• 한국항공우주학회지
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• 제30권6호
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• pp.31-38
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• 2002

본 논문에서는 4인승 커나드 항공기에 측정 센서와 데이터 처리 장비를 장착하고, 비행 성능 시험을 수행하여 획득한 비행데이터를 분석하였다. 실속 시험을 통하여 주익 실속이 원천적으로 방지되는 커나드 항공기 고유의 안전성을 확인하였다. 상반각효과, 역 빗놀이 현상 및 롤 조종력을 살펴보았고, 종 안정성을 좌우하는 중립점 위치를 추정하였다. 더치롤모드 등의 동운종 특성도 분석하였다. 일반적인 변수추정방법을 사용하지 않고 정상비행 상태에서의 비행데이터로부터 공렬 미계수 값을 직접 추정하거나 공렬 미계수 간의 관계식을 구하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2014년도 전력전자학술대회 논문집
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• pp.221-222
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• 2014

본 논문에서는 3레벨 NPC 인버터의 전원전압변조 방식을 이용하여 넓은 변조 지수에서 제어 가능한 간단한 중성점 제어 방법을 제안하였다. 제안한 제어 방법은 전원 전압 변조방법을 이용한 중성점 균형 계수와 정확한 옵셋 전압의 제한치를 이용하여 계산된다. 중성점 균형 계수는 전류의 극성과 상하 커패시터의 전압에 의해서 정의되어 진다. 제안된 제어 방법은 중성점 제어를 위해 공간전압 PWM과 불연속 PWM까지 동작범위를 확장하여 동작되어 진다. 제안된 방법은 넓은 변조지수에서 전원전압변조를 이용하여 공간전압 PWM방법을 쉽게 구현할 수 있다. 제안된 중성점 제어 방법의 타당성은 시뮬레이션을 통하여 검증하였다.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.408-411
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• 2009

In this paper, conventional PI, fuzzy neural network(FNN) and adaptive teaming mechanism(ALM)-FNN for rotor field oriented controlled(RFOC) induction motor are studied comparatively. The widely used control theory based design of PI family controllers fails to perform satisfactorily under parameter variation nonlinear or load disturbance. In high performance applications, it is useful to automatically extract the complex relation that represent the drive behaviour. The use of learning through example algorithms can be a powerful tool for automatic modelling variable speed drives. They can automatically extract a functional relationship representative of the drive behavior. These methods present some advantages over the classical ones since they do not rely on the precise knowledge of mathematical models and parameters. Comparative study of PI, FNN and ALM-FNN are carried out from various aspects which is dynamic performance, steady-state accuracy, parameter robustness and complementation etc. To have a clear view of the three techniques, a RFOC system based on a three level neutral point clamped inverter-fed induction motor drive is established in this paper. Each of the three control technique: PI, FNN and ALM-FNN, are used in the outer loops for rotor speed. The merit and drawbacks of each method are summarized in the conclusion part, which may a guideline for industry application.

• Journal of Power Electronics
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• 제13권6호
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• pp.939-954
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• 2013

The Direct Torque Control (DTC) technique for Permanent Magnet Synchronous Motors (PMSM) is receiving increased attention due to its simplicity and robust dynamic response when compared with other control techniques. The classical switching table based DTC results in large flux and torque ripples in the motors. Several studies have been reported in the literature on classical DTC. However, there are only limited studies that actually discuss or evaluate the classical DTC. This paper proposes, novel switching table / DTC methods for PMSMs to reduce torque ripples. In this paper, two DTC schemes are proposed. The six sector and twelve sector methodology is considered in DTC scheme I and DTC scheme II, respectively. In both DTC schemes a simple modification is made to the classical DTC structure. The two level inverter available in the classical DTC is eliminated by replacing it with a three level Neutral Point Clamped (NPC) inverter. To further improve the performance of the proposed DTC scheme I, the available 27 voltage vectors are allowed to form different groups of voltage vectors such as Large - Zero (LZ), Medium - Zero (MZ) and Small - Zero (SZ), where as in DTC scheme II, all of the voltage vectors are considered to form a switching table. Based on these groups, a novel switching table is proposed. The proposed DTC schemes are comparatively investigated with the classical DTC and existing literatures through theory analysis and computer simulations. The superiority of the proposed DTC method is also confirmed by experimental results. It can be observed that the proposed techniques can significantly reduces the torque ripples and improves the quality of current waveform when compared with traditional and existing methods.

• 대한조선학회논문집
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• 제59권6호
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• pp.423-431
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• 2022

In this paper, the results of Planar Motion Mechanism (PMM) test for a 1/15 scaled model of the MARIN Joubert BB2 submarine is dealt with to derive the maneuvering coefficients for surface condition. For the depth of surface navigation, the top of the sail was exposed 0.46 m above the water surface in the model scale, and it corresponds to 6.9 m in the full scale. The resistance and self-propulsion tests were conducted, and the model's self-propulsion point was obtained for 1.328 m/s, which corresponded to 10 knots in the full scale. The maneuvering tests were performed at the model's self-propulsion point, and the maneuvering coefficients were obtained. Based on the maneuvering coefficients, a turning simulation was performed for starboard 30 degree of stern fins. The straight-line stability and control effectiveness in the horizontal plane were analyzed using the maneuvering coefficients and compared with the appropriate range. For the analysis of the neutral fin angle of the X-type stern fin, the stern fin test with drift angles was carried out. As a result, the flow straightening effect at lower and upper parts of the stern fin was discussed.

• Journal of Veterinary Science
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• 제25권1호
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• pp.2.1-2.14
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• 2024

Background: Sufficient surgical resection is necessary for effective tumor control, but is usually limited for vertebral tumors, especially in the cervical spine in small animal neurosurgery. Objective: To evaluate the primary stability and safety of customized three-dimensional (3D)-printed implants for cervical spine reconstruction after total vertebrectomy. Methods: Customized guides and implants were designed based on computed tomography (CT) imaging of five beagle cadavers and were 3D-printed. They were used to reconstruct C5 after total vertebrectomy. Postoperative CT images were obtained to evaluate the safety and accuracy of screw positioning. After harvesting 10 vertebral specimens (C3-C7) from intact (group A) and implanted spines (group B), implant stability was analyzed using a 4-point bending test comparing with groups A and C (reconstituted with plate and pins/polymethylmethacrylate after testing in Group A). Results: All customized implants were applied without gross neurovascular damage. In addition, 90% of the screws were in a safe area, with 7.5% in grade 1 (< 1.3 mm) and 2.5% in grade 2 (> 1.3 mm). The mean entry point and angular deviations were 0.81 ± 0.43 mm and 6.50 ± 5.11°, respectively. Groups B and C significantly decreased the range of motion (ROM) in C3-C7 compared with intact spines (p = 0.033, and 0.018). Both groups reduced overall ROM and neutral zone in C4-C6, but only group B showed significance (p = 0.005, and 0.027). Conclusion: Customized 3D-printed implants could safely and accurately replace a cervical vertebra in dog cadavers while providing primary stability.

• 전기학회논문지
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• 제67권2호
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• pp.233-238
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• 2018

This paper proposes a seamless MPPT operation mode transfer method of photovoltaic system. The photovoltaic system consists of a DC-DC boost converter, a DC-Link, and a 3-level neutral point clamp (NPC) type inverter. The PV voltage fluctuates due to the output characteristics of the solar pane1 depending on the irradiation amount and the temperature. The photovoltaic system requires seamless MPPT mode transfer method that the discontinuity does not occur in order to supply the stable power to system without affecting the fluctuation of the PV voltage. MPPT operation is divided into two modes by the voltage reference. Under the condition that the PV voltage is below 650V, the DC-DC boost converter performs MPPT through duty control based on perturb & observe (P&O) method, and the inverter conducts DC-link voltage and grid current controls in synchronous reference frame. On the other hand, when the PV voltage exceeds above 650V, inverter performs MPPT in accordance with the variation of DC-link voltage control while the converter stops operating. Two MPPT operation modes is smoothly transferred through the proposed method that DC-link voltage or grid current commands are appropriately adjusted from the certain criteria. The feasibility of the MPPT operation mode transfer method is verified using a 10kW solar photovoltaic system, experimental results have good performances that the fluctuation of PV current is reduced to 100%.

• 전력전자학회논문지
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• 제15권6호
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• pp.451-459
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• 2010

본 논문은 대규모 풍력단지를 교류 전력망에 연계하기 위한 3-레벨 PWM 컨버터와 3-레벨 24-펄스 컨버터로 구성된 하이브리드 Back-to-Back 컨버터의 성능을 비교한 결과에 대해 기술하고 있다. 또한 3-레벨 24-펄스 컨버터를 점호각만 제어하는 경우와 영 전압제어를 같이 수행하는 경우 각각이 제어와 고조파레벨에 미치는 영향을 비교 분석하였다. 구체적인 성능비교를 위해 먼저 PSCAD/EMTDC 소프트웨어를 사용하여 시뮬레이션을 실시하고 이를 바탕으로 2 kVA 용량의 하드웨어 축소모형을 제작하고 실험을 실시하였다. 시뮬레이션과 실험을 통해 영전압과 점호각을 동시에 조절하는 방식과 점호각만 제어하는 방식의 성능비교분석을 하였다.

• 한국의류학회지
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• 제36권3호
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• pp.259-268
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• 2012

This study suggests quantitative guidelines for inside clothing temperatures to improve the heat tolerance of 20's females in summer. First, the inside clothing temperatures ($T_{cl}$) of each subject was measured in daily use. The subjects were asked to record subjective thermal sensations, clothing items worn, clothing weight, and activities during an experiment designed to determine the comfort zone of $T_{cl}$. In a thermally neutral state, the comfort zone of $T_{cl}$ was decided on a mean value $T_{cl}{\pm}1{\sigma}$. Second, the subjects were asked to wear clothing that would enable them to feel 'slightly warm but still comfortable'. The rest of the processes were the same as previous steps that were designed to understand the way and degree of clothing control. The comfort zone of $T_{cl}$ was decided in the same manner as the previous step. The two comfort zones were combined and named the combined comfort zone of the definitive comfort zone. The results were as follows: 1. Thermally comfortable $T_{cl}$, Hcl were $34.0{\pm}1.1^{\circ}C$, $40{\pm}9%%RH$ and the thermally comfortable ambient climate was $25.0{\pm}1.6^{\circ}C$, $53{\pm}7%$RH. 2. When subjects were asked to wear 'slightly warm but still comfortable', there were difference in thermally comfortable $T_{cl}$, clothing weight and clothing layer by subject. 3. In this study, the optimal $T_{cl}$ was decided on the mid-point of the definitive comfort zone of $T_{cl}$.

• Journal of Electrical Engineering and Technology
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• 제10권4호
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• pp.1540-1551
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• 2015

The detection of position and speed in BLDC motors without using position sensors has meant many efforts for the last decades. The aim of this paper is to develop a sensorless technique for detecting the position and speed of BLDC motors, and to overcome the drawbacks of position sensor-based methods by improving the performance of traditional approaches oriented to motor phase voltage sensing. The position and speed information is obtained by computing the derivative of the terminal phase voltages regarding to a virtual neutral point. For starting-up the motor and implementing the algorithms of the detection technique, a FPGA board with a real-time processor is used. Also, a versatile hardware has been developed for driving BLDC motors through pulse width modulation (PWM) signals. Delta and wye winding motors have been considered for evaluating the performance of the designed hardware and software, and tests with and without load are performed. Experimental results for validating the detection technique were attained in the range 5-1500 rpm and 5-150 rpm under no-load and full-load conditions, respectively. Specifically, speed and position square errors lower than 3 rpm and between 10º-30º were obtained without load. In addition, the speed and position errors after full-load tests were around 1 rpm and between 10º-15º, respectively. These results provide the evidence that the developed technique allows to detect the position and speed of BLDC motors with low accuracy errors at starting-up and over a wide speed range, and reduce the influence of noise in position sensing, which suggest that it can be satisfactorily used as a reliable alternative to position sensors in precision applications.