• 한국통계학회:학술대회논문집
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• 한국통계학회 2004년도 학술발표논문집
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• pp.307-312
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• 2004

In our fast-moving information and knowledge society, skills and know-how rapidly become outdated. Virtual learning environments play a key role in meeting today's growing demand for customized educational and vocational training and lift-long teaming. The scope of multimedia-based and web-supported education is illustrated by means of an interdisciplinary multimedia project 'New Statistics' funded by the German government. The project output contains more than 70 learning modules covering the complete curriculum of an introductory statistics course. All modules are based on a statistical laboratory and on a multitude of Java applets, animations and case studies. The paper focuses on presenting the statistical laboratory and the applets. These components present the main project pillars and are particularly suitable for international use, independently from the original project framework. This article also demonstrates the application of Java applets and other multimedia developments from the educational world to official statistics for interactive presentation of statistical information.

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1720-1730
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• 2005

Automatic guided vehicle in the factory has an important role to advance the flexible manufacturing system. In this paper, we propose a novel object-transportation control algorithm of cooperative AGV systems to apply decentralized control to multiple AGV systems. Each AGV system is under nonholonomic constraints and conveys a common object-transportation in a horizontal plain. Moreover it is shown that cooperative robot systems ensure stability and the velocities of augmented systems convergence to a scaled multiple of each desired velocity field for cooperative AGV systems. Finally, the application of proposed virtual passivity-based decentralized control algorithm via system augmentation is applied to trace a circle. Finally, the simulation and experimental results for the object-transportation by two AGV systems illustrates the validity of the proposed virtual-passivity decentralized control algorithm.

• 한국컴퓨터그래픽스학회논문지
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• 제9권1호
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• pp.19-27
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• 2003

Most interaction schemes in virtual environment are indirect in one way or another. ln particular, without a haptic device (which introduces its own problems due to its cumbersomeness), users must rely on visual (or/and aural) feedback, and can not directly appreciate the 3Dness of the interaction object even with stereoscopy. This causes a drop in object presence because people are used to, for instance, observing objects in one's hand, rotating and manipulating them with physical contact. To alleviate this problem, this paper proposes a hand-held cubic screen, named TangibleScreen, on which the appearance of the target interaction object is projected. We choose the Relief Texture Mapping as the rendering method to correctly generate the viewer dependent textures to be projected on the non-planar surfaces of the TangibleScreen.

• Journal of Power Electronics
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• 제18권4호
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• pp.1111-1126
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• 2018

In modern power systems, distributed generators (DGs) result in high stress on system frequency stability. Apart from the intermittent nature of DGs, most DGs do not contribute inertia or damping to systems. As a result, a new control method referred to as a virtual synchronous machine (VSM) has been proposed, which brought new characteristics to inverters such as synchronous machines (SM). DGs employing an energy storage system (ESS) provide inertia and damping through VSM control. Meanwhile, energy storage presents some physical constraints in the VSM implementation level. In this paper, a VSM mathematical model is built and analyzed. The dynamic responses of the output active power are presented when a step change in the frequency occurs. The influences of the inertia constant, damping factor and operating point on the ESS volume margins are investigated. In addition, physical constraints are proposed based on these analyses. The proposed physical constraints are simulated using PSCAD/EMTDC software and tested through RTDS experiment. Both simulation and RTDS test results verify the analysis.

• 한국지능시스템학회논문지
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• 제14권6호
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• pp.732-736
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• 2004

현재, 인터넷의 보급이 보편화되고 있다. 그래서 인터넷을 이용할 수 있는 기술과 장비가 개발되고 발전되어 가고 있다. 이러한 시대적 흐름을 공학 연구에서도 잘 이용할 수 있다. 언제 어디서나 인터넷을 쉽게 이용할 수 있다는 장점을 이용하여 수시로 지능형 로봇에 대한 실험과 그 결과를 얻을 수 있다. 뿐만 아니라 다른 실험장비에 대해서도 위와 같은 실험과 결과를 얻을 수 있다 지능형 로봇은 제어 컴퓨터가 탑재 가능하여 랜 선의 제약을 받지 않는다. 다만 무선 인터넷이 가능한 공간에서만 실험 가능하다. 본 논문에서는 지능형 로봇에 탑재한 제어 컴퓨터(클라이언트)와 일반 컴퓨터(서버)구조를 가지며 다중 제어 인터페이스를 구현한다.

• 한국자동차공학회논문집
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• 제14권3호
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• pp.68-74
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• 2006

The evaluation of durability performance in Virtual Testing Laboratory(VTL) is a new concept of vehicle design, which can reduce the automotive design period and cost. In this study, the multibody dynamics model of a car is built with a reverse engineering design. Hard points and masses of components are measured by a surface scanning device and imported into CAD system. In order to simulate the non-linear dynamic behavior of force elements such as dampers and bushes, components and materials are tested with specialized test equipments. An optimized numerical model for the damping behavior is used and the hysteresis of bush rubber is considered in the simulation. Loads of components are calculated in VTL and used in the evaluation of durability performance. In order to verify simulation results, loads of components in the vehicle are measured and durability tests are performed.

• 대한의생명과학회지
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• 제25권2호
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• pp.139-148
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• 2019

The role of electroencephalography (EEG) in the development of brain-computer interface (BCI) technology is increasing. In particular, the importance of the analysis of event related potential (ERP) in various situations is becoming more significant in BCI technology. Studies on past maze and fire situations have been difficult due to risks and realistic problems. Nowadays, according to the development of virtual reality (VR) technology, realistic maze and fire situation can be realized. In this study, ERPs (P300, and evented related negativity) were analyzed to collect objective data on case determination in an emergency situation. In order to overcome the limitations of previous methods that evaluating the EEG frequency change, ERPs were derived by setting epochs for stimulation and standardizing them, and evaluated for ERPs in this study. P3a and P3b, which are subcomponents of P300, were analyzed and the evented related negativity (ERN) was analyzed together with error positivity (Pe). As a result of the study, statistically significant changes of ERPs were observed, this result, which has little related research, is considered to be meaningful as medical basic statistics.

• 공학교육연구
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• 제2권1호
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• pp.51-58
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• 1999

본 연구는 가상 현실(virtual reality)을 활용하여 실제 고가의 실험장비를 구입하지 않고도 개인용 컴퓨터에서 인터넷상으로 가상적인 프레스를 이용한 압축실험을 할 수 있도록 하는 것이다. 가상압축실험의 구현은 인터넷을 통하여 세 개의 모듈 즉 입력, 계산, 결과로 나누어 계산되어진다. 입력모듈에서는 압축실험을 위하여 인터넷 사용자가 재료의 실험적인 특징을 입력하고 그 입력 값을 서버 컴퓨터로 보내주는 과정이며, 계산모듈은 서버 컴퓨터에 있는 시뮬레이션 해석프로그램을 이용하여 입력모듈의 입력 값을 받아들여 결과를 계산한 후 파일로 저장하는 과정이다. 결과모듈에서는 서버 컴퓨터에서 계산된 결과를 인터넷 사용자에게 도표와 그림 그리고 3차원 애니메이션을 보여주는 과정으로 되어있다. 이를 구현하기 위하여 인터넷의 언어인 HTML, CGI, VRML, JAVA를 사용하였으며, 유한요소법(FEM)을 이용한 해석프로그램은 포트란(Fortran) 언어로 제작되었다. 현재 인터넷상에서의 가상현실을 이용한 응용분야가 급속히 확대되므로 앞으로 공학적인 가상 실험에 관한 연구가 많이 이루어져 실제 실험을 대체할 것이다.

• Journal of Power Electronics
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• 제19권5호
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• pp.1224-1234
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• 2019

Hybrid rotor position estimation methods that integrate a fundamental model and high frequency (HF) signal injection are widely used for the wide speed-range sensorless control of interior permanent-magnet synchronous machines (IPMSMs). However, the direct transition of two different schemes may lead to system fluctuations or system instability since two estimated rotor positions based on two different schemes are always unequal due to the effects of parameter variations, system delays and inverter nonlinearities. In order to avoid these problems, a seamless transition strategy to define and construct a virtual q-axis inductance is proposed in this paper. With the proposed seamless transition strategy, an estimated rotor position based on a fundamental model is forced to track that based on HF signal injection before the transition by adjusting the constructed virtual q-axis inductance. Meanwhile, considering that the virtual q-axis inductance changes with rotor position estimation errors, a new observer with a two-phase phase-locked loop (TP-PLL) is developed to accurately obtain the virtual q-axis inductance online. Furthermore, IPMSM sensorless control with maximum torque per ampere (MTPA) operations can be tracked automatically by selecting the proper virtual q-axis inductance. Finally, experimental results obtained from an IPMSM demonstrate the feasibility of the proposed seamless transition strategy.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.847-852
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• 2004

The virtual engineering technologies have been broadly used for the design, testing, manufacturing and maintenance works of industrial product. Recently many VR systems with walk through navigation and web databases; such as design and installation database. load history database, maintenance history database et al. are developed. However, the virtual engineering in railroad industry is not well developed compared to other industries like automobile, air, shipbuilding. In this paper, we explain the strategy that we have applied the virtual engineering technology to the design works of rolling stock and our plan to build the virtual testing laboratory(VTL) in the Korea Railroad Research Institute.