• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.201-204
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• 2008

The mobile robot is known as a nonlinear system with constraints. The general tracking controller for the mobile platform has been divided into the kinematic and the dynamic controller. The reason of dividing controller is the constraints. We can get some information through some numerical experiments. When the reference linear and angular velocity were given, the stability of mobile robot without the kinematic controller depend on the start point of reference cart. Therefore this paper composed of two controller for solving tracking problem. The main controller is the dynamic controller which used generally such as the PID controller. And this paper adopts the auxiliary controller in order to compensate the difference of initial point between the reference cart and a mobile robot. Finally, the numerical experiment is performed in order to show the validity of our method.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.197-201
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• 1997

The momentum, heat and mass trasfer phenomena in the silicon melt of the Czochralki crystal growth system are calculated using a three dimensional numerical simulation thechnique. Even though axisymmetrical boundary conditions are imposed to all calculations in a 3cm diameter crucible, several types of non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles of velocities, temperature and oxygen concentration appeared in the melt. Because of the non-axisymmetric profiles and rotations of fluid induced by the crucible rotation, temperatures and oxygen concentrations in the silicon melt fluctuate. The rotating velocity of the profile is calculated from the phase shift of the data of temperature or oxygen at two different points which have same radius from center but 90 degree angular difference. From this calculation, it is found that the rotating veolocity of the oxygen and temperature is different from the crucible rotation rates. Therefore the frequencies of the oscillating temperature and oxygen concentrations are not same to the frequencies of the crucible rotations. Futhermore, the components of the frequencies of the temperature and oxygen concentration at the same point are not same. The fluctuation behaviors of the temperature or oxygen themselves are also different when the points are different. The calculation show that the temperature and the oxygen concentration near the interface also fluctuate. The results suggest that the striation pattern found in the grown silicon single crystals may ben generated by the oxygen concentration and the temperature oscillations of the melt occurred near the interface.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.355-364
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• 2010

Filiform hairs that respond to movements of the surrounding medium are the mechanoreceptors commonly found in arthropods and vertebrates. In these creatures, the filiform hairs function as a sensory system for raider detection. Parametric analyses of the motion response of filiform hairs are conducted by using a mathematical model of an artificial flow sensor to understand the possible operating ranges of a microfabricated device. It is found that the length and diameter of the sensory hair are the major parameters that determine the mechanical sensitivities and responses in a mean flow with an oscillating component. By changing the hair length, the angular displacement, velocity, and acceleration could be detected in a wide range of frequencies. Although the torques due to drag and virtual mass are very small, they are also very influential factors on the hair motion. The resonance frequency of the hair decreases as the length and diameter of the hair increase.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.7
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• pp.95-102
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• 2016

Geomagnetic sensors are widely utilized for sensing heading direction of quadrotors. However, measurement from a geomagnetic sensor is easily corrupted by environmental magnetic field interference and roll/pitch directional motion. In this paper, a measurement method of a quadrotor heading direction is proposed for application to yaw attitude control. In order to eliminate roll/pitch directional motion effect, the geomagnetic sensor data is compensated using the roll/pitch angles measured for stabilization control. In addition, yaw-directional angular velocity data from a gyroscope sensor is fused with the geomagnetic sensor data using a complementary filter which is a simple and intuitive sensor fusion method. The proposed method is applied to experiments, and the results are presented to prove validity and effectiveness of the proposed method.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.179-190
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• 2008

The purpose of this study was to identify whether or not in one-leg vertical jump of each limb asymmetry between both sides is present and to identify how the discrepancies between both limbs affect two-leg jumping performance, that is bilateral deficit. We had 13 healthy subjects perform one-leg jump for both sides and two-leg countermovement jump. The result of biomechanical analysis showed significantly difference of 4-7% in net impulses and work output between dominant and non-dominant one-leg jump and bilateral deficit of 24% when sum of those of each one-leg jump was compared with two-leg jump. But asymmetry in lower extremity was not significantly correlated with bilateral deficit. Two-leg jump could be characterized by relatively short propulsion time, long propulsion distance and high joint angular velocity compared with one-leg jump. These factors seemed to contribute to decreased performance in two-leg jump. Furthermore bilateral deficit was attributed to lower activities of extensor muscles found in two-leg jump.

• Korean Journal of Applied Biomechanics
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• v.18 no.1
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• pp.53-62
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• 2008

The purpose of this research was to analyze the kinematics of the 205B movement in platform diving. For the experiment, 2 athlete from the national diving team were chosen as the subject and two S -VHS video cameras were used. For this diving players preparing for the olympics participated. It was shown that the mean total took $1.112{\pm}0.12s$. In order to perform better, the divers time must be increased, at take off and rotation must be done high up and the horizontal distance must be shorted to main entrance of the water. To enter the water safely, the jump has to be high, the horizontal speed slow and the vertical speed as fast as possible. At E1 the lower limbs change in speed should decrease and after the rotation begins at E2. At take off, the jump is more important than the rotation for the performance of the dive. At take off, the trunk angular velocity was high, and this was needed to jump high for moment of inertia for rotation because for efficient jumping the upper body has to spread out and increase the height of the center of mass.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.193-201
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• 2015

This paper deals with the influence of leakage flow existing in SHF pump model on the analysis of internal flow behaviour inside the vane diffuser of the pump model performance using both experiments and calculations. PIV measurements have been performed at different hub to shroud planes inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, the PIV measurements have been trigged with different angular impeller positions. The performances and the static pressure rise of the diffuser were also measured using a three-hole probe. The numerical simulations were carried out with Star CCM+ 9.06 code (RANS frozen and unsteady calculations). Some results were already presented at the XXth IAHR Symposium for three flowrates for RANS frozen and URANS calculations. In the present paper, comparisons between URANS calculations with and without leakages and experimental results are presented and discussed for these flow rates. The performances of the diffuser obtained by numerical calculations are compared to those obtained by the three-holes probe measurements. The comparisons show the influence of fluid leakages on global performances and a real improvement concerning the efficiency of the diffuser, the pump and the velocity distributions. These results show that leakage is an important parameter that has to be taken into account in order to make improved comparisons between numerical approaches and experiments in such a specific model set up.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.207-214
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• 2015

The preliminary design of a radial inflow turbine using R134a as the working fluid at 5 kW of power for application to ocean thermal energy conversion (OTEC) is performed to obtain the trends for the efficiency and geometrical dimensions of the turbine. Using input conditions that included a turbine inlet temperature of $25^{\circ}C$, an outlet static pressure of 4.9 bar, and a mass flow rate of 1.16 kg/s, the results of a mean flow analysis show the major dimensions of the turbine, along with an angular velocity of 12,820 rpm. Based on these results, a three-dimensional turbine model is constructed for a computational fluid dynamics (CFD) analysis. The flow characteristics inside the turbine, including the volute and nozzle, are investigated using the CFD software ANSYS CFX. For a pertinent number of nozzle guide vanes, ranging from 10 to 15, the turbine efficiency was higher than 80%, with the highest efficiency shown by a nozzle with 15 guide vanes.

• Korean Journal of Applied Biomechanics
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• v.15 no.1
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• pp.177-195
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• 2005

The purpose of this study was to analyze the kinematic variables of ankle joints and EMG signal of the lower limbs muscle activity for the different walking speed. The subjects were 6 males of twenties. It was classified into three different walking speed-0.75m/s, 1.25m/s, 1.75m/s. The walking performances were filmed by high speed video camera and EMG signal was gained by ME3000P8 Measurement Unit. Tibialis anterior(TA), Gastrocnemius medial head(GM), Gastrocnemius lateral head(GL), Ssoleus(SO) were selected for the dorsiflexion and plantarflexion of the ankle joint. The result of this study were as follows: 1. In the gait cycle, The time parameters for the phases were showed significant difference without the terminal stance phase and terminal swing phase for the different walking speed. 2. The angle of ankle joint was no significant difference for each time point and MDF, MPF but increasing walking speed the angle had the increasing pattern slightly. 3. The angular velocity of ankle joint was showed the significant difference for LHC, RTO, RKC, LHU, MPF and MDF point along the walking speed. 4. TA was showed about 2-3 times muscle activity at the 1.75m/s than 1.25m/s in some phases. And it was showed the similar muscle activity between the 0.75m/s and 1.25m/s but, showed a little much muscle activity in the 0.75m/s. GM was showed about 2-3 times muscle activity in the 1.75m/s than 1.25m/s, and even much muscle activity at the 0.75m/s than 1.25m/s in some phases. GL was showed increasing pattern of muscle activity specially in the initial swing phase as the walking speed increased. SO was showed about 3 times muscle activity in the 1.75m/s than 1.25m/s during the plantarflexion of ankle joint. It was showed the similar muscle activity between the 0.75m/s and 1.25m/s but, showed a little much muscle activity in the 1.25m/s.

• Korean Journal of Applied Biomechanics
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• v.22 no.3
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• pp.315-324
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• 2012

The purpose of current study was to investigate the effects of the heights on the lower extremities, torso and neck segments for energy dissipation during single-leg drop landing from different heights. Twenty eight young healthy male subjects(age: $23.21{\pm}1.66yr$, height: $176.03{\pm}4.22cm$, weight: $68.93{\pm}5.36kg$) were participated in this study. The subjects performed the single-leg drop landing from the various height(30, 45 & 60 cm). Force plates and motion-capture system were used to capture ground reaction force and kinematics data, respectively. The results were as follows. First, the ROM at the ankle, knee, hip and trunk was increased with the increased heights but the ROM at the neck was increased in the 60cm. Second, the angular velocity, moment and eccentric work at the ankle, knee, hip, trunk, and neck was increased with the increased heights. Third, the contribution to total work at the knee joint was not significantly different, while the ankle joint rate was decreased and hip and neck rate was increased in the 60cm, and trunk rate was increased with the increased heights. Lastly, the increase in landing height was able to augment the level of energy dissipation not only at the lower extremities but also at the trunk and neck. The findings showed that drop landing affect trunk and neck with lower extremity joints. Therefore, we need to consider that trunk and neck strengthening including stability should be added to reduce sports injury during prevention training.