• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.577-589
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• 2021

Drone mapping systems can be applied to many fields such as disaster damage investigation, environmental monitoring, and construction process monitoring. To integrate individual sensors attached to a drone, it was essential to undergo complicated procedures including time synchronization. Recently, a variety of composite sensors are released which consist of visual sensors and GPS/INS. Composite sensors integrate multi-sensory data internally, and they provide geotagged image files to users. Therefore, to use composite sensors in drone mapping systems, mapping accuracies from composite sensors should be examined. In this study, we analyzed the mapping accuracies of a composite sensor, focusing on the data acquisition area and pre-calibration effect. In the first experiment, we analyzed how mapping accuracy varies with the number of ground control points. When 2 GCPs were used for mapping, the total RMSE has been reduced by 40 cm from more than 1 m to about 60 cm. In the second experiment, we assessed mapping accuracies based on whether pre-calibration is conducted or not. Using a few ground control points showed the pre-calibration does not affect mapping accuracies. The formation of weak geometry of the image sequences has resulted that pre-calibration can be essential to decrease possible mapping errors. In the absence of ground control points, pre-calibration also can improve mapping errors. Based on this study, we expect future drone mapping systems using composite sensors will contribute to streamlining a survey and calibration process depending on the data acquisition circumstances.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.6
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• pp.457-462
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• 2022

Recently, a variety of cultural life using drones as an entertainment tool has been created, and in order to realize this, more and more users are using drones with good performance enough to invade the no-flight zone. Drones for satisfying entertainment activities must have long flight times and be able to fly long distances, which can often cause great damage by invading no-flight zones or causing unwanted flight crashes. In this study, in order to solve this problem, a no-flight zone is set with GCS(Ground Control System), and when flying at a critical speed of 10km/h or less, the drone is safely operated by not entering the critical distance 10m away from the no-flight zone, and the critical speed A method was proposed to prevent the drone from entering the no-flight zone by allowing the drone to self-drop by GCS control when it flies beyond the threshold and enters the critical distance. As a result of a total of 44 repeated experiments in a specific experimental area with the proposed method, the drone safely self-dropped except for the case where it crossed the restricted area once or twice. It was found to be an appropriate way to prevent this.

• Journal of KIISE
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• v.44 no.6
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• pp.601-606
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• 2017

Recently, we have frequently encountered flying drones with the growth of drone industry. However, it is difficult for a driver to stabilize the motor speed of drones, since the voltage of a Lithium polymer battery used in drones may suddenly drop or rise when its power is exhausted. The instability of the motor speed precludes the drone from maintaining a flight altitude, so that the fuselage of a drone performs ascending and descending repeatedly. For solving this problem, existing techniques either add a compensator considering voltage drop of battery or change the control model. Since these techniques use hardware-implemented modules or depend on motor type and experimental results, there is a problem that new suitable modules should be implemented in accordance with the used motor of the fuselage. For solving this problem, in this paper, we implement a motor speed controller in the firmware of drones by considering voltage drop of battery to enhance drone flight stability.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.522-525
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• 2019

To overcome the limitation of ground inspection for Navigational Aid, Korea Airport Corporation (KAC) developed a drone system for Navigational Aid inspection. This drone system has the advantage that they can inspect the air radio signal at the perspective of user (aircraft). Since drones have more free flight paths and easier control of flight speeds compared to aircrafts, drones can check sections of suspected airborne radio wave distortions at desired paths and speeds. Recently, with the acceleration of the development around the airport, there is a concern about the deterioration of the quality of radio signal of Navigational Aid. In order to analyze radio distortion of Navigational Aid, a radio wave environmental survey was conducted using drones. When the signal received by each flight path of the drone was measured, the origin of the reflected wave was identified by analyzing the section in which the radio signal was distorted.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.917-926
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• 2019

At present, TICN has been developed and distributed for military command control. TICN is known as the 3.5G mobile communication technology based on WiBro, which shows technical limitation in the field operation situation. Accordingly, the drone-type base station platform is attracting attention as an alternative to overcome technical limitations such as difficulty in securing communication LoS and limiting expeditious network configuration. In this study, we performed simulation performance evaluation of drone-type base station operation in 28 GHz that is considered most suitable for cellular communication within mmWave frequency band. Specifically, we analyzed the changes in throughput and fairness performance according to radio resource management policies such as frequency reuse and scheduling in multi-cell topology. Through this, we tried to provide insights on the operation philosophy on drone-type base station.

• Journal of Korea Multimedia Society
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• v.21 no.2
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• pp.250-260
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• 2018

In order to control the quadcopter using reinforcement learning, hovering of 1-axial drones prototype is implemented through reinforcement learning. A complementary filter is used to measure the correct angle, and the range of angles is from -180 degrees to +180 degrees using modified complementary filter. The policy gradient method is used together with the REINFORCE algorithm for reinforcement learning. The prototype learned in this way confirmed the difference in performance depending on the length of the episode.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.3-4
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• 2020

공연을 위한 드론 군집비행의 제어시스템에 관한 기존의 연구 결과들은 실시간으로 반응하지 않으며, 비숙련자가 제어하기 어렵다는 문제점이 있다. 본 논문에서는 첫 번째로 HCI를 기반으로 한 웨어러블 형태의 장갑 컨트롤러를 사용한다. 두 번째로 각각의 음 정보에 실시간으로 반응하도록 FFT를 사용한 주파수 정보를 컴퓨터로 수신 받는다. 세 번째로 각각의 군집비행 움직임 정보를 복수의 드론에게 송신하는 새로운 방법의 드론 실시간 군집비행 제어시스템을 설계하였다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.01a
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• pp.131-132
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• 2020

본 논문에서는 OpenCV의 Marker Detection 기술을 이용하여 특정지점의 마커를 영상처리기술로 인식하여 드론의 자동 이착륙 및 주변 위기상황, 미션수행 등을 마커를 통해서 드론에게 전달하여 비행 제어할 수 있는 체계를 개발한다. 드론은 OpenCV Aruco모듈을 이용하여 Marker ID별로 특정 명령어를 데이터 베이스와 비교하여 비행제어 명령을 수행한다. 지상에서는 마커의 변경을 통해서 실시간으로 미션변경을 할 수 있다. 이를 통해 드론은 제어용 송수신 채널을 통해서 통신을 하고는 있으나, 주파수 채널수가 제한이 되어 있으므로 구체적인 비행 제어 명령을 마커를 통해 이착륙시 추가적이며, 자동적인 진행이 가능하다.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.6
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• pp.448-453
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• 2023

As the production of small quadcopter drones has diversified and multi-sensors have been installed in FC due to the spread of MCU capable of high-speed processing, small drones that can perform special-purpose operations rather than simple operations have been realized. Hovering, attitude control, and position movement control were possible through the IMU in the FC mounted on the drone, but control is not easy when GPS connection and video communication are not possible in a closed building with a complex structure. In this study, when encountering an obstacle with a change in altitude in such a space, we proposed a method to overcome the obstacle and perform autonomous flight using optical flow and IR sensors using the Lucas-Kanade method. Through experiments, the drone's altitude flight on stairs that replace the complex structure of a closed space with stable hovering motion has a success rate of 98% within the tolerance of 10 [cm] due to external influences, and reliable autonomous flight up and down is achieved.

• Journal of the Korean earth science society
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• v.38 no.4
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• pp.251-262
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• 2017

The system of magnetic exploration with a drone flight was constructed and applied to the iron mine site. The magnetic probe system installed on the drone used a sensor as Bartington's fluxgate type magnetometer, Mag639 and the A/D converter to collect magnetic intensity values on the tablet PC. The drone flight control module is a highly expandable Pixhawk with allowing 15 minutes of flight by loading 3kg. Experiments on the magnetic field interference range were performed to remove the erroneous effect from the drone with applying RTK GPS to obtain the magnetic intensity value at the accurate position. The accurate location information enabled to obtain the gradient measurement of magnetic field by measuring twice at different altitudes. Also, by using the terrain information, we could eliminate the terrain effect by setting the flight path to fly along the terrain. These results are in line with the field experiments using the nuclear proton magnetometer G-858 of Geometrics Co., Ltd, which adds to the reliability of the drone based aeromagnetic survey system we constructed.