• The Journal of Korean Physical Therapy
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• 제34권2호
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• pp.51-56
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• 2022

Purpose: This study examined the effects of gym ball stabilization exercises on the physical functions of elementary school baseball players. Methods: The elementary school baseball players were assigned to an experimental group (n=21). The group performed gym ball stabilization exercises and the changes in the physical functions were measured using the visual response speed test, functional movements, physical balance ability, and pulmonary function. Results: The results of the visual response speed test showed changes in the time response speed. There was a significant change in the number of touches in 15 seconds in the upper arms and left and right legs (p<0.05) after 10 weeks. Also, there was a significant change in the reaction times of the left and right legs after 10 weeks (p<0.05). Further, there were significant differences in functional movements involving rotational stability and the total functional scores after 10 weeks (p<0.05). The player's body balance ability showed a significant difference after 10 weeks in the posterior-lateral and posterior-medial composite scores of the left and right legs (p<0.05). There was a significant change in the forced lung capacity and forced expiratory volume in 1 second after 10 weeks (p<0.05). Conclusion: These results show that the gym ball stabilization exercises effectively improved the visual response speed and functional movements, balance, and vital capacity of elementary school baseball players.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.436-447
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• 2002

In this study, the dynamic response of a catenary system that supplies electrical power to high-speed trains is investigated. One of the important problems which is accompanied by increasing the speed of a high-speed rail, is the performance of stable current collection. Another problem which has been encountered, is maintaining continuous contact force between the catenary and the pantograph without loss of panhead. The dynamic analyses of the catenary based on the Finite Element Method (FEM) are performed to develop a pantograph suitable for high speed operation. The static deflection of the catenary, the stiffness variation in contact lines, the dynamic response of the catenary undergoing the force of a constantly moving load and the contact force were calculated. It was confirmed that a catenary model is necessary to study the dynamic characteristics of the pantograph system.

• 한국구조물진단유지관리공학회 논문집
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• 제28권2호
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• pp.61-68
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• 2024

국내 경부선 및 호남선의 고속철도교량은 대부분 PSC-box 형식으로 설계되어 있고, 경간장35~40m인 경우 약 4~5Hz 정도의 1차 휨 고유진동수를 가지고 있다. 이때 KTX 고속열차가 290~310 km/h 속도로 주행할 경우, 열차에 의한 가진 진동수가 교량의 1차 휨 고유진동수에 근접하면서 공진 유사 현상이 발생하게 된다. KTX와 함께 향후 운행예정인 EMU-320 고속열차의 증속에 대해서도 철도교량의 동적 응답을 통한 안전성 분석이 필요한 상황이다. 본 연구에서는 실제 철도교량에서 계측된 응답을 기반으로 구조해석모델 개선 기법을 통해 대상 철도교량과 거동이 유사한 해석모델을 구현하였다. 개선된 구조해석모델은 고속철도교량에 KTX가 주행할 때 계측된 응답과 비교하여 검증하고, 이를 통해 KTX와 EMU-320 고속열차가 증속할 경우 동적 응답 특성을 분석하였다. 또한, 결과적으로, 교량 중앙부의 최대 수직변위와 가속도의 변화는 철도설계기준과 비교하여 주행 안전성을 평가하였다.

• 조명전기설비학회논문지
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• 제27권7호
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• pp.95-100
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• 2013

In this paper, we propose an active controller for high-speed pantograph in order to improve the transient response. Electrical power is delivered from a catenary to the train via a pantograph and thus it is very important to regulate the contact force between catenary and pantograph. By regarding the catenary displacement as an unknown disturbance input and analyzing the frequency response from the disturbance to contract force. we present an active controller that utilizes the lead compensator and resonant controller. It is shown by the computer simulation that the substantial improvement in transient response can be achieved by the proposed controller.

• Journal of Electrical Engineering and Technology
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• 제10권5호
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• pp.2170-2178
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• 2015

This paper presents the effective and reliable speed control of PMDC motors under variable loads and reference speeds. As is known DC motors are more preferred in industrial practices. This is that, the PMDC motors don’t require brush and commutator care and to increase in torque per motor depending on developments in power electronics. In this study, proportional-integral controller (PI) and fuzzy logic controller (FL) have been designed for speed control of PMDC motor. In the design of these controllers, characteristics such as minimum overrun time, response time to the load, settling time and ideal rise time have been taken into consideration for better stability performance. In this design, the best system response was searched by examining the effect of different defuzzification methods onto the fuzzy logic system response. In conclusion, it has been seen that FL controller has a better performance for variable speed-load control of PMDC motor compared to PI controller.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1022-1027
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• 2007

This paper presents a method to analyze the unbalance response of a high speed polygon mirror scanner motor supported by sintered metal bearing and flexible structures by using the finite element method and the mode superposition method considering the asymmetry of the gyroscopic effect and sintered metal bearing. The eigenvalues and eigenvectors are calculated by solving the eigenvalue problem and the adjoint eigenvalue problem by using the restarted Arnoldi iteration method. The decoupled equations of motion can be obtained from global finite element motion equations by using the orthogonal relation between the right eigenvectors and left eigenvectors. The decoupled equations of motion are used to analyze the unbalance response of a high speed polygon mirror scanner motor. The validity of the proposed method is verified by comparing the simulated unbalance response with the experimental results.

• 디지털산업정보학회논문지
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• 제10권3호
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• pp.119-125
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• 2014

Echo cancellation is required for a dual-duplex high speed communication such as digital subscriber line(DSL), in order to allow each individual loop to operate in a full duplex fashion. Echo cancellation was one of the most difficult aspects of DSL design, requiring high linearity and total echo return loss in excess of 70 dB. For a long and rapidly changing echo response, if the echo is cancelled by an adaptive echo canceller, the echo canceller needs more taps and its performance is decreased. But if the response is divided into several responses, which response is estimated by a adaptive digital filter and combined, the computation complexities are decreased and the performance is increased. Therefore, the adaptive multi-stage echo canceller is proposed to decrease the computation complexity and increase the performance of echo return loss, in which the echo canceller is composed of several stage echo canceller estimating each divided echo response. Through computer simulations, this multi-stage echo canceller is verified to have merits for high speed communications such as DSL application.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.95-98
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• 1996

Response speed of generator/control system kas increased with the aid of the development of power electronics. Even though it is desirable to enhance response speed for the control system(AVR/Gov) of generator itself, in case a certain generator/control system with high response excitation system is connected with bulk power system, terminal voltage and active power of some generators can oscillate with adjoining generators or near area when even a little of disturbance take place. PSS(Power System Stabilizer) is used to damp rotor swing by adding the supplementary signal in phase with speed. As the stable AVR response is very important before PSS is installed, modeling and analysis of generator/control system was performed. Next we have analysed PSS response of Hanlim's gas turbine by transmission line open/close test.

• 디자인융복합연구
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• 제16권6호
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• pp.153-167
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• 2017

오늘 날 많은 로봇들이 탁상용으로 개발되면서, 사용자들은 작업환경에서 로봇과 음성을 기반으로 상호작용을 한다. 그러나 현재 기술적 한계로 인하여, 대안이 필요한 실정이다. 이에 생체신호 중 무조건 반사를 활용하여 사용자와 상호작용을 하는 로봇을 디자인하고자 본 연구를 설계하였다. 본 연구에서는 생체신호를 로봇에 보다 효과적으로 적용하기 위하여, 로봇 외형의 구체화 정도와 로봇의 반응 속도에 따라 사용자가 느끼는 로봇에 대한 전체적 서비스평가와 인지된 로봇의 지능, 적합성, 신뢰성, 사회성을 평가하였다. 실험 결과 로봇의 외형이 구체화되지 않은 2D로봇보다 외형이 구체화된 3D 로봇이 인지된 지능과 적합성이 긍정적으로 평가되었고, 반응 속도가 느릴 때보다 반응 속도가 빠를 때 전체적 서비스평가와 인지된 로봇의 지능, 적합성, 신뢰성, 사회성에서 긍정적으로 평가되었다. 또한 서비스, 신뢰성, 사회성 평가에서 로봇 외형의 구체화 정도와 로봇 반응 속도에 따른 교호효과가 있었다.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.338-343
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• 2006

본 논문에서는 직류전동기 구동 시스템의 전류 및 속도 제어를 위하여 dSPACE 1104 시스템을 이용하여 전류 궤환을 갖는 속도 제어시스템을 구현하였다. 전류 및 속도 제어기의 설계는 MATLAB/SIMULINK 프로그램을 사용하여 간편하고 손쉽게 구현하였으며, 직류전동기 속도제어의 안정성과 응답성을 향상시킬 수 있었다. 직류전동기의 전류제어 및 속도제어는 DSP 보드와 dSPACE 시스템을 사용하여 수행하였으며, 속도의 궤환은 속도센서인 엔코더 펄스를 이용해서 QEP로 처리하였고, 전류의 궤환은 전류센서인 홀센서를 통해서 A/D 변환기로 처리하였다. 제어기들은 각각 PI 전류제어기 및 PI 속도제어기를 설계하였고 시뮬레이션과 실험을 통해서 전류 및 속도 응답을 확인하였다.