• 드라이브 ㆍ 컨트롤
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• 제19권4호
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• pp.1-9
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• 2022

The structure and operating principle of the 2-speed shift reducer were explained, the allowable bending stress value of the material was compared with the analysis result through FM structural analysis program, and the average stress distribution value of von Mises was performed on the gear root atmosphere. The structural safety of the 2-speed planetary gear reducer was verified through FM structural analysis. The natural frequency was calculated by applying the specifications of the planetary gears of the 2-speed gearbox, and the critical speed of resonance was calculated by calculating the natural frequency and the transmission error of the engaged gear pair. As a result of analyzing the critical speed, since it is formed higher than the actual operating speed range, it is considered safe because there is no resonance problem due to the suggested specifications of the planetary gears of the 2-speed shift reduction.

• International Journal of Internet, Broadcasting and Communication
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• 제16권2호
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• pp.169-178
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• 2024

This study aimed to investigate the effects of water depth and speed on the activation of lower muscles during squat exercises, utilizing electromyography(EMG). It involved ten male participants in there. Participants performed 30 squats over a minute at a speed of 60bpm and maximum speed squats until exhaustion within a minute. The Integrated electromyography(iEMG) readings for the rectus femoris showed statistically significant differences due to water depth and speed, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the biceps femoris also showed statistically significant differences, with a significant interaction effect between depth and speed during squat exercises. The iEMG readings for the gastrocnemius showed statistically significant differences according to water depth and speed. However, the interaction effect of water depth and speed during squat exercises did not show a statistically significant difference. In contrast, the iEMG readings for the tibialis anterior demonstrated statistically significant differences, with a statistically significant interaction effect during squats. These findings suggest that water depth and speed positively influence the activation patterns of lower muscles. Therefore, appropriately tailored aquatic exercises based on water depth for individuals with musculoskeletal discomfort, including the elderly or those with physical impairments, can effectively reduce physical strain and enhance balance, as well as physical and perceptual aspects. It is concluded that such exercises could provide a safer and more effective method of exercise compared to ground-based alternatives.

• 한국항행학회논문지
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• 제16권6호
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• pp.1123-1133
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• 2012

논문에서는 극저속 영역 및 저속 영역에서 안정적이고 동특성이 우수한 벡터제어 시스템을 구성하여, 축소차원 상태관측기를 이용한 순시속도 관측기와 극 저속 제어, 회전자 속도를 추정하는 벡터제어 시스템에 관한 방법을 제안하였다. 본 시스템에서 제안된 관측기는 축소차원 상태관측기를 부하토크 추정에 적용하여 속도추정에 이용함으로서 시스템구성을 간단히 구현 하면서도 극 저속 영역에서 정확한 순시속도 추정이 가능하였다. 또한, 시스템 잡음에 의한 영향을 줄이고, 관측기의 극을 변화시키는 일 없이 부하외란 이나 모델화 오차, 측정 잡음 등에 강인한 유도전동기 속도제어 시스템을 제시하였다.

• 한국안전학회지
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• 제33권1호
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• pp.103-108
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• 2018

Since tower cranes are susceptible to wind loads, the operation of the tower crane should be ceased when it exposed to a strong wind. For this reason, even in Korea, the operation limit for wind loading on the tower crane is regulated by a law. Recently the Korean law in which provided the wind speed limit to cease the tower crane operation has been revised from "instantaneous wind speed of 20 m/s" to "instantaneous wind speed of 15 m/s". Although this revision is expected to reduce safety risks in tower crane operation, some field operators still insist to lower the wind speed limit. However, in many countries "wind speed of 20 m/s" is normally used as the maximum in-service wind speed for tower cranes. Therefore, the investigation of the proper wind speed for regulation would be helpful to secure the safety of the tower crane operation under windy condition. In this study the validity of the revised wind speed limit is investigated with the surveys targeted to both tower crane practitioners and parties of concerned in construction companies, in which various questions was provided for a suitable wind speed limit and the answers were analyzed. The results showed that the revised wind speed limit is acceptable to tower crane practitioners as well as the parties of concerned in construction companies and is satisfying the structural stability requirement for in-service state tower crane. Therefore, it can be concluded that the revised wind speed limit is valid in humanly safety point of view.

• Journal of Power Electronics
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• 제18권3호
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• pp.714-722
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• 2018

This paper presents a wide-range speed control scheme of brushless DC (BLDC) motors based on a hall sensor with separated low- and normal-speed controllers. However, the use of the hall sensor signal is insufficient to detect motor speed in the low-speed region because of low sensor resolution and time delay. In the proposed method, a micro-stepping current control method according to the torque angle variation is presented. In this mode, the motor current frequency and rotating angle are determined by the reference speed without the actual speed fed by the hall sensor. The detected torque angle is used to adjust the current value in a limited band to control the current value in accordance with the load. The torque angle is detected exactly at the changing point of the hall sensor signal. The rotor can follow the rotating flux with the variable torque angle. In a normal speed range, the conventional vector control scheme is used to control the motor current with a PI speed controller using the hall sensor. The torque characteristics are analyzed on the basis of the back EMF and current shape. To adopt the vector control scheme, the continuous rotor position is estimated by the measured speed and hall sensor position. At the mode changing point between low and normal speed range, the proper initial current command and reference rotor position are calculated. The calculated current command can reduce the torque ripple during transient mode. The proposed method is simple but effective in extending the speed control range of a conventional BLDC motor with hall sensor without the need for a high-resolution encoder. The effectiveness of the proposed method is verified by various experiments on a practical BLDC motor.

• 한국ITS학회 논문지
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• 제23권2호
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• pp.32-49
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• 2024

본 논문에서는 도로교통 여건과 제한속도 변화가 교통소통과 안전에 미치는 영향을 분석하였다. 교통소통지표로 통행속도와 순행속도, 「순행속도-통행속도」, 편차, 대편차비율, 상충횟수 등을 안전지표로 설정하고 도로교통 여건과 제한속도 변화가 이들에 미치는 영향을 분석하였다. 분석 결과에 의하면 제한속도는 소통지표에는 크게 영향을 주지만 안전지표에는 크게 영향을 주지 않는 것으로 분석되었다. 통계적 유의성 검정 결과 제한속도가 증가함에 따라 소통지표는 증가한다는 것이 유의하다고 입증되었다. 그러나 안전지표들은 증가하는 경우가 많지만 통계적으로는 유의성이 입증되지 않았다. 그러므로 다양한 도로여건과 교통량 변화에 따른 교통흐름 상태를 현실적으로 고려해서 제한속도가 설정되고 운영된다면 운전자들이 주행하는 속도에 부합되고 교통소통과 안전이 향상된다고 할 수 있다. 따라서 본 논문에서 제시한 교통소통지표와 안전지표들을 고려하여 제한속도를 산정하고 교통량 변화에 따라 제한속도를 운영할 경우 도로상의 교통 흐름을 안정화시키는 데 기여할 것으로 기대된다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.140-144
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• 2011

As a result of that the domestic railway technology has been progressed as times go by, the 1st and the 2nd steps for Gyeongbu HSR at the speed of more than 300km/h, were completed and Honam HSR - its operational speed is 350km/h - is under construction. Additionally, As a part of the expressization project for general lines, the Seoul-Chuncheon route at the speed of more than 180[km/h] is under construction and the Jeolla route is under design. At present, 11 countries (e.g. France, Germany, Belgium, Italy, the Netherlands, Spain, England, Japan, China and Taiwan) including Korea have high speed railways operated at the speed of more than 300[km/h]. As shown in the above, the domestic railway has high speed trains as good as those of countries outside Korea, but the schedule speed, which is calculated by dividing distance to destination by time, is lower than that of overseas trains. For overseas railway, the ratio of schedule speed to the highest speed is above 65%, while that of domestic railways is over 50%. It shows a significant difference between them. It is expected that the schedule speed improvement will increase the number of train operation and line capacities than now, so it shall achieve smooth transportation flow and improve the passengers' satisfaction. In this paper we describe the necessity for the improvement of schedule speed, by analyzing foreign cases related to the improvement of schedule speed in order to satisfy the increasing traffic demand.

• 대한방사선기술학회지:방사선기술과학
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• 제16권1호
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• pp.67-80
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• 1993

Recently, a large number of new screen-film systems have become available for use in diagnostic radiology. These new screens are made of materials generally known as rare-earth phosphors which have high x-ray absorption and high x-ray to light conversion efficiency compared to calcium tungstate phosphors. The major advantage of these new systesms is reduction of patient exposure due to their high speed or high sensitivity. However, a system with excessively high speed can result in a significant degradation of radiographic image quality. Therefore, th speed is important parameters for users of these system. Our aim of in this was to determine accurately and precisely the absolute speed and relative speeds of both new and conventional screen-film system. We determined the absolute speed in condition of BRH phantom beam qulity and the relative speed were measured by a split-screen technique in condition of BRH and ANSI phantom beam qulity. The absolute and the relative speed were determined for 8 kinds of screen-4 kinds of film in regular system and 7 kinds of screen-7 kinds of film in ortho system. In this study we could know the New Rx, T-MAT G has the highest film speed, also know Green system's stndard deviation of relative speed larger than blue system. It was realized that there were no relationship between the absolute speed and the blue system. It was realized that there were no relationship between the absolute speed and the relative speed in ortho or regular system.

• Journal of Astronomy and Space Sciences
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• 제25권4호
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• pp.481-490
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• 2008

반작용휠은 인공위성의 기동 및 자세제어에 사용되는 주요 구동기 중의 하나로 회전체의 속도를 변화시켜 발생하는 토크로 위성의 자세제어를 수행하므로 정밀한 자세제어를 위해서는 정확한 회전속도의 측정이 요구된다. 타코 펄스를 이용한 고속 회전모터의 대표적인 속도 측정방법에는 Elapsed-time측정방법과 Pulse-count측정방법의 두 가지가 있으며 이 연구에서는 반작용휠의 속도 측정을 하는 동안 발생할 수 있는 속도 측정의 오차 및 정밀도를 두 가지 방법에 대해 분석, 비교하였다. 그 결과 Pulse-count측정방법은 반작용휠의 등속 구동 시 회전속도에 상관없는 일정한 오차를 가지는데 비해 Elapsed-time측정방법은 회전속도가 작을수록 오차가 줄어드나 저속일 때 오차가 현저히 커질 수 있음을 해석적으로 확인하였다.

• 한국철도학회논문집
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• 제15권1호
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• pp.37-41
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• 2012

경부고속철도는 운영환경(차량,구배,곡선,시설물 등)에 따라 궤도회로를 여러 개의폐색으로 분할하여 운행하는 고정폐색방식의 열차제어시스템으로 운행된다. 고정폐색방식 열차제어시스템은 선행열차의 점유폐색을 기준으로 진입/진출폐색속도, 목표거리, 감속도와 같은 운행정보를 차상열차제어장치로 전송하여 연속적으로 열차를 제어하는 방식으로, 경부고속철도 열차제어시스템은 열차가 해당 폐색의 진입/진출속도를 초과할 경우, 비상제동명령을 내려 열차의 안전한 운행을 보장한다. 본 논문에서는 안전한 운행을 위해 폐색에 할당되는 속도제어코드의 생성원리를 분석하여, 최고운행속도와 운행차량특성에 따른 속도제어코드를 도출하고, 도출된 속도제어코드에 따른 운행시격 분석을 통해 열차 운행효율을 분석하였다. 이와 같은 연구는 기존 고속철도의 증속 및 신규 고속철도 열차제어시스템 설계 자료로 활용될 수 있다.