• Proceedings of the KIEE Conference
• /
• 2003.07d
• /
• pp.2221-2223
• /
• 2003

다양한 공정에 범용 적으로 적용할 수 있는 PID 제어기 동조 방법이 많이 연구되고 있다. 한 가지 방법으로서 실제공정에 대한 축소모델을 구하고 축소모델로부터 파라메터를 동조하는 방법이 사용되고 있다. 본 논문에서는 시간응답으로부터 최소 자승법을 이용하여 고차 시스템을 2차계로 축소하는 방법을 제안하였다. 2차계 시스템을 차분 방정식으로 표현하고, 시간응답의 입출력 데이터로부터 최소 자승법을 이용하여 차분 방정식의 계수를 구하였다. 차분 방정식을 이산시간상태방정식으로 변환, 이산시간 상태방정식을 연속시간 상태방정식으로 변환하는 과정을 유도하여, 차분 방정식의 계수로부터 연속시간 상태방정식을 구하는 방법을 제시하였다. 시뮬레이션을 통하여 축소모델의 정확성 및 실제공정과의 특성을 비교하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.8
• /
• pp.823-833
• /
• 2010

For the study of thermophysical properties of kerosene for the liquid rocket and aviation fuels, the surrogate models are investigated. The density distributions based on the real gas equations of state(Soave modification of Redlich-Kwong and Peng-Robinson equation of state) and NIST SUPERTRAPP(extended corresponding state principle) are compared with the previous experimental results at supercritical conditions. The error range of thermophysical properties analyzed for the surrogate models as well. Peng-Robinson equation of state and extended corresponding state principle are especially accurate for the hydrocarbon fuels but the appropriate surrogate models need to be chosen to the operation conditions such as pressure and temperature.

• Proceedings of the KIPE Conference
• /
• 2019.11a
• /
• pp.204-205
• /
• 2019

리튬 이온 전지를 사용하기 위해선 내부 상태를 추정하는 알고리즘이 필요하다. 알고리즘 적용을 위해 리튬 이온 전지에서 나오는 전압과 전류신호를 이용해 전기적 등가 회로 모델을 설계한다. 이 모델은 전압원, 저항, 캐패시터로 구성되어 있으며, 충전과 방전 시 발생하는 전기적 신호를 모사한 것이다. 전기적 등가 회로 모델 분석에 사용되는 상태방정식은 알고리즘과 상황에 따라 변경된다. 본 논문에서는 연속시간 상태방정식과 이산시간 상태방정식에 대해 다루었다. 그리고 실제 알고리즘에 적용해 성능을 확인하였다.

• Journal of the Korean Institute of Gas
• /
• v.14 no.2
• /
• pp.22-26
• /
• 2010

In this study, experimental vapor pressures and densities of vapor and liquid phases versus temperature were estimated using PC-SAFT equation. The estimated results were compared with those using PR equation of state. For the vapor phase densities, both equations well predicted the literature data. However, PC-SAFT equation showed better prediction capability for liquid phase densities. In the comparison of vapor-liquid equilibrium prediction capability for the binary systems of methane and ethane, PC-SAFT equation was better than the PR equation.

• Journal of Advanced Marine Engineering and Technology
• /
• v.35 no.2
• /
• pp.216-223
• /
• 2011

TVC is a kind of ejector which entrains low pressure working fluid by using the high pressure working fluid. While most papers relating with ejectors treat the working fluid as an ideal gas for convenience, the fluid doesn't behave as the ideal gas when phase change occurs. In this study, numerical analysis is conducted by applying Redlich-Kwong equation of state instead of ideal gas equation of state. Two turbulent models are compared for the better prediction and SST k-${\omega}$ model is preferred rather than realizable k-${\epsilon}$ model by comparison. Energy loss at the diffuser inlet and throat using the real gas equation of state is relatively greater than that using ideal gas law. For the real gas case, pressure increase due to shock train at the diffuser outlet is relatively smaller than the ideal gas case, but both cases have the same pressure increase due to a pseudo shock.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.2
• /
• pp.906-918
• /
• 2012

In this study, we compared with results simulated by EOS(Equation of State) using Peng-Robinson model and GERG-2004 model for estimating vapor pressure, latent heat of vaporation, liquid density, and binary isotherm vapor-liquid equilibrium on pure components composing natural gases. We obtained the simulated results that while EOS using GERG-2004 model is more accurate than EOS using Peng-Robinson model for estimating liquid density, but rather it is less accurate for estimating binary isotherm vapor-liquid equilibrium. On the other hand, the use of Costald model in EOS using Peng-Robinson model for increasing more accuracy to calculate liquid density is almost same as EOS using GERG-2004 model within the error of 1 % compared with experimental data. Also, we confirmed that on the estimation of binary isotherm vapor-liquid equilibrium, EOS using GERG-2004 model is more accurate than EOS using Peng-Robinson model, but they are almost same.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.4
• /
• pp.47-60
• /
• 1999

The stability and efficiency of structural control systems depend on the accuracy of mathematical model of the system to be controlled. In this study, state equation models of a small scale test structure and an AMD(active mass damper) are obtained separately using OKID(observer/Kalman filter identification) which is a time domain system identification method. The test structure with each floor acceleration as outputs is identified for two inputs - the ground acceleration and the acceleration of the moving mass of AMD relative to the installation floor - individually and the two identified state equation models are integrated into one by model reduction method. The AMD is identified with the motor control signal as an input and the relative acceleration of the moving mass as an output, and it is shown that the identified model has large damping ratio and phase shift. The transfer functions and the time histories reconstructed from the identified models of the test model and the AMD match well with those measured from the experiment.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.5
• /
• pp.1747-1753
• /
• 2010

In this study, a comparative study was performed to predict the vapor-liquid equilibria with maximum azeotropic pressure for ethanol-benzene binary system between an equation of state model and a liquid activity coefficient model. Peng-Robinson equation of state model with a Panatiotopoulos mixing rules (PRP) was used and NRTL liquid activity coefficient model proposed by Renon was selected. The PRP model, even though it has only two binary adjustable parameters, was not inferior to the NRTL model to predict vapor-liquid equilibria for low pressure region of ethanol-benzene system and showed a better prediction capability for high pressure region of ethanol-benzene system than the NRTL model with three binary interaction parameters.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.37 no.2
• /
• pp.85-93
• /
• 2024

In this paper, we propose a method for establishing a state-space equation model for the motion analysis of floating structures subjected to wave loads, by applying system-identification techniques. Traditionally, the motion of floating structures has been analyzed in the time domain by integrating the Cummins equation over time, which utilizes a convolution integral term to account for the effects of the retardation function. State-space equation models have been studied as a way to efficiently solve floating-motion equations in the time domain. The proposed approach outlines a procedure to derive the target transfer function for the load-displacement input/output relationship in the frequency domain and subsequently determine the state-space equation that closely approximates it. To obtain the state-space equation, the method employs the N4SID system-identification method and an optimization approach that treats the coefficients of the numerator and denominator polynomials as design variables. To illustrate the effectiveness of the proposed method, we applied it to the analysis of a single-degree-of-freedom model and the motion of a six-degree-of-freedom barge. Our findings demonstrate that the presented state-space equation model aligns well with the existing analysis results in both the frequency and time domains. Notably, the method ensures computational accuracy in the time-domain analysis while significantly reducing the calculation time.

• Proceedings of the Korean Institute of Intelligent Systems Conference
• /
• 2000.11a
• /
• pp.145-148
• /
• 2000

근래 퍼지 제어 시스템의 설계는 대부분 Takagi-Sugeno 퍼지 모델에 기반하여 행해지고 있다. 이러한 TS퍼지 모델은 각 규칙의 결론부에 선형 상태 방정식의 형태를 위하고 있는데 각각의 상태 방정식은 원 비선형 시스템으로부터 얻어지고 있다. 하지만 시스템이 복잡해지고 비선형성이 강하면 TS퍼지 모델을 얻는데도 어려움이 따른다. 이에 본 논문에서는 TS퍼지 모델을 얻기 위한 한가지 방법을 제안한다. 먼저 시스템을 선형항과 비선형항으로 나누어 비선형항을 선형화하여 퍼지 모델화 하는 일련의 과정에 한가지 법칙을 도입하게 된다. 이렇게 얻어진 퍼지 모델을 기반으로 한 제어에는 많은 연구가 있었으며 본 논문에서는 극배치 방법을 이용한다. 마지막으로 모의 실험을 통하여 제안된 방법의 효용성을 검증한다.