• International Journal of Naval Architecture and Ocean Engineering
• /
• 제6권2호
• /
• pp.257-268
• /
• 2014

In this study, flow-driven rotor simulations with a given load are conducted to analyze the operational characteristics of a vertical-axis Darrieus turbine, specifically its self-starting capability and fluctuations in its torque as well as the RPM. These characteristics are typically observed in experiments, though they cannot be acquired in simulations with a given tip speed ratio (TSR). First, it is shown that a flow-driven rotor simulation with a two-dimensional (2D) turbine model obtains power coefficients with curves similar to those obtained in a simulation with a given TSR. 3D flow-driven rotor simulations with an optimal geometry then show that a helical-bladed turbine has the following prominent advantages over a straight-bladed turbine of the same size: an improvement of its self-starting capabilities and reduced fluctuations in its torque and RPM curves as well as an increase in its power coefficient from 33% to 42%. Therefore, it is clear that a flow-driven rotor simulation provides more information for the design of a Darrieus turbine than a simulation with a given TSR before experiments.

• 제어로봇시스템학회논문지
• /
• 제19권11호
• /
• pp.984-990
• /
• 2013

Pick and placement systems need high speeds and reliability for the position alignment process of semiconductor packages in picking up and placing them on placement trays. Image processing is usually adopted for position aligning where finding out the most suitable method is considered most important aspect of the process. This paper proposes a method for judging the performance of different image processing algorithms based on the PCI (Process Capability Index). The PCI is an index which represents the error distribution acquired from many experimental data. The bigger the index, the more reliable the results or the lower the deviation. Two compared and candidate methods are Hough Transform and PCA (Principal Component Analysis), both of which are very suitable for oblong or rectangular type packages such as BGA's. Comparing the two approaches through a CPI with enough experimental results leads to the conclusion that the PCA is much better than the Hough Transform in not only reliability, but also processing speed.

• Journal of Biosystems Engineering
• /
• 제31권3호
• /
• pp.182-187
• /
• 2006

Aerial application using an unmanned agricultural helicopter can reduce labor and pollution. The development of an agricultural helicopter became urgent for both precise and timely spraying. In this study, a rotor system for unmanned helicopter capable of 20 $kg_f$ payload, was developed and lift capability was evaluated. A lift force over the dead weight of the helicopter was obtained at the pitch angle of $6^{\circ}$. As the pitch angle increased to $8^{\circ}\;and\;10^{\circ}$, the total lift increased to $74{\sim}81\;kg_f\;and\;86{\sim}93\;kg_f$, respectively. A range of engine speed at the rated flight condition, lifting mean payload of 23 $kg_f$ was determined. The data acquired from this study will be used for designing tail system and RF console in the next stage of the research. The rated lift capability was enough for loading 20 liters of spray material including spraying equipments.

• 대한지리학회지
• /
• 제43권6호
• /
• pp.1002-1015
• /
• 2008

이 논문에서는 기상관측소의 기온 및 강수 관측치를 이용한 공간적 분포도 작성에 수치표고모델(DEM)과 다변량 크리깅의 적용 가능성을 검토하였다. 기온 및 강수와 상관성을 가지면서 연구지역의 모든 지점에서 값을 제공하는 고도자료를 분포도 작성에 이용함으로써, 미관측 지점에서의 정보 부재 효과를 완화하면서 지형효과를 잘 반영하는 분포도를 작성하고자 하였다. 제주도 지역의 2005년 1월, 4월, 8월 및 10월의 월평균기온 및 월강수량 분포도 작성 사례 연구를 통해, 고도자료를 공동 크리깅에 의해 통합하였을 때 평활화 효과를 완화하면서 지형효과를 잘 반영하는 기온 및 강수 분포도 작성이 가능하였다. 또한 단변량 지구통계 기법인 정규 크리깅과 비교하였을 때, 보다 향상된 예측 능력을 나타내었다. 부가적으로 고도자료와의 상관성이 높을수록, 상대적 너겟 효과가 적을수록 예측 능력이 향상됨을 확인할 수 있었다.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
• /
• pp.163-166
• /
• 2000

Fiber Bra99 grating (FBG) sensor, one of the fiber optic sensor (FOS) offers lots of advantages for structural health monitoring due to its multiplexing capability. Also, it is proper to measure the structural vibration with no mass concentration effect. In this paper, we constructed two sensor arrays composed of 9 FBG sensors for the vibration and mode sensing of a composites beam. For an accurate measurement of wavelength shift, a signal processing board with an electric circuit based on time-interval counting was developed. This sensor system showed a good resolution of dynamic strain (<10${\mu}{\varepsilon}$). Using this sensor system, dynamic strains at 9 points of composite beam was measured and strain measured mode shape of the beam was calculated from the acquired strains and compared with numerical results by ABAQUS.

• 한국군사과학기술학회지
• /
• 제7권4호
• /
• pp.79-86
• /
• 2004

This paper has presented to the design results of the analog and digital signal processor for the 2nd generation thermal imaging system using $480\times6$ infrared focal plane array In order to correct non-uniformities of detector arrays, we have developed the 2-point correction method using the thermo electric cooler. Additionally, to enhance the image of low contrast and improve the detection capability, we developed the new technique of histogram processing being suitable for the characteristics of contrast distribution of thermal imagery. Through these image processing techniques, we obtained a high qualify thermal image and acquired good result.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 추계학술대회 논문집
• /
• pp.187-192
• /
• 2001

In this paper, a practical method to generate task strategies applicable to charmfulness and high-precision assembly, is proposed. The difficulties in devising reliable assembly strategies result form various forms of uncertainty such as imperfect knowledge on the parts being assembled and functional limitations of the assembly devices. In approach to cope with these problems, the robot is provided with the capability of learning the corrective motion in response to the force signal through iterative task execution. The strategy is realized by adopting a learning algorithm and represented in a binary tree type database. To verify the effectiveness of the proposed algorithm, a series of simulations and experiments are carried out under assimilated real production environments. The results show that the sensory signal-to-robot action mapping can be acquired effectively and, consequently, the assembly task can be performed successfully.

• 한국군사과학기술학회지
• /
• 제18권5호
• /
• pp.566-573
• /
• 2015

The most important factor for the penetration performance of shaped charge is the liner design. By designing the liner to have properties of both high jet tip velocity and long jet break-up time, the better penetration performance could be acquired. Usually it is very difficult to satisfy above two conditions simultaneously. In this study, the liner with the shape of ogive was developed to have relatively larger jet mass compared to the conventional trumpet liner. The designed shaped charge showed jet properties with high jet tip velocity and long jet break-up time by using ogive liner and wave shaper. A commercially available hydro-dynamic code AUTODYN-2D was used for numerical analysis of jet formation. The flash X-ray test and the static penetration test were conducted to verify the results of numerical analysis.

• 전기학회논문지
• /
• 제67권11호
• /
• pp.1506-1511
• /
• 2018

This study presents a human sensibility evaluation method using neural network and multiple-template method on electroencephalogram(EEG). We used a multi-layer perceptron type neural network as the sensibility classifier using EEG signal. For our research objective, 10-channel EEG signals are collected from the healthy subjects. After the necessary preprocessing is performed on the acquired signals, the various EEG parameters are estimated and their discriminating performance is evaluated in terms of pattern classification capability. In our study, Linear Prediction(LP) coefficients are utilized as the feature parameters extracting the characteristics of EEG signal, and a multi-layer neural network is used for indicating the degree of human sensibility. Also, the estimation for human comfortableness is performed by varying temperature and humidity environment factors and our results showed that the proposed scheme achieved good performances for evaluation of human sensibility.

• Smart Structures and Systems
• /
• 제15권4호
• /
• pp.1103-1120
• /
• 2015

A self-sensing magnetorheological (MR) damper with embedded piezoelectric force sensor has recently been devised to facilitate real-time close-looped control of structural vibration in a simple and reliable manner. The development and characterization of the self-sensing MR damper are presented based on experimental work, which demonstrates its reliable force sensing and controllable damping capabilities. With the use of experimental data acquired under harmonic loading, a nonparametric dynamic model is formulated to portray the nonlinear behaviors of the self-sensing MR damper based on NARX modeling and neural network techniques. The Bayesian regularization is adopted in the network training procedure to eschew overfitting problem and enhance generalization. Verification results indicate that the developed NARX network model accurately describes the forward dynamics of the self-sensing MR damper and has superior prediction performance and generalization capability over a Bouc-Wen parametric model.