• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.62.3-62
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• 2002

In this paper, we proposed a control technique that can be applied to various processes. The most of the process can bereduced to second order plus time delay (SOPTD) model. And we proposed improved model reduction algorithm using geneticalgorithm. This method considered four points to reduce the error between original model and reduced model in the Nyquistcurve. And, to compensate time delay, the Smith predictor plus PID controller is adopted. And a new PID tuning algorithm wasproposed, which got from numerical analysis and can be obtained the optimal performance. The PID parameters are obtainedfrom the coefficients and time delay of reduced model. The simulation results show the validity.

• International Journal of Control, Automation, and Systems
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• v.6 no.6
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• pp.836-844
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• 2008

This paper presents an approach to order reduction of linear parameter varying controller for polytopic model. Feasible solutions which satisfy relevant linear matrix inequalities for constructing full-order parameter varying controller evaluated at each polytopic vertices are first found. Next, sufficient conditions are derived for the existence of a right coprime factorization of parameter varying controller. Furthermore, a singular perturbation approximation for time invariant systems is generalized to reduce full-order parameter varying controller via parameter varying right coprime factorization. This generalization is based on solutions of the parameter varying Lyapunov inequalities. The closed loop performance caused by using the reduced order controller is developed. To examine the performance of the reduced-order parameter varying controller, the proposed method is applied to reduce vibration of flexible structures having the transverse-torsional coupled vibration modes.

• Journal of Korean Society for Quality Management
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• v.38 no.4
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• pp.491-503
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• 2010

This paper presents a research model, which identifies a relationship between medical error reduction, efficiency of organizational systems, and employee satisfaction with organizational support. The proposed model was tested through hypotheses, based on data collected from 210 respondents from the medical staff of large -sized (i.e., more than 500 beds) residential hospitals in cities of South Korea. The results of the study showed that medical error reduction is associated with corrective system and employee satisfaction with organizational support. Therefore, it is very important that organizations improve their employees' satisfaction by providing sufficient support (e.g., information support and sharing, work guide book, etc.) for their work. In addition, in organizational systems, the corrective system has positive relationship with medical error reduction. In terms of corrective procedures, leaders or managers can make improvements by providing and supporting a friendly work environment where errors may be reported without blame and discussed in order to be corrected.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.46-50
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• 2011

In order to perform the satellite structural analysis, FE-Model(Finite Element Model) considering all mechanical properties is necessary. Generally, different companies develop several satellite components, and sometimes it is very difficult to obtain FE-Model. In this case, FE-Model reduction using superelement method can be good solution. For developing satellite, antenna manufacturer required satellite FE-Model to calculate microvibration induced by antenna operation, and condensed model using superelement method was provided. Superelement method is based on Craig-Bampton method, and it is applied to spacecraft FE-Model reduction in this paper. From modal analysis and the frequency response analysis results between full FE-Model and condensed model, the usefulness of reduced model is confirmed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1496-1503
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• 2009

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty to stabilize greenhouse gas concentrations in the atmosphere. In order to fulfil the commitments of the countries in an economically efficient way, the UNFCCC adapted the emission trading scheme in the Kyoto Protocol. If the UNFCCC's scheme is enforced in the country, considerable changes in electric power industry are expected due to the imposed greenhouse gas emission reduction. This paper proposes a game theoretic model of the case when generation companies participate in both competitive electricity market and emission market simultaneously. The model is designed such that generation companies select strategically between power quantity and greenhouse gas reduction to maximize their profits in both markets. Demand function and Environmental Welfare of emission trading market is proposed in this model. From the simulation results using the proposed model the impact of the emission trading on generation companies seems very severe in case that the emission prices are significantly high.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.10
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• pp.89-96
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• 2015

Explicit numerical integration methods for power system transient stability simulation require very small time steps to avoid numerical instability. The EXST1 exciter model is a primary source of fast dynamics in power system transients. In case of the EXST1, the required small integration time step for entire system simulation increases the computational demands in terms of running time and storage. This paper presents a practical exciter model reduction approach which allows the increase of the required step size and thus the method can decrease the computational demands. The fast dynamics in the original EXST1 are eliminated in the reduced exciter model. The use of a larger time step improves the computational efficiency. This paper describes the way to eliminate the fast dynamics from the original exciter model based on linear system theory. In order to validate the performance of the proposed method, case studies with the GSO-37 bus system are provided. Comparisons between the original and reduced models are made in simulation accuracy and critical clearing time.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.8
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• pp.1062-1070
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• 2018

This paper presents a simple identification method for discrete-time low-order model of unknown delay process from pulse response. The key idea is to find the parameters of the model such that the first N moments of the unknown process and the model are equal. We first show that the k-th moment of a process can be determined by the moments of the input and output. The parameters and delay are estimated separately. It is shown that for a given delay, the parameters of the low-order model can be determined by solving linear equations in a matrix form. Delay of the model is estimated such that the integral of the absolute errors (IAE) of the candidate models with possible delays minimizes. The illustrative example shows that the proposed method can directly identify low-order models without order reduction process from a single pulse response.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.31 no.8
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• pp.33-38
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• 1982

This paper deals with the simplification of the transfer function in a frequency domain, viz. the integral of the squared errors between the original and the simplified model is minimized and the latter is estimated by the Walsh function. It tries to minimize the errors between the frequency responses of the two functions. This method is compared with the existing method by means of a numercal example. The frequency response of this simplified model approximates closely to that of the original model. The proposed method is simpler in analysis and easier in implementation than the existing methods. Though the Walsh function can be easily generated with the discrete values, it has errors because its zero crossings are not continuous. This method aims at the reduction of the errors in the real parts and the imaginary parts of the two functions by dividing into the more sub-intervals, and selecting the reduced-order model according to the response of the model. As a result, it can be applied for the simplification of higher order functions into lower order functions and for the design of control systems.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.53 no.1
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• pp.16-21
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• 2004

This paper presents an approximation method for simplifying a high-order transfer function to a low-order transfer function. A model reduction is based on minimizing the error function weighted by the numerator polynomial of reduced systems. The proposed methods provide better low frequency fit and a computer aided algorithm that estimates the coefficients vector for the numerator and denominator polynomial on the simplified systems from an overdetermined linear system constructed by frequency responses of the original systems. Two examples are given to illustrate the feasibilities of the suggested schemes.

• Journal of Institute of Control, Robotics and Systems
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• v.4 no.1
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• pp.19-25
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• 1998

발란싱 축소모델의 상태변수는 플랜트의 상태변수에 대한 정보를 주지 못한다. 발란싱 축소모델을 좌표 변환하여 얻은 상태유지 축소모델은 그 축소오차가 발란싱 축소모델의 축소오차와 같음을 증명하였다. 상태축소오차를 정의하였고, 이 오차를 구하는 방법을 제시하였는데, 이 오차는 축소모델의 차수가 정해지면 불변임을 증명하였다. 상태유지 축소모델의 상태변수는 그 상태축소오차가 작은 경우 원 시스템의 상태변수를 근사하는 장점이 있다. 상태유지 축소모델을 저차원제어기 설계에 적용하여 저차원 상태변수가 플랜트의 상태변수를 근사하는 예를 보여주었다.