important role in control methodologies such as gainscheduling controls or robust controls for systems having slowly varying parameters. We begin with a review of the first extension, which shows that the inputs may vary fastly, but once its ‘average’ is slowly varying, then the same stability property still holds. The second extension deals with the case when a (transcritical) bifurcation occurs so that the

assumptions of the stability property are violated. We propose a Jump & Wait strategy which will still guarantee the stability property even under this case. Finally we prove that the Jump & Wait strategy can be employed not with the input itself but with the average of the input if the proposed structural condition is satisfied.},

keywords = {Slowly varying input},

pubstate = {published},

tppubtype = {article}

}

@article{SeoShimBack09,

title = {Consensus of High-order Linear Systems using Dynamic Output Feedback Compensator: Low Gain Approach},

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

doi = {10.1016/j.automatica.2009.07.022},

issn = {0005-1098},

year  = {2009},

date = {2009-11-01},

journal = {Automatica},

volume = {45},

number = {11},

pages = {2659-2664},

abstract = {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.},

keywords = {Multi-agent systems},

pubstate = {published},

tppubtype = {article}

}

@article{SonJoShimJeong09,

title = {Low-Pass Filter Property of an Input-Dimensional Output Feedback Passification Controller for Rotary Inverted Pendulum},

author = {Young Ik Son and Nam Hoon Jo and Hyungbo Shim and Goo-Jong Jeong},

doi = {10.1587/transfun.E92.A.2133},

issn = {0916-8508},

year  = {2009},

date = {2009-08-01},

journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},

volume = {92},

number = {8},

pages = {2133-2136},

abstract = {A rotary inverted pendulum is stabilized by a single first order dynamic output feedback system. Numerical simulations and experimental results show that the proposed control law has low-pass filter property as well as it can successfully replace the velocity measurements for LQR control law.},

keywords = {rotary inverted pendulum},

pubstate = {published},

tppubtype = {article}

}

@article{BackShim09,

title = {An Inner-loop Controller Guaranteeing Robust Transient Performance for Uncertain MIMO Nonlinear Systems},

author = {Juhoon Back and Hyungbo Shim},

doi = {10.1109/TAC.2009.2017962},

issn = {0018-9286},

year  = {2009},

date = {2009-07-01},

journal = {IEEE Transactions on Automatic Control  },

volume = {54},

number = {7},

pages = {1601-1607},

abstract = {An output-feedback controller has been recently proposed that has the following features: 1) it is an inner-loop controller so that it can be added on the existing closed-loop system working in harmony with a pre-designed (possibly non-robust) outer-loop controller; 2) it robustifies the closed-loop system in a way that the uncertain plant under external disturbance behaves like a disturbance-free nominal plant; and 3) it recovers the trajectory of the nominal closed-loop system in time domain. However, it is restricted to the single-input-single-output nonlinear systems. In this technical note, we extend this result for a class of multi-input-multi-output (MIMO) nonlinear systems having the same number of inputs and outputs. The tools used in this synthesis are the singular perturbation theory and the multi-variable circle criterion. An example shows the effectiveness of the proposed method.},

keywords = {Multi-input-multi-output},

pubstate = {published},

tppubtype = {article}

}

@article{SeoBackShimSeo09,

title = {Robust Adaptive Control for a Class of Nonlinear Systems with Complex Uncertainties},

author = {Sang-Bo Seo and Juhoon Back and Hyungbo Shim and Jin Heon Seo},

doi = {doi.org/10.5370/JEET.2009.4.2.292},

issn = {1975-0102},

year  = {2009},

date = {2009-06-30},

journal = {Journal of Electrical Engineering and Technology},

volume = {4},

number = {2},

pages = {292-300},

abstract = {This paper considers a robust adaptive stabilization problem for a class of uncertain nonlinear systems which include an unknown virtual control coefficient, an unknown constant parameter, and a time-varying disturbance whose bound is unknown, We propose a new estimator for an un-known virtual control coefficient and present a robust adaptive backstepping design procedure which results in a smooth state feedback control law, a new two-dimensional parameter update law, and a C1 Lyapunov function which is positive definite and proper.},

keywords = {Robust control},

pubstate = {published},

tppubtype = {article}

}

@article{ShimJoChangSeo09,

title = {A System Theoretic Study on a Treatment of AIDS Patient by Achieving Long-term Non-progressor},

author = {Hyungbo Shim and Nam Hoon Jo and H. Chang and Jin Heon Seo},

doi = {10.1016/j.automatica.2008.09.021},

issn = {0005-1098},

year  = {2009},

date = {2009-03-01},

journal = {Automatica},

volume = {45},

number = {3},

pages = {611-622},

abstract = {There has been much recent interest in the long-term non-progressor (LTNP), who has been infected with human immunodeficiency virus (HIV) but does not proceed to AIDS. Under the assumption that a mathematical model describing the HIV infection and drug effects is true for real systems, we claim that it is possible to steer the state of any patients to that of LTNP if the model parameters belong to the proposed parameter intervals. Once the state is transferred close to LTNP, CTL memory is established and the viral load remains very low level even after the medication is stopped. In order to justify the claim, we first analyze the stability and the bifurcation of the model and show that there exists an equilibria curve towards LTNP, which is stable for all fixed constant inputs except some singular points. Then, we propose a new treatment strategy based on a useful property of Non-vanishing Basin of Attraction (NvBA)-stability. An extensive simulation study is also included to validate the proposed treatment for various initial conditions and to show the robustness against the parameter uncertainty. From a practical perspective, it deserves further investigation whether the proposed treatment strategy could switch a patient into LTNP in the real world.},

keywords = {HIV/AIDS},

pubstate = {published},

tppubtype = {article}

}

@article{ShimJo09,

title = {An Almost Necessary and Sufficient Condition for Robust Stability of Closed-loop Systems with Disturbance Observer},

author = {Hyungbo Shim and Nam Jo},

doi = {10.1016/j.automatica.2008.10.009},

issn = {0005-1098},

year  = {2009},

date = {2009-01-01},

journal = {Automatica},

volume = {45},

number = {1},

pages = {296-299},

abstract = {The disturbance observer (DOB)-based controller has been widely employed in industrial applications due to its powerful ability to reject disturbances and compensate plant uncertainties. In spite of various successful applications, no necessary and sufficient condition for robust stability of the closed loop systems with the DOB has been reported in the literature. In this paper, we present an almost necessary and sufficient condition for robust stability when the Q-filter has a sufficiently small time constant. The proposed condition indicates that robust stabilization can be achieved against arbitrarily large (but bounded) uncertain parameters, provided that an outer-loop controller stabilizes the nominal system, and uncertain plant is of minimum phase.},

keywords = {Disturbance observer},

pubstate = {published},

tppubtype = {article}

}

@article{BackShim08,

title = {Adding Robustness to Nominal Output Feedback Controllers for Uncertain Nonlinear Systems: A Nonlinear Version of Disturbance Observer},

author = {Juhoon Back and Hyungbo Shim},

doi = {10.1016/j.automatica.2008.02.024},

issn = {0005-1098},

year  = {2008},

date = {2008-10-01},

journal = {Automatica},

volume = {44},

number = {10},

pages = {2528-2537},

abstract = {The linear disturbance observer (DOB) approach has been successfully employed as a tool for robust control and disturbance rejection in practice. In this paper, we present a nonlinear DOB which inherits all the benefits of the classical linear DOB approach. In particular, we prove that the proposed nonlinear DOB recovers not only the steady-state performance but also the transient performance of the nominal closed-loop system under plant uncertainties and input disturbances. One novel feature of the proposed controller is that it is an add-on type inner-loop output-feedback controller; thus any type of outer-loop controller can be combined to enhance the closed-loop system performance. Our result is a semi-global one and the stability proof is given when the nonlinear system has a well-defined relative degree with a stable zero dynamics.},

keywords = {Robust control},

pubstate = {published},

tppubtype = {article}

}

@article{KimYoonShimSeo08,

title = {Switching Adaptive Output Feedback MPC for a Class of Input-constrained Linear Plants},

author = {Jung-su Kim and Tae Woong Yoon and Hyungbo Shim and Jin Heon Seo},

doi = {10.1049/iet-cta:20070120},

issn = {1751-8644},

year  = {2008},

date = {2008-07-01},

journal = {IET Control Theory and Applications},

volume = {2},

number = {7},

pages = {573-582},

abstract = {An adaptive output feedback model predictive control (MPC) for an uncertain input-constrained neutrally stable linear plant using control-relevant switching is presented. By employing an input-to-state stabilising MPC as the multi-controller, switching adaptive output feedback MPC is proposed for the system. Unlike previous methods for handling uncertainties on the basis of minmax MPC laws or techniques for linear parameter varying systems, the proposed MPC scheme employs model switching to deal with modelling uncertainties through adaptation; a best model is selected for the MPC law from time to time. The proposed scheme using finite prediction horizon guarantees global stability. Simulation results are given to show the effectiveness of the scheme.},

keywords = {Adaptive control},

pubstate = {published},

tppubtype = {article}

}

@article{BackKangShimSeo08,

title = {Locally Optimal and Robust Backstepping Design for Systems in Strict Feedback Form with C1 Vector Fields},

author = {Juhoon Back and Sejin Kang and Hyungbo Shim and Jin Heon Seo},

issn = {1598-6446},

year  = {2008},

date = {2008-06-01},

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

volume = {6},

number = {3},

pages = {364-377},

abstract = {Due to the difficulty in solving the Hamilton-Jacobi-Isaacs equation, the nonlinear optimal control approach is not very practical in general. To overcome this problem, Ezal et al. (2000) first solved a linear optimal control problem for the linearized model of a nonlinear system given in the strict-feedback form. Then, using the backstepping procedure, a nonlinear feedback controller was designed where the linear part is same as the linear feedback obtained from the linear optimal control design. However, their construction is based on the cancellation of the high order nonlinearity, which limits the application to the smooth (C ∞ ) vector fields. In this paper, we develop an alternative method for backstepping procedure, so that the vector field can be just C 1 , which allows this approach to be applicable to much larger class of nonlinear systems.},

keywords = {Backstepping Design},

pubstate = {published},

tppubtype = {article}

}

@article{ShimJi08,

title = {Determination of Stability with respect to Positive Orthant for a Class of Positive Nonlinear Systems},

author = {Hyungbo Shim and Nam Hoon Jo},

doi = {10.1109/TAC.2008.921018},

issn = {0018-9286},

year  = {2008},

date = {2008-06-01},

journal = {IEEE Transactions on Automatic Control},

volume = {53},

number = {5},

pages = {1329-1334},

abstract = {When dealing with positive nonlinear systems, conventional theory requires too much for the stability of equilibrium points located on the boundary of the positive orthant, which encourages the consideration of stability with respect to the positive orthant. Generalizing this concept to the stability of a family of equilibrium points with non-vanishing Basin of attraction (NvBA)-stability has been introduced, which often becomes of interest when positive systems undergo bifurcations. In this technical note, we present a simple condition that can be employed for determining the NvBA-stability with respect to the positive orthant. The proposed condition is applicable to a class of nonlinear systems of certain Jacobian structure and is tailormade for this system. An illustrative example is included in order to help the exposition of the technical note.},

keywords = {nonlinear systems},

pubstate = {published},

tppubtype = {article}

}

@article{CheongBackShimSeo07,

title = {Nonsmooth feedback stabilizer for strict-feedback nonlinear systems that may not be linearizable at the origin},

author = {S. G. Cheong and Juhoon Back and Hyungbo Shim and Jin Heon Seo},

doi = {10.1016/j.sysconle.2007.04.009},

issn = {0167-6911},

year  = {2007},

date = {2007-11-01},

journal = {Systems & Control Letters},

volume = {56},

number = {11-12},

pages = {742-752},

abstract = {We present a continuous feedback stabilizer for nonlinear systems in the strict-feedback form, whose chained integrator part has the power of positive odd rational numbers. Since the power is not restricted to be larger than or equal to one, the linearization of the system at the origin may fail. Nevertheless, we show that the closed loop system is globally asymptotically stable (GAS) with the proposed continuous (but, possibly not differentiable) feedback. We formulate a condition that enables our design by characterizing the powers of the given system. The condition also shows that our result is an extension of Qian and Lin [Non-lipschitz continuous stabilizers for nonlinear systems with uncontrollable unstable linearization, Systems Control Lett. 42 (2001) 185–200] where the power of odd positive integers has been considered. New result on the global finite time stabilization problem is also presented.},

keywords = {Power integrator},

pubstate = {published},

tppubtype = {article}

}

@article{BaangChoiShim07,

title = {Perfect tracking control for linear systems with state constraint},

author = {Dane Baang and Jin Young Choi and Hyungbo Shim },

isbn = {1598-6446},

year  = {2007},

date = {2007-04-01},

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

volume = {5},

number = {2},

pages = {218-222},

abstract = {This paper presents a new Perfect Tracking Control (PTC) scheme for linear systems with state constraint. The proposed controller increases the number of the steps on-line for perfect tracking to satisfy the given ellipsoid-type state constraint. The unavoidable step delay that we impose is minimized by solving LMI feasibility problems and the possible feedback information loss is avoided. The proposed schemes are easy to develop, theoretically simple and clear, and include the conventional PTC as its special case.},

keywords = {Linear Systems},

pubstate = {published},

tppubtype = {article}

}

@article{YuBackSeo07,

title = {Constructive algorithm for dynamic observer error linearization via integrators: Single output case},

author = {Kyungtak Yu and Juhoon Back and Jin Heon Seo},

doi = {10.1002/rnc.1117},

issn = {1099-1239},

year  = {2007},

date = {2007-01-01},

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

volume = {17},

number = {1},

pages = {25-49},

abstract = {Dynamic observer error linearization which has been introduced recently is a new framework for observer design. Although this approach unifies several existing results on the problem and extends the class of systems that can be transformed into an observable linear system with an injection term of known signals, constructive algorithms to check the applicability are not available yet. In this paper, a constructive algorithm is proposed to solve the problem under some restrictions on the system structure and on the auxiliary dynamics introduced in the problem. The algorithm is constructive in the sense that the components of the transformation can be obtained step-by-step. Copyright © 2006 John Wiley & Sons, Ltd.},

keywords = {Dynamic observer},

pubstate = {published},

tppubtype = {article}

}

@article{BackYuSeo06,

title = {Dynamic observer error linearization},

author = {Juhoon Back and Kyung Tak Yu and Jin Heon Seo},

doi = {10.1016/j.automatica.2006.07.009},

issn = {0005-1098},

year  = {2006},

date = {2006-12-01},

journal = {Automatica},

volume = {42},

number = {12},

pages = {2195-2200},

abstract = {In this paper, a new framework of observer error linearization problem is proposed. The main idea of our approach is twofold. The one is to introduce an auxiliary dynamics whose input is the system output, and the other is to transform the augmented system into an observable linear system with an injection term which contains the system output as well as the state of the auxiliary dynamics. It is a natural extension of the recently developed dynamic observer error linearization where the injection term contains only newly defined output. It is also shown that whenever an n dimensional system is immersible into an  dimensional linear system up to an output injection, then it can be also dynamically observer error linearizable in our sense with a d dimensional auxiliary dynamics. Moreover, we show that the converse is not true by providing a counterexample, which implies that our approach is applicable to a strictly wider class of systems than that of the system immersion method.},

keywords = {Nonlinear observer},

pubstate = {published},

tppubtype = {article}

}

@article{YuJoSeo06,

title = {On the number of integrators needed for dynamic observer error linearization via integrators},

author = {Kyung Tak Yu and Nam Hoon Jo and Jin Heon Seo},

doi = {10.1093/ietfec/e89-a.3.817},

issn = {0916-8508},

year  = {2006},

date = {2006-03-01},

journal = {IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences},

volume = {E89-A},

number = {3},

pages = {817-821},

abstract = {In this letter, an illustrative example is given, which shows that the number of integrators needed for the dynamic observer error linearization using integrators can not be bounded by a function of the dimension of the system and the number of outputs in contrast to dynamic feedback linearization results.},

keywords = {Mathematics of computing},

pubstate = {published},

tppubtype = {article}

}

@article{BackSeo06,

title = {An algorithm for system immersion into nonlinear observer form: SISO case},

author = {Juhoon Back and Jin Heon Seo},

doi = {10.1016/j.automatica.2005.09.014},

isbn = {0005-1098},

year  = {2006},

date = {2006-02-01},

journal = {Automatica},

volume = {42},

number = {2},

pages = {321-328},

abstract = {The class of nonlinear systems that can be put into nonlinear observer form (linear system with output injection) can be broadened if we employ the system immersion. We provide an immersion algorithm for SISO nonlinear systems with relative degree r. The proposed algorithm is an extension of the previous results and does not require the relative degree 1 assumption. In addition, it is seen that the immersion can always be computed via algebraic computations and simple integrations except in a very special case in which the relative degree equals the system dimension (in this case, only one first order differential equation appears in the algorithm).},

keywords = {Observer design},

pubstate = {published},

tppubtype = {article}

}

@article{SonShimJoKim05,

title = {A new approach to design of a dynamic output feedback stabilizing control law for LTI systems},

author = {Young Ik Son and Hyungbo Shim and Nam Hoon Jo and Kab-II Kim},

doi = {10.1007/BF02916183},

issn = {1738-494X},

year  = {2005},

date = {2005-02-01},

journal = {Journal of Mechanical Science and Technology},

volume = {19},

number = {2},

pages = {618-624},

abstract = {We present a new state-space approach to construct a dynamic output feedback controller which stabilizes a class of linear time invariant systems All the states of the given system are not measurable and only the output is used to design the stabilizing control law In the design scheme, however, we first assume that the given system can be stabilized by a feedback law composed of the output and its derivatives of a certain order Beginning with this assumption, we systematically construct a dynamic system which removes the need of the derivatives The mam advantage of the proposed controller is regarding the controller order, which may be smaller than that of conventional output feedback controller Using a simple numerical example, it is shown that the order of the proposed controller is indeed smaller than that of reduced-order observer based output feedback controller},

keywords = {Linear system},

pubstate = {published},

tppubtype = {article}

}

@article{NohJoSeo04,

title = {Nonlinear observer design by dynamic observer error linearization},

author = {Daejong Noh and Nam Hoon Jo and Jin Heon Seo},

doi = {10.1109/TAC.2004.835397},

issn = {0018-9286},

year  = {2004},

date = {2004-10-08},

journal = {IEEE Transactions on Automatic Control},

volume = {49},

number = {10},

pages = {1746-1753},

abstract = {In this note, we address the problem of transforming a nonlinear system into nonlinear observer canonical form in the extended state-space with the aid of dynamic system extension and introduction of virtual outputs. As an intermediate step for the general problem, we consider a restricted structure of dynamic extension, which is obtained, roughly speaking, by adding the chains of integrators to the outputs of original system. We propose sufficient conditions which can be verified using the system dynamics expressed in their original coordinates. An illustrative example is included that demonstrates the advantage of the proposed method over the conventional method.},

keywords = {Nonlinear dynamical systems},

pubstate = {published},

tppubtype = {article}

}

@article{SonShimSeo04,

title = {A dynamic output feedback control law for elastic joint robots via feedback-passivity approach},

author = {Young Ik Son and Hyungbo Shim and Jin Heon Seo},

doi = {10.1016/j.jfranklin.2004.05.001},

issn = {0016-0032},

year  = {2004},

date = {2004-09-01},

journal = {Journal of the Franklin Institute},

volume = {341},

number = {6},

pages = {477-490},

abstract = {Motivated by recent dynamic output feedback passivation results, a new set-point control law is presented for an elastic joint robot when the velocity measurements are not available. The proposed methodology designs an additional dynamics with which the parallel-connected system is feedback passive. That is, the composite nonlinear robot system has relative degree one with a new output and its zero-dynamics subsystem becomes the virtual closed-loop system with a simple proportional-derivative (PD) control law. This approach provides an alternative way of replacing the role of the velocity measurements for the PD law. With the proposed control law, the transfer function of the additional system has the form of sG(s) with a strictly positive real (SPR) G(s). Robustness analysis is also given with regard to uncertainties on the robot parameters. The performance of the proposed control law is illustrated in the simulation studies of a manipulator with three revolute elastic joints.},

keywords = {Nonlinear system},

pubstate = {published},

tppubtype = {article}

}

@article{KellettShimTeel04,

title = {Further results on robustness of (possibly discontinuous) sample and hold feedback},

author = {Christopher M. Kellett and Hyungbo Shim and Andrew R. Teel},

doi = {10.1109/TAC.2004.831184},

issn = {0018-9286},

year  = {2004},

date = {2004-07-01},

journal = {IEEE Transactions on Automatic Control  },

volume = {48},

number = {7},

pages = {1081-1089},

abstract = {We demonstrate that sample and hold state feedback control (possibly discontinuous with respect to the state) is robust when the closed loop system possesses an appropriate Lyapunov function. We first show that if a Lyapunov decrease over sampling periods exists for the nominal system, this decrease can be maintained with some degradation relative to a sufficiently small additive perturbation. We then proceed to catalog several applications of this robustness, e.g., robustness to measurement noise, computational delays, or fast actuator dynamics.},

keywords = {Noise robustness},

pubstate = {published},

tppubtype = {article}

}

@article{ChwaChoiSeo04,

title = {Compensation of actuator dynamics in nonlinear missile control},

author = {Dongkyoung Chwa and Jin Young Choi and Jin Heon Seo},

doi = {10.1109/TCST.2004.825046},

issn = {1063-6536},

year  = {2004},

date = {2004-07-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {12},

number = {4},

pages = {620-626},

abstract = {This brief presents an approach to the compensation of the actuator dynamics in nonlinear missile control. In general, actuator dynamics are not considered in nonlinear missile control systems. Here, we analyzed the influences of actuator dynamics on the nonlinear missile controller and found that the second-order actuator dynamics showed risks of potentially destabilizing the overall system. Thus, to accommodate for the influence of the actuator dynamics, a compensator is proposed where the information of the nonlinear control input and the actual fin deflection is incorporated. We also conducted performance and stability analysis for the proposed control system, including actuator dynamics. We were able to confirm the validity of the proposed approach based on simulation results for the first- and second-order actuator dynamics.},

keywords = {Actuators},

pubstate = {published},

tppubtype = {article}

}

@article{SonYangShimSeo04,

title = {Feedback passivity approach to output feedback disturbance attenuation for uncertain nonlinear systems},

author = {Young Ik Son and Jongwook Yang and Nam Hoon Jo and Hyungbo Shim and Jin Heon Seo},

doi = {10.1080/00207720410001734246},

issn = {0020-7721},

year  = {2004},

date = {2004-03-16},

journal = {International Journal of Systems Science},

volume = {35},

number = {8},

pages = {467-477},

abstract = {The problem of output feedback disturbance attenuation for a class of uncertain nonlinear systems is studied based on output feedback passification. Previous work on output feedback disturbance attenuation is extended to the case where (1) the nominal system is not transformable into the normal form and (2) the uncertainty is parameterized nonlinearly. An adaptive output feedback controller is also provided that makes a nonlinear system passive. The paper then considers the output feedback disturbance attenuation problem for a class of uncertain nonlinear systems in the normal form and of relative degree one. The difference is that the result is applicable to nonlinear systems that include the uncertainty in the input matrix and do not satisfy the matching condition.},

keywords = {nonlinear systems},

pubstate = {published},

tppubtype = {article}

}

@article{BackSeo04,

title = {Immersion of non-linear systems into linear systems up to output injection: characteristic equation approach},

author = {Juhoon Back and Jin Heon Seo},

doi = {10.1080/00207170410001715040},

issn = {0020-7179},

year  = {2004},

date = {2004-01-01},

journal = {International Journal of Control},

volume = {77},

number = {8},

pages = {723-734},

abstract = {There exists a class of non-linear systems which cannot be transformed into non-linear observer form via diffeomorphism, but can be immersed into higher dimensional non-linear observer form. This paper investigates when n dimensional non-linear systems can be immersed into (n + m)-dimensional non-linear systems in non-linear observer form, and provides a necessary and sufficient condition. We also present an algorithm to check the immersibility. In general, at the first step of the algorithm, one should solve a differential equation with m + 1 unknowns rather than solving one with n + m unknowns simultaneously. When a solution to the differential equation can be obtained, the immersibility can be checked by a recursive algorithm. Moreover, when 2m ≤ n, a straightforward algorithm is provided to check the immersibility.},

keywords = {Non-Linear Systems},

pubstate = {published},

tppubtype = {article}

}

@article{BackJoSonShimSeo04,

title = {Nonlinear observer design via approximate normal form: ball and beam system on a vibrating frame},

author = {Juhoon Back and Nam Hoon Jo and Young Ik Son and Hyungbo Shim and Jin Heon Seo},

url = {https://www.researchgate.net/publication/237065066_Nonlinear_Observer_Design_via_Approximate_Normal_Form_Ball_and_Beam_System_on_a_Vibrating_Frame},

issn = {0916-8508},

year  = {2004},

date = {2004-01-01},

journal = {IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences},

volume = {87},

number = {3},

pages = {716-724},

abstract = {There exists a class of nonlinear systems which fail to have a well-defined relative degree but have a robust relative degree. We have removed the full relative degree assumption which the previous results required, and have provided a local state observer for nonlinear systems that have robust relative degree γ ≤ n and have detectability property in some sense. The proposed observer utilizes the coordinate change which transforms the system into an approximate normal form. Using the proposed method, we constructed an observer for the ball and beam system on a vibrating frame. Simulation results reveal that substantial improvement in the performance is achieved compared with other local observers.},

keywords = {Nonlinear observer desig},

pubstate = {published},

tppubtype = {article}

}

@article{SonShimKim03,

title = {A design method of an SPR system for stabilization of a crane without velocity mesurement},

author = {Young Ik Son and Hyungbo Shim and Kab-il Kim},

url = {https://www.researchgate.net/publication/237065067_A_Design_Method_of_an_SPR_System_for_Stabilization_of_a_Crane_without_Velocity_Measurement},

issn = {0916-8508},

year  = {2003},

date = {2003-11-01},

journal = {IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences},

volume = {86},

number = {11},

pages = {2894-2896},

abstract = {In order to stabilize a convey-crane with only cart position measurement, this paper designs an additional dynamics with which the parallel-connected system is feed-back passive. Since the crane system can be stabilized with a proportional-derivative (PD) law, the additional system is constructed by using the PD gains, and the closed-loop system exhibits almost same performances with the PD law. With the proposed control law, the transfer function of the additional system has the form of sH(s) with a strictly positive real (SPR) H(s).},

keywords = {SPR System},

pubstate = {published},

tppubtype = {article}

}

@article{SonShimBackJo03,

title = {An adaptive algorithm applied to a design of robust observer},

author = {Young Ik Son and Hyungbo Shim and Juhoon Back and Nam Hoon Jo},

doi = {10.1007/BF02982323},

isbn = {1738-494X},

year  = {2003},

date = {2003-10-01},

journal = {KSME International Journal},

volume = {17},

number = {10},

pages = {1443-1449},

abstract = {Primary goal of adaptive observers would be to estimate the true states of a plant. Identification of unknown parameters is of secondary interest and is achieved frequently with the persistent excitation condition of some regressors. Nevertheless, two problems are linked to each other in the classical approaches to adaptive observers; as a result, we get a good state estimate once after a good parameter estimate is obtained. This paper focuses on the state estimation without parameter identification so that the state is estimated regardless of persistent excitation. In this direction of research, Besancon (2000) recently summarized that most of adaptive observers in the literature share one common canonical form, in which unknown parameters do not affect the unmeasured states. We enlarge the class of linear systems from the canonical form of (Besancon. 2000) by proposing an adaptive observer (with additional dynamics) that allows unknown parameters to affect those unmeasured states. A recursive algorithm is presented to design the proposed dynamic observer systematically. An example confirms the design procedure with a simulation result.},

keywords = {Adaptive Observer},

pubstate = {published},

tppubtype = {article}

}

@article{ShimHanChungNamSeo03,

title = {Optimal Scheduling of Drug Treatment for HIV Infection: Continuous Dose Control and Receding Horizon Control},

author = {Hyungbo Shim and Seung-Ju Han and Chung Choo Chung and Sang Won Nam and Jin Heon Seo},

url = {https://pdfs.semanticscholar.org/534c/036146e9209129802942dc4a6130b1a90988.pdf},

issn = {1598-6446},

year  = {2003},

date = {2003-09-01},

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

volume = {1},

number = {3},

pages = {282-288},

abstract = {It is known that HIV (Human Immunodeficiency Virus) infection, which causes AIDS after some latent period, is a dynamic process that can be modeled mathematically. Effects of available anti-viral drugs, which prevent HIV from infecting healthy cells, can also be included in the model. In this paper we illustrate control theory can be applied to a model of HIV infection. In particular, the drug dose is regarded as control input and the goal is to excite an immune response so that the symptom of infected patient should not be developed into AIDS. Finite horizon optimal control is employed to obtain the optimal schedule of drug dose since the model is highly nonlinear and we want maximum performance for enhancing the immune response. From

the simulation studies, we found that gradual reduction of drug dose is important for the optimality. We also demonstrate the obtained open-loop optimal control is vulnerable to parameter variation of the model and measurement noise. To overcome this difficulty, we finally present nonlinear receding horizon control to incorporate feedback in the drug treatment. },

keywords = {Optimal Scheduling},

pubstate = {published},

tppubtype = {article}

}

@article{SonShimJoSeo03,

title = {Further results on passification of non-square linear systems using an input-dimensional compensator},

author = {Young Ik Son and Hyungbo Shim and Nam Hoon Jo and Jin Heon Seo},

url = {https://www.researchgate.net/publication/290308947_Further_Results_on_Passification_of_Non-square_Linear_Systems_Using_an_Input-Dimensional_Compensator},

issn = {0916-8508},

year  = {2003},

date = {2003-08-01},

journal = {IEICE Transactions on Fundamentals of Electronics Communications and Computer Sciences},

volume = {E86A},

number = {8},

pages = {2139-2143},

abstract = {Passification of a non-square linear system is considered by using a parallel feedforward compensator (PFC) and a squaring gain matrix. In contrast to the previous result, a technical assumption is removed by modifying the structure of the PFC. As a result, the broader class of non-square systems can be made passive by the proposed design method. Using the static output feedback (SOF) algorithms, the input-dimensional PFC and the squaring matrix can be designed systematically. The effectiveness of the proposed method is illustrated by practical system examples in the control literature.},

keywords = {input-dimensional compensator},

pubstate = {published},

tppubtype = {article}

}