• Journal of the Korean Vacuum Society
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• v.19 no.4
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• pp.256-264
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• 2010

In this paper, a digital controller of magnetic bearing system for a high vacuum turbomolecular pump (TMP) is designed and examined. For stabilizing and providing damping in magnetic bearing, the digital PID controller is applied for each 5 control axes, and the inter-axis cross feedback controller is also applied to suppress low frequency vibration caused by gyroscopic moment of the rotor at high speed of rotation. The fabricated rotor-shaft has its first flexible natural frequency lower than maximum speed, about 614Hz, so the two lead filters are applied to increase damping of flexible mode. Notch filters with rotating frequency were selected to reduce vibration of the pump housing caused by unbalance load. The implemented controllers are verified by examination of frequency response and rotating test up to 40,000 rpm, which is higher than critical speed of backward flexible mode.

• Journal of Korea Game Society
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• v.19 no.5
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• pp.91-102
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• 2019

In this paper, we propose an improved method of plane tracking in developing AR games for smartphones using magnetic field sensor. The previous method based on ARCore is a VIO method using a mixture of SLAM and IMU of smartphones. The disadvantages of accelerometers and gyroscopes in IMUs cause errors in tracking the plane. We propose an improved method of planar tracking by adding the magnetic field sensor as well as the existing IMU sensors. Experimental results shows that our method reduces the error of the smartphone posture estimation.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.151-156
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• 2017

In case of massive water leakage, it's crucial for field manager to quickly positioning the problematic valve and related ones. However, it's not easy for the system to find the corresponding valve and even if it's found, it can not respond quickly because it can't know the relevant information immediately. In this paper, we implement the system for identifying sluice valve positions using GPS and AR techniques. The proposed system is composed of hand held android device, remote database server and data acquisition device for DB creation. We utilize the android device's sensors including GPS, gyro, accelerometer, magnetic sensor. The system identifies the valve with matching between the position data from the remote database server, and current GPS locations of device. We use AR techniques to overlay the graphics pattern of valve positions and some additional informations on captured real scene. With this system, it will be fast and accurate for maintenance of sluice valve of municipal water system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.168-172
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• 2005

An autopilot system of a ship is very important for a safe and convenient navigation, which is realized with getting an azimuth data from a gyrocompass, a magnetic compass and a GPS(Global Positioning System) compass. Magnetic compass an azimuth error is generated by a vessel magnetism material such as steels. The magnetic pole is detected by the magnetic field sensor, it does not coincide with the true north, therefore, the detected azimuth data can not but accompany error. In this paper, in order to detect the minimum change of azimuth data which generates errors of azimuth information, a search algorithm using the Kalman Filtering method is utilized. The digital electronic compass is designed with the integration algorithm using the merits of an earth's magnetic field sensor and a GPS receiver.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1002-1009
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• 2009

Precision guidance filter design for a tactical missile with a strapdown seeker aided by low-cost strapdown sensors has been addressed in this paper. The low-cost strapdown sensors consist of an IMU with 3-axis accelerometers and gyroscopes, 3-axis magnetometers, and a barometer. Missile's position, velocity, attitude, and bias error of the barometer are considered as state variables. Since the state and measurement equations are highly nonlinear, we adopt UKF(Unscented Kalman Filter). The proposed guidance filter has a function of a navigation filter if target position error is not considered. In the case that the target position error is introduced, the proposed filter can effectively estimate the relative states of the missile to the true target. For specific engagement scenarios, we can observe that observability problems occur.

• Journal of Aerospace System Engineering
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• v.12 no.1
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• pp.27-34
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• 2018

In this study, the generating of torque regarding the Control Moment Gyro (CMG) is proportional to the angular velocity of gimbal. This is the case because gimbal affects the attitude control of the satellite directly, and it is necessary to reduce the incidence of torque ripple of gimbal. In this paper, the cause of the torque ripple of gimbal is reviewed and mathematically modeled by assuming the friction imbalance of bearing, the magnetic field and the phase current imbalance of the motor. We are able to confidently estimate the modeling parameters of gimbal disturbance using a constant speed test, and then analyze the influence of applying feedforward control to our modeling. Additionally, the simulation results show that the torque ripple and angular velocity fluctuations are reduced when apply this modeling to the identified study parameters. Finally, we present the disturbance reduction technique using our disturbance modeling.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.1-8
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• 2019

The electromagnetic forces generate a torque on the gimbal motor, and changes in the coil current causes torque ripple. This affects the gimbals' speed and results to unstable satellite attitude. It is therefore essential to reduce the torque ripple of the gimble motor with the aim of improving the attitude control accuracy of the satellite. This paper theoretically analyzes the torque generated from the modeling of a motor for general concentrated winding and distributed winding. The prototype was designed and fabricated through selection of the winding that reduces the torque ripple through simulation results. The results of the magnetic fields' theoretical analysis and the back electromotive force of the prototype were compared with the calibrated results for verification of conformity and manufacture of the design. The low-speed test proved that the torque ripple is reduced by improving the speed stability.

• Proceedings of the KIEE Conference
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• 2004.07d
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• pp.2218-2220
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• 2004

조종사 없이 사전에 입력된 프로그램 또는 인공지능에 의해 기체 스스로 판단하여 자율비행하는 비행체를 무인 항공기라 한다.[6] 이러한 비행을 위해서는 기체의 위치, 자세, 속도 등의 정보가 필요하다. 본 논문에서는 3축 가속도센서 1개 및 1축 자이로센서 3개를 서로 수직으로 구성하는 관성항법 시스템에 자기콤파스, 고도센서, GPS등의 비관성센서를 추가로 구성하여 시스템을 설계하였으며 칼만필터를 이용하여 시스템의 오차를 추정하고 이를 되먹임 시킴으로써 오차를 정정한다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.25 no.1
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• pp.104-109
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• 1996

고추의 효능을 높이기 위한 방법의 하나로 향신성 분을 보유하면서 자기저자이 가능한 oleoresin을 추출하여 유화제로 수용성을 부여시킨 후, 이때의 유화안 정성과 고온에서 조리를 하였을 때 고추 oleoresin의 항산화 활성을 검토하였다. 100mesh로 분쇄한 고추에 증류수에 가하여 감압증류시켜 정유성분을 추출하고, 잔사에 에틸 알코올을 가하여 $25^{\circ}C에서$ 3시간 진탕 추출한 후 여과, 농축시켜 정유성분과 합하였다. 여기에 물과 유화제 (PGDR)를 첨가, 유화시켜 고추 oleoresin으로 하였다. $60^{\circ}C에서$ 24시간 방치했을때의 enulsion 생성율은 PGDR을 4% 첨가한 경우가 94.5%로 가장 높았고, 또한 100분간 원심분리(200$\times$g) 시킨 후에도 emulsion 잔존율은 80%정도로서 유화안전성이 가장 좋았다. 고추 oleoresin의 항산화 활성은 가열조리 온도 100$\times$의 경우 BHA의 효과 만큼은 미치지 못하나 상당한 항상화성을 나타내었고, 온도 $150^{\circ}C의$ 경우는 BHA 첨가와 마찬가지로 항산화성 효과를 인정하기 어려웠다.

• Geophysics and Geophysical Exploration
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• v.17 no.3
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• pp.147-154
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• 2014

For analyzing the distribution of chromite, magnetic survey was carried out on the chromium mineralized belt in Bophi Vum area, northwestern Myanmar. As a result, the magnetic susceptibility of chromite is lower than those of dunite and harzburgite, which are background rocks of chromite. Also, the locations of low magnetic anomaly zone and low magnetic susceptibility models of 3D magnetic inversion result are spatially well matched with those of chromite occurrences confirmed by the surface geological survey and trench survey. Some of low magnetic effects are expanded to the periphery area of chromite occurrences. Considering the magnetic susceptibility characteristics of various rocks in this area, the expanded low magnetic anomaly zones are estimated as the high potential areas bearing chromite. For confirming the potential area of chromite pointed by coarse magnetic survey, the additional detail exploration need to be carried out in future.