• Journal of Mechanical Science and Technology
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• v.15 no.12
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• pp.1768-1774
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• 2001

Drifting Cups on a Meandering Stream (Kyokusui-no-En) is a Poetry Party that had its origin In ancient China, and was introduced to Japan passing through Korea. The flow of the meandering stream was made clear using the flow visualization techniques, surface floating method, PTV and the numerical simulation. At the same time, the motions of floating cup, the floating speed, relating speed and the trajectory of the cup were also analysed by using an originally developed image processing technique. Based on these researches, the model channel was considered. To make this party interesting the channel must has the characteristic that the drifting cups take the random pass and stagnant at the unexpected place. This model channel is satisfied with these conditions and the fluid mechanics consideration is performed on the both points of the experimental visualization and numerical simulation.

• Journal of Magnetics
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• v.17 no.1
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• pp.27-32
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• 2012

Transcranial magnetic stimulation requires an electric field composed of dozens of V/m to achieve stimulation. The stimulation system is composed of a stimulation coil to form the electric field by charging and discharging a capacitor in order to save energy, thus requiring high-pressure kV. In particular, it is charged and discharged in capacitor to discharge through stimulation coil within a short period of time (hundreds of seconds) to generate current of numerous kA. A pulse-type magnetic field is formed, and eddy currents within the human body are triggered to achieve stimulation. Numerous pulse forms must be generated to initiate eddy currents for stimulating nerves. This study achieved high internal pressure, a high number of repetitions, and rapid switching of elements, and it implemented numerous control techniques via introduction of the half-bridge parallel load method. In addition it applied a quick, accurate, high-efficiency charge/discharge method for transcranial magnetic stimulation to substitute an inexpensive, readily available, commercial frequency condenser for a previously used, expensive, high-frequency condenser. Furthermore, the pulse repetition rate was altered to control energy density, and grafts compact, one-chip processor with simulation to stably control circuit motion and conduct research on motion and output characteristics.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.5
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• pp.404-414
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• 2000

This paper addresses the development of a 3-fingered humanoid robot hand system and a real-time grasp synthesis of multifingered robot hands to find grasp configurations which satisfy the force closure condition of arbitrary shaped objects. We propose a fast and efficient grasp synthesis algorithm for planar polygonal objects, which yields the contact locations on a given polygonal object to obtain a force closure grasp by the multifingered robot hand. For an optimum grasp and real-time computation, we develop the preference and the hibernation process and assign physical constraints of the humanoid hand to the motion of each finger. The preferences consist of each sublayer reflecting the primitive preference similar to the conditional behaviors of humans for given objectives and their arrangements are adjusted by the heuristics inspired from human's grasping behaviors. The proposed method reduces the computational time significantly at the sacrifice of global optimality, and enables the grasp posture to be changable within two-finger and three-finger grasps. The performance of the presented algorithm is evaluated via simulation studies to obtain the force-closure grasps of polygonal objects with fingertip grasps. The architecture suggested is verified through experimental implementation to our robot hand system by solving the 2- or 3-finger grasp synthesis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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• pp.913-920
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• 2005

Compared to previous in-vitro test, FE model showed reliable motion patterns. A finite element model of a 50th percentile male neck was developed to study the mechanics of whiplash injury while the rear impacts. The model was consisted of the whole cervical vertebrae including part of occipital, intervertebral discs. which were modeled using linear viscoelastic materials and posterior elements. The sliding interfaces were defined to simulate contact phenomena in facet joints and in odontoid process. All ligaments and atlanto-occipital membrane were modeled as nonlinear bar elements. Only muscle elements were not considered. Motion of each cervical vertebra was obtained from the dynamic simulation with a MADYMO model for 15 km/h $40\%$ rear end offset impacts. Soft tissue neck injury(STNI) was investigated with a developed FE model. In FE model analysis, the high stress was appeared at C3/C4 disc in offset impact. Further research is still needed in order to improve the developed neck FE model for many different crash patterns.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.1
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• pp.1-9
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• 2016

In this paper, we propose a new learning control scheme for various walk motion control of biped robot with same learning-base by neural network. We show that learning control algorithm based on the neural network is significantly more attractive intelligent controller design than previous traditional forms of control systems. A multi layer back propagation neural network identification is simulated to obtain a dynamic model of biped robot. Once the neural network has learned, the other neural network control is designed for various trajectory tracking control with same learning-base. The biped robots have been received increased attention due to several properties such as its human like mobility and the high-order dynamic equation. These properties enable the biped robots to perform the dangerous works instead of human beings. Thus, the stable walking control of the biped robots is a fundamentally hot issue and has been studied by many researchers. However, legged locomotion, it is difficult to control the biped robots. Besides, unlike the robot manipulator, the biped robot has an uncontrollable degree of freedom playing a dominant role for the stability of their locomotion in the biped robot dynamics. From the simulation and experiments the reliability of iterative learning control was illustrated.

• Korean Journal of Applied Biomechanics
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• v.23 no.1
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• pp.53-62
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• 2013

The methods of fitting a circle to measured data, geometric fit and algebraic fit, have been studied profoundly in various areas of science. However, they have not been applied exactly to a biomechanics discipline for locating the center of rotation of a human joint. The purpose of this study was to generalize the methods to fitting spheres to the points in 3-dimension, and to estimate the center of rotation of a hip joint by three of geometric fit methods(Levenberg-Marquardt, Landau, and Sp$\ddot{a}$th) and four of algebraic fit methods(Delogne-K${\aa}$sa, Pratt, Taubin, and Hyper). 1000 times of simulation experiments for flexion/extension and ad/abduction at an artificial hip joint with four levels of range of motion(10, 15, 30, and $60^{\circ}$) and three levels of angular velocity(30, 60, and $90^{\circ}$/s) were executed to analyze the responses of the estimated center of rotation. The results showed that the Sp$\ddot{a}$th estimate was very sensitive to the marker near the center of rotation. The bias of Delogne-K${\aa}$sa estimate existed in an even larger range of motion. The Levenberg-Marquardt algorithm of geometric fit and the Pratt of algebraic fit showed the best results. The combination of two methods, using the Pratt's estimate as initial values of the Levenberg-Marquardt algorithm, could be a candidate of more valid estimator.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.667-673
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• 2010

This paper proposes a control method based on a pseudo-impedance model to control the motion of biped robots walking on an uneven surface. The pseudo-impedance model simulates the action of the ankle of a foot landing on the ground when a human walks. When the foot is in contact with the ground, the human ankle goes through two different phases. In the first phase, the human exerts little or no effort and applies no torque on the ankle so that the orientation of the foot is effortlessly and passively adjusted with respect to the ground. In the second phase of landing, the ankle generates a significant amount of torque in order to rotate and move the main part of the human body forward and to support the weight of the human; this phase is called the weight acceptance phase. Computer simulations of a 12-DOF biped robot with a 6-DOF environment model were performed to determine the effectiveness of the proposed pseudo-impedance control. The simulation results show that stable locomotion can be achieved on an irregular surface by using the proposed model.

• The Journal of Korea Robotics Society
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• v.15 no.4
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• pp.323-329
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• 2020

This paper presents a control algorithm for a wearable walking aid robot for subjects with paraplegia after stroke. After a stroke, a slow, asymmetrical and unstable gait pattern is observed in a number of patients. In many cases, one leg can move in a relatively normal pattern, while the other leg is dysfunctional due to paralysis. We have adopted the so-called assist-as-needed control that encourages the patient to walk as much as possible while the robot assists as necessary to create the gait motion of the paralyzed leg. A virtual wall was implemented for the assist-as-needed control. A position based admittance controller was applied in the swing phase to follow human intentions for both the normal and paralyzed legs. A position controller was applied in the stance phase for both legs. A power controller was applied to obtain stable performance in that the output power of the system was delimited during the sample interval. In order to verify the proposed control algorithm, we performed a simulation with 1-DOF leg models. The preliminary results have shown that the control algorithm can follow human intentions during the swing phase by providing as much assistance as needed. In addition, the virtual wall effectively guided the paralyzed leg with stable force display.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.7
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• pp.1438-1445
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• 2002

For robotic endoscope, some researchers suggest pneumatic actuators based on inchworm motion. But, the existing endoscopes have not been replaced completely because human intestine is very sensitive and susceptible to damage. We design and test a new locomotion of robotic endoscope that allows safe maneuverability in the human intestine. The actuating mechanism is composed of two solenoids at each side and a single permanent magnet. When the current direction is reversed, repulsive force and attractive at the opposition side propels permanent magnet. Impact force against robotic endoscope transfers momentum from moving magnet to endoscope capsule. The direction and moving speed of the actuator can be controlled by adjustment of impact force. Modeling and simulation experiments are carried out to predict the performance of the actuator. Simulations show that force profile of permanent magnet is the dominant factor for the characteristic of the actuator. The results of simulations are verified by comparing with the experimental results.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.1593-1597
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• 2003

The home service robot supports human beings by performing various kinds of works at home. This paper presents a simple control method for opening a door from the viewpoint of the mobile manipulation. The simulation shows various results of path planning and motion planning for opening a door. The joint trajectories were generated by the simulation system. In general, a six-axis force/torque sensor at an end-effector is needed in order to maintain the static equilibrium of the manipulator. But we show another method. From three components of applied forces which was directly obtained by the three-axis force sensor and three components of applied forces which was indirectly estimated by the joint-torque sensors, all of joint torques that will exactly balance forces at the end-effector in the static situation can be found. It is more practical method than using a six-axis force sensor in a wrist. Experimental results have shown that the opening a door can be realized more effectively from the suggested control method of mobile manipulation.