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 = {Nominal performance recovery, Sliding mode control, Uncertain systems},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{ParkShimJoo18,

title = {Recovering Nominal Tracking Performance in an Asymptotic Sense for Uncertain Linear Systems},

author = {Gyunghoon Park and Hyungbo Shim and Youngjun Joo},

doi = {10.1137/17M1122657},

year  = {2018},

date = {2018-03-01},

journal = {SIAM Journal on Control and Optimization},

volume = {56},

number = {2},

pages = {700-722},

abstract = {In this paper, we consider the problem of recovering a (predefined) nominal output trajectory in the presence of model uncertainty and external disturbance. In particular, whereas the nominal performance recovery (NPR) has been studied in an approximate fashion in the literature, we extend the notion of the NPR in an asymptotic sense from the perspective of the internal model principle: that is, as long as the disturbance and reference signals are generated by an exogenous system, the actual output not only is kept close to the nominal trajectory as much as desired but also asymptotically converges to the nominal one as time elapses. It is shown via the singular perturbation theory that the asymptotic NPR can be achieved for uncertain minimum-phase systems under arbitrarily large (but bounded) model uncertainty. A disturbance observer (DOB) approach is employed in the controller design, with the internal model embedded into the so-called Q-filter, which is a key component of the DOB. Simulation results for mechanical positioning systems illustrate that the asymptotic NPR can enhance robust performance of control systems.},

keywords = {Disturbance observer, Internal model principle, Nominal performance recovery, Robustness},

pubstate = {published},

tppubtype = {article}

}

@article{ParkKim18,

title = {Adaptive Regulation to Nominal Response for Uncertain Mechanical Systems and Its Application to Optical Disk Drive},

author = {Gyunghoon Park and Hyungjong Kim},

doi = {10.1109/TIE.2017.2733480},

year  = {2018},

date = {2018-02-01},

journal = {IEEE Transactions on Industrial Electronics},

volume = {65},

number = {2},

pages = {1450-1458},

abstract = {In this paper, we present an add-on type robust controller for uncertain mechanical systems with a sinusoidal disturbance of an unknown frequency. The main purpose is to recover (predefined) nominal tracking performance in an “asymptotic” sense, that is, the actual output asymptotically converges to the nominal trajectory, as well as the maximum difference between them is maintained small enough during the operation. As a key component of the proposed controller, a disturbance observer that contains an internal model is proposed. Especially, the parameters of the internal model are updated in an “adaptive” fashion in order to cope with the unknown frequency of the disturbance, for which a frequency identifier is employed in the controller design. The nominal performance recovery of the proposed controller is analyzed in the sense of Lyapunov and singular perturbation theory. Both simulation and experimental results point out that the proposed control scheme can serve as a robust track following controller for uncertain optical disk drive systems where eccentricity of disk causes a sinusoidal disturbance.},

keywords = {Frequency estimation, Mechanical system, Nominal performance recovery, Robustness},

pubstate = {published},

tppubtype = {article}

}