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한성익 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.1
In this paper, a tracking control problem for a mechanical servo system with nonlinear dynamic friction is treated. The nonlinear friction model contains directly immeasurable friction state and the uncertainty caused by incomplete modeling and variations of its parameter. In order to provide the efficient solution to these control problems, we propose a hybrid control scheme, which consists of a robust friction state observer, a RFNN estimator and an approximation error estimator with sliding mode control. A sliding mode controller and a robust friction state observer is firstly designed to estimate the unknown internal state of the LuGre friction model. Next, a RFNN estimator is introduced to approximate the unknown lumped friction uncertainty. Finally, an adaptive approximation error estimator is designed to compensate the approximation error of the RFNN estimator. Some simulations and experiments on the mechanical servo system composed of ball-screw and DC servo motor are presented. Results demonstrate the remarkable performance of the proposed control scheme.
한성익,이진우,이태오,이권순 제어로봇시스템학회 2009 제어로봇시스템학회 국내학술대회 논문집 Vol.2009 No.9
In this article, we develop a hybrid control scheme of a dynamic structured learning recurrent fuzzy neural network (DRFN) and a dynamic friction observer. The DRFN controller with the adaptive dynamic friction observer based on the LuGre friction is designed to position the servo system and estimate the friction parameters and a directly immeasurable friction state variable. Next, a reconstructed error estimator is also designed to give additional robustness to the control system under the presence of the model uncertainty. A proposed composite control scheme is applied to the position tracking control of the servo system.
Barrier Lyapunov function-based model-free constraint position control for mechanical systems
한성익,하현욱,이장명 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.7
In this article, a motion constraint control scheme is presented for mechanical systems without a modeling process by introducing a barrier Lyapunov function technique and adaptive estimation laws. The transformed error and filtered error surfaces are defined to constrain the motion tracking error in the prescribed boundary layers. Unknown parameters of mechanical systems are estimated using adaptive laws derived from the Lyapunov function. Then, robust control used the conventional sliding mode control, which give rise to excessive chattering, is changed to finite time-based control to alleviate undesirable chattering in the control action and to ensure finite-time error convergence. Finally, the constraint controller from the barrier Lyapunov function is designed and applied to the constraint of the position tracking error of the mechanical system. Two experimental examples for the XY table and articulated manipulator are shown to evaluate the proposed control scheme.
비선형 동적시스템에 대한 비선형 미분 외란관측기를 이용한 유한시간 Dynamic Surface 제어기 설계
한성익 제어·로봇·시스템학회 2019 제어·로봇·시스템학회 논문지 Vol.25 No.8
This study proposes a finite-time dynamic surface control (DSC) combined with a nonlinear differentiator disturbanceobserver for nonlinear systems, in which dynamics are partially known. The nonlinear differentiator disturbance observer, virtualstabilizing controllers, and final controller were designed based on finite-time convergent theorem via the recursive steps in conventionalDSC system. In conclusion, the study results show that the filtered output error due to the first-order filter in a conventionalDSC, which is the source of controller design complexity and stability, can be bypassed; this is because stability is provided by afinite-time Lyapunov function comprised of newly defined variables instead of the tracking error variables used in conventionalDSCs. Thus, the controller design procedure and stability analysis can be more intuitive than those of a conventional DSC. Anotherimportant study result is the design of a nonlinear differentiator disturbance observer for nonlinear systems to estimate uncertainty infinite-time. The study shows that very competitive results can be achieved using the proposed method, as shown by the simulationresults for an articulated manipulator system.
분수-체계 외란 관측기와 분수-체계 슬라이딩 모드 제어기를 적용한 Euler-Lagrange 시스템에 대한 위치 제어
한성익 제어·로봇·시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.9
. A fractional-order based sliding mode controller and disturbance observer were developed for enhanced positioning performance of Euler Lagrange systems. First, an issue of a fractional-order sliding control was addressed to obtain rapid convergence compared to the conventional standard and terminal sliding mode controls. Next, a fractional-order disturbance observer based on the fractional-order sliding surface was developed to obtain more enhanced estimation performance over the integer-order based disturbance observer. In order to demonstrate the superior properties of the proposed strategies, simulations were performed for a three-link articulated manipulator.
한성익,이장명 제어·로봇·시스템학회 2012 International Journal of Control, Automation, and Vol.10 No.4
Output-constrained backstepping dynamic surface control (DSC) is proposed for the purpose of output constraint and precise output positioning of a strict feedback single-input, single-output dynamic system in the presence of deadzone and uncertainty. A symmetric barrier Lyapunov function (BLF) is employed to meet the output constraint requirement using DSC as an alternative method of backstepping control that is adopted mainly to deal with the BLF’s constraint control. However, using the ordinary DSC method with the BLF limits the selection of the control gain whereas this limitation does not exist in the backstepping structure. To remove this limitation, we propose a partial backstep-ping DSC method in which backstepping control is added only in the first recursive DSC design step. For precise positioning, an inverse deadzone method and adaptive fuzzy system are introduced to handle unknown deadzone and unmodeled nonlinear functions. We show that the semiglobal boundedness of the overall closed-loop signals is guaranteed, the tracking error converges within the prescribed region, and precise positioning performance is ensured. The proposed control scheme is experimentally evaluated using a robot manipulator.
비선형시스템에 대한 오차동역학 기준 비선형 관측기를 갖는 명령필터 적용 강인한 백스테핑 제어
한성익 제어·로봇·시스템학회 2020 제어·로봇·시스템학회 논문지 Vol.26 No.12
A command filtered robust backstepping control (BSC) scheme for a nonlinear system is studied in this paper. To avoid the repeated differentiation of the conventional BSC system, the command filter is introduced and newly defined auxiliary error surface is considered to obtain robustness to uncertainty. Based on this error surface dynamics, a nonlinear disturbance observer is constructed to estimate uncertainty due to perturbation and external disturbance. The stability of the closed-loop system for the designed controller, observer, and compensating signal is proved by the finite-time Lyapunov theorem. The efficacy of the proposed control system was evaluated by simulations of two nonlinear example systems. .
스프링 연결 병렬형 탄성 역진자의 비선형 $H_2/H_\infty/LTR$ 제어
한성익 제어로봇시스템학회 2000 제어·로봇·시스템학회 논문지 Vol.6 No.5
In this paper, a nonlinear $H_2/H_\infty/LTR$ control for the flexible inverted pendulum of a parallel type with Coulomb friction is presented. The dynamic equation for this system is derived by the Hamilton's principle and assumed-mode method. This hard nonlinear system can be modeled by a the quasi-linear state space model using the REF method. It is shown that the $H_2/H_\infty$ control can be applied to the nonlinear controller design of the system having Coulomb frictions if the proper LTR conditions are satisfied. In order to present the usefulness of the suggested control method, the nonlinear $H_2/H_\infty/LTR$ controller is designed to control the Position of the end point of the flexible inverted pendulum that has Coulomb frictions present in actuator parts. The results are given via computer simulations.