• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.73-74
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• 2015

본 논문에서는 인체의 움직임에서 발생하는 낮은 주파수의 진동 에너지를 전기 에너지로 수확하는 전자기유도 현상 기반의 고효율 에너지 하베스터를 제작하였다. 제안된 하베스터는 기어모듈을 이용하여 사람이 인가하는 직선운동을 회전운동으로 바꾸는 방식으로 동작한다. 회전수를 늘리기 위해서 증속기어모듈을 달아 높은 회전비를 갖게 한다. 그리고 발전부의 자석들은 할바흐 배열을 통해 불필요한 곳의 자속을 최소한으로 하고 필요한 곳의 자속은 최대한으로 하여 높은 효율을 낼 수 있게 하였다. 제작된 전자기 에너지 하베스터의 출력전압은 230.9 mV이며 $18{\Omega}$에서 2.96 mW의 최대 피크 전력을 전달한다.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.423-424
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• 2020

기후변화 규제에 대응하기 위해 자동차 산업에서는 엔진의 배기가스는 줄이고, 출력은 향상시키는 과급기를 필요로한다. 전동식 과급기에 필요한 압축기는 초고속의 모터회전이 필요하고, 압축기 전기모터의 속도, 회전자의 위치 추정을 위해서는 센서가 필요하다. 하지만 센서의 사용은 비용의 증가, 신뢰도저하 등과 같은 문제점들이 있고, 이러한 문제점들을 해결하기 위해 여러 센서리스 방식들이 사용되고 있다. 본 논문에서는 PSIM 시뮬레이터를 이용하여 전류모델 기반의 센서리스 방식으로 동기전동기(SPMSM)를 구동하는 0.8초 내로 90000rpm의 속도까지 도달하도록 시뮬레이션을 구현하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.543-548
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• 2003

In this paper, we have proposed and fabricated a two-axis rotational micro-mirror with large tilt angle. Such a micro-mirror is a key element for N$\times$N high capacity optical cross-connect switches. The micro-mirror is required to have large tilt angle to increase the capacity of the cross-connect switches. For larger micro-mirror tilt angle between the grounded mirror plate and the bottom electrode is to be large enough to provide space for the tilting of the mirror. For our proposed structure, the gap was produced in such a way that the grounded mirror plate and the bottom electrode were made separately in different substrates by using the bulk micromachining technology, and combined later by employing self-align technique. As a result, a large tilt angle has been achieved without using additional actuators. The measured tilt angles were as large as $\pm$5.5$^{\circ}$ and $\pm$8.4$^{\circ}$ in the x and y direction respectively, and the pull-in voltages for the two directions were 380 V and 275 V respectively. Finally the fabricated mirror was successfully utilized to steer the optical beam. To our knowledge, our micro-mirror has the best performance among the micro-mirrors reported internationally so far.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.207-208
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• 2012

• Journal of Animal Environmental Science
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• v.11 no.1
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• pp.11-16
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• 2005

The round bale wrappers are generally used for rice straw after the harvesting of low land rice by combine harvester. In this situation, the bale wrappers should be well adapted under the travelling over raised borders and temporary ditches in soft soil of narrow rice fields. The study was conducted to improve the performance of bale wrapper through the new design for compact size, lowered gravity center and lowered power consumption. The prototype of round bale wrapper had been designed and assembled to tractor with three point hitch mounted. The machine type is one roll driving system with one roll for rotating and one roll for wrapping. The driving torque and work performance of the machines were measured and analysed. The torque requirement of the prototype and conventional type was 6kgf-m and 12kgf-m, respectively. The prototype shaved less friction resistance between bale driving roll and round bale. and the power requirement can also be reduced from 12kgf-m in the conventional to 6kgf-m in the prototype. The work efficiency of the new bale wrapper was $45\%$ higher than the conventional wrapper, and the working cost of the prototype can be reduced $17\%$ than that of the conventional.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.481-490
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• 2008

Reaction wheel is one of the actuators for spacecraft attitude control, which generates torque by changing an inertial rotor speed inside of the wheel. In order to generate required torque accurately and estimate an accurate angular momentum, wheel speed should be measured as close to the actual speed as possible. In this study, two conventional speed detection methods for high speed motor with digital tacho pulse (Elapsed-time method and Pulse-count method) and their resolutions are analyzed. For satellite attitude maneuvering and control, reaction wheel shall be operated in bi directional and low speed operation is sometimes needed for emergency case. Thus the bias error at low speed with constant acceleration (or deceleration) is also analysed. As a result, the speed detection error of elapsed-time method is largely influenced upon the high-speed clock frequency at high speed and largely effected on the number of tacho pulses used in elapsed time calculation at low speed, respectively.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.229-231
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• 2006

본 논문은 매입형 영구자석 전동기의 고정자 전압방정식으로부터 관측기를 구성하고, 회전자 좌표계상에서 추정속도를 구하여 퍼지제어기를 이용한 속도 보상 센서리스제어를 수행하였다. 전동기의 전압방정식과 퍼지제어기만을 이용하기 때문에 전동기의 기계적 방정식에서 발생하는 기계적 제정수의 영향에 대해 강인한 특성을 갖는다. 제안된 알고리즘의 타당성과 강인함은 실제 구동을 통하여 증명한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.9-15
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• 2018

The turbochargers, which are used widely in diesel and gasoline engines, are an effective device to reduce fuel consumption and emissions. On the other hand, turbo-lag is one of the main problems of a turbocharger. Bearing friction losses is a major cause of turbo lag and is particularly intense in the lower speed range of the engine. Current turbochargers are mostly equipped with floating bearings: two journal bearings and one thrust bearing. This study focused on the bearing friction at the lower speed range and the experimental equipment was established with a drive-motor, load-cell, magnetic coupling, and oil control system. Finally, the friction losses of turbochargers were measured considering the influence of the rotating speed from 30,000rpm to 90,000rpm, oil temperature from $50^{\circ}C$ to $100^{\circ}C$, and oil supply pressure of 3bar and 4bar. The friction power losses were increased exponentially to 1.6 when the turbocharger speed was increased. Friction torques decreased with increasing oil temperature and increased with increasing oil pressure. Therefore, the oil temperature and pressure must be maintained at appropriate levels.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.211-216
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• 2015

Large hydraulic excavator weighted 90 tons used the several pumps installed in parallel to use the hydraulic pump driving gearbox to improve fuel consumption by improving the energy efficiency of the hydraulic system. Gearbox connected to hydraulic pump supply the mechanical output to the high pressure and low pressure pump to be supplied by torque and rotation, which are the mechanical power, through a input shaft connected to large size engine of the excavator. So, gearbox connected to hydraulic pump is same as main artery in the human body and is required long life because it operates the hydraulic pump continuously during operating the engine. This study had used oil contamination analysis method to check the wear characteristics of the gearbox and frequency response characteristic analysis method to check the failure of the teeth failures of gearbox, while the test equipment adopted by the electrical feedback method to reduce the energy consumption was operating for the life assessment, in which the required power was 600 kW input power.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.119-122
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• 2001

본 논문은 브러시리스 DC 모터 드라이브에서 위치센서를 제거하기 위해, 측정한 상전압 및 상전류로부터 쇄교자속과 쇄교자속의 미분간에 의해 속도를 구하고 이를 이용하여 위치를 추정하는 새로운 센서리스 구동방식을 제안한다 이러한 센서리스 구동알고리즘은 ${\alpha}-{\beta}$ 기준축을 이용하여 구현하였다. 구동시스템을 구현하기 위한 제어기는 고속연산이 가능하면서도 저가인 고정소수점 연산 DSP인 TMS320F241을 채택하였다. 제안된 알고리즘은 그 원리가 간단하고 우수한 제어특성을 나타냄으로써 실제적인 브러시리스 DC 전동기의 센서리스 구동을 위한 훌륭한 대안이 될 수 있을 것이다.