• Journal of the Korea Computer Graphics Society
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• v.9 no.1
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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 the Korea Society for Simulation
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• v.22 no.1
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• pp.53-61
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• 2013

The purpose of this paper is to examine how the humans learn and perceive the weight of objects corresponding to visual information in virtual environment. We conducted two kinds of load-on-tasks with two virtual objects that have same weight but different visual cues; have same visual cues but changed weight by trails. We found that the subject could not generate appropriate force for the smaller and changed weight objects in the beginning of the trials. the discrepancy between the expected weight and actual force consequences sue to visually invoked size and previous experience made subjects perceive the small object were heavier. one the other hand, after the tasks were repeated, the subject responded the weights were the same or very similar when the mismatch between the expected weight and the actual weight became vanished. this means that the sensorimotor feedback influences the anticipatory control scheme and weight perception aggressively in virtual environment.

• Journal of the Korea Computer Graphics Society
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• v.26 no.3
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• pp.79-86
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• 2020

It is important to exercise in the correct posture in order to increase the exercise effect of the core exercise. This paper introduces a system that can train an exercise posture by providing feedback so that a user who performs core exercise in a virtual reality environment can take an accurate posture. It targeted three core movement postures, such as squat, lunge, and bridge, and provides visual feedback and haptic feedback to the user to take an accurate posture. The reference posture is generated by adjusting the expert's posture to the user's body length, and the accuracy of the exercise posture is calculated by comparing the user's posture with the reference posture. The effectiveness of the feedback was verified through user experiments, and the training effects according to the design of the feedback were compared.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.396-401
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• 2019

A virtual rigid is modeled as the parallel structure of a virtual spring and a virtual damper. The reflective force from the virtual model is designed to be as large as possible to improve the realism of the virtual environment while maintaining the stable interaction. So, it is important to analyze the stability boundary of the virtual spring and damper. In the previous researches, the stability boundary is analyzed based on the zero-order-hold (ZOH) method, but it is analyzed based on the first-order-hold (FOH) method and the virtual damper in the paper. The boundary value of the stable virtual damper is inverse proportional to the sampling time and the maximum value of stable virtual stiffness is inverse proportional to the square of the sampling time. And the maximum value in the FOH method is increased to 110% of the value in the ZOH method. If the virtual damper is smaller than about 50% of the boundary value of the virtual damper in the FOH method, the stable virtual stiffness in the FOH method is several times larger than that in the ZOH method.

• Journal of the Korean Institute of Intelligent Systems
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• v.19 no.4
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• pp.451-456
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• 2009

In this paper, a virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.135-138
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• 2005

Robotic devices have been widely used in many medical applications due to their accuracy and programming ability. One of the applications is a virtual reality medical simulator, which trains medical personnel in a computer generated environment. In this paper, we are going to present an application, an epidural anesthesia trainer. Because performing epidural injections is a delicate task, it demands a high level of skill and precision from the physician. This trainer uses a robotic device and computer controlled solenoid valve to recreate interaction forces between the needle and the various layers of tissues around the spinal cord. The robotic device is responsible for generation of interaction forces in real time and can be used to be haptic guidance that allows the user to follow a previous recorded expert procedure and feel the encountered forces.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.2078-2079
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• 2009

This research suggests the framework for human body learning system using various forms of bidirectional interfaces. The existing systems mostly use the limited and unidirectional methods which are merely focused on the visual information. Our system provides more realistic visual information using 3D organ models from the real human body. Also we combine the haptic and augmented reality techniques into our system for wider range of interaction means. Through this research, we aim to overcome the limitation of existing science education systems and explore the effective scheme to fuse the real and virtual educational environment into one.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.6
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• pp.746-753
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• 2008

In this paper, we introduce the improved control method are communicated between a master and a slave robot in the teleoperation systems. When the master and slave robots are located in different places, time delay is unavoidable under the network environment and it is well known that the system can become unstable when even a small time delay exists in the communication channel. The time delay may cause instability in teleoperation systems especially if those systems include haptic feedback. This paper presents a control scheme based on the estimator with virtual master model in teleoperation systems over the network. As the behavior of virtual model is tracking the one of master model, the operator can control real master robot by manipulating the virtual robot. And LQG/LTR scheme was adopted for the compensation of un-modeled dynamics. The approach is based on virtual master model, which has been implemented on a robot over the network. Its performance is verified by the computer simulation and the experiment.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2753-2758
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• 2003

Tactile sensation is essential for many manipulation and exploration tasks not only in a real environment but also in a virtual environment. In this paper, we discuss a conceptual design of an integrated tactile display system. The system comprises two parts: a 2 DOF force feedback device for kinesthetic display and a tactile feedback device for displaying the normal stimulation to skin and the skin slip/stretch. Psychophysical experiments measure the effects of fingerpad selection, the direction of finger movements and the texture width on tactile sensitivity. We also investigate characteristics of lateral finger movement while subjects perceive different textures. From the experimental results, the principal parameters for designing a tactile display are suggested. A tactile display device is implemented using eight piezoelectric bimorphs and a linear actuator, and is attached to a 2 DOF translational force feedback device to simultaneously simulate texture and stiffness of the object.

• 한국HCI학회:학술대회논문집
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• 2007.02a
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• pp.447-454
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• 2007

본 논문에서는 사용자의 가상환경 내의 위치 정보에 대한 감각을 향상시키는 방법론으로서 햅틱 피드백(haptic feedback)과 사운드 피드백(sound feedback)의 모달리티를 활용한 그리드(grid)를 제안한다. 제안된 그리드는 사용자의 3차원 공간 내의 움직임(explorative procedure)에 추가적인 비 시각적인(non-visual) 위치정보 피드백을 부여하는데 그 목적을 두고 있다. 햅틱 모달리티를 활용한 3차원 그리드는 SensAble사의 PHANTOM(R) Omni$^{TM}$ 를 활용하여 설계되었으며, 사운드 모달리티를 활용한 경우 저주파 배경음의 주파수 특성(frequency characteristics of sound source)을 사용자 손의 공간 좌표값에 근거하여 재생 시의 표본 추출 비율(sampling rate)를 연속적으로 바꾸는 방식으로 설계되었다. 이러한 공간 그리드는 두 모달리티 각각의 독립적인 제시 및 동시 제시/제거를 통해 평가되었으며, 동시 제시의 경우 두 모달리티간의 어긋남(cross-modal asynchrony)이 없도록 설계되어 사용자의 공간 작업 시 모달리티간의 조화 (manipulating congruency)를 확보할 수 있도록 하였다. 실험을 통해 얻어진 결과는 그것의 통계적 유의미성을 분석하기 위해 다원변량분석과 사후검증(Turkey. HSD)을 거쳐 해석이 되었다. 공간 내 특정 좌표 선택을 기준으로 하는 그리드의 사용자 평과 결과, 3차원 내의 움직임에 대해 햅틱 및 사운드 피드백의 비 시각적 피드백은 사용자의 공간 작업의 오차를 줄여 주고 있음이 확인되었다. 특히 시각적인 정보만으로 확인하기 어려운 Z축 상의 움직임은 그리드의 도움으로 그 오차정도가 50% 이상 줄어 드는 것으로 확인되었다(F=19.82, p<0.01). 이러한 시각적 정보를 보존하는 햅틱, 사운드 피드백 방식을 HCI의 중요한 요소인 사용성과 유용성과 연관시켜 MMHCI(multimodal human-computer interaction) 방법론으로의 적용 가능성을 검토해 본다.