• 한국정밀공학회지
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• 제25권12호
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• pp.89-99
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• 2008

In this paper, the position tracking control problem of the servo system with nonlinear dynamic friction is issued. The nonlinear dynamic friction contains a directly immeasurable friction state variable and the uncertainty caused by incomplete parameter modeling and its variations. In order to provide the efficient solution to these control problems, we propose the composite control scheme, which consists of the robust friction state observer, the FNN approximator and the approximation error estimator with sliding mode control. In first, the sliding mode controller and the robust friction state observer is designed to estimate the unknown internal state of the LuGre friction model. Next, the FNN estimator is adopted to approximate the unknown lumped friction uncertainty. Finally, the adaptive approximation error estimator is designed to compensate the approximation error of the FNN estimator. Some simulations and experiments on the servo system assembled with ball-screw and DC servo motor are presented. Results show the remarkable performance of the proposed control scheme. The robust friction state observer can successfully identify immeasurable friction state and the FNN estimator and adaptive approximation error estimator give the robustness to the proposed control scheme against the uncertainty of the friction parameters.

• 한국공작기계학회논문집
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• 제18권1호
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• pp.90-102
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• 2009

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 infernal 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.

• 융합신호처리학회논문지
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• 제2권2호
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• pp.95-102
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• 2001

일반적으로 피지시스템은 compact한 공간에 대한 어떠한 비선형 함수도 일정오차 이내에서 근사할 수 있다. 그러나 퍼지시스템의 응용은 퍼지규칙의 수가 많아지는 경우, 특히 고차의 비선형 시스템에 대하여는 사용되기 어렵다는 단점을 가지고 있다. 본 논문에서는 근사하고자 하는 비선형 함수의 분해를 이용한, 병렬형과 종속형의 두 가지 형태의 퍼지시스템 재구성 방식을 제안한다. 이 두 가지 형태의 재구성을 적절히 이용하여 퍼지규칙의 수를 기하급수적으로 줄일 수 있다. 제안된 알고리즘은 적응구조를 가진 퍼지시스템에 대하여 응용 가능하며 두 가지 적웅 퍼지 슬라이딩제어 예를 통하여 그 타당성을 보인다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.35.1-35
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• 2002

$\textbullet$ Sliding mode control (SMC) with nonlinear interpolation in variable boundary layer (VBL) is proposed $\textbullet$ A sigmoid function is used for nonlinear interpolation in VBL. $\textbullet$ The Parameter of the sigmoid function is tuned by fuzzy controller $\textbullet$ The choice of parameter for the sigmoid function is guided by FC. $\textbullet$ The parameter is continuously updated as boundary layer thickness varies. $\textbullet$ The proposed method hasbetter tracking performance than the conventional linear interpolation $\textbullet$ To demonstrate its performance the proposed control algorithm is applied to a nonlinear system.

• 한국지능시스템학회논문지
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• 제11권9호
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• pp.788-792
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• 2001

일반적으로 슬라이딩모드 제어는 외란이나 시스템의 변수변환에 강인한 특성을 가지나, 그 변화의 최대 경계 값을 알아야한다. 그러나, 이 값은 쉽게 얻어질 수가 없다. 퍼지 논리는 잘 정의되어 있지 않거나 복잡한 시스템의 제어기 설계에 효과적인 방법을 제시하나, 과도응답을 미리 결정할 수가 없다. 본 논문에서는 두 이론의 장점을 결합하여 새로운 제어 알고리듬을 제시한다. 최적의 퍼지변수 값을 결정하기 위하여 적응이론을 도입한다. 마지막으로 제안한 제어 알고리듬의 타당성을 살펴보기 위하여 수치적인 예를 가변길이진자시스템에 적용한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제2권2호
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• pp.146-152
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• 2002

Mold level control has been a major control task for continuous casting plants. The system involves nonlinearities such as stick-slip friction in the sliding gate, time-delay, friction force variations between molten steel and the inner wall of mold, and nozzle logging/unclogging. These complex problems should be solved to control mold level for steel cast. In this paper, we propose a neural fuzzy mold level control technique for solving these complex problems and give experiment studies to show the mold level control in continuous casting process.

• International Journal of Automotive Technology
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• 제7권6호
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• pp.729-739
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• 2006

This paper describes an active fault-tolerant control system for an induction motor drive that propels an Electrical Vehicle(EV) or a Hybrid one(HEV). The proposed system adaptively reorganizes itself in the event of sensor loss or sensor recovery to sustain the best control performance given the complement of remaining sensors. Moreover, the developed system takes into account the controller transition smoothness in terms of speed and torque transients. In this paper which is the sequel of (Diallo et al., 2004), we propose to introduce more advanced and intelligent control techniques to improve the global performance of the fault-tolerant drive for automotive applications(e.g. EVs or HEVs). In fact, two control techniques are chosen to illustrate the consistency of the proposed approach: sliding mode for encoder-based control; and fuzzy logics for sensorless control. Moreover, the system control reorganization is now managed by a fuzzy decision system to improve the transitions smoothness. Simulations tests, in terms of speed and torque responses, have been carried out on a 4-kW induction motor drive to evaluate the consistency and the performance of the proposed fault-tolerant control approach.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.548-551
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• 1991

The Sliding Mode Control of Variable Structure System is applied to robot manipulators or servo system for its merits of robustness to variable system parameters and disturbances. But Switching frequency of control input is excessively high during sliding mode operation. In this paper, a new control algorithm usings fuzzy logic is proposed to solve this problem. With the proposed algorithm, a dc motor speed control system has been simulated and the result shows expected performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 B
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• pp.536-538
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• 1997

In this paper, a sliding mode control-based fuzzy controller is suggested. It is a robust control method and can be applied in the presence of model uncertainties and parameter disturbances. An inverted pendulum is effectively controlled by the proposed method in spite of existing model uncertanties and parameter disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.164.2-164
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• 2001

Sliding mode control (SMC) with variable nonlinear boundary layer is proposed. Two Fuzzy logic controllers (FLCs) are used to decide both boundary layer thickness and nonlinear interpolation using sigmoid function in the boundary layer. The nonlinear interpolation in the boundary layer suing FLC reduces stead state error and chattering. Sigmoid function is used to nonlinear interpolation in the boundary layer sigmoid function parameter with FLC. To demonstrate its performance, the Proposed control algorithm is applied to a simple nonlinear system.