• Journal of Navigation and Port Research
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• v.28 no.3
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• pp.199-205
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• 2004

We have developed a composite grid method for the solution of the radiation problem We divide the domain into two different grids; one is a moving grid system and the other is a fixed grid system. This numerical method is applied to calculation of the radiation forces generated by the submerged plate oscillating near a free surface. The experimental data are compared with the numerical ones obtained by the present method and a linear potential theory. As a result, we can confirm the accuracy of the present method. Finally, Lie have evaluated the effect of nonlinear and viscous damping on the hydrodynamic forces acting on the submerged plate.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.8-17
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• 1992

There has been considerable reseach on the representation of a hull form which is a 3-dimensional free surface. A form parameter method to describe the hull form by means of form parameters which represent the characteristics of the given hull form geometry has been recently paid special attention with the advent of powerful computer. However, there have been reported many problems to the conventional form parameter for the practical hull form generation. In the present paper, an attempt has been made to creak hull form by combining the form parameter method with the B-spline curve which can be best fitted to free surfaces. In an application, the present method is used to generates a Bulk carrier hull form and compared with the existing hull form to prove its applicability for the hull form generation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.1-13
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• 2005

Kinematics of grasping and manipulation by a multi-fingered robotic hand where multi-fingertip surfaces are in contact with an object is solved. The surface of the object was represented by B-spline surfaces in order to model the objects of various shapes. The fingers were modeled by cylindrical links and a half ellipsoid fingertip. Geometric equations of contact locations have been solved for all possible contact combinations between the fingertip surface and the object. The simulation system calculated joint displacements and contact locations for a given trajectory of the object. Since there are no closed form solutions for contact or intersection between these surfaces, kinematics of grasping was solved by recursive numerical calculation. The initial estimate of the contact point was obtained by approximating the B-spline surface to a polyhedron. As for the simulation of manipulation, exact contact locations were updated by solving the contact equations according to the given contact states such as pure rolling, twist-rolling or slide-twist-rolling. Several simulation examples of grasping and manipulation are presented.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.6
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• pp.217-222
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• 2017

Any object located in the earth's gravitational field experiences a force in the direction of the center of the earth. In order to describe the motion of objects in the field, the solutions to a system of simultaneous vector kinematic equations need to be obtained. In the analysis of freely-falling objects, the reference direction +y is usually defined to be the downward direction. In the analysis of the motion of objects thrown upward, the reference direction +y is usually defined to be the upward direction. In the analysis of the motion of objects thrown downward, the reference direction +y is usually defined to be the downward direction. In this paper, we show that the choice of reference axis in either upward or direction gives the same results by adopting a scalar product of two vectors in solving the vector kinematic equations. It is rare to find other examples of using a scalar product of two vectors in solving vector kinematic equations describing the motion of objects. An application of this study is that we can arbitrarily choose the reference direction for objects moving in a horizontal direction, including projectile motions.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.816-824
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• 2010

The forces applying to an object in the transferring pipe of waste are analyzed and the equation of motion is established in this paper. It is shown that the equation of motion becomes the 1st order non-linear differential equation. Using its general solution, the velocity of the object in the transferring pipe of waste can be expressed in the explicit form. Noting that the velocity of object is impact velocity to the elbow or curved part of the transferring pipe of waste, the kinetic energy of the object can be calculated and the necessary impact strength of inner wall is obtained. The velocity of object is also calculated and presented in the graphic forms with the condition of air velocity 30m/sec. The impact test of cast basalt tube is carried out by the free fall of a weight and the test results show that the impact strength of the cast basalt tube is sufficient to apply to protecting inner wall of the transferring pipe of waste.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.5
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• pp.221-228
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• 2022

With the application of artificial intelligence technology, robots can provide efficient services in real life. Unlike industrial manipulators that do simple repetitive work, this study presented design methods of 6 degree of freedom robot arm and intelligent object search and movement methods for use alone or in collaboration with no place restrictions in the service robot field and verified performance. Using a depth camera and deep learning in the ROS environment of the embedded board included in the robot arm, the robot arm detects objects and moves to the object area through inverse kinematics analysis. In addition, when contacting an object, it was possible to accurately hold and move the object through the analysis of the force sensor value. To verify the performance of the manufactured robot arm, experiments were conducted on accurate positioning of objects through deep learning and image processing, motor control, and object separation, and finally robot arm was tested to separate various cups commonly used in cafes to check whether they actually operate.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.3
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• pp.131-139
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• 1992

By introducing a body potential, the high-oder spectal method of Dommermuth and Yue(1987) is extended to treat the nonlinear interactions between the free surface and the submerged cylinder. A 2-dimensional numerical wave tank is developed based on this numerical scheme, and applied to the wave resistance problem and the wave maker problem. In the simulations, it is shown that the transient waves due to the impulsive start of the body motion make a practical obstacle to the acquisition of useful data from the numerical experiments. Gradual starting procedures are devised, and successful result of the quasi-steady state or the uniform regular wave group was obtained. Within the author's present knowledge, the present numerical scheme is one of the most efficient numerical schemes which can treat the nonlinear interactions between the free surface and the body motion in time-domain.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.3
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• pp.507-514
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• 2022

Mobile manipulators are getting lime light in the field of home automation due to their mobility and manipulation capabilities. In this paper, we developed a small size manipulator system that can be mounted on a mobile robot as a preliminary study to develop a mobile manipulator. The developed manipulator has four degree-of-freedom. At the end-effector of manipulator, there are a camera and a gripper to recognize and manipulate the object. One of four degree-of-freedom is linear motion in vertical direction for better interaction with human hands which are located higher than the mobile manipulator. The developed manipulator was designed to dispose the four actuators close to the base of the manipulator to reduce rotational inertia of the manipulator, which improves stability of manipulation and reduces the risk of rollover. The developed manipulator repeatedly performed a pick and place task and successfully manipulate the object within the workspace of manipulator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.607-616
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• 2019

Free body diagram analysis is done for key parts of pilot stage of LLV (Load Limit Valve) which is used to protect overload for static structural test of aerospace flight vehicle. It is shown through the analysis that diameter ratio($D_2)^{ten}/D_2)^{comp}$) of two poppets in a pilot stage must be equal to piston area ratio($A_{comp}/A_{ten}$) of a hydraulic actuator for making a poppet open consistently at constant force applied by an actuator. The result of the analysis is verified by measuring geometries of the poppets in the four different LLVs which are corresponding to four actuators with different capacity and have been used after being imported in this laboratory. Results of "Adjuster resolution tests" with two different pilot stages show the max. deviation of Fi(actuator force in instant of opening poppet) from average Fi obtained for each turn of adjuster is 0.3KN and max. deviation of the Fi normalized by average Fi of each turn of adjuster is 3.7%. From the results, it is verified that the two pilot stages with same poppet diameter ratio make a poppet consistently open at Fis within ${\pm}3.7%$ deviation from the average Fi. The deviation is shown to be caused from frictional force of O-ring in the poppet. Additionally, design factors for poppet spring and adjuster, which are also key parts of the pilot stage, are distinguished and procedure for deciding the factors are also shown in this study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.261-266
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• 1995

본 연구에서는 자기부상시스템에 대해 흡인식 자기부상방식을 채택하고 쇠구슬에 대한 운동을 상하 1자유도로 가정하여 운동방정식을 세운다. 이때 전자석이 자기 부상력은 전자석에 흐르는 전류와 인덕턴스의 함수라 가정하고, 모델의 불확실성은 자기부상계의 운동 방정식으로부터 선형화 할 때 발생하는 오차 및 파라미터 변동으로 생각한다. 또한 모델의 불확실성이 존재하더라도 정상편차 없이 부상하는 서보제어계를 설계한다. 그런데 저자등은 강인성 문제 및 정상편차 없는 것에 역점을 두어 H$_{\infty}$ 제어이론에 기초한 1형 로바스트 서보 제어기를 구하여 자기부상 시스템의 안정화 제어계로써 적용한 적이 있다. 이때 중심해 이외의 해를 이용하여 설계한 서보 제어계는 자기부상계의 과도상태시에 일어나는 오버슈트를 줄일 수 없었다. 따라서 시스템 내부 안정화를 위하여 H$_{\infty}$ 제어이론에 의해 설계된 피드백(feedback) 제어기와 물체가 부상할 때 오버슈트를 줄이고 제어량이 목표치에 잘 추종하기 위해 설계된 피드 포워드(feed forward) 제어기로써 2자유도를 갖는 제어계를 설계한다. 이렇게 설계한 2자유도 제어계를 가지고 모의 응답실험과 본 연구자들이 만든 자기부상 시스템의 실험결과를 비교함으로써 설계된 제어기의 타당성을 조사한다.