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KiSu Kim,Youngho Ko,Doyeon Hwang,Seong Young Ko,Jong-oh Park,Sukho Park 제어로봇시스템학회 2013 제어로봇시스템학회 국제학술대회 논문집 Vol.2013 No.10
As demands of microrobots in medical applications increases, micro-actuators for the microrobots are actively studied. However, miniaturized motors cannot be easily applied to microrobots owing to the limitations of their sizes and generating forces. Therefore, a new functional smart material for microrobots should be developed. Among various smart materials, we focused on a ferro-actuator using ferrofluid. The ferro-actuator is regarded as a smart material and can show large displacements, excellent repetition performances, and relative small actuation forces. In this paper, a cellulose is used to make a paper backbone membrane because it has superior properties compared with any others conventional papers. The cellulose paper backbone membrane is easily fabricated as complex shapes and shows a large displacement in a magnetic field. In detail, patterned ferropaper actuator is made of cellulose acetate using general MEMS procedure and PDMS molding method. Finally, through bending experiments and alignment experiments of the fabricated ferropaper actuator using an electromagnetic actuation (EMA) system, the patterned ferropaper actuator was characterized.
Ferro-fluid의 흡착을 통한 paper actuator의 개발
김기수(Kisu Kim),황도연(Doyeon Hwang),고성영(Seong Young Ko),박종오(Jong-Oh Park),박석호(Sukho Park) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11
As a demand of a microrobot in medical and defense fields, micro-actuators for the actuation of the microrobot have been actively studied. The miniaturization, controllability and robustness on environmental changes are vital factors in the development of the micro-actuator. In this study, we proposed a new paper actuator using ferro-fluid absorption. The paper actuator was fabricated by the absorption of nanoscale Fe particles on a paper membrane and it was strongly magnetized and responded by external magnetic field. First, we synthesized a ferro-fluid using FeCl2 and FeCl3, and the ferro-fluid was absorbed on various papers such as facial tissue, coffee filter, Whatman filter and Hanji. In addition, the adsorptions of the Fe particles on the various paper membranes were investigated by SEM images. Finally, we fabricated cantilever type actuators from the ferro-fluid absorbed papers and executed bending and alignment tests using an electromagnetic actuation system. Through the experiments, it was validated that Hanji based paper actuator has the good magnetization and shows the best actuation performances compared with other paper actuators.
Lead-free BaTiO3 nanowires-based flexible nanocomposite generator.
Park, Kwi-Il,Bae, Soo Bin,Yang, Seong Ho,Lee, Hyung Ik,Lee, Kisu,Lee, Seung Jun RSC Pub 2014 Nanoscale Vol.6 No.15
<P>We have synthesized BaTiO3 nanowires (NWs) via a simple hydrothermal method at low temperature and developed a lead-free, flexible nanocomposite generator (NCG) device by a simple, low-cost, and scalable spin-coating method. The hydrothermally grown BaTiO3 NWs are mixed in a polymer matrix without a toxic dispersion enhancer to produce a piezoelectric nanocomposite (p-NC). During periodical and regular bending and unbending motions, the NCG device fabricated by utilizing a BaTiO3 NWs-polydimethylsiloxane (PDMS) composite successfully harvests the output voltage of 7.0 V and current signals of 360 nA, which are utilized to drive a liquid crystal display (LCD). We also characterized the instantaneous power ( 1.2 μW) of the NCG device by calculating the load voltage and current through the connected external resistance.</P>
김기수(Kisu Kim),신춘식(Choonsik Shin),윤성민(Sungmin Yoon),박창규(Changkyu Park),강경훈(Kyeonghoon Kang) 한국추진공학회 2011 한국추진공학회 학술대회논문집 Vol.2011 No.11
군에서 사용하는 탄약의 보관 및 취급상 발생할 수 있는 외형결함을 가정하여 그것이 사거리에 미치는 영향을 예측하였다. 외형결함은 탄체두부의 오자이브 형상에 각 1.5mm, 3.3mm의 축대칭 함몰부가 생기는 것으로 가정하였다. FLUENT를 사용하여 마하수 별 항력계수를 해석하였고, 탄도해석 프로그램인 PRODAS에 항력계수 데이터를 입력하여 탄도해석을 하였다. 공력해석결과 1.5mm, 3.3mm 함몰 탄체의 항력증가율은 정상탄체와 비교했을 때 아음속 영역에서는 큰 차이를 보이지 않았으나, 초음속 영역에서 각각 평균 3%, 9% 의 증가율을 보였다. 최대 사거리는 포구속도 650m/s를 기준으로 각각 1%, 3% 감소한 결과를 보였다. Projectile can be damaged during the storage and handling. Maximum range calculation of the ammunition was performed on the assumption that each projectiles have 1.5mm/3.3mm axisymetric dent on the surface. Drag coefficient for trajectory calculation was delivered from CFD using commercial software FLUENT. In the result of CFD, damaged projectiles those have 1.5mm/3.3mm axisymetric dent have similar drag coefficient compare with normal projectile in the region of subsonic. But, in supersonic region, drag coefficient was increased 3%, 9% each in average. In the result of trajectory calculation, Maximum rage was decreased 1%, 3% each.