• 한국생산제조학회지
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• 제23권2호
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• pp.157-163
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• 2014

In this paper, a robust MRAC (model reference adaptive control) scheme is applied to control an electrohydraulic positioning system under various loads. The inverse dead-zone compensator in the control system cancels out the dead-zone response, and an integrator added to the controller provides good position-tracking ability. LQG/LTR (linear quadratic Gaussian control with loop transfer recovery) closed-loop model is used as the reference model for learning the MRAC system. LQG/LTR provides a systematic technique to design the linear controller that optimizes the objective function using some compromise between the control effort and the system performance in the frequency domain. Different external load tests are performed to investigate the effectiveness of the designed MRAC system in real time. The experimental results show that the tracking performance of the proposed system is highly accurate, which offers considerable robustness even with a large change in the load.

• Fibers and Polymers
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• 제6권1호
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• pp.55-65
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• 2005

Extensible elastica solutions of two-dimensional deflection of crimped fiber cantilever of circular wavy crimp were obtained for one end clamped boundary under concentrated, inclined and dead tip load Fiber was also regarded as a linear elastic material. Crimp was described as a combination of semicircular arcs smoothly connected with each other having con­stant curvature of all the same magnitude and alternative sign. Also the inclined load direction was taken into account. The solutions were expressed as the recursive forms of integrals in two different cases, which can also be transformed to elliptic integrals respectively. Comparing the data with inextensible ones was carried out. Consequently in the solution, the normal strain of neutral axis is expressed in terms of cross-sectional area, second moment of area and normalized load parameter. Examples of the circular cross-sectioned fiber are presented. As a result, the differences of normalized load between inexten­sible and extensible elastica solutions when the radius ratio becomes 0.1 were maximum $\Lambda$ = 0.1.

• 전력전자학회논문지
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• 제14권5호
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• pp.379-386
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• 2009

ITER 핵융합 장치에 사용되는 Vertical Stabilization(VS) 컨버터는 4상한 운전 모드의 대용량 부하에 전력을 공급하기 위해서 4개의 직렬구조 12펄스 컨버터를 역병렬 연결하여 구성한다. 스위칭 소자로 싸이리스터를 사용하는 VS 컨버터는 정역 운전모드 변환과정에서 컨버터의 안전운전을 위해 Dead Time 구간을 필요로하며, 이 과정에서 유도성 부하에 영(Zero)전류 불연속 구간이 발생하는 단점이 있다. VS 컨버터의 출력 전류제어에 순환전류를 이용할 경우에는 빠른 정역 운전모드 변환이 가능하며, 부하에 발생하는 영전류 불연속 구간을 제거할 수 있다. 본 논문은 ITER VS 컨버터에서 출력전류의 정역 운전을 위해 순환전류를 이용하는 부하 전류제어 알고리즘을 제안하고, PSIM 시뮬레이션을 통해 결과를 검증하였다.

• 전기학회논문지
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• 제66권1호
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• pp.55-60
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• 2017

Capacitor Charging Power Supply(CCPS) is one of the most important components of a pulsed power system. The CCPS is widely used in source of lasers, accelerators and plasma generators. This paper presents design of a dead time control circuit and operation characteristics for stable high repetition rate of high voltage CCPS. The CCPS consists of battery, high voltage transformer and controller with a dead time control circuit. A dead time control circuit was simulated by PSpice. The performance test of the CCPS was carried out with a 7[nF] load capacitor at output voltage of 50[kV] and a pulse repetition frequency of 100[Hz]. As a result, we can verify that charging and discharging waveform is stable at 100[Hz]. The experiment results indicate that 3[ms] dead time made it possible for stable high repetition rate of 100[Hz]. This paper paves the way for designing an advanced CCPS which is more applicable outside experiments.

• 전자공학회논문지S
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• 제36S권11호
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• pp.120-127
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• 1999

PWM 전압형 인버터의 스위칭 신호에 삽입되는 데드타임은 인버터의 출력에 왜형을 발생시키다. 그 결과, 지령에 대비한 기본파분 전압의 크기 및 위상의 편차가 발생한다. 뿐만 아니라 인버터 출력에 고조파를 증가시킨다. 본 논문에서는 스위칭 데드타임에 기인한 인버터 출력의 왜형분 전압에 대한 수식적 해석을 수행하였다. 연산 결과로써, 전압변조율, 부하 기본파 역율 및 데드타임에 다른 출력 전압의 기본파 전압 이득 및 위상 편차를 나타내었다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.830-835
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• 1998

This paper describes a new digital control method of 3-phase PWM inverter with LC filter for uninterruptible power supply(UPS). The overall control system is based on the dead beat control, which has the minor loop of current control within the voltage control major loop. In this paper, the full-order disturbance observer is proposed to compensate the disturbances generated due to a sudden change of load currents. The proposed disturbance observer is composed of dead beat observer which estimates state values within a finite time, and cancels the disturbances by adding feedforward compensation loop in the control system. In addition, on order to remove a defect of oscillation generated in output of conventional dead beat controller, a modified dead beat algorithm is proposed in this paper.

• 동력기계공학회지
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• 제3권1호
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• pp.16-22
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• 1999

The purpose of this study is to prevent the stick, scuffing, scratch between piston and cylinder, is to contribute the piston design such as piston profile, clearance by calculating reaction force by over-lap of piston skirt, as measuring the temperature distributions of cylinder wall. The experiment has been peformed to obtain data during actual engine operation. Temperature gradient in peripheral and axial distributions of cylinder wall according to torque and speed of engine were measured by use of an 800cc class gasoline engine. The results obtained are summarized as follows ; 1) The temperature of cylinder wall at TDC was about $50{\sim}75^{\circ}C$ higher than temperature of cooling water. 2) The rear side temperature of top dead center was $141^{\circ}C$(1/4 load) in axial distribution, whereas the rear side of midway position temperature was $98^{\circ}C$. 3) The temperature of cylinder wall increased in according to rising temperature of cooling water. 4) The thrust side temperature of cylinder wall was about $15^{\circ}C$ in all load test. 5) The rear side temperature of top dead center was $159^{\circ}C$ (1/2 load) in peripheral distribution, it was about $39^{\circ}C$ higher than thrust side temperature.

• 한국산학기술학회논문지
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• 제11권7호
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• pp.2702-2707
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• 2010

본 논문에서는 신형식 강합성 교량에 대한 3차원 유한요소해석을 ABAQUS를 이용하여 실시하여, 연석 사하 중 재하에 따른 하중분배값을 검토하였다. 하중분배계수 검토에 고려된 변수로는 콘크리트 슬래브 두께, 강판 두께, 주형길이가 적용되었다. 해석을 통해 얻어진 하중 분배율은 AASHTO Standard와 AASHTO LRFD 설계기준의 제안식 및 기존 연구자들이 제안한 식들과 비교 검토되었다. 본 논문에서는 신형식 강합성 교량의 설계 간편성을 고려하여 외측주형의 경우 0.67, 내측주형의 경우 0.34의 하중분배율을 제안하였다.

• Structural Engineering and Mechanics
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• 제71권2호
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• pp.165-173
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• 2019

This paper investigates the probability of failure of reinforced concrete beams for limit state of collapse for flexure and shear. The influence of randomness of the variables on the failure probability is also examined. The Indian standard code for plain and reinforced concrete IS456:2000 is used for the design of beams. Probabilistic models are developed for flexure and shear according to IS456:2000. The loads considered acting on the beam are live load and dead load only. Random variables associated with the limit state equation such as grade of concrete, grade of steel, live load and dead load are identified. Probability of failure is evaluated based on the limit state equation using First Order Reliability Method (FORM). Importance of the random variables on the limit state equations are observed and the variables are accordingly reduced. The effect of the reduced parameters is checked on the probability of failure. The results show the role of each parameter on the design of beam. Thus, the Indian standard guidelines for plain and reinforced concrete IS456:2000 is investigated with the probabilistic and risk-based analysis and design for a simple beam. The results obtained are also compared with the literature and accordingly some suggestions are made.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1303-1308
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• 2008

Keeping cooling water temperature higher within the allowable range helps marine engines to run in more efficient condition especially when the engine load is low. Temperature control of jacket cooling water in outlet side of main engine has been more widely adopted to ships these days for the purpose to reduce fuel consumption rate. But If the temperature sensor for the control loop is placed at the outlet of engine, it brings more difficulties in attaining stable and desirable properties due to dead times included in pipe length and engine itself comparing to the case where the measuring point is at the inlet side of main engine. In relation with this problem, Feed-forward control could be one of realistic solutions as it reveals good properties and requires less cost for system configuration. This study suggests a forward control system which leads to improved temperature control performances to disturbance signals which could arise from variation of engine load or weather condition. Two dead times in the modelling were described, considering pipe length between the actuator and the engine as well as the thermal process inside the engine. The results of analysis were shown by simulations to confirm responses under different conditions.