• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.27-36
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• 2009

The purpose of this study was to identify effects of restricted trunk motion on the performances of the maximum vertical jump. Ten healthy males performed normal countermovement jump(NJ) and control type of countermovement jump(CJ), in which subjects were required to restrict trunk motion as much as possible. The results showed 10% decreases of jumping height in CJ compared with NJ, which is primarily due to vertical velocity at take off. NJ with trunk motion produced significantly higher GRF than RJ, especially at the early part of propulsive phase, which resulted from increased moments on hip joint. And these were considered the main factors of performance enhancement in NJ. There were no significant differences in the mechanical outputs on knee and ankle joint between NJ and RJ. With trunk motion restricted, knee joint alternatively played a main role for propulsion, which is contrary on the normal jump that hip joint was highest contributor. And restricted trunk motion resulted in the changes of coordination pattern, knee-hip extension timing compared with normal proximal-distal sequence. In conclusion these results suggest that trunk motion is effective strategy for increasing performance of vertical jumping.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.39-47
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• 2005

In this paper, a method of station keeping strategy using relative orbital motion and numerical optimization technique is presented for geostationary spacecraft. Relative position vector with respect to an ideal geostationary orbit is generated using high precision orbit propagation, and compressed in terms of polynomial and trigonometric function. Then this relative orbit model is combined with optimization scheme to propose a very efficient and flexible method of station keeping planning. Proper selection of objective and constraint functions for optimization can yield a variety of station keeping methods improved over the classical ones. Results from the nonlinear simulation have been shown to support such concept.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.11
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• pp.1153-1160
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• 2013

SMISMO valve configuration is now starting to draw attention of the researchers of the construction equipment industry to increase the fuel efficiency of their equipment like excavators and wheel-loaders. An open-loop control strategy for grading operation of hydraulic excavator systems using SMISMO valve configuration is investigated in this paper. Tabor's algorithm for 1 d.o.f. SMISMO system under the assumption of quasi-static operation is revealed as not adequate for multi d.o.f. system with large moment of inertia even though the motion of the system is slow. New parameters are proposed in this paper. It modifies Tabor's open-loop control strategy for the grading operation of hydraulic excavators using SMISMO valve configuration. A simulation-based parameter tuning method is also proposed. It uses GA (Genetic Algorithm) to find the best parameter values. Simulation study for a practical hydraulic excavator shows the validity of the proposed open-loop control strategy.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.4
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• pp.368-374
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• 2013

Maintenance works for current high-rise buildings significantly depend on human labor, unlike other construction processes that are gradually being automated. Herein, this paper proposes robotic building maintenance system using motion control, in specific, reducing a system jerk which is directly subjected to improve the process performance and economic feasibility. The sensor for detecting straight and curvature section of the building facade, moreover rail-joint segment can be detected and be utilized for reducing jerk of the system. Analysis of the proposed system error caused by excessive vibration, e.g. jerk motion is introduced. To enhance the stability and safety of the system, herein, the strategy is proposed for enhancing the performance of the system based on anti-jerk motion control algorithm which comes out increasing the stability and sustainability of the integrated system, as well.

• Journal of Ocean Engineering and Technology
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• v.19 no.3
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• pp.66-73
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• 2005

The sway motion control problem of a container hanging on the trolley is considered in this paper. In the container crane control problem, the main issue involves suppressing the residual swing motion of the container at the end of acceleration, during deceleration, or for an unexpected disturbance input. For this problem, in general, many trolley motion control strategies are introduced and applied. In this paper, we introduce and synthesize a swing motion control system, in which a small auxiliary mass is installed on the spreader. In this control system, the actuator reacting against the auxiliary mass applies inertial control forces to the container to reduce the swing motion in the desired manner. In many studies, the controllers used to suppress the vibration have been synthesized for the given mathematical model of plants. In many cases, the designers have not been able to utilize the degree of freedom to adjust the structural parameters for the control object. To overcome this problem, so called "Structure/Control Simultaneous Method" is used. From this, in this paper the simultaneous design method is used to achieve optimal system performance. And the experimental result shows that the proposed control strategy is useful, to the case of that the controlled system is exposed to the uncertainties and, robust to disturbances like wind.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.5
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• pp.2313-2326
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• 2018

The method of operating a game could determine the psychological distance between the player and the game character, and thus, in the Virtual Reality, players' control methodologies are important to enhance their immersion. This study has the objective of examining the difference in games according to the method of operation based on the player's movements. This study researched the effect of the method of operating movement conforming to the movement of the character and the physical operation of the body on forming game experiences for the player. The result of performing an experiment increased reality for the game player through a controller in the shape of the actual control, to increase focus in the game. As so, game play through movements, including actual movements by the player displayed to enhance game satisfaction. In the part of media remediation field, Game can be defined as media which has their own unique hypermediacy. Especially, in the motion based game, players' movement mediates players and the game, therefore, players' movement could make players' experience augmented or immediate in accordance with the characteristics of movements. Even though sports and dances genres of motion-based games are common, RPG or adventure genres are rare. It can be explained that the characteristics of the action have been explained in the immediacy. In a game of fantasy, which is difficult to experience in real-life situations, the nature of the player's motion can increase the immersion of the game, which can contribute to utilization of players' motion and experience design in the various genres and suggestion of grounds theory. In addition, through this study, it is able to design motion-based games of various genres.

• Korean Journal of Applied Biomechanics
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• v.29 no.3
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• pp.145-155
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• 2019

Objective: The purpose of this study was to compare the physical characteristics (bone mineral density, joint muscle strength) and running biomechanics between older adults and young adult runners to understand the changes of running strategy by aging. Method: Bone mineral density (Dual Energy X-ray Absorptiometry, USA) of lower lower extremity and muscle strength (Cybex Humac Norm [DEXA], CSMI, USA) were measured to identify the physical characteristics of 10 elderly (age: $67.70{\pm}3.30yrs$, height: $1.68{\pm}0.04m$, mass: $67.70{\pm}3.80kg$) and 10 young adults (age: $21.20{\pm}0.42yrs$, height: $1.73{\pm}0.06m$, mass: $72.11{\pm}4.15kg$). Running data was collected by using an instrumented treadmill (Bertec, USA) and 7 infrared cameras (Oqus 300, Qualisys, Sweden). Two-way repeated ANOVA analysis was used to analyze results at a significant level of .05 with Bonferroni post hoc analysis. Results: Compared to the young adult group, the elderly group showed statistically significant difference in physical characteristics and in running characteristics. Elderly runners showed lower BMD and muscle strength compared with young runners (p<.05). In the running parameters, elderly runners tend to show shorter contact time and stride length compared with young runners (p<.05). In the joint angles, elderly runners showed smaller range of ankle motion compared with young runners (p<.05). Finally, elderly runners showed lower level of joint moment, joint power, and GRF compared with young runners in each running speed (p<.05). Conclusion: The running behavior of the elderly performed periodic running was similar to many variables of young adults. However, there were noticeable differences found in the ankle joints and most kinetic variables compared with young adult runners. This discrepancy may propose that elderly runners should consider appropriate running distance and intensity in the program.

• Journal of The Korean Association For Science Education
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• v.8 no.1
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• pp.43-55
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• 1988

This study intended to find the differences between expert's and novice's thinking processes when they solve physics problems. Five physics professors and twenty sophomore students in a physics department were participated in the study. The researcher investigated their thinking processes in solving three physics problems on NEWTON's law of motion. The researcher accepted so called "Thinking Aloud" method. The thinking processes were recorded and transfered into protocols. The protocols were analysised by problem solving process coding system which was developed by the researcher on the basis of Larkin's problem solving process model. The results were as follows: (1) There was no difference of time required in solving physics problem of low difficulty between expert and novices; but, it takes 1.5 times longer for novices than experts in solving physics problems which difficulties are high and average. (2) Novices used working forward strategy and working backward strategy at the similiar rate in solving physics problems which difficulties were average and low. while Novices mo mostly used working backward strategy in solving physic problems which difficulty was high. Experts mostly used working forward strategy in solving physics problems whose difficulties was average and low, however experts used working forward strategy and working backward strategy at the similiar rate in solving physics problem which difficulty was high. (3) Novices usually wrote only a few information on the diagram of figure they drawn, on the other hand experts usually wrote almost all the information which are necessary for solving the problems. (4) Experts spent much time in understand the problem and evaluation stage than novices did, however experts spent less time in plan stage than novices did. (5) Physics problems are solved in sequence of understanding the problem, plan, carrying out the plan, and evaluation steps regardless of problem difficulty.

• Journal of the Korean Society of Industry Convergence
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• v.19 no.4
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• pp.167-175
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• 2016

We present a method for improving adaptability of Learning from Demonstration (LfD) strategy by combining the LfD and Particle Swarm Optimization (PSO). A trajectory generated from an LfD is modified with PSO by minimizing a fitness function that considers constraints. Finally, the final trajectory is suitable for a task and adapted for constraints. The effectiveness of the method is shown with a target reaching task with a manipulator in three-dimensional space.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.428-431
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• 2002

Yard cranes are very useful equipments for handling of heavy containers. But rope-driven yard cranes must have a little of sway and skew motion because ropes are passive mechanical device. So many researches have been concentrated on anti-sway algorithm controlling trolley speed. But control algorithm of trolley speed is not practical in windy weather. In this paper, we are going to propose a new structure for anti-sway. This structure uses aux. ropes. The control strategy with auxiliary rope is very useful to sway control of yard crane because rope length is shorter than quay-side container cranes. In this paper, we derive equations of motion of trolley system which have anti-sway controller to use auxiliary rope. And main schemes are introduced and explained briefly.