Research

L1 control for nonlinear systems:  L1 performance, persistent bounded disturbances, worst case input/output relation, reachable set, forward invariance, controlled invariance, regulation map, set-valued analysis (semi-continuity, continuous selection), acceleration control (as application)

Safety control & Learning: barrier function, control barrier function, quadratic programming (QP), minimal norm selection, epsilon-nets, estimation of control barrier function with neural networks, adaptive cruise control (as application), safety of robotic manipulators (as application)

Linear matrix inequalities and their applications: mixed-norm gain for linear systems (L_2, L_infty), time-delay systems, communication delays, delay-independent controller synthesis, event-triggered control systems, piecewise linear (or affine) systems

H. T. Choi, J. H. Kim*, R. G. Sanfelice, “Barrier function approach for nonlinear L1 control,” accepted for presentation at IEEE Conf. Dec. Control (CDC 2025), Rio de Janerio, Brazil, Dec. 09--12, 2025.

H. T. Choi, H. Y. Park, T. Kim, J. H. Kim*, “A novel anomaly forecasting in time-series data: Feedback connection between forecasting and detecting algorithms with applications to power systems,” Adv. Intellg. Syst., vol. 7, no. 5, article no. 2401141, 2025. (Link)

H. T. Choi, J. H. Kim*, “An L∞ performance control for time-delay systems with time-varying delays: Delay-independent approach via ellipsoidal D-invariance,” AIMS Math., vol. 9, no. 11, pp. 30384--30405, 2024. (Link)

H. T. Choi, J. H. Kim*, T. Hagiwara, “Characterizing L1 output-feedback controller for nonlinear systems: Existence conditions via output controlled invariance domain,” Int. J. Robust Nonlin. Control, vol. 34, no. 17, pp. 11760--11785, 2024. (Link)

H. T. Choi, J. H. Kim*, “The L1 controller synthesis for piecewise continuous nonlinear systems via set invariance principles,” Int. J. Robust Nonlin. Control, vol. 33, no. 14, pp. 8670–8692, 2023. (Link)

H. Y. Park, H. T. Choi, J. H. Kim*, “The ℓp/q-gains for discrete-time observer-based event-triggered systems,” Int. J. Robust Nonlin. Control, vol. 33,
no. 11, pp. 6121–6134, 2023. (Link)

H. T. Choi, H. Y. Park, J. H. Kim*, “Output-based event-triggered control for discrete-time system with three types of performance analysis,” AIMS Math., vol. 8, no. 7, pp. 17091–17111, 2023. (Link)

H. T. Choi, J. H. Kim*, “Set-invariance-based interpretations for the L1 performance of nonlinear systems with non-unique solutions,” Int. J. Robust Nonlin. Control, vol. 33, no. 3, pp. 1858–1875, 2023. (Link)