• 비파괴검사학회지
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• 제24권1호
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• pp.38-44
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• 2004

본 연구에서는 크레인 훅을 광탄성 재료의 일종인 '포토플렉스'를 이용, 2차원으로 모델링하여 힘을 가하였을 경우, 최대 압축 및 인장 응력이 발생되는 선상에서 광탄성실험법, 단순 곡선보 이론 및 유한요소법을 이용하여 응력을 측정하고 계산하였다. 특히, 광탄성 실험은 재래식 측정법에 의한 타디보간법, 프릭지 세선처리법 그리고 최근 개발된 4단계 위상이동법 등 세 가지 방법을 이용하였다. 광탄성 4단계 위상이동범은 주응력 방향, 즉 등경선이 일정한 선상에서는 연속적인 응력분포를 얻을 수 있는 장점이 있다. 크레인 훅에서 주응력 방향이 일정한 선상에 발생된 응력은 3가지 서로 다른 광탄성 실험법에 의해 측정된 길과가 잘 일치하였다 광탄성법에 의한 결과는 훅의 끝단 부근을 제외하고는 단순곡선보 이론이나 유한요소 해석결과와 대체적으로 비슷하였으나, 정확히 일치하지는 않았다. 이러한 차이는 크레인 훅의 실제 시편의 곡률등 형상과 하중조건이 단순곡선보 이론이나 유한요소 모델링 형상과 약간 다르기 때문에 나타난 것으로 추정된다. 광탄성실험법은 형상이 불규칙하고 하중조건이 복잡할 경우 실제 발생되는 응력을 전체적으로 정밀하게 측정할 수 있으므로 응력해석에 대한 이를 및 수치해석 법을 검증하는데 활용될 수 있다.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1843-1850
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• 2014

In this paper, we investigate a group building based power consumption scheduling to minimize the electricity cost. We consider the demand shift to reduce the peak load and suggest the compensation function reflecting the relationship between the change of the building demand and the occupants' comfort. Using that, the electricity cost minimization problem satisfied the convexity is formulated, and the optimal power consumption scheduling algorithm is proposed based on the iterative method. Extensive simulations show that the proposed algorithm achieves the group management gain compared to the individual building operation by increasing the degree of freedom for the operation.

• Journal of Power Electronics
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• 제8권4호
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• pp.317-324
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• 2008

This paper proposes a Multiband Shunt Hybrid Active Filter (SHAF) with sensorless control. A plant is modeled in the discrete- time domain and a controller is designed using the Pole shifting law in the polynomial domain. This control approach is very useful for filtering the load harmonics with reduced sensor counts where a low cost solution like SHAF is required. Multiple Synchronous Reference Frames (MSRF) and low pass filters are used to measure the $5^{th}$ and $7^{th}$ harmonic components separately from the load and filter currents. Individual current controllers are designed for the $5^{th}$ and $7^{th}$ harmonic currents. Control is realized in the stationary, three-phase (abc) reference frame. Performance of the controller is validated through simulation, using realistic plant and controller models, as well as experimentally on a full-scale distribution system.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1996년도 봄 학술발표회 논문집
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• pp.1-8
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• 1996

Many studies showed that small imperfections can also have a considerable influence on the behaviour of structures. Especially, in Single-Layer Latticed Domes, initial imperfection occurred by human error and construction error is very important to the buckling load. The definition of imperfection is that a node of structure shifts from perfect condition. For example, in the case of truss structures, imperfections are represented by shifting the location of nodal points relative to the position in which they would be for a perfect structure. This paper uses Arc-length Method in nonlinear iteration analysis, choosing star dome, in which many studies have been accomplished, as a model. The results of analysis show that initial imperfection can reduce the buckling load of structures.

• 대한기계학회논문집
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• 제14권6호
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• pp.1689-1699
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• 1990

본 연구에서는 Z-Mill의 압연판 형상 예측을 위한 이론 및 컴퓨터 시뮬레이션 에 관한 사항과 설비조건, 압연조건, 소재조건이 판형상에 미치는 영향에 대해 논하고 자 한다.

• Journal of Power Electronics
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• 제18권3호
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• pp.892-901
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• 2018

SiC MOSFETs have been used to improve system efficiency in high frequency converters due to their extremely high switching speed. However, this can result in undesirable parasitic oscillations in practical systems. In this paper, models of the key components are introduced first. Then, theoretical formulas are derived to calculate the switching oscillation frequencies after full turn-on and turn-off in clamped inductive circuits. Analysis indicates that the turn-on oscillation frequency depends on the power loop parasitic inductance and parasitic capacitances of the freewheeling diode and load inductor. On the other hand, the turn-off oscillation frequency is found to be determined by the output parasitic capacitance of the SiC MOSFET and power loop parasitic inductance. Moreover, the shifting regularity of the turn-off maximum peak voltage with a varying switching speed is investigated on the basis of time domain simulation. The distortion of the turn-on current is theoretically analyzed. Finally, experimental results verifying the above calculations and analyses are presented.

• 한국생산제조학회지
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• 제18권6호
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• pp.565-575
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• 2009

A forklift (also called a lift truck) is a powered industrial truck that is used to lift and transport materials. It has become an indispensable piece of equipment in manufacturing and warehousing operations. The modem forklift is equipped with automatic transmission to meet the requirement of loading and easy operation of the vehicle. This paper proposes the design of TECU(Transmission Electronic Control Unit) which is applied to PSD322-Axle transmission. Garofalo's control technique is generally used to the automatic transmission. We consider the work quality and market requirement that does not want to control engine throttle. This paper proposes new controller system which guarantees efficient speed changes with simple system. This new system does not control the engine throttle spontaneously. But it has the load of engine and vehicle as a maximum disturbance. The scope of the disturbance is limited to the stoll area of the torque converter. This paper proposes a ideal control commander that converges relative velocity of the input and ouput of a clutch into a zero. We design linear controller to execute the idea control commander. We applied the control algorithm to the forklift of PSD322-Axle type and the performance of this controller was verified.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.11-19
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• 2018

With the development of smart grid technology, it has become a hotspot to increase benefits of both residential users and electric power companies through demand response technology and interactive technology. In this paper, the game theory is introduced to the interaction between residential users and an electric company, making a mutually beneficial situation for the two. This paper solves the problem of electricity pricing and load shifting in the interactive behavior by building the game-theoretic process, proposing the interaction strategy and doing the optimization. In the simulation results, the residential users decrease their cost by 11% mainly through shifting the thermal loads and the electric company improves its benefits by 5.6% though electricity pricing. Simulation analysis verifies the validity of the proposed method and shows great revenue for the economy of both sides.

• ETRI Journal
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• 제46권4호
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• pp.708-715
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• 2024

We propose a 10-GHz 2 × 2 phased-array radio frequency (RF) receiver with an 8-bit linear phase and 15-dB gain control range using 65-nm complementary metal-oxide-semiconductor technology. An 8 × 8 phased-array receiver module is implemented using 16 2 × 2 RF phased-array integrated circuits. The receiver chip has four single-to-differential low-noise amplifier and gain-controlled phase-shifter (GCPS) channels, four channel combiners, and a 50-Ω driver. Using a novel complementary bias technique in a phase-shifting core circuit and an equivalent resistance-controlled resistor-inductor-capacitor load, the GCPS based on vector-sum structure increases the phase resolution with weighting-factor controllability, enabling the vector-sum phase-shifting circuit to require a low current and small area due to its small 1.2-V supply. The 2 × 2 phased-array RF receiver chip has a power gain of 21 dB per channel and a 5.7-dB maximum single-channel noise-figure gain. The chip shows 8-bit phase states with a 2.39° root mean-square (RMS) phase error and a 0.4-dB RMS gain error with a 15-dB gain control range for a 2.5° RMS phase error over the 10 to10.5-GHz band.

• Journal of Power Electronics
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• 제4권3호
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• pp.138-151
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• 2004

In this paper, a constant frequency phase shifting PWM-controlled voltage source full bridge-type series load resonant high-frequency inverter using the $4^{th}$ generation IGBT power modules is presented for innovative consumer electromagnetic induction heating applications, such as a hot water producer, steamer and super heated steamer. The bridge arm side link passive capacitive snubbers in parallel with each power semiconductor device and AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is evaluated and discussed on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency inverter topology, what is called, DE class type, including the variable-power variable-frequency regulation function can expand zero voltage soft switching commutation area even under low output power setting ranges, which is more suitable and acceptable for newly developed induction heated dual pack fluid heaters. Furthermore, even the lower output power regulation mode of this high-frequency load resonant tank inverter circuit is verified so that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.