• International Journal of Control, Automation, and Systems
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• 제4권4호
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• pp.414-427
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• 2006

This paper presents an adaptive feedback linearization control scheme for induction motors with simultaneous variation of rotor and stator resistances. Two typical modeling techniques, rotor flux model and stator flux model, have been developed and successfully applied to the controller design and adaptive observer design, respectively. By using stator fluxes as states, over-parametrization in adaptive control can be prevented and control strategy can be developed without the need of nonlinear transformation. It also decrease the relative degree for the flux modulus by one, thereby, yielding, a simple control algorithm. However, when this method is used for flux observer, it cannot guarantee the convergence of flux. Similarly, the rotor flux model may be appropriate for observers, but it is not so for adaptive controllers. In addition, if these two existing methods are merged into overall adaptive control system, it brings about structural complexies. In this paper, we did not use these two modeling methods, and opted for the airgap flux model which takes on only the positive aspects of the existing rotor flux model and stator flux model and prevents structural complexity from occuring. Through theoretical analysis by using Lyapunov's direct method, simulations, and actual experiments, it is shown that stator and rotor resistances converge to their actual values, flux is well estimated, and torque and flux are controlled independently with the measurements of rotor speed, stator currents, and stator voltages. These results were achieved under the persistent excitation condition, which is shown to hold in the simulation.

• 한국지진공학회논문집
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• 제21권4호
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• pp.163-170
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• 2017

The need for eco-friendly building materials such as engineered wood has increased to reduce carbon emissions. Although the range and height of engineered wood buildings are gradually increasing in North America and Europe, engineered wood is mainly used for low-rise residential buildings in Korea. In order to reduce carbon emissions more, therefore, it needs to expand the use of engineered wood by applying it to various buildings with different uses or more stories. With this background, the aim of this study is to investigate the applicability of engineered wood for 9-story office buildings. Since a 9-story building with engineered wood only is not allowed in KBC, an example building has RC ordinary shear walls as the lateral force resisting system while engineered wood is only used for gravity load resisting moment frames. Another example building is also used for comparison where both lateral and gravity load resisting systems are designed by RC. The applicability of engineered wood is investigated by comparing the seismic performance and the amount of carbon emission of both buildings. The result shows that the seismic performance of both buildings was not significantly different while the amount of carbon emission of the engineered wood building was much less then the RC building. Based on this result, engineered wood is sufficiently applicable to 9-story office buildings even though it still needs to pay attention to the shear design of reinforce concrete walls.

• 한국도로학회논문집
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• 제14권6호
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• pp.139-148
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• 2012

PURPOSES : The accuracy of travel time information is a key measure of effectiveness and reliability of advanced traveler information systems. This study aims at investigating drivers' perception on the acceptable level of information accuracy and their corresponding valuations. METHODS : A questionnaire survey was executed for collecting driver perception data to capture the expectation level of travel time information provided and their willingness to pay for the information. A Tobit model was adopted for exploring the relationship among the acceptable level, driver socioeconomic characteristics and travel attributes. Since drivers' willingness to pay for accurate travel time information can be different according to their travel lengths, a piecewise linear regression model was developed to capture the sensitivity of values of travel time information to travel length. RESULTS : The analysis results suggest that trip purpose and travel time are two dominant factors to determine drivers' acceptable level of travel time information. For business and short trips, drivers want more accurate information than for non-business and long trips. Drivers' willingness to pay for travel time information also varies depending on their incomes, trip purposes and travel lengths. The results also show that drivers' valuation of travel time information provided is sensitive to their travel length. For longer trips, drivers are less sensitive to travel time information and then put less value on the information provided. CONCLUSIONS : Censored nonlinear regression models are developed to estimate drivers' acceptable accuracy for travel time information and their valuation using questionnaire survey data. The findings on drivers perception to the required accuracy of travel time information and their corresponding willingness to pay can be used in the design and deployment of advanced traveler information system to improve its effectiveness and usefulness through high compliance.

• 제어로봇시스템학회논문지
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• 제13권1호
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• pp.6-14
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• 2007

Modem version of supersonic jet fighter aircraft must have been guaranteed appropriate controllability and stability in HAoA(High Angle of Attack). Limit value of aircraft entering into the departure in HAoA is related to aircraft configuration design. But, the control law such as AoA and yaw-rate limiter is implemented in digital Fly-By-Wire flight control system of supersonic jet fighter to guarantee the aircraft's safety in HAoA. The HAoA flight control law have two parts, one is control law of departure prevention and the other is control law of departure recovery support. The control laws of departure prevention for advanced jet trainer consist AoA limiter, roll command limiter and rudder fader. The control laws of departure recovery support are consist yaw-rate limiter and MPO(Manual Pitch Override) mode. The guideline of pitch rocking using MPO mode is simple, but operating skill of pitch rocking is very difficult by the pilot with inexperience of departure situation. This paper addresses the design and validation of APR(Automatic Pitch Rocker) control law instead of MPO in order to automatic recovery without manual pitch rocking by the pilot. And, recovery characteristic with APR verifies by the nonlinear analysis and pilot evaluation.

• 한국지반공학회논문집
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• 제19권4호
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• pp.55-64
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• 2003

흙의 건조현상은 기상조건에 지배받는 evaporativity와 지반의 물 전달 능력에 지배받는 evaporability의 영향을 받는다. 지표면증발은 점토로 매립된 지반에서 건설장비의 주행성을 확보하기 위해서는 필요불가결한 요소이다. 본 논문에서는 준설 점토 지반에서의 증발현상을 규명할 수 있는 모델을 제시하였다. 이 모델은 포화토 및 불포화토에서의 수분과 물의 이동 및 열전달에 대한 식으로 구성되어 있다. 흙수분 특성곡선을 구하기 위하여 압력판추출시험(pressure plate extractor test)과 데시케이터실험이 수행되었으며 일차원 증발현상을 규명하기 위하여 컬럼증발실험을 수행하였다. 체적이 변하는 흙에서의 물, 증기 및 열전달 비선형 미분방정식을 풀기 위하여 유한차분프로그램을 개발하였으며 실험결과와 이론해를 비교하였다.

• 한국지능시스템학회논문지
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• 제19권3호
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• pp.337-342
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• 2009

본 논문은 비선형 시스템의 퍼지 모델을 적용한 시간 지연 간격에 종속적인 안정도 분석 및 제어기 설계에 대해서 논의한다. 먼저, 시간 지연을 포함하는 비선형 시스템을 T-S 퍼지 시스템으로 모델링한다. 시간 지연을 포함하는 전체 페루프 비선형 시스템은 다중 시간 지연을 갖는 T-S 퍼지 시스템이 된다. 전체 폐루프 퍼지 시스템의 안정도를 분석하고, 안정화 시키는 퍼지 제어기 설계를 위한 필요충분 조건을 유도한다. 유도된 안정도 및 제어기 설계 조건이 시간 지연 간격에 종속적임을 확인하다. 기존의 시간 지연에 종속적인 안정도 및 제어기 설계 조건 보다 넓은 범위를 나타냄을 확인한다. 제안된 필요충분 조건을 선형 행렬 부등식의 형태로 나타내고, 기존의 다양한 프로그래밍 기법을 이용하여 제어기 이득값을 구한다. 예제를 통하여 제안된 이론의 타당성을 확인한다.

• 한국포장학회지
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• 제12권2호
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• pp.97-102
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• 2006

Shock and vibration inputs are transmitted from the transporting vehicle through the packaging to the fruit. The vibration causes sustained bouncing of fruits against each other and the container wall. The steady state vibration input may cause serous fruit injury, and the damage is particularly severe if the fruits are bounced at its resonance frequency. The determination of the resonance frequencies of the fruits and vegetables may help the packaging designer to determine the proper packaging system providing adequate protection for the fruits, and to understand the complex interaction between the components of the fruits when they relate to expected transportation vibration inputs. To analyze the vibration properties of the watermelon for optimum packaging design during transportation, sinusoidal sweep vibration tests were carried out. The resonance frequency of the watermelon ranged from 19 to 32 Hz and the amplitude at resonance was between 1.6 and 2.9 G. The resonance frequency and amplitude at resonance frequency band of the watermelon decreased with the increase of the sample mass. The multiple nonlinear regression equation for predicting the resonance frequency of the watermelon were developed using the independent variables such as mass, input acceleration and sphericity.

• 대한기계학회논문집A
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• 제35권11호
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• pp.1471-1476
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• 2011

자동차 배기계의 앞쪽에 배치된 촉매변환기는 배기가스 중 유해한 성분을 무해한 것으로 변환하는 제품이다. 이것의 중심부인 담체는 단면의 윤곽이 원형이나 타원형이고 내부는 미세한 격자형 벽으로 채워진다. 담체를 매트로 두르고 캔에 넣는 캐닝공정 중 과대한 압력을 받아서 담체가 취성파괴될 것이 염려된다. 담체의 파괴를 방지하고자 매트의 압력의 분포를 예측하는 유한요소 프로그램을 개발하였다. 이것은 Microsoft EXCEL로 작성되어 입출력이 모두 간편하다. 담체는 강체, 캔은 선형탄성체로 단순하게 취급하고 매트의 재료비선형성을 고려하였다. 캔은 굽힘과 균일인장이나 압축에 저항하는 것으로 모델링하였다. 편의상 요소의 갯수는 35개, 반복 횟수는 20회로 제한하였다. ABAQUS의 해석결과와 잘 일치하여 본 프로그램의 타당성을 입증하였다.

• 한국수자원학회논문집
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• 제33권3호
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• pp.375-382
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• 2000

대유역의 지표면 수문현상은 추계학적 변동에 의해 야기되는 안정된 상태의 변이와 함께 몇 개의 발생빈도가 높은 안정된 상태의 영향을 받기가 쉬운데 그 이유는 지표면과 대기 상호관계의 밀접한 조합과도 관계가 있다. 따라서 각 안정상태에서의 체류기간 즉, 가뭄기나 홍수기의 지속기간이 중요한 연구 과제라 할 수 있으며 본 연구에서는 한강유역에 대하여 안정상태의 평균 변이기간을 분석하였다. 비선형 물수지모형을 한강 유역에 대하여 과거의 자료를 바탕으로 검정하였고 모형을 통한 물리과정의 추계학적 표현과 산정된 모형변수들로부터 안정상태사이의 평균 변이기간이 계산되었다. 본 연구는 안정상태 사이의 변이기간 혹은 거주기간, 즉 시스템이 주어진 안정상태에 머무는 기간(가뭄이나 홍수상태의 지속기간)의 예측과 밀접한 관계가 있다.

• Earthquakes and Structures
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• 제18권2호
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• pp.147-162
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• 2020

This paper presents a novel precast energy dissipation shear wall (PEDSW) structure system that using mild steel dampers as dry connectors at the vertical joints to connect adjacent wall panels. Analytical studies are systematically conducted to investigate the seismic performance of the proposed PEDSW under sequence-type ground motions. During earthquake events, earthquake sequences have the potential to cause severe damage to structures and threaten life safety. To date, the damage probability of engineering structures under earthquake sequence has not been included in structural design codes. In this study, numerical simulations on single-story PEDSW are carried out to validate the feasibility and reliability of using mild steel dampers to connect the precast shear walls. The seismic responses of the PEDSW and cast-in-place shear wall (CIPSW) are comparatively studied based on nonlinear time-history analyses, and the effectiveness of the proposed high-rise PEDSW is demonstrated. Next, the foreshock-mainshock-aftershock type earthquake sequences are constructed, and the seismic response and fragility curves of the PEDSW under single mainshock and earthquake sequences are analyzed and compared. Finally, the fragility analysis of PEDSW structure under earthquake sequences is performed. The influences of scaling factor of the aftershocks (foreshocks) to the mainshocks on the fragility of the PEDSW structure under different damage states are investigated. The numerical results reveal that neglecting the effect of earthquake sequence can lead to underestimated seismic responses and fragilities, which may result in unsafe design schemes of PEDSW structures.