• Wind and Structures
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• v.38 no.2
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• pp.119-128
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• 2024

The aerodynamic damping is an essential factor that can considerably affect the dynamic response of the cable-stayed bridge induced by crosswind load. However, developing an accurate and efficient aerodynamic damping model is crucial for evaluating the crosswind load-induced response on cable-stayed bridges. Therefore, this study proposes a new method for identifying aerodynamic damping of the bridge structures under crosswind load using an extended Kalman filter (EKF) and the particle filter (PF) algorithm. The EKF algorithm is introduced to capture the aerodynamic damping ratio. PF technique is used to select the optimal spectral representation of the noise. The effectiveness and accuracy of the proposed solution were investigated through full-scale vibration measurement data of the crosswind-induced on the bridge's girder. The results show that the proposed solution can generate an efficient and robust estimation. The errors between the target and extracted values are around 0.01mm and 0.003^o, respectively, for the vertical and torsional motion. The relationship between the amplitude and the aerodynamic damping ratio is linear for small reduced wind velocity and nonlinear with the increasing value of the reduced wind velocity. Finally, the results show the influence of the level of noise.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.31-37
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• 2010

Based on the analyses of satellite range measurement, the optimal operation for satellite range measurement of KOMPSAT II, which operates in the low-earth orbit, was proposed in this paper. The orbital motion of the satellite was analyzed in viewpoints of radial velocity, acceleration and speed of acceleration. Correspondingly the effects for satellite ranging signal due to satellite motion were analyzed in viewpoints of doppler phenomena, which are doppler frequency, doppler rate and speed of doppler rate. The accuracy and ambiguity probability of the satellite range measurement were quantitatively analyzed under various circumstances. The optimal operation parameters for satellite range measurement were also analyzed based on the analyzed results. The analyzed results in this paper can be utilized in design of small-sized ground station for satellite range measurement.

• Journal of the Society of Naval Architects of Korea
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• v.41 no.4
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• pp.68-76
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• 2004

Inherent strain method for analyzing deformation of line-heating is substituting experiments of high cost, because of its high accuracy and quickness. Nowadays, the progressing forms of line-heating are not straight moving motions used to traditional studies, but weaving motions which can diversely input heat source. In shipyard, reasons of weaving motions are induction of a special characteristic by water cooling, maximum temperature limitation for keeping plates from melting, and rhythm for workman's maintaining velocity. On this study, a method which can obtain optimal weaving heating condition was presented, some examples were introduced, and the results corresponded to works of shipyard. Lastly, what the specifications of plates on efficiency are is presented, through the quality standard of shipyard and FEM heat transfer simulation. The ultimate purpose of line heating is the automation, so in case of plates which need weaving heating, the optimal heating condition suggested by this study can be used well in designing coil specifications of induction heaters which are heat input sources of new generation.

• Journal of Biosystems Engineering
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• v.38 no.2
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• pp.138-148
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• 2013

Purpose: Determining an appropriate path is a top priority in order for a robot to maneuver in a dynamically efficient way especially in a pick-and-place task. In a non-standardized work environment, current robot arm executes its motion based on the kinematic displacements of joint variables, though resulting motion is not dynamically optimal. In this research we suggest analyzing and applying motion patterns of the human arm as an alternative to perform near optimum motion trajectory for arbitrary pick-and-place tasks. Methods: Since the motion of a human arm is very complicated and diverse, it was simplified into two links: one from the shoulder to the elbow, and the other from the elbow to the hand. Motion patterns were then divided into horizontal and vertical components and further analyzed using kinematic and dynamic methods. The kinematic analysis was performed based on the D-H parameters and the dynamic analysis was carried out to calculate various parameters such as velocity, acceleration, torque, and energy using the Newton-Euler equation of motion and Lagrange's equation. In an attempt to assess the efficacy of the analyzed human motion pattern it was compared to the virtual motion pattern created by the joint interpolation method. Results: To demonstrate the efficacy of the human arm motion mechanical and dynamical analyses were performed, followed by the comparison with the virtual robot motion path that was created by the joint interpolation method. Consequently, the human arm was observed to be in motion while the elbow was bent. In return this contributed to the increase of the manipulability and decrease of gravity and torque being exerted on the elbow. In addition, the energy required for the motion decreased. Such phenomenon was more apparent under vertical motion than horizontal motion patterns, and in shorter paths than in longer ones. Thus, one can minimize the abrasion of joints by lowering the stress applied to the bones, muscles, and joints. From the perspectives of energy and durability, the robot arm will be able to utilize its motor most effectively by adopting the motion pattern of human arm. Conclusions: By applying the motion pattern of human arm to the robot arm motion, increase in efficiency and durability is expected, which will eventually produce robots capable of moving in an energy-efficient manner.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.7
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• pp.83-91
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• 2011

Even if smoke, fumes, mist or dust particles are removed by electrostatic precipitators (ESPs), the occurrence of ozone, which is harmful to human body, has to be severely restricted in the indoor environments of hospitals, offices, and workshops. Therefore, the two-stage ESP generating positive corona at the ionizer is typically used because it creates less ozone than the two-stage ESP generating negative corona at the ionizer. In order to predict the collection performance and the optimal design of the two-stage ESP applied to positive high-voltage, particle concentration is experimentally investigated in this paper. In addition, particle motion within the collector section is also numerically analyzed. The positive corona discharge current of the ionizer is found to be affected by the applied voltage in the collector section but less so by the particle concentration. Particle concentration shows a minimum near the high voltage electrode of the collector section. The minimum value of the collection efficiency is almost proportional to gas velocity. When the collector length decreases, the minimum value of the collection efficiency increases. Charged particles entering the collector region are linearly deflected towards the grounded plate by an electric field. From the above experimental and numerical results, two empirical equations on the concentration ratio and the collection efficiency are derived, and are in good agreement with the experimental data.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.727-730
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• 2002

Most of battery industries are growing explosively as a core strategy industry for the development of the semi-conductor, the LCD, and the mobile communication device. Dynamic characteristic analysis consists of dynamic behavior analysis and finite element analysis and is necessary for effective design of machines. In the dynamic behavior analysis, the displacement, velocity, applied force and angular velocity of each components are simulated according to each part. In the FEA, stress analysis, mode analysis, and frequency analysis are performed far each part. The results of these simulations are used for the design specification investigation and compensation for optimal design of cell manufacturing line. Virtual Engineering of the separator inserting machine on the automatic cell assembly line systems are modeled and simulated. 3D motion behavior is visualized under real-operating condition on the computer window. Virtual Prototype make it possible to save time by identifying design problems early in development, cut cost by reducing making hardware prototype, and improve quality by quickly optimizing full-system performance. As the first step of CAE which integrates design, dynamic modeling using ADAMS and FEM analysis using NASTRAN are developed.

• Journal of the Korean Society of Physical Medicine
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• v.9 no.2
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• pp.161-170
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• 2014

PURPOSE: This study concerns the wheelchair-based rehabilitation of elderly people, investigating muscle activity and coordination of upper limbs during wheelchair-based new millennium health gymnastics with varying elbow exercise velocity. METHODS: Twelve elderly people participated in new millennium gymnastics twice per week during 12-weeks. The group was separated into 0.4, 1.0, and 1.6 Hz groups (controlled by the metronome speed). Range of motion was measured by electrogoniometer, electromyography signals used root mean square values. The data application was normalized using reference voluntary contraction (%RVC). Upper limb (wrist and elbow joint) data gathered while standing up after the "falling on hips" was investigated in terms of coordination of angle-angle plots. One-way ANOVA, paired t-test and Scheffe's post hoc comparisons, were used for statistical analyses. RESULTS: There were results taken before and after the experiments. The results demonstrated a significant improvement in the triceps brachii and flexor carpi radialis of the 0.4 Hz group (p<.05). There was significant difference in the triceps brachi of the 1 Hz group. No significant differences were found in all muscles of the 1.6 Hz group. Muscle co-activation indexes of the 0.4 Hz group were larger than the others. The 0.4 Hz graph was turning point synchronized clockwise. The 1 Hz graph was out of phase with the negative slope. The 1.6 Hz graph was turning point synchronized counterclockwise, and uncontrolled factor phase was offset on angle-angle plots. CONCLUSION: It is found that improvement of muscle activity and upper limbs coordination of elderly people using wheelchair-based new millennium gymnastics is optimal with elbow exercise velocity with a frequency of 0.4 Hz.

• Korean Journal of Applied Biomechanics
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• v.18 no.3
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• pp.61-69
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• 2008

The purpose of this study is to examine the success or failure on the balance beam in element group requirements posture which is bending salto side-ward tucked through kinetic analysis. The national team players were participated. The goal was to present training methods to coaches and athletes so as to provide scientifically useful information. The results from this study were summarized as below. When the performance was successful, the features of the body's center of gravity during the side somersault motion showed to spread from the center of the balance beam and the center of the gravity moved to the direction of the body's rotation. In the spring sections - event2 and 3, when the performance was successful, up/down fluctuation became more wider and increased air time. It supported the result that the projecting variable was higher than in failure trial. In addition, the right side hip joint angles and speed, and angular velocity as jumping up for a leap were larger than in failure trial. Those variables showed the optimal conditions for a leap. By increasing the speed of the upper limb from the shoulder and the speed of the shoulder joint angular velocity, the momentum was increased. Especially the right side shoulder joint angular velocity increased dramatically because the right leg was held. As to the side somersault motion, the angular momentum of successful trial with respect to x-axis was bigger than failed trial. It indicated that the increasing angular momentum with respect to x-axis was an important factor in flying motion. Besides, as to side somersault, the appropriate proportion of angular momentum with respect to y-axis and z-axis was a key to successful trails.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.720-723
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• 2005

Ship motion is a complex controlled process with several hydrodynamic parameters that vary in wide ranges with respect to ship load condition, speed and surrounding conditions (such as wind, current, tide, etc.). Therefore, to effectively control ships in a designed track is always an important task for ship masters. This paper presents an effective adaptive autopilot ships that ensure the optimal accuracy, economy and stability characteristics. The PID control methodology is modified and parameters of a PID controller is designed to satisfy conditions for an optimal objective function that comprised by heading error, resistance and drift during changing course, and loss of surge velocity or fuel consumption. Designing of the controller for course changing process is based on the Model Reference Adaptive System (MRAS) control theory, while as designing of the automatic course keeping process is based on the Self Tuning Regulator (STR) control theory. Simulation (using MATLAB software) in various disturbance conditions shows that in comparison with conventional PID autopilots, the designed autopilot has several notable advantages: higher course turning speed, lower swing of ship bow even in strong waves and winds, high accuracy of course keeping, shorter time of rudder actions smaller times of changing rudder direction.

• Ocean Systems Engineering
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• v.4 no.1
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• pp.63-82
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• 2014

Declutching control is applied to a hemispherical wave energy converter with direct linear electric Power-Take-Off systems oscillating in heave direction in both regular and irregular waves. The direct linear Power-Take-Off system can be simplified as a mechanical spring and damper system. Time domain model is applied to dynamics of the hemispherical wave energy converter in both regular and irregular waves. And state space model is used to replace the convolution term in time domain equation of the heave oscillation of the converter due to its inconvenience in analyzing the controlled motion of the converters. The declutching control strategy is conducted by optimal command theory based on Pontryagin's maximum principle to gain the controlled optimum sequence of Power-Take-Off forces. The results show that the wave energy converter with declutching control captures more energy than that without control and the former's amplitude and velocity is relatively larger. However, the amplification ratio of the absorbed power by declutching control is only slightly larger than 1. This may indicate that declutching control method may be inapplicable for oscillating wave energy converters with direct linear Power-Take-Off systems in real random sea state, considering the error of prediction of the wave excitation force.