• 한국해양환경ㆍ에너지학회지
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• 제18권4호
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• pp.282-290
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• 2015

부이의 수직운동으로부터 파랑에너지를 추출하는 파력발전기의 추출효율을 극대화하기 위하여 Sheng et al.(2015)이 제안한 래칭 제어기법을 적용하였다. 래칭 제어기법은 부이를 구속하는 래칭 시간을 조절하여 추출효율을 높이는 위상제어 방법이다. 래칭 제어기법을 규칙파중 수직운동하는 부이에 적용한 결과, 공진조건을 만족하지 않았음에도 불구하고 부이의 운동속도와 추출파워는 크게 증가하였다. 부이의 수직운동으로부터 파랑에너지를 흡수하는 파력발전기에 이러한 래칭 제어기법을 도입하면 추출파워의 증가와 더불어 부이의 흘수와 PTO감쇠력을 줄일 수 있어 제작비용을 크게 낮출 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.86-101
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• 2021

This study examined the effects of buoy shape and Nonlinear Froude-Krylov force (NFK) on a heaving-buoy-type Wave Energy Converter (WEC). Based on the Maclaurin expansion, the theoretical solutions of the NFK were derived for three different buoy shapes; hemispheric buoy, circular vertical cylinder, and truncated conical cylinder. A hydraulic power take-off system was adopted, and the latching control strategy was applied to maximize the extracted power from the WEC. The nonlinear effects of the Froude-Krylov force and restoring force on the heaving point absorber were investigated by comparing the heave Response Amplitude Operator (RAO) and time-averaged power extraction. The results showed that the conventional linear analyses were overestimated by up to 50% under the high amplitude wave condition. The latching control strategy was the most effective when peak wave period of regular or irregular wave was 0.4-0.45 times the heave natural period of the buoy.

• 한국전기전자재료학회논문지
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• 제30권8호
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• pp.520-524
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• 2017

Electrical relay in an essential part of smart grids, electrical vehicles, and LED lightning systems. Therefore, studying relay reliability is important. Relays using permanent magnet actuators (PMAs), which are energy efficient, are also in the spotlight. However, most of the permanent magnets used in PMAs have a characteristic wherein the magnetic flux decreases as the temperature increases. When the magnetic flux is reduced, the force acting on the actuator is reduced. Therefore, in this study, we measured the decrease in the relay operating speed with permanent magnet reduction due to temperature rise. In addition, changes in the bouncing phenomena due to magnetic flux reduction were analyzed. As a result, the operating speed of the relay has decreased and the bouncing phenomenon has not significantly changed.

• 항공우주시스템공학회지
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• 제13권3호
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• pp.78-86
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• 2019

본 연구에서는 전개성능을 고려한 대형 전개형 SAR 안테나의 회전스프링 힌지의 강성 최적설계에 대해 기술한다. 대형 전개형 SAR 안테나는 발사환경에서는 접혀 있다가 궤도에서 임무를 수행할 때 펼치게 된다. 이러한 조건에서 여러 장으로 구성된 안테나 패널을 주어진 시간 내에 최소의 충격으로 전개할 수 있도록 회전스프링 힌지의 적절한 강성을 찾는 것은 매우 중요하다. 회전스프링 강성이 강하면 완전 전개시점에서 발생하는 큰 충격하중이 구조체에 손상을 주며, 약하면 전개 저항으로 인해 완전전개를 보장할 수 없기 때문이다. 이러한 문제를 해결하기 위해서 RecurDyn을 이용한 다물체동역학 해석모델을 생성하였으며 전개해석을 통해 전개성능(전개시간 전개충격하중)을 도출하였다 최적의 회전스프링 강성을 찾기 위해 이에 따른 전개성능을 반응표면법을 통해 근사화 시켰으며 최적설계를 수행하여 적절한 회전스프링의 강성 값을 도출하였다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제14권3호
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• pp.147-151
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• 2014

An actuator latch device of a hard disk drive is installed for locking an actuator to hold a magnetic head parked in a parking zone. Applying an external force to the drive, the head can move away from the parking zone and destroy data on the disk. A magnet latching mechanism is used to prevent the actuator from moving when the computer is not in use. A permanent magnet holds the actuator when the head is in the parking zone. When the computer is turned on, the actuator has to overcome the latch magnet in order to move. A stronger latch magnet will hold the actuator adequately, but the actuator will not be released when unlocking is required. A breakthrough solution is needed to improve the reliability of the drive without any deterioration of its performance. In order to obtain the idea for resolving this technical contradiction, we analyse patents for actuator latch device of a hard disk drive. A practical way for solving contradictions in product development using TRIZ is proposed in this paper.