• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 춘계학술대회 논문집
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• pp.661-665
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• 1996

An inverse kinemetics problem of a reclaimer which digs and transports ironstones or coals in the raw yard is investigated. Because of the special features of the reclaimer of which scooping buckets are attached around the rotating drum at the end of boom, kinematic redundancy occurs in determining the joint varialbes For a given reclaiming point in space the forward kinematics yields 3 equations, however the number of involved variables in the equations are four. A plane equation approximating the surface near a reclaiming point is obtained by considering 8 adjacent points surrounding the reclaiming point. One extra equation to overcome redunduncyis further obtained from the condition that the normal vector at a reclaiming point is perpendicular to the plane. An approximate solution for a simplified problem is first discussed, Numerical solution for the oritinal nonlinear porblem with a constraint equation is also investigated. Finally a closed form solution which is not exact but sufficiently close enough is proposed by exploiting geometric constraint.

• 제어로봇시스템학회논문지
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• 제21권3호
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• pp.250-256
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• 2015

We present a novel method to model the body posture of a worm for vision-based automatic monitoring and analysis. The worm considered in this study is a Caenorhabditis elegans (C. elegans), which is popularly used for research in biological science and engineering. We model the posture by an open chain of a few curved or rigid line segments, in contrast to previously published approaches wherein a large number of small rigid elements are connected for the modeling. Each link segment is represented by only two parameters: an arc angle and an arc length for a curved segment, or an orientation angle and a link length for a straight line segment. Links in the proposed method can be readily related using the Denavit-Hartenberg convention due to similarities to the kinematics of an articulated manipulator. Our method was tested with real worm images, and accurate results were obtained.

• Journal of Ship and Ocean Technology
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• 제4권1호
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• pp.11-20
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• 2000

Reynolds-averaged Navier-Stokes equations are numerically solved using a secondorder finite difference method for the analysis of turbulent flows around single and tandem hydrofoils advancing under the free surface. The location of the free surface, not known a priori, is computed from the kinematic free surface condition and the computational grid is conformed at each iteration to the free surface deformation. The eddy viscosity model of Baldwin-Lomax is employed for the turbulence closure. The method is validated through the comparision of the numerical results with the experimental data for a single hydrofoil of a Joukowski foil section. A computational study is also carried out to investigate the effect of the submergence depth and the Froude number on the lift and the drag of the hydrofoil. For tandem hydrofoils, computations are performed for several separation distances between the forward and aft foils to see the interference effect. The result shows clearly how the lift and drag change with the separation distance.

• Tribology and Lubricants
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• 제26권2호
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• pp.97-104
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• 2010

A new magnetoelastic technique of oil viscosity measurement, where the oil viscosity is estimated by frequency shift of natural oscillations of magnetoelastic ribbon, is implemented in this study. Laboratory tests of the detector prototype are performed for measurement of viscosity of base synthetic and mineral oils. It was found that measurement accuracy was better when damping factor was estimated in comparison with accuracy of frequency of damped oscillations. Thus the oil viscosity was calibrated as a function of number of pulses of the damped oscillations of magnetoelastic ribbon. Result generally showed that developed detector is promising for in line oil viscosity measurement in wide viscosity range from 10 cSt up to 600 cSt, while the viscosity measurement was relatively instable when the viscosity of test oil was over 400 cSt.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.364-370
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• 2005

A stable walking pattern generation method for a biped robot is presented in this paper. In general, the ZMP (zero moment point) equations, which are expressed as differential equations, are solved to obtain a stable walking pattern. However, the number of differential equations is less than that of unknown coordinates in the ZMP equations. It is impossible to integrate the ZMP equations directly since one or more constraint equations are involved in the ZMP equations. To overcome this difficulty, DAE (differential and algebraic equation) solution method is employed. The proposed method has enough flexibility for various kinematic structures. Walking simulation for a virtual biped robot is performed to demonstrate the effectiveness and validity of the proposed method. The method can be applied to the biped robot for stable walking pattern generation.

• 대한기계학회논문집A
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• 제27권4호
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• pp.647-655
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• 2003

This paper studies the observability of calibration system with a constraint movement by a constraint operator. The calibration system with the constraint movement need only simple sensing device to check whether the constraint movements are completed within an established range. However, it yields the concern about the poor parameter observability due to the constraint movements. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters are examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a parallel typed machining center and the calibration results are presented. These results verify that the calibration system with low-cost indicators and simple planar table is accurate as well as reliable.

• Tribology and Lubricants
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• 제10권1호
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• pp.78-88
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• 1994

For the study of chemical and mechanical properties of the synthetic and mineral oil added with two different Zn-DTPs, base and formulated oils were analyzed and compared. Kinematic viscosity and total acid number (TAN) were tested at high temperature for formulated oils. Also the oils added with different alkyl groups of Zn-DTP were tested for thermal stability and TAN changes. The 4-ball machine was used to test for the mechanical properties, such as the coefficient of friction and wear. The worn areas after sliding test were analyzed with microscope and EDX, too. From the study, mineral and synthetic oil have different effects according to the various added ratio of the primary and secondary alkyl groups of Zn-DTP. Also the temperature of test oil affected the anti-wear and friction property of the formulated oils. For synthetic oil, the primery alkyl group of Zn-DTP made better friction properties than that of secondary, while, for mineral oil, secondary alkyt group was better only at low temperature for mineral oil.

• 한국자동차공학회논문집
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• 제8권3호
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• pp.139-150
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• 2000

Although a number of neck injuries are generated, the data which quantify the kinematic response of the human head and cervical spine in low-speed rear-end automobile collisions is very limited. On this problem, just few in vitro experimental research or some experimental research using dummy on neck injury by rear-end collision was conducted, thus systematic research is requested on full scale injury mechanism. An occupant model for the response of the occupant subject to rear-end collision using commercial dynamics package DADS was developed. Developed model shows more close agreement with the experimental data compared with the MADYMO simulation results for the cases of ${\delta}V=16$ kph in sled test. For the case of ${\delta}V=8$ kph and 33.5 kph with production seat, model also shows its reliable response compared with experimental results using Hybrid III and Hybird III with RID.

• 융합신호처리학회논문지
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• 제7권1호
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• pp.38-44
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• 2006

The omnidirectional mobility of a mobile robot may lose significance in motion control, unless the isotropy characteristics of the mechanism is maintained well. This paper investigates the local and global isotropy of an omnidirectional mobile robot with three caster wheels. All possible actuations with different number and combination of rotating and steering joints are considered. First, the kinematic model based on velocity decomposition and the algebraic conditions for the local isotropy are obtained. Second, the geometric conditions for the local isotropy are derived and all isotropic configurations are fully identified. Third, the global isotropy index is examined to determine the optimal parameters in terms of actuation set, characteristic length, and steering link length.

• Journal of Ship and Ocean Technology
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• 제4권2호
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• pp.13-23
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• 2000

A low-order potential based boundary element method is applied to the prediction of the flow around the cavitating propeller in steady or in unsteady inflow. For given cavitation number, the cavity shape is determined in an iterative manner until the kinematic and the dynamic boundary conditions are both satisfied on the approximate cavity boundary. In order to improve the solution behavior near the tip region, a hyperboloidal panel geometry and a modified split panel method are applied. The method is then extended to include the analysis of time-varying cavitating flows around the propeller blades via a time-step algorithm in time domain. In the method, the steady state oscillatory solution is obtained by incremental stepping in the itme domain. Finally, the present method is validated through comparison with other numerical results and experimental data.