• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.4
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• pp.447-452
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• 1995

In this paper a simple method of a position control for brushless DC motor is presented. For precise position control, a high performance torque controller is needed and a novel current control method is proposed. The current controller detects the uncommutating mode current for every 60.deg. (elec. angle) and controls it with PI controller. The current control loop includes the feedforward of back EMF and the feedforward of the neutral voltage between the neutral point of the inverter and the neutral point of the machine. In the position control, the acceleration pattern is calculated from the position reference. Then the speed trajectory is calculated from the acceleration pattern. The experimental results are presented to verify the proposed methods.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.5
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• pp.941-949
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• 2010

The present study investigated the swimming pattern and appendage postures of a copepod species, Calanus sinicus, which prevails in the south-east sea of the Korean peninsula, by employing a digital holographic particle tracking velocimetry(PTV) technique. The results showed that the copepod Calanus sinicus had various swimming patterns such as hover, hop, sink, cruise, and downward cruise. Most frequent pattern was the 'hop and sink'. The average swimming speeds ranged from 1.1 to 45.7 body-lengths/s, and the corresponding flow Reynolds number ranged from $10^0$ to $10^2$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.16 no.6
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• pp.1-15
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• 2017

Recently terrorism targets unspecified masses and causes massive destruction, which is so-called Super Terrorism. Many countries have tried hard to protect their citizens with various preparation and safety net. With inexpensive and advanced technologies of sensors, the surveillance systems have been paid attention, but few studies associated with the classification of the pedestrians' trajectories and the difference among themselves have attempted. Therefore, we collected individual trajectories at Samseoung Station using an analytical solution (system) of pedestrian trajectory by LiDAR sensor. Based on the collected trajectory data, a comprehensive framework of classifying the types of pedestrians' trajectories has been developed with data normalization and "trajectory association rule-based algorithm." As a result, trajectories with low similarity within the very same cluster is possibly detected.

• Journal of Environmental Science International
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• v.33 no.8
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• pp.591-604
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• 2024

To investigate the frequency and trajectories of volcanic ash from Mt. Baekdu reaching the Korean Peninsula, a forward trajectory analysis was conducted using the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. Through a cluster analysis of air parcel trajectories, we identified the main pathways of the volcanic ash from Mt. Baekdu entering the Korean Peninsula and analyzed the synoptic meteorological conditions on those days. The frequency of volcanic ash reaching the Korean Peninsula was 82 times at an altitude of 1000 m and 70 times at 2000 m, with an increasing trend from 2016 to 2022. This increase is attributed to the weakening of westerly winds and the strengthening of north-south winds due to global warming. Five and three trajectory clusters were classified at 1000 m and 2000 m, respectively. At a starting altitude of 1000 m, most air parcels originating from Mt. Baekdu entered the Korean Peninsula under weather conditions (C2, C3) where the pressure gradient from the northwest to the southeast was small, resulting in weak northerly winds. C2 and C3 showed shorter trajectories, which occurred in all seasons, except summer. At a starting altitude of 2000 m, air parcels mostly passed over the Korean Peninsula in a synoptic pattern similar to that at 1000 m in altitude; however, the air parcels had simpler paths and less frequent inflow. C2, at a starting altitude of 2000 m, originates from Mount Baekdu, crosses the center of the Korean Peninsula, and continues to the central region. At a starting altitude of 1000 m, volcanic ash can enter the Korean Peninsula when there is no strong low-pressure system to the southeast of the Korean Peninsula, whereas at 2000 m, volcanic ash can enter the Korean Peninsula when the Siberian high-pressure system is weak.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.263-266
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• 2001

The performance of the powertrain can be analyzed using dynamic models including transient characteristics, and the equations of motion can also be derived from the dynamic models of the powertrain. In this study, the shift transient characteristics of the vehicle equipped with Ravigneaux type planetary gears automatic transmission has been investigated.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.845-849
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• 1992

The disturbance and time delay can often cause a significant error in the estimation of trajectory of a underwater vehicle. The time delay considered in this study is due to the delayed rudder response to the rudder input from the guidance control part. The simulation tests are performed on maneuver with constant rudder angle, zigzag maneuver, dive-climb maneuver, and corridor pattern maneuver. The results are compared with those of without delay cases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.466-471
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• 1994

To make a dynamic system a given desired motion trajectory, a new feedback error learning scheme is proposed which is based on the repeatability of dynamic system motion. This method is composed of feedforward and feedback control laws. A benefit of this control scheme is that the input pattern that generates the desired motion can be formed without estimating the physical parameters of system dynamics. The numerical simulations show the good performance of the proposed scheme

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.897-898
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• 2009

본 논문은 사용자의 일상적인 이동 경로 패턴을 분석하여 일상화 지수를 측정하고, 이를 통해 GPS 신호 검색 주기를 동적으로 변경하는 동적 GPS 신호 검색 주기 변경 시스템을 제안한다. 고정된 GPS 신호 검색 주기는 불필요하게 많은 전력을 소모하기 때문에 제안 시스템을 이용하여 이동 단말기의 전력 소모 문제를 개선할 수 있다.

• Journal of Power Electronics
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• v.11 no.4
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• pp.449-455
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• 2011

Electric drive vehicles (EDV) have received much attention recently because of their environmental and energy benefits. In an EDV, the motor drive system directly influences the performance of the propulsion system. However, the available DC voltage is limited, which limits the maximum speed of the motors. At high speeds, the inverter voltage increases if the square wave (SW) voltage (six-step operation) is used. Although conventional direct torque control (DTC) has several advantages, it cannot work in the six-step mode required in high-speed applications. In this paper, a single-mode seamless DTC for AC motors is proposed. In this scheme, the trajectory of the reference flux changes continuously between circular and hexagonal paths. Therefore, the armature voltage changes smoothly from a high-frequency switching pattern to a square wave pattern without torque discontinuity. In addition, because multi-mode controllers are not used, implementation is more straightforward. Simulation results show the voltage pattern changes smoothly when the motor speed changes, and consequently, torque control without torque discontinuity is possible in the field weakening area even with a six-step voltage pattern.

• Journal of the Korean Society of Safety
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• v.26 no.5
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• pp.17-22
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• 2011

This study proposes feature extraction method of pattern recognition by evaluation of weld defects in weld zone of titanium. For this purpose, analysis objectives in this study are features of attractor quadrant and fractal dimension. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics resulting from distance shifts such as porosity of weld zone. These differences in characteristics of weld defects enables the evaluation of unique characteristics of defects in the weld zone. In quantitative fractal feature extraction, feature values of 0.87 and 1.00 in the case of part of 0.5 skip distance and 0.72 and 0.93 in the case of part of 1.0 skip distance were proposed on the basis of fractal dimensions. Attractor quadrant point, feature values of 1.322 and 1.172 in the case of ${\phi}1{\times}3mm$ porosity and 2.264 and 307 in the case of ${\phi}3{\times}3mm$ porosity were proposed on the basis of distribution value. The Proposed feature extraction of pattern recognition in this study can be used for safety evaluation of weld zone in titanium.