• 한국지진공학회논문집
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• 제5권4호
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• pp.75-81
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• 2001

지진하중을 받는 구조물의 능동제어를 위한 퍼지관리제어기법(fuzzy supervisory control technique)에 관하여 연구하였다. 제시하는 제어기법은, 구조물에 발생하는 변위 및 속도 등의 정보를 이용하여 퍼지추론과정을 거쳐서 구조물의 상태를 파악함으로써 기설계된 제어이득들을 실시간으로 관리 및 조정한다. 알고리즘의 검증을 위하여 지진하중을 받는 3자유도 구조물에 대하여 수치모사를 수행하여 정적이득을 갖는 LQR제어기와 비교하였으며, 해석결과 제시한 제어기는 지진응답의 제어에 매우 효과적임을 알 수 있다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.113-119
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• 1994

Vibration control of offshore structures subjected to wave loads is studied. The reduction of the dynamic responses of offshore towers subjected to wind generated random ocean waves is an important issue in the aspect of serviceability, fatigue life and safety of the structure. In this thesis, the effectiveness of the active tuned mass damper(ATMD) compared with the tuned mass damper(TMD) is mainly considered. Instantaneous optimal control scheme is employed for the active vibration control and Kalman filtering technique is used for the estimation of unmeasured response of structures. In practice, displacements and velocities could not be measured as easily as accelerations. So the state estimation methods like Kalman filter is very important. Numerical simulation is conducted for guarantee the effectiveness of ATMD for offshore structures.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1410-1415
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• 2001

Active control of sound radiation from a vibrating rectangular plate by a steady-state harmonic point force disturbance is experimentally studied. Structural excitation is achieved by two piezoceramic actuators mounted on the panel. Two accelerometers are implemented as error sensors. Estimated radiated sound signals using vibro-acoustic path transfer function are used as error signals. The vibro-acoustic path transfer function represents system between accelerometers and microphones. The approach is based on a multi-channel filtered-x LMS algorithm. The results shows that attenuation of sound levels of 11dB, 10dB is achieved.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.662-667
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• 2007

A new neuro-control scheme for active control of structures is proposed. It utilizes lattice pattern of state vector as training data of probabilistic neural network(PNN). Therefore. it is the so-called lattice probabilistic neural network(LPNN). PNN makes control forces by using all the training patterns. Therefore, it takes much time to obtain a control force in application. This inevitably may delay the control action. However. control force of LPNN is calculated by using only the adjacent information of LPNN input. So, the response of LPNN is greatly faster than PNN. The proposed control algorithm is applied for three story building under California and El Centro earthquakes. Also, control results of the LPNN are compared with those of the conventional PNN. The structural responses have been suppressed effectively by the proposed algorithm.

• 한국자동차공학회논문집
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• 제1권1호
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• pp.90-100
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• 1993

This paper presents some inherent characteristics of a semi-active variable damper featuring electro-rheological (ER) fluid. The damping force of the damper can be selectively adjusted or controlled by employing electric field to the ER fluid domain. This is possible owing to the pressure drop across the piston occured by field-dependent variable yield stress of the ER fluid. This is fundamentally different than the performance of a conventional adjustable viscous damper. To demonstrate the effectiveness and superiority over the conventional one, the proposed damper is incorporated with a suspension system. A quarter car model with the suspension system is formulated and represented by a state equation. By choosing numerical values based on realistic package size, power requirements and suitable ER properties, the performance characteristics of the suspension system are obtained and evaluated in both frequency and time domains. The effects of constant electric field and on-off controlled electric field which relates to the damping force are also examined.

• Structural Engineering and Mechanics
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• 제32권1호
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• pp.179-191
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• 2009

A stochastic response spectrum method is proposed for simple evaluation of the structural response of an actively controlled aseismic structure. The response spectrum is constructed assuming a linear structure with an active mass damper (AMD) system, and an earthquake wave model given by the product of a non-stationary envelope function and a stationary Gaussian random process with Kanai-Tajimi power spectral density. The control design is executed using a linear quadratic Gaussian control strategy for an enlarged state space system, and the response amplification factor is given by the combination of the obtained statistical response values and extreme value theory. The response spectrum thus produced can be used for simple dynamical analyses. The response factors obtained by this method for a multi-degree-of-freedom structure are shown to be comparable with those determined by numerical simulations, demonstrating the validity and utility of the proposed technique as a simple design tool. This method is expected to be useful for engineers in the initial design stage for structures with active aseismic control.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년 학술대회 논문집 정보 및 제어부문
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• pp.266-268
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• 2006

In this paper, we design a Linear Quadratic Gaussian(LQG) controller for active suspensions. We can improve the inherent suspension problem, trade-off between the ride quality and the suspension travel by selecting appropriate weights in the LQ-objective function. Using an optimization-algorithm, Evolution Strategy(ES), we find the proper control gains for selected frequencies, which have major effects on the vibrations of the vehicle's state variables. The frequencies and proper control gains are used for the neural network data. During a vehicle running, the trained on-line neural network is activated and provides the proper gains for non-trained frequencies.

• Journal of Information Display
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• 제9권2호
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• pp.5-8
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• 2008

Bottom gate thin film transistors (TFTs) with microcrystalline and amorphous Si (a-Si) double active layers (DAL) were fabricated. Since the process of DAL TFTs can use that of conventional a-Si TFTs, these DAL TFT process has advantages, such as low cost, large substrate, and mass production capacity. In order to analyze the degradation characteristics in saturation region for driving TFTs of active matrix organic light emitting diode, three different dynamic stresses were applied to DAL TFTs and a-Si TFTs. The threshold voltage shift of DAL TFTs and a-Si TFTs during 10,000 second stress is 0.3V and 2V, respectively. DAL TFTs were more reliable than a-Si TFTs.

• 대한기계학회논문집A
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• 제24권3호
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• pp.543-549
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• 2000

Results of theoretical investigations of the stability characteristics of an actively controlled externally pressurized air journal bearing are presented. Proportional control and derivative control are used for the control algorithm of active air bearing. The stability characteristics of the actively controlled bearing operating at zero steady-state eccentricity is investigated with the step jump method. The speed at onset of instability is raised for both proportional control and derivative control of bearing. Proportional control increased the stability threshold without affecting the whirl ratio. But for derivative control of bearing, stability threshold increase is accompanied by a parallel reduction of the whirl ratio. Results show active control of bearing can be adopted for the stability improvement of air journal bearing.

• Wind and Structures
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• 제6권4호
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• pp.249-262
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• 2003

The purpose of this study is to propose a procedure for evaluating quantitatively the increase of the equivalent damping ratio of a structure with passive/active vibration control systems subjected to a stationary wind load. A Lyapunov function governing the response of a structure and its differential equation are formulated first. Then the state-space equation of the structure coupled with the secondary damping system is solved. The results are substituted into the differential equation of the Lyapunov function and its derivative. The equivalent damping ratios are obtained from the Lyapunov function of the combined system and its derivative, and are used to assess the control effect of various damping devices quantitatively. The accuracy of the proposed procedure is confirmed by applying it to a structure with nonlinear as well as linear passive/active control systems.