• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.963-968
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• 1990

An iterative learning control scheme for tracking control of a class of uncertain nonlinear systems is presented. By introducing a model reference adaptive controller in the learning control structure, it is possible to achieve zero tracking of unknown system even when the upperbound of uncertainty in system dynamics is not known apriori. The adaptive controller pull the state of the system to the state of reference model via control gain adaptation at each iteration, while the learning controller attracts the model state to the desired one by synthesizing a suitable control input along with iteration numbers. In the controller role transition from the adaptive to the learning controller takes place in gradually as learning proceeds. Another feature of this control scheme is that robustness to bounded input disturbances is guaranteed by the linear controller in the feedback loop of the learning control scheme. In addition, since the proposed controller does not require any knowledge of the dynamic parameters of the system, it is flexible under uncertain environments. With these facts, computational easiness makes the learning scheme more feasible. Computer simulation results for the dynamic control of a two-axis robot manipulator shows a good performance of the scheme in relatively high speed operation of trajectory tracking.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.265-271
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• 2005

Randomness exists in engineering. Tolerance, assemble-error, environment temperature and wear make the parameters of a mechanical system uncertain. So the behavior or response of the mechanical system is uncertain. In this paper, the uncertain parameters are treated as random variables. So if the probability distribution of a random parameter is known, the simulation of mechanical multibody dynamics can be made by Monte-Carlo method. Thus multibody dynamics simulation results can be obtained in statistics. A new concept called functional reliability is put forward in this paper, which can be defined as the probability of the dynamic parameters(such as position, orientation, velocity, acceleration etc.) of the key parts of a mechanical multibody system belong to their tolerance values. A flexible mechanical arm with random parameters is studied in this paper. The length, width, thickness and density of the flexible arm are treated as random variables and Gaussian distribution is used with given mean and variance. Computer code is developed based on the dynamic model and Monte-Carlo method to simulate the dynamic behavior of the flexible arm. At the same time the end effector's locating reliability is calculated with circular tolerance area. The theory and method presented in this paper are applicable on the dynamics modeling of general multibody systems.

• 한국지능시스템학회논문지
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• 제8권2호
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• pp.117-127
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• 1998

전력계통은 번개, 폭우, 고장등이 여러요인으로 인해 변화하는 동특성을 갖는다. 전송선로의 리액터스가 사고로 인해 변하는 것도 그 대표적인 예이며 전력게통에 불확성을 야기시키는 원인이 된다. 이경우, 이와같은 불확실성에 대해 견실한 성능을 발휘하는 제어기가 필요하다. 한편, 최근의 연구들을 통해 비파라미터적인 불확실서을 갖는 계통에 대해 퍼지제어기가 우수한 성능을 발휘함이 입증되었다. 따라서, 본 논문에서는 선로의 고장 발생시, 전력계통의 발전기 단자전압을 일정값으로 유지하며 계통을 안정화시킬 수 있는 적응퍼지제어기를 궤환선형화 기법에 근거하여 설계하고자 한다. 아울러 본 논문에서는 불확실한 계통에 있어서, 리아프노프 안정도를 보장 받기우해 필요한 불확실한 항의 상계를 퍼지계통에 으해 추정하는 방법을 제안한다. 시뮬레인션 결고, 설계된 제어기가 선로고장에도 불구하고 계통의 전압유지와 과도 안정도를 잘 보장해 줌을 확인할 수 있었다.

• International Journal of Control, Automation, and Systems
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• 제6권6호
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• pp.960-967
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• 2008

This paper shows that design of a robustly stable repetitive control system is equivalent to that of a feedback control system for an uncertain linear time-invariant system satisfying the well-known robust performance condition. Once a feedback controller is designed to satisfy the robust performance condition, the feedback controller and the repetitive controller using the performance weighting function robustly stabilizes the repetitive control system. It is also shown that we can obtain a steady-state tracking error described in a simple form without time-delay element if the robust stability condition is satisfied for the repetitive control system. Moreover, using this result, a sufficient condition is provided, which ensures that the least upper bound of the steady-state tracking error generated by the repetitive control system is less than or equal to the least upper bound of the steady-state tracking error only by the feedback system.

• Journal of Advanced Marine Engineering and Technology
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• 제27권2호
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• pp.218-228
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• 2003

A hydraulic system is modeled as the second order differential equation with uncertain system parameters and disturbance composed of modeling errors. To Position the load of the hydraulic system to a desired point. the servo valve of the hydraulic system is controlled. As a control scheme. a global sliding mode control(GSMC) is Proposed Since the servo valve has a torque limit. the GSMC is designed to coordinate the position of the load along the minimum time trajectory within the torque limit. The Proposed control scheme can be designed with ranges of parametric uncertainties and specified torque limits. By the proposed control scheme, the closed form solution of the arriving time at the desired position can be estimated.

• 대한기계학회논문집A
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• 제24권1호
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• pp.7-15
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• 2000

This paper suggests an auto-tuning I'll) control algorithm that uses the advantage of PID controller and improves the system performance. The PID gains being designed by th- conventional method are tuned through the plant parameter estimation. The Extended Kalman Filter is used for the estimation. It works as an observer and noise filter. Moreover, as the plant state and the uncertain parameter could be estimated simultaneously, the proposed algorithm is very useful in the tracking control of a system with uncertain parameter. The auto-tuning I'll) controller could maintain the system performance in the case that the plant parameters are uncertain or varying. The proposed control algorithm requires a correct estimation of the plant parameter. The controller stability and the performance is considered through the stability criteria and a servo motor model. The Kalman filter estimates the most sensitive plant parameter, which is determined by the sensitivity analysis.

• 한국지능시스템학회논문지
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• 제15권3호
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• pp.324-329
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• 2005

본 논문에서는 시간 지연을 갖는 이산 시간 비선형 시스템을 $H\infty$ 의미에서 안정하게 하는 정적 출력 제한 퍼지 제어기 설계를 제시한다. 먼저 대상이 되는 비선형 시스템은 Takagi-Sugeno 퍼지 모델로 표현 되어진다. 그리고 parallel distributed compensation technique을 이용하여 퍼지 제어기의 형태를 만든다. 하나의 Lyapunov 함수를 정하여서 폐루프 시스템의 전역 점근적 안정성과 외란에 대한 강인성을 bilinear matrix inequality 형태로 제시한다. 그리고 합동변환법과 동질성 변환법을 통해 이것을 선형 행렬 부등식 (linear matrix inequality) 으로 표현한다. 제안된 방법의 효율성과 가능성을 보여주기 위해 한 예제를 포함한다.

• Journal of applied mathematics & informatics
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• 제40권1_2호
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• pp.351-370
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• 2022

The design of mechanical structures aims to meet criteria, together with the safety of operators and lives in the vicinity of the equipment. Thus, there are several cases that meeting the desired specification causes the mechanical device to perform unstable and, sometimes, chaotic behavior. In these cases, control methods are applied in order to stabilize the device when in operation, aiming at the physical integrity of the component and the device operators. In this work, we will develop a study about the influence of a controller applied in a non-ideal capsule system operating with uncertain parameters, being non-existent in the literature. For this, two initial conditions were used: one that the capsule starts from rest and another that it is already in motion. Thus, the effectiveness of the controller can be assessed in both initial conditions, restricting the movement of the internal vibration-impact system to the capsule.

• Structural Engineering and Mechanics
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• 제87권3호
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• pp.231-242
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• 2023

A novel combinatorial type-2 adaptive neuro-fuzzy inference system (T2-ANFIS) and robust proportional integral derivative (PID) control framework for intelligent vibration mitigation of uncertain structural system is introduced. The fuzzy logic controllers (FLCs), are designed independently of the mathematical model of the system. The type-1 FLCs, have a limited ability to reduce the effect of uncertainty, due to their fuzzy sets with a crisp degree of membership. In real applications, the consequent part of the fuzzy rules is uncertain. The type-2 FLCs, are robust to the fuzzy rules and the process parameters due to the fuzzy degree of membership functions and footprint of uncertainty (FOU). The adaptivity of the proposed method is provided with the optimum tuning of the parameters using the neural network training algorithms. In our approach, the PID control force is obtained using the generalized type-2 neuro-fuzzy in such a way that the stability and robustness of the controller are guaranteed. The robust performance and stability of the presented framework are demonstrated in a numerical study for an eleven-story seismically-excited building structure combined with an active tuned mass damper (ATMD). The results indicate that the introduced type-2 neuro-fuzzy PID control scheme is effective to attenuate plant states in the presence of the structured and unstructured uncertainties, compared to the conventional, type-1 FLC, type-2 FLC, and type-1 neuro-fuzzy PID controllers.

• 한국지능시스템학회논문지
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• 제17권2호
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• pp.185-189
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• 2007

본 연구에서는 T-S 퍼지시스템으로 모델된 불확실한 시변 파라메터를 갖는 비선형 시스템의 고장검출 시스템 설계법을 제안한다. 이를 위하여 퍼지시스템에 대한 소인수 분해를 정의하고 좌 소인수를 이용하여 오차발생기를 설계한다. 오차발생기의 출력으로부터 고장검출을 판정하는 검출기준을 제시한다. 제시된 방법의 효용성을 입증하기 위하여 역도립 진자시스템에 적용하여 컴퓨터 모의실험을 수행한다.