• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.37.5-37
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• 2001

A robust control for robot manipulators actuated by induction motors using neural networks(NNs) is considered. The control is designed to compensate for nonlinear dynamics associated with the mechanical subsystem and the electrical subsystems only with the measurements of link position, link velocity and stator winding currents. Two-layer NNs are used to approximate unknown functions occurring from parameter variation during backstepping design process. Specially, through the use of nonlinear observers for rotor flux, observed backstepping controller is designed to achieve uniform ultimately bounded link position tracking of the given reference signal ...

• 대한기계학회논문집A
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• 제37권8호
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• pp.1007-1013
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• 2013

이 논문은 터빈 로터의 형상변화에 따른 공력 특성에 대하여 분석하였다. 본 논문의 터빈은 헬리콥터의 보조동력 장치로 사용되는 소형엔진이다. 소형엔진은 팁 형상의 구조적 취약성 때문에 성능을 향상시키기 어렵다. 그러므로, 터빈의 허브를 개선하는 것이 여러 가지 측면에서 유리하다. 터빈의 작동유체는 고온 고압의 가스이다. 터빈표면의 열전달률이 고려되었을 때, 열부하에 의한 블레이드의 손상을 줄이기 위해서는 블레이드 표면의 열전달률 분포를 고찰하여야 한다. 수치모사 결과를 검증용 실험값과 비교하였을 때, SST난류모델은 공력 특성을 잘 반영하고 열전달 예측성능도 우수하였다. 결론적으로, 허브측 선단에서 구륜설계(bulbous design)를 적용하였을 때 공력효율이 향상되었고, 전체 공력 손실 중 끝벽 손실은 15% 감소되었다.

• 한국항공우주학회지
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• 제37권2호
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• pp.139-146
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• 2009

능동 비틀림 제어기법을 이용한 복합재료 로터 블레이드의 헬리콥터 진동억제에 대한 수치연구를 수행하였다. 허브에 작용하는 진동하중 억제를 위해 복합재료 블레이드의 탄성 연계와 함께 압전 소재의 전단변형 메커니즘을 이용하였다. 로터 블레이드는 표면에 압전 작동기를 부착한 박벽 상자형 단면을 갖는 복합재료 보로 모델링하였다. 회전익에 대한 지배 운동방정식은 Hamilton 원리를 이용하여 구성하였고, 공력하중은 자유후류모델을 포함하는 비정상 공력 이론을 이용하여 구했다. 다양한 탄성연계 적층과 능동 작동기를 부착한 복합재료 블레이드에 대해 허브진동 하중 특성을 고찰하였다. 수치해석 결과 최적 제어 알고리듬을 적용하여 $N_b$/rev 진동하중을 대폭 줄일 수 있음을 보였다.

• 한국항공우주학회지
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• 제37권11호
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• pp.1073-1079
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• 2009

본 연구에서는 전진 비행하는 헬리콥터 로터 블레이드 표면의 압력장에 대한 공력 특성 분석 및 차수축소모델 구축을 위해 적합직교분해 (POD) 방법을 이용하였다. 에너지가 큰 특정 모드를 기반으로 전진 비행하는 비정상 로터 블레이드에 대한 공기역학적 특성을 분석하였으며, CFD 계산 결과의 검증을 위해 제자리비행에 대한 실험 결과와 비교하였다. 수렴속도를 향상시키기 위해 Multi-grid 기법을 사용하였으며, 회전하는 로터 블레이드 주위의 비정상 유동을 모사하기 위해 슬라이딩 격자를 이용하였다. 그 결과 240개의 Snapshot에 대해 에너지율 99% 이상을 포함하는 지배적인 POD 모드 7개가 선정되었으며, POD 모드와 전개 계수를 이용하여 차수축소모델을 성공적으로 구축하였다.

• Tribology and Lubricants
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• 제37권1호
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• pp.31-40
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• 2021

This study describes the effects of a thrust labyrinth seal applied to the backside of a centrifugal impeller on the axial thrust force for high speed turbomachinery. The bulk flow model using Neumann's equation calculates the seal cavity pressures and leakage flow rate of the thrust labyrinth seal based on three configurations: teeth-on-rotor (TOR), teeth-on-stator (TOS), and interlocking labyrinth seal (ILS). Prediction results show that the ILS is superior to the TOR and TOS in terms of leakage flow rate. A mathematical model of a centrifugal impeller with a thrust labyrinth seal on its backside calculates the force components corresponding to the impeller inlet, shroud, impeller backside outer, backside seal, and backside inner pressures. A summation of the force components renders the total axial thrust force acting on the centrifugal impeller. The Newton-Raphson numerical scheme iteratively calculates the pressures and leakage flow rate through the impeller wall gap. The prediction results reveal that the leakage flow rate and total axial thrust force increase with rotor speed, and the ILS significantly decreases the leakage flow rate, whereas it slightly increases the axial thrust force when compared to TOR and TOS. Increasing the seal clearance causes an increase in the leakage flow rate and a slight decrease in the axial thrust force with the ILS.

• Environmental Engineering Research
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• 제25권2호
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• pp.171-177
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• 2020

Removal through adsorption is the most widely used and effective treatment method for volatile organic compounds (VOCs) in exhaust gases. However, at high temperatures and humidity, adsorption is competitive due to the presence of moisture and unsmooth physical adsorption thereby deteriorating adsorption performance. Therefore, water adsorption honeycomb (WAH) and VOCs adsorption honeycomb (VAH) were prepared to improve VOCs adsorption at high temperatures and humidity. Adsorbed toluene amounts on single honeycomb (SH), containing only VAH, and combined honeycomb (CH), containing WAH and VAH, were determined. Further, the toluene adsorption rates of honeycomb adsorbents mounted on rotary systems, VAH-single rotor (SR) and WAH/VAH-dual rotor (DR) were determined. Toluene adsorption by WAH/VAH-CH (inlet temperature: 40-50℃; absolute humidity: 28-83 gH₂O/kg-dry air) was 1.6 times that by VAH-SH, and the water adsorption efficiency of WAH/VAH-CH was 1.7 times that of VAH-SH. The adsorption/removal efficiency of the WAH/VAH-DR (inlet temperature: 45℃; absolute humidity: 37.5 gH₂O/kg-dry air) was 3% higher than that of VAH-SR. This indicates that the WAH at the rotor inlet selectively removed water, thereby improving the adsorption efficiency of the VAH at the outlet.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.33-37
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• 2004

Slotless Permanent magnet Brushless DC Motor(PM BLDC) with the characteristics of high speed and high power density has been more widely used in industrial and automatic machine. Generally, PM BLDC meter is necessary that the three Hall-ICs evenly be distributed around the stator circumference in case of the 3 phase motor. The Hall-ICs are set up in this motor to detect the main flux from the rotor. therefore the output signal from Hall-ICs is used to drive a power transistor to control the stator winding current. However, instead of using three Hall-ICs, if only we used one Hall-IC, we estimate information of the others phase in sequence through a revolving rotor. This paper identified the characteristics and performance by using one Hall-IC for the 3 phase PM BLDC whose six stator and two rotor designed.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권1호
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• pp.37-46
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• 2004

A novel rotor speed estimation method using model reference adaptive control(MRAC) is proposed to improve the performance of a sensorless vector controller. In the proposed method, the stator current is used as the model variable for estimating the speed. In conventional MRAC methods, the relation between the two model errors and the speed estimation error is unclear. In the proposed method, the stator current error is represented as a function of the first degree for the error value in the speed estimation. Therefore, the proposed method can produce a fast speed estimation. The robustness of the rotor flux-based MRAC, back EMF-based MRAC, and proposed MRAC is compared based on a sensitivity function about each error of stator resistance, rotor time constant, mutual inductance. Consequently, the proposed method is much more robust than the conventional methods as regards errors in the mutual inductance, stator resistance. Therefore, the proposed method offers a considerable improvement in the performance of a sensorless vector controller at a low speed. In addition, the superiority of the proposed method and the validity of sensitivity functions were verified by simulation and experiment.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제51권7호
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• pp.292-297
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• 2002

In this paper, a flat-type $L_{-}$-$B_{8}$ mode Ultrasonic Motor[USM] having the size of 80 x 20 x ${1.5}mm^3$($l{\times}\omega{\times}t$) was designed and fabricated to examine the characteristics of an ultrasonic vibration. We used ANSYS simulation program based on FEM to get the optimum design of this USM. As results of experiment, the fastest speed of revolution(v), the maximum torque(T) and the efficiency(n) were 37.5cm/s, 5.0 mN.m and 1.17% when 27.9KHz, 150N, 50V were applied respectively. And this flat-type $L_{-}$-$B_{8}$ mode USM could be controlled the speed of rotor revolution by applied voltage, frequency and pre-load of rotor as well as showed the characteristics of typical drooping torque-speed, large torque and high speed. So, we think that this flat-type $L_{-}$-$B_{8}$ mode USM has characteristics of enough torque and velocity to be usable for applications in forwarding device of an electric card or a paper, etc.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.160-167
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• 2008

The effects of squealer rim height on three-dimensional flows and aerodynamic losses downstream of a high-turning turbine rotor blade have been investigated for a typical tip gap-to-chord ratio of h/c=2.0%. The squealer rim height-to-chord ratio is changed to be $h_{st}/c$=0.00(plane tip), 1.37, 2.75, 5.51, and 8.26%. Results show that as $h_{st}/c$ increases, the tip leakage vortex tends to be weakened and the interaction between the tip leakage vortex and the passage vortex becomes less severe. The squealer rim height plays an important role in the reduction of aerodynamic loss when $h_{st}/c{\leq}2.75%$. In the case of $h_{st}/c{\geq}5.51%$, higher squealer rim cannot provide an effective reduction in aerodynamic loss. The aerodynamic loss reduction by increasing $h_{st}/c$ is limited only to the near-tip region within a quarter of the span from the casing wall.