• Advances in aircraft and spacecraft science
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• v.3 no.3
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• pp.271-298
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• 2016

In this paper, we study a problem of passive suppression of helicopter Ground Resonance (GR) using a single degree freedom Nonlinear Energy Sink (NES), GR is a dynamic instability involving the coupling of the blades motion in the rotational plane (i.e. the lag motion) and the helicopter fuselage motion. A reduced linear system reproducing GR instability is used. It is obtained using successively Coleman transformation and binormal transformation. The analysis of the steadystate responses of this model is performed when a NES is attached on the helicopter fuselage. The NES involves an essential cubic restoring force and a linear damping force. The analysis is achieved applying complexification-averaging method. The resulting slow-flow model is finally analyzed using multiple scale approach. Four steady-state responses corresponding to complete suppression, partial suppression through strongly modulated response, partial suppression through periodic response and no suppression of the GR are highlighted. An algorithm based on simple criterions is developed to predict these steady-state response regimes. Numerical simulations of the complete system confirm this analysis of the slow-flow dynamics. A parametric analysis of the influence of the NES damping coefficient and the rotor speed on the response regime is finally proposed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2001.04a
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• pp.182-187
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• 2001

This study deals with CARS (Computer Aided ROMUM System) which is a computer version of ROMUM (RObot Modularization of the Unit Motion). ROMUM was a method developed by the concept of modularization of the unit motion of robots. Because CARS is a computer assisted method of menu-driven type for human interface, this method can be easily applied for analyzing the work motion and measuring the execution time of robots. Therefore, it will be helpful for reducing the analysis effort and time of robot work.

• Korean Journal of Computational Design and Engineering
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• v.17 no.1
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• pp.62-70
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• 2012

This paper proposes a novel discomfort assessment method for truck ingress and egress motions based on the maximum-voluntary-contraction (MVC) ratios of muscles obtained by biomechanical analysis of human musculoskeletal models. In this study, a human motion to enter and exit a truck cabin with different types and heights of footsteps is first measured using an optical motion capture system and load sensors. Next, in a biomechanical analysis system, a human musculoskeletal model with contacting conditions on footsteps and handles is modeled, and then joint torques and muscles forces are calculated by inverse dynamics of the musculoskeletal model with the motion data. Finally, the MVC ratios for the muscles are calculated and their statistical values are used as the measure of discomfort. To ensure the feasibility of our method, subjective discomfort levels have been investigated through the participants' experiments and questionnaires and compared to the results of our method. Comparing to the existing methods based on joint angles or torques, our approach provide a more essential criterion for discomfort because it is based on the muscle contraction by which an active human motion is basically generated.

• Journal of the Korean Society of Industry Convergence
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• v.17 no.4
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• pp.211-216
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• 2014

In general, gantry robot is very useful handling of heavy objects. But rope-driven yard cranes must have a little of sway and skew motion because ropes are passive mechanical device. So many researches have been concentrated on anti-sway algorithm controlling trolley speed. These approaches require sway angle. But it is very difficult to know sway angle and its derivative. Therefore control algorithm of trolley speed is not practical in general. On the contrary, control strategy using auxiliary rope is very useful to sway control of yard crane because rope length is shorter than quay-side container cranes. In this paper, we derive equations of motion of trolley system which have anti-sway controller to use auxiliary rope. And we propose the control strategy and analyse the behavior of the proposed system.

• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.6
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• pp.774-779
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• 2010

This paper analyzes the fundamental dynamic motion of a robotic arm and body mechanism on the platform of a mobile manipulation system. For the purpose, we reveal the dynamic coefficients of a robotic arm and body mechanism, and identify their dominant behaviors in an exemplar trajectory following simulation. We also discuss on their influence for the motion of the body, shoulder, and elbow joints. It is finally expected that this analysis is helpful for effective manipulation tasks by using mobile manipulation systems with an arm and body mechanism.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.40-45
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• 1998

There are two kinds of methods in the analysis of ship motion in irregular waves. The one is the spectral method in which the ship motion is assessed with spectral of irregular waves times R.A.O. of a ship. The other is, so called, time domain analysis, in which the irregular waves are used directly in the equation of ship motion to calculate the responses. In this paper, both methods are applied for the calculation of course keeping motion of a ship in irregular waves with auto-pilot control. And, the differences and useful1ness of the two methods in the assessment of auto-pilot system are compared.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.721-733
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• 2020

In nuclear engineering, the occurrence of critical heat flux (CHF) is complicated for rod bundle, and it is much more difficult to predict the CHF when it is in natural circulation under motion condition. In this paper, the dryout-type CHF is investigated for the rod bundle in a natural circulation loop under rolling motion condition based on the coupled analysis of subchannel method, a one-dimensional system analysis method and a CHF mechanism model, namely the three-fluid model for annular flow. In order to consider the rolling effect of the natural circulation loop, the subchannel model is connected to the one-dimensional system code at the inlet and outlet of the rod bundle. The subchannel analysis provides the local thermal hydraulic parameters as input for the CHF mechanism model to calculate the occurrence of CHF. The rolling motion is modeled by additional motion forces in the momentum equation. First, the calculation methods of the natural circulation and CHF are validated by a published natural circulation experiment data and a CHF empirical correlation, respectively. Then, the CHF of the rod bundle in a natural circulation loop under both the stationary and rolling motion condition is predicted and analyzed. According to the calculation results, CHF under stationary condition is smaller than that under rolling motion condition. Besides, the CHF decreases with the increase of the rolling period and angular acceleration amplitude within the range of inlet subcooling and mass flux adopted in the current research. This paper can provide useful information for the prediction of CHF in natural circulation under motion condition, which is important for the nuclear reactor design improvement and safety analysis.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.126-135
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• 1997

A sensorless motion planner which succeeds in grasping a polygonal part firmly into a desired orientation has been developed through the dynamic analysis. The analytical results on the impact process with friction are used for modeling the contact motionduring the parallel-jaw grasp operation, which is com- posed of the pushing and the squeezing process. The developed planner succeeds in grasping a part into a specified orientation in the face of uncertainties of initial position and orientation of the part, motion direction of the finger, and the physical parameters such as the coefficients of friction and restitution. The motion planner has been fully implemented into a viable package on the computer system, and verified experimentally. The motion of parts is recorded using a high-speed video camera, and then compared to the results of the planner and the graphic simulation results that illustrate the simulated motion of the grasp operation.

• Journal of Korea Multimedia Society
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• v.23 no.1
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• pp.15-23
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• 2020

Recently, the increase in the elderly population due to an aging society has led to a relative increase in senile diseases such as vascular dementia or Alzheimer's disease, and the social burden for rehabilitation has increased. In addition, studies have been conducted for the risk assessment and prevention of musculoskeletal disorders. The purpose of this study is to suggest a system that can be used to help with dementia prevention training by tracking the movement of motion and virtual reality contents for the risk factors of musculoskeletal disorders of the elderly. We propose a training method for preventing dementia through musculoskeletal motion analysis algorithm and virtual reality content. Through motion recognition algorithm based on motion region design, we will track and analyze the moving radius of the target joint. The purpose of this study is to calculate and evaluate scores based on the time to accomplish the goals on virtual reality contents for the prevention of musculoskeletal disorders and the support of dementia prevention training, and the degree of difficulty, and to analyze the correlation between the results of performing K-MMSE and VR contents.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.467-467
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• 2000

In this paper, a structural design method of robust motion controllers for high-accuracy positioning systems, which makes it possible to predict the performance of the whole closed-loop system, is proposed. First, a stabilizing control input is designed based on robust internal-loop compensate.(RTC) for the system in the presence of uncertainty and disturbance. Next, using the structural characteristics of the RIC, disturbance attenuation properties and the performance of the closed-loop system determined by the variation of controller gains are analyzed. Through this analysis, in some specific applications, it is shown that if the control gain of RIC is increased by N times, the magnitude of error is reduced to its 1/N. Finally, the proposed method is verified through experiments using a high-accuracy positioning system used in the semiconductor chip mounting devices.