• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.406-409
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• 2001

This study is an investigation for the ADS optimum design by using FEA. We write out program which express ADS perfectly and reduce the required time for correcting of model to the minimum in solution and manufacture result. We complete algorithm which can plan optimum forming of model by feedback error information in CAE. Then we correct model by feedback date obtaining in solution process, repeat course following stress solution again and do modeling rachet wheel for optimum forming. That is our aim. In rachet wheel, greatest equivalence stress originates in key groove corner and KS standard is proved the design for security.

• 한국소음진동공학회논문집
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• 제14권9호
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• pp.801-810
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• 2004

Parameter modification of a linear finite element model(FEM) based on modal sensitivity matrix is usually performed through an effort to match FEM modal data to experimental ones. However, there are cases where this method can't be applied successfully; lack of reliable modal data and ill-conditioning of the modal sensitivity matrix constitute such cases. In this research, a novel concept of introducing feedback loops to the conventional modal test setup is proposed. This method uses closed-loop natural frequency data for parameter modification to overcome the problems associated with the conventional method based on modal sensitivity matrix. We proposed the whole procedure of parameter modification using the closed-loop natural frequency data including the modal sensitivity modification and controller design method. Proposed controller design method is efficient in changing modes. Numerical simulation of parameter estimation based on time-domain input/output data is provided to demonstrate the estimation performance of the proposed method.

• International Journal of Control, Automation, and Systems
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• 제2권4호
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• pp.407-422
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• 2004

A new method for the design of predictive controllers for SISO systems is presented. The proposed technique allows uncertainties and constraints to be concluded in the design of the control law. The goal is to design, at each sample instant, a predictive feedback control law that minimizes a performance measure and guarantees of constraints are satisfied for a set of models that describes the system to be controlled. The predictive controller consists of a finite horizon parametric-optimization problem with an additional constraint over the manipulated variable behavior. This is an end-constraint based approach that ensures the exponential stability of the closed-loop system. The inclusion of this additional constraint, in the on-line optimization algorithm, enables robust stability properties to be demonstrated for the closed-loop system. This is the case even though constraints and disturbances are present. Finally, simulation results are presented using a nonlinear continuous stirred tank reactor model.

• 대한전자공학회논문지
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• 제25권12호
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• pp.1625-1632
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• 1988

This paper aims not only to introduce the concept of linear singular systems, geometric structure, and feedback but also to provide applications of the multivariable linear singular system theories to electric circuits which may appear in some electronic equipments. The impulsive or discontinuous behavior which is not desirable can be removed by the set of admissible initial conditions. The output-nulling supremal (A,E,B) invariant subspace and the singular system structure algorithm are applied to this double-input double-output electric circuit. The Weierstrass form of the pencil (s E-A) is related to the output-nulling supremal (A,E,B) invariant subspace from which the time domain solutions of the finite and the infinite subsystems are found. The generalized Lyapunov equation for this application with feedback is studied and finally, the use of orthogonal functions in singular systems is discussed.

• 한국산업정보학회논문지
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• 제9권1호
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• pp.43-48
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• 2004

본 논문에서는 GF(2m)상에서 Linear Feedback Shift Register 구조기반의 새로운 구조를 제안한다. 먼저 모듈러 곱셈기와 제곱기를 제안하고, 이를 기반으로 곱셈과 제곱을 동시에 수행할 수 있는 구조를 설계한다. 제안된 구조는 기약다항식으로 모든 계수가 1인 속성의 All One Polynomial 을 이용한다. 제안된 구조는 구조복잡도면에서 기존의 구조들보다 훨씬 효율적이다. 제안된 곱셈기는 공개키 암호의 핵심이 되는 지수기의 구현을 위한 효율적인 기본구조로 사용될 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 B
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• pp.992-994
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• 2004

In this paper, hybrid electromagnets using NdFeB permenant magnet are designed by 3-dimensional finite element analysis. Four hybrid magnets levitate the carrier of which total weight including control circuits and battery is 14[kg]. The nominal air gap length of the hybrid magnet is 3[mm]. The control circuit consists of DSP, 4-quadrant chopper, and gap sensor as feedback sensors. As a result, some experimental results for the magnetic levitation control by PI feedback control theory are shown.

• Nuclear Engineering and Technology
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• 제34권4호
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• pp.286-300
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• 2002

An algorithm for the sodium boiling model has been developed for calculation of the void reactivity feedback as well as the fuel and cladding temperatures in the KALIMER core after onset of sodium boiling. Modeling of sodium boiling in liquid metal reactors using sodium as a coolant is necessary because of phenomenon difference comparing with that observed generally in light water reactor systems. The applied model to the algorithm is the multiple-bubble slug ejection model. It allows a finite number of bubbles in a channel at any time. Voiding is assumed to result from formation of bubbies that (ill the whole cross section of the coolant channel except for the liquid film left on the cladding surface. The vapor pressure, currently, is assumed to be uniform within a bubble The present study is focused on not only demonstration of the vapor bubble behavior predicted by the developed model, but also confirmation of a qualitative acceptance for the model. As a result, the model can represent important phenomena in the sodium boiling, but it is found that further effort is also needed for its completition.

• Smart Structures and Systems
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• 제20권3호
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• pp.273-283
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• 2017

This paper presents and compares three feedback control strategies for active control of noise inside a 3-D vibro-acoustic cavity. These are a) control strategy based on direct output feedback (DOFB) b) control strategy based on linear quadratic regulator (LQR) to reduce structural vibrations and c) LQR control strategy with a weighting scheme based on structural-acoustic coupling coefficients. The first two strategies are indirect control strategies in which noise reduction is achieved through active vibration control (AVC), termed as AVC-DOFB and AVC-LQR respectively. The third direct strategy is based on active structural-acoustic control (ASAC). This strategy is an LQR based optimal control strategy in which the coupling between the various structural and the acoustic modes is used to design the controller. The strategy is termed as ASAC-LQR. A numerical model of a 3-D rectangular box cavity with a flexible plate (glued with piezoelectric patches) and with other five surfaces treated rigid is developed using finite element (FE) method. A single pair of collocated piezoelectric patches is used for sensing the vibrations and applying control forces on the structure. A comparison of frequency response function (FRF) of structural nodal acceleration, acoustic nodal pressure, and piezoelectric actuation voltage is carried out. It is found that the AVC-DOFB control strategy gives equal importance to all the modes. The AVC-LQR control strategy tries to consume the control effort to damp all the structural modes. It is seen that the ASAC-LQR control strategy utilizes the control effort more intelligently by adding higher damping to those structural modes that matter more for reducing the interior noise.

• 한국전자파학회논문지
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• 제23권10호
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• pp.1180-1187
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• 2012

본 논문에서는 협력 무선 통신 시스템의 순방향 링크에서, 각 이동국의 제한된 피드백 정보를 이용하여, 인접한 다수의 기지국들에서 동시에 코히어런트(coherent)하게 하나의 이동국에 데이터를 전송하는 결합 전송 공간 분할 다중 접속(Joint Transmission Space Division Multiple Access: JT-SDMA) 기술을 제안한다. JT-SDMA 기술을 위해, 공간상관도가 높은 각 collaborative base transceiver station(C-BTS)의 하향 링크 채널과 공간상관도가 낮은 다른 C-BTS들 간의 하향 링크 채널 특성에 적합한 unitary precoding 행렬 코드북을 디자인하였다. 또한, 제안하는 JT-SDMA 기술에서, 각 이동국의 제한된 피드백 정보량을 이용하여 다중 사용자 다이버시티 이득을 증가시키는 클러스터에서 수행되는 집중 스케줄링 기술을 제안하였다. 시뮬레이션의 통해 JT-SDMA 기술이 제한된 피드백 정보량을 이용하여, 다중 사용자 다이버시티 오더가 충분하지 않은 환경에서 셀 간 간섭을 효과적으로 억제하여, 클러스터 전송 용량을 향상시킬 수 있음을 확인하였다.

• 한국항공우주학회지
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• 제34권9호
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• pp.45-52
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• 2006

압전재료를 사용한 복합재료 패널의 플러터 억제 방법으로서 비선형 모델을 기반으로 하는 비선형 제어기법 중의 하나인 궤환 선형화에 의한 제어방법을 소개하였다. 기존의 패널 플러터 제어기에 대한 대부분의 연구들은 선형모델을 기반으로 설계된 선형2차제어기(LQR: Linear Quadratic Regulator)였음에 비해, 본 연구에서 제안한 비선형제어기는 시스템이 갖고 있는 비선형 특성들을 모두 고려해서 설계하였다. 압전 작동기로서는 PZT를 사용하였다. 가상변위의 원리와 4절점 사각형 요소를 사용하여 이산화된 비선형 운동방정식을 유도하였으며 제어기 설계를 위해 모달 변환을 통해 상태공간에서의 비선형 연계-모달 방정식으로 변환하였다. 본 논문에서 제안한 비선형 제어기에 의한 제어 결과와 선형모델을 기반으로 한 LQR 제어결과를 Newmark 수치적분법을 통해 시간영역에서 비교하였다.