• 한국산학기술학회논문지
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• 제20권6호
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• pp.396-401
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• 2019

가상환경 속 가상 강체는 가상 스프링과 가상 댐퍼의 병렬구조로 모델링되며 가상 강체의 현실감을 증강시키기 위해서는 가상 모델로부터의 반력을 안정적으로 최대한 크게 제시해야 한다. 따라서 햅틱 인터페이스의 안정성을 유지시킬 수 있는 가상 스프링과 가상 댐퍼의 영역을 분석하여 가상 강체모델을 선정하는 것이 중요하다. 기존에는 영차홀드를 이용하는 시스템에 대해 안정성 영역이 분석되었으나, 본 논문에서는 일차홀드 방식과 가상 댐퍼를 이용하는 햅틱 시스템에 대한 안정성 영역을 분석한다. 안정적인 가상 댐퍼 영역의 경계값은 샘플링 주기와 반비례 관계를 가지며, 안정적인 가상 스프링 영역의 최대값은 샘플링 주기의 제곱에 반비례 관계를 갖는다. 그리고 그 최대값은 일차홀드 방식을 이용하여 기존의 영차홀드의 경우보다 약 110% 향상시킬 수 있다. 가상 댐퍼의 크기가, 일차홀드 방식에서의 안정적인 가상댐퍼 경계값의 약 50% 보다 작다면, 일차홀드를 이용함으로써 기존의 영차홀드의 경우보다 안정적인 가상 스프링의 영역을 수 배 더 크게 할 수 있다.

• 한국산업융합학회 논문집
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• 제20권5호
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• pp.419-424
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• 2017

The purpose of this study is to develop a virtual testbed capable of predicting the functional performance of a linear electromagnetic actuator for a high voltage relay in order to reduce its development costs and time. The virtual testbed is defined by a multiphysics coupling approach in order to consider the complex interactions of multi-domains such as the solenoid model of electromagnets, the mass-spring-damper model of mechanical systems, the electric circuit model for an external control unit, and the thermal model for predicting temperature variations. The performances of the existing high voltage relay were estimated by the virtual testbed, and then the effectiveness and validation of the proposed testbed were discussed in comparison with the experimental test results. This study showed that the virtual testbed can be applied in design, optimization, and investigation of high voltage relays.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2006년도 추계학술발표대회 논문집
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• pp.196-201
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• 2006

Existing model houses have played an important role in allow the customers to choose apartment. As the information technology has been advanced (e.g. a high-speed internet available in unit), customers' personality and preference to the design of apartment and the purchasing pattern have been changed. Construction firms have introduced VR(Virtual Reality) model house (e.g. Quick Time Virtual Reality) to meet the customers' expectation and need. The reality-based QTVR model house does not provide enough quality to satisfy the customers' expectation. To complement the shortcoming of the QTVR model house, this study presents a web-based cyber model house developed by using Turntool and Javascript. The cyber model house allows to communicate between supplier and customer over the internet.

• 한국자동차공학회논문집
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• 제21권2호
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• pp.26-36
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• 2013

Purpose of this study is to develop virtual components and environment for developing a controller of an Active Air Suspension System in laboratory that slough off existing development environment using real vehicle test. This paper presents an air spring modeling and analysis of air suspension system for a commercial vehicle. Preferentially, It was performed vehicle test for pneumatic system and an air spring for characteristic analysis of system. Each component of an air spring suspension system was developed through emulations and modeling of system for pressure and height sensors in the basis on test results in SILS environment. Non-linear characteristics of air spring are accounted for using the measured data. Also, pressure and volume relations for vehicle hight control is considered. After performance verification of virtual model was performed, we developed virtual environment based on HILS for an Active Air Suspension System. We studied estimation and verification technology for control algorithm that developed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 D
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• pp.2510-2512
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• 2002

In this paper, we investigated 2-DOF haptic device and the method of virtual environment modeling for virtual reality. We designed an modified five bar link system to improve the performance. The haptic control system is composed of calculating kinematics and statics, controlling actuator, and describing the virtual environment. Using this system, we realized the virtual spring model and the freely falling ball model.

• 동력기계공학회지
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• 제13권2호
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• pp.71-82
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• 2009

This paper presents a real-time haptic rendering method for a realistic force feedback in a remote environment with varying communication time-delay. The remote environment is assumed as a virtual environment based on a computer graphics, for example, on-line shopping mall, internet game and cyber-education. The properties of a virtual object such as stiffness and viscosity are assumed to be unknown because they are changed according to the contact position and/or a penetrated depth into the object. The DARMAX model based output estimator is proposed to trace the correct impedance of the virtual object in real-time. The output estimator is developed on the input-output relationship. It can trace the varying impedance in real-time by virtue of P-matrix resetting algorithm. And the estimator can trace the correct impedance by using a white noise that prevents the biased input-output information. Realistic output forces are generated in real-time, by using the inputs and the estimated impedance, even though the communication time delay and the impedance of the virtual object are unknown and changed. The generated forces trace the analytical forces computed from the virtual model of the remote environment. Performance is demonstrated by experiments with a 1-dof haptic device and a spring-damper-based virtual model.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권2호
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• pp.671-686
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• 2020

Due to the long training time and high training cost of traditional surgical training methods, the emerging virtual surgical training method has gradually replaced it as the mainstream. However, the virtual surgical system suffers from poor authenticity and high computational cost problems. For overcoming the deficiency of these problems, we propose an optimized model for the local compression deformation of soft tissue. This model uses a simulated annealing algorithm to optimize the parameters of the soft tissue model to improve the authenticity of the simulation. Meanwhile, although the soft tissue deformation is divided into local deformation region and non-deformation region, our proposed model only needs to calculate and update the deformation region, which can improve the simulation real-time performance. Besides, we define a compensation strategy for the "superelastic" effect which often occurs with the mass-spring model. To verify the validity of the model, we carry out a compression simulation experiment of abdomen and human foot and compare it with other models. The experimental results indicate the proposed model is realistic and effective in soft tissue compression simulation, and it outperforms other models in accuracy and real-time performance.

• 한국산학기술학회논문지
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• 제19권1호
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• pp.12-17
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• 2018

가상환경에 대한 현실감을 증강시키기 위해서는 햅틱 시스템의 안정성을 유지하면서 가상환경 모델의 강성을 최대한 크게 할 수 있는 방법이 필요하다. 이에 기존 연구에서 영차홀드 대신 일차홀드를 적용하는 방법이 제시되었고, 영차홀드를 이용할 때보다 가상 스프링의 안정성 영역을 더 크게 확보할 수 있음을 시뮬레이션을 통해 제시했다. 그렇지만 실제로 시스템을 구현하는 측면에서 보면, 영차홀드가 일반적이고 손쉬운 방법이다. 이에 본 논문에서는 영차홀드를 사용하지만, 일차홀드와 동등한 안정성 영역을 확보하기 위한 방법으로 외삽법과 고주파 영차홀드 출력 방법을 제안한다. 제안된 방법에 대한 시뮬레이션을 통해 고주파 영차홀드의 샘플링 주기가 작아질수록 가상 스프링의 안정성 영역이 일차홀드를 적용한 경우와 거의 같아짐을 보였고, 기존 연구에서 제시된 영차홀드만을 적용한 경우보다는 수 배에서 수십 배 안정성 영역이 더 커질수 있음을 보였다. 따라서 제안된 방법을 통해 가상 환경 속 강체에 대한 현실감을 증강시킬 수 있을 것으로 기대된다.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1787-1792
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• 2016

Previous walking pattern generation methods could generate walking patterns that allow only straight walking on flat and uneven terrain. They were unable to generate modifiable walking patterns whereby the sagittal and lateral step lengths and walking direction can be changed at every footstep. This paper proposes a novel walking pattern generation method to realize modifiable walking of humanoid robots on unknown uneven terrain. The proposed method employs a walking pattern generator based on the 3-D linear inverted pendulum model (LIPM), which enables a humanoid robot to vary its walking patterns at every footstep. A control strategy for walking on unknown uneven terrain is proposed. Virtual spring-damper (VSD) models are used to compensate for the disturbances that occur between the robot and the terrain when the robot walks on uneven terrain with unknown height. In addition, methods for generating the foot and vertical center of mass (COM) of the 3-D LIPM trajectories are developed to realize stable walking on unknown uneven terrain. The proposed method is implemented on a small-sized humanoid robot platform, DARwIn-OP and its effectiveness is demonstrated experimentally.

• Journal of Advanced Marine Engineering and Technology
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• 제32권2호
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• pp.250-255
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• 2008

Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression. principle of virtual work is adapted. And this theory was programming using MATLAB software. To compare FEM using MATLAB software was applied MSC. Nastran software. The geometry model for MSC. Patran was produced by 3-D design modeling software. Finite element model was produced by MSC. Patran. Finite element was applied tetra (CTETRA) having 10 node. The analysis results of the MATLAB and MSC. Nastran are fairly well agreed with those of various experiments. Using MATLAB program proposed in this paper and MSC. Nastran, spring constants and stresses can be predicted by input of few factors.