• Journal of Power Electronics
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• 제19권6호
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• pp.1575-1581
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• 2019

Due to the mismatched line impedance among distributed generation units (DGs) and uncontrolled harmonic current, the droop controller has a number of problems such as inaccurate reactive power sharing and voltage distortion at the point of common coupling (PCC). To solve these problems, this paper proposes a resistive-capacitive virtual impedance control method. The proposed control method modifies the DG output impedance at the fundamental and harmonic frequencies to compensate the mismatched line impedance among DGs and to regulate the harmonic current. Finally, reactive power sharing is accurately achieved, and the PCC voltage distortion is compensated. In addition, adaptively controlling the virtual impedance guarantees compensation performance in spite of load changes. The effectiveness of the proposed control method was verified by experimental results.

• 한국멀티미디어학회논문지
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• 제24권2호
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• pp.328-335
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• 2021

In the era of 'Untact', virtual reality-based job training platforms are actively being used as part of non-face-to-face education for students with developmental disabilities. Because the people with developmental disabilities may lack sufficient cognitive abilities, it is difficult to conduct untact training seamlessly without the help of a third party. Therefore, it is necessary for training programs to identify the right timing to provide help so that the training can be continued. This research analyzed the visual attention of students with developmental disabilities in virtual reality-based job training program in order to determine the point of time when an intervention is required by the trainee. Results showed that students who completed the mission tended to have intense visual attention on a small number of objects for a certain period of time; the visual attention of the students who failed tended to shift erratically among multiple objects.

• International Journal of Advanced Culture Technology
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• 제11권4호
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• pp.322-327
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• 2023

Recent advances in augmented reality (AR) and virtual reality (VR) technologies have led to a significant increase in metaverse platforms. Metaverses are setting a new direction for the digital world. This paper examines the phenomenon of virtual worlds that are becoming an issue these days, focusing on [Ready Player One]. One of the common features of the metaverse platform in [Ready Player One] and the platforms currently in use is the concept of open world. This is a feature that goes beyond simply moving around in a virtual world and allows users to freely reset, participate in, and control the environment. This innovative concept is a hallmark of metaverse platforms, and it is becoming increasingly important and influential. Through this study, we focused on the [open world system] of the platform in the movie and the modern metaverse platform, and suggested and studied how the scalability of the metaverse will present a turning point in the future.

• 한국CDE학회논문집
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• 제16권4호
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• pp.305-313
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• 2011

This paper proposes a method for reusing kinematic design data for virtual facilities, Making a virtual model of a facility involves two major activities: geometric design (virtual model visualization) and kinematic design that should be remodeled frequently whenever design changes occur, Conventionally, a virtual model of an automated facility focuses on the design level, which mainly deals with design verification, alternative comparison, and geometric model diagnosis, Although a design level model can be designed with the information of past models from PLM system, a simulation level model is not sufficient utilized to be reused for kinematic design purpose, We propose a method for reusing kinematic information of a past simulation model to cope with this problem, We use the concept or the 'center of mass', which is a point representing the mean position of the matter in a body or system. And we also use comparison method of a boundary box to identity which 3D objects have to be involved from the design model to a link structure that is contained in the simulation model. Because a proposed method only use not a historical approach but a geometrical approach, it is more effective to apply to the field.

• 한국의류산업학회지
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• 제19권5호
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• pp.595-601
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• 2017

Advances in 3D garment simulation technology contribute greatly to consumers becoming more immersed in movies and games by realistically expressing the garments the characters in the movie or game are wearing. The fashion industry has reached a point where it needs to maximize efficiency in production and distribution to go beyond time and space in order to compete on the global market. The processes of design and product development in the fashion industry require countless hours of work and consume vast resources in terms of materials and energy to repeat sample production and assessment. Therefore, the design and product development tools and techniques must aim to reduce the sample making process. Therefore, this study aims to study a case for comparing the real garment sample making process to the virtual garment sample making process. In this study, we have analysed the differences between the real and virtual garment making processes by choosing designated patterns. As we can see from the study results, the real and virtual garments generally are made through similar processes in manufacturing, while the time consumed for each shows great variation. In real garment making, scissoring and sewing require the greatest number of work hours, whereas in virtual garment making, most of the time was spent in the simulation process.

• 한국인터넷방송통신학회논문지
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• 제10권4호
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• pp.77-82
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• 2010

본 연구에서는 가상낚시시스템(VFS, Virtual Fishing System)을 위해 제작된 햅틱장치인 FishBot을 개발한다. FishBot는 XY테이블에 휠축을 장착한 3자유도 로봇으로 구성된다. 물고기의 동작을 모사하기 위해 XY 축 제어는 토크값을 가변적으로 제한하는 모션 위치 제어 모드로 하고 휠 축은 힘제어 모드로 하였다. 낚싯대는 실제 낚싯대에 LED를 장착하고 웹 카메라를 튜닝하여 낚싯대의 위치를 인식할 수 있도록 하였다. 결과적으로 제작된 Fishbot은 물고기와 같이 위치와 속도를 변화하고 DAC를 통해 낚는 힘을 제어할 수 있으며 낚싯대 끝단의 위치를 관측하여 가상현실시스템(Virtual Reality System)상에서 연동할 수 있게 하였다.

• 전력전자학회논문지
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• 제20권1호
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• pp.81-90
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• 2015

This paper investigates the droop control-based real and reactive power load sharing with a virtual inductor when the line impedance between inverter and Point of Common Coupling (PCC) is partly and unequally resistive in high-capacity systems. In this paper, the virtual inductor method is applied to parallel inverter systems with resistive and inductive line impedance. Reactive power sharing error has been improved by applying droop control after considering each line impedance voltage drop. However, in high capacity parallel systems with large output current, the reference output voltage, which is the output of droop controller, becomes lower than the rated value because of the high voltage drop from virtual inductance. Hence, line impedance voltage drop has been added to the droop equation so that parallel inverters operate within the range of rated output voltage. Additionally, the virtual inductor value has been selected via small signal modeling to analyze stability in transient conditions. Finally, the proposed droop method has been verified by MATLAB and PSIM simulation.

• Journal of information and communication convergence engineering
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• 제8권6호
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• pp.690-696
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• 2010

Web-based virtual collaboration is increasingly gaining popularity in almost every area in our society due to the fact that it can bridge the gap imposed by time and geographical constraints. However, in medical field, such collaboration has been less popular than other fields. Some of the reasons were timeliness, security, and preciseness of the information they are dealing with. In this paper, we are proposing a web-based distributed medical collaboration system called Virtual Collaboration System for Medicine (VCSM) for medical doctors that meet the needs. The proposed system consists of two parts - multimedia presentation and recordable virtual collaboration. The former supports synchronized multimedia presentation using Synchronous Multimedia Integration Language (SMIL.) It allows synchronization of the contents of a PowerPoint presentation file and a video file. The presentation may be provided to the participants before the discussion begins. Next, in the virtual collaboration stage, participants can use text along with associated symbols during the discussion over the presented medical images. The symbols such as arrows or polygons can be set or removed dynamically to represent areas of interest in digital images using so called layered architecture that separates image layer from annotation layer. XML files are used to record participants' opinions along with the symbols over some particular images

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.727-731
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• 2009

In this paper, we propose a method to generate a free viewpoint image using multi-viewpoint images which are taken by cameras arranged circularly. In past times, we have proposed the method to generate a free viewpoint image based on Ray-Space method. However, with that method, we can not generate a walk-through view seen from a virtual viewpoint among objects. The method we propose in this paper realizes the generation of such view. Our method gets information of the positions of objects using shape from silhouette method at first, and selects appropriate cameras which acquired rays needed for generating a virtual image. A free viewpoint image can be generated by collecting rays which pass over the focal point of a virtual camera. However, when the requested ray is not available, it is necessary to interpolate it from neighboring rays. Therefore, we estimate the depth of the objects from a virtual camera and interpolate ray information to generate the image. In the experiments with the virtual sequences which were captured at every 6 degrees, we set the virtual camera at user's choice and generated the image from that viewpoint successfully.

• 한국자동차공학회논문집
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• 제17권1호
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• pp.169-175
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• 2009

Real-time multibody vehicle dynamics software has been developed for virtual handling tests. The software can be utilized for HILS(Hardware In the Loop Simulations) and consists of three modules such as a graphical vehicle modeling preprocessor, a real time dynamics solver, and a virtual reality graphic postprocessor for virtual handling tests. In the graphical vehicle modeling preprocessor, vehicle hard point data for a suspension model are automatically converted into multibody vehicle model. In the real time dynamics solver, the efficient subsystem synthesis method is used to create multibody equations of motion for a subsystem by a subsystem. In the virtual reality graphic postprocessor, an animator has been also developed by using Matlab Virtual Reality Toolbox for virtual handling tests.