• 한국게임학회 논문지
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• 제9권5호
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• pp.43-52
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• 2009

본 연구는 게임 물리 엔진을 실시간 물리 기술의 관점으로 고찰한다. 실시간 물리 기술이란 물리 시뮬레이션 기술을 게임에 적용하기 위해서 간략화 하는 기술을 말한다. 조사 대상으로 상용 물리 엔진인 Havok Physics SDK와 NVIDIA PhysX SDK를 선택하였고, 오픈 소스기반 물리 엔진인 ODE와 Bullet을 선택하였다. 그 결과 물리 엔진은 강체 역학, 변형체 시뮬레이션, 유체 시뮬레이션을 구현하고 있었고, 실시간 시뮬레이션을 위해서 수식의 간략화, 충돌 처리의 효율성 재고 등 소프트웨어 측면의 기술과 멀티 코어 CPU의 이용, PPU, GPU 활용 등 병렬처리 하드웨어 기술을 사용하고 있었다.

• 자동차안전학회지
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• 제3권2호
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• pp.34-41
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• 2011

Side collisions (or side crash) account for 51.6% of all car to car accidents occurred in 2010. It is necessary to analyze those vehicles' structure deformation and passengers' injuries in the side collisions. A moving barrier (950kg) is currently used in the KNCAP side impact test. However, in order to enhance a passengers' safety in the side collisions, we introduce an AE-MDB (1500kg) which provides more severe conditions for this test. In this study, the test results using both barriers are compared and analyzed.

• 한국해양공학회지
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• 제23권6호
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• pp.7-11
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• 2009

The dynamic responses and drift forces in waves of a floating circular fish cage are analyzed considering hydroelastic effects. The method of generalized mode is used to calculate the hydroelastic responses of the floater of cage. The elastic mode shapes, generalized mass, and stiffness in dry mode are evaluated by using a structural analysis code. The higher-order boundary element method is adopted to analyze the interaction between fluid and deformable structure. Some results of vertical motions and drift forces are shown and compared with those for a rigid body.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.450-455
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• 2004

There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D. The results of those analysis represent that the contact algorithm proposed in this study works properly.

• 대한기계학회논문집A
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• 제29권1호
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• pp.30-37
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• 2005

There is few research about contact problem for a rigid surface with an arbitrary shape in SPH. The variational equation based on the virtual work principle is derived and its solution is obtained by the penalty method. It is proposed a new method that can determine the parameters for a penetration and a penetration rate used in the penalty method. The reproducing condition is adopted to correct the deficiency of kernel on the boundary. In order to calculate a penetration of particles, after checking boundary particles for deformable body, boundary normal vectors were determined on the rigid surface. Numerical simulations for models which have rigid surface with an arbitrary shape were conducted to validate the proposed method in 2D Cartesian and cylindrical coordinate. The results of those analysis represent that the contact algorithm proposed in this study works properly.

• 센서학회지
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• 제31권5호
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• pp.293-300
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• 2022

Flexible, wearable, and implantable electronic sensors have started to gain popularity in improving the quality of life of sick and healthy people, shifting the future paradigm with high sensitivity. However, conventional technologies with a limited lifespan occasionally limit their continued usage, resulting in a high cost. In addition, traditional battery technologies with a short lifespan frequently limit operation, resulting in a substantial challenge to their growth. Subsequently, utilizing human biomechanical energy is extensively preferred motion for biologically integrated, self-powered, functioning devices. Ideally suited for this purpose are piezoelectric energy harvesters. To convert mechanical energy into electrical energy, devices must be mechanically flexible and stretchable to implant or attach to the highly deformable tissues of the body. A systematic analysis of piezoelectric nanogenerators (PENGs) for personalized healthcare is provided in this article. This article briefly overviews PENGs as self-powered sensor devices for energy harvesting, sensing, physiological motion, and healthcare.

• Advances in nano research
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• 제14권4호
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• pp.329-334
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• 2023

Organic ferroelectric material found vast application in a verity of engineering and health technology fields. In the present study, we investigated the application of the deformable organic ferroelectric in motion measurement and improving performance in tennis players. Flexible ferroelectric material P(VDF-TrFE) could be used in wearable motion sensors in tennis player transferring velocity and acceleration data to collecting devises for analyzing the best pose and movements in tennis players to achieve best performances in terms of hitting ball and movement across the tennis court. In doing so, ferroelectric-based wearable sensors are used in four different locations on the player body to analyze the movement and also a sensor on the tennis ball to record the velocity and acceleration. In addition, poses of tennis players were analyzed to find out the best pose to achieve best acceleration and movement. The results indicated that organic ferroelectric-based sensors could be used effectively in sensing motion of tennis player which could be utilized in the optimization of posing and ball hitting in the real games.

• 한국컴퓨터그래픽스학회논문지
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• 제15권3호
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• pp.1-9
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• 2009

최근 역감, 촉감 피드백을 생성할 수 있고 3 차원 상호작용이 가능한 컴퓨터 인터페이스 기술이 발전하면서 기존의 입출력 장치에 의존하던 컴퓨터 시뮬레이션의 한계가 줄어들어 그 종류가 다양해지고 있다. 특히, 가상현실 기반 수술 시뮬레이터의 수요가 증가 하면서 사실적인 가상환경을 제공하는 방법에 관련된 연구가 활발히 진행 되고 있으며 그 중에서 가상 장기 모델의 사실적인 표현 기술은 사용자의 몰입감을 높여주는데 중요한 역할을 하기 때문에 반드시 필요한 분야이다. 가상 장기 모델의 사실성을 높이기 위해서는 사용자의 상호작용에 따라 변형되는 시각적 피드백과 알맞은 햅틱 피드백을 전달해야한다. 본 연구에서는 이 두 가지 피드백은 사람이 인지하는 방법과 시스템의 요구 사항이 다르기 때문에 보다 효과적인 시뮬레이션을 하기 위하여 서로 다른 두 모델을 구현하고 두 모델간의 동기화를 위한 기술로써 적응성 질량-스프링 모델 기법을 제안한다. 또한, 유연체 변형에 대하여 표면의 세부 형태를 보여주는 시각모델과 사용자의 상호작용에 따른 햅틱 피드백을 전달하는 햅틱 모델, 그리고 이 두개의 모델을 연동시키는 동기화 모델을 통하여 유연체의 거동을 실시간, 사실적으로 제공할 수 있는 가변형 모델 시뮬레이션 프레임워크를 설계한다.

• 방송공학회논문지
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• 제24권2호
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• pp.264-272
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• 2019

본 논문은 비디오로부터 추출한 프레임으로부터 3차원 인체 형상과 자세 복원을 수행하고 이를 시간 축에서 자연스럽고 부드러운 움직임을 나타내도록 보정하는 기법을 제안한다. 제안하는 기법은 우선 비디오로부터 추출한 개별 프레임으로부터 convolutional neural network을 이용하여 관절의 위치와 인체의 윤곽을 추정한다. 인체의 형상 및 자세는 매개변수 기반의 3차원 변형가능 모델(morphable model)을 2차원 영상으로 투영후 정합하여 최적의 매개변수 값을 추정한다. 이 때 각 프레임에 대한 복원이 개별적으로 수행되면 시간 축에서 자세의 연속성과 체형의 일관성이 보장되지 못하고 올바르지 못한 복원 결과가 나타난다. 제안하는 기법은 이러한 문제점을 보완하기 위하여 각 프레임으로부터 복원된 3차원 변형가능 모델의 주성분 매개변수의 분석 및 보간을 수행한다. 실험결과 3차원 인체 복원에 오류가 발생한 프레임에 대해 이전과 이후 프레임들 사이의 관계를 통해 오류가 보정되어 개선된 복원 결과를 얻을 수 있음을 보인다.

• 센서학회지
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• 제31권3호
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• pp.156-162
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• 2022

This study estimates the relative position between body segments using segment orientation and segment-to-joint center (S2J) vectors. In many wearable motion tracking technologies, the S2J vector is treated as a constant based on the assumption that rigid body segments are connected by a mechanical ball joint. However, human body segments are deformable non-rigid bodies, and they are connected via ligaments and tendons; therefore, the S2J vector should be determined as a time-varying vector, instead of a constant. In this regard, our previous study (2021) proposed a method for determining the time-varying S2J vector from the learning dataset using a regression method. Because that method uses a deformation-related variable to consider the deformation of S2J vectors, the optimal variable must be determined in terms of estimation accuracy by motion and segment. In this study, we investigated the effects of deformation-related variables on the estimation accuracy of the relative position. The experimental results showed that the estimation accuracy was the highest when the flexion and adduction angles of the shoulder and the flexion angles of the shoulder and elbow were selected as deformation-related variables for the sternum-to-upper arm and upper arm-to-forearm, respectively. Furthermore, the case with multiple deformation-related variables was superior by an average of 2.19 mm compared to the case with a single variable.