• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.11
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• pp.988-995
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• 2014

Two axis gimbal type X-band antenna system has been widely used to effectively transmit the real time image data from the observation satellite to the ground station. The micro-vibration generated by stepping motor actuation and imperfect intermeshed gear configuration of the antenna is one of the sources to degrade the image quality. To guarantee a high quality image of high resolution observation satellite, micro-vibration isolation of X-band antenna is required. In this paper, the X-band antenna vibration isolation system using pseudoelastic SMA(Shape Memory Alloy) mesh washer has been newly suggested. The basic characteristics of the SMA mesh washer isolator proposed in this study has been measured through static load tests and its effectiveness has been demonstrated by the micro-vibration isolation test of the X-band antenna.

• Current Research on Agriculture and Life Sciences
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• v.32 no.2
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• pp.79-84
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• 2014

The precision aerial application of agricultural unmanned helicopters has become a new paradigm for small farms with orchards, paddy, and upland fields. The needs of agricultural applications require easy and affordable control systems. Recent developments of MEMS technology based on inertial sensors and high speed DSP have enabled the fabrication of low-cost attitude system. Therefore, this study evaluates inertial MEMS sensors for estimating the attitude of an agricultural unmanned helicopter. The accuracies and errors of gyro and acceleration sensors were verified using a pendulum system. The true motion values were calculated using a theoretical estimation and absolute encoder measurement of the pendulum, and then the sensor output was compared with reference values. When comparing the sensor measurements and true values, the errors were determined to be 4.32~5.72%, 3.53~6.74%, and 3.91~4.16% for the gyro rate and x-, z- accelerations, respectively. Thus, the measurement results confirmed that the inertial sensors are effective for establishing an attitude and heading reference system (AHRES). The sensors would be constructed in gimbals for the estimating and proving attitude measurements in the following paper.

• Journal of the Korean Institute of Intelligent Systems
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• v.27 no.2
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• pp.89-98
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• 2017

The control moment gyroscope(CMG) can be used for essential balancing control of a one-wheeled mobile robot. A single-gimbal CMG has a simple structure and can supply strong restoring torque against external disturbances. However, the CMG generates unwanted directional torque also besides the restoring torque; the unwanted directional torque causes instability in the one-wheeled robot control system that has high rotational degrees of freedom. This study proposes a control system for a one-wheeled mobile robot by using a CMG scissored pair to eliminate the unwanted directional torque. The well-known LQR control algorithm is designed for robustness against modeling error in the dynamic motion equations of a one-wheeled robot. Computer simulations for 3D nonlinear dynamic equations are carried out to verify the proposed control system with the CMG scissored pair and the LQR control algorithms.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.46-58
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• 2018

A two-axis gimbal-type X-band antenna is widely used to transmit bulk image data from high-resolution observation satellites. However, undesirable microvibrations induced by driving the antenna should be attenuated, because they are a main cause of image-quality degradation of the observation satellite. In this study, a pseudoelastic memory alloy (SMA) gear was proposed to attenuate the microvibrations by driving the antenna in an azimuth angle. In addition, the proposed gear can overcome the limitations of the conventional titanium blade gear, which is not still enough and is vulnerable to plastic deformations under excessive torque. To investigate the basic characteristics of the proposed SMA mesh washer gear, a static load test was performed on the thickness of the SMA mesh washer and the rotation of the gear. Moreover, The microvibration measurement test demonstrated that the SMA mesh washer gear proposed in this study is effective for microvibration attenuation.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.595-600
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• 2006

GOCI is the core paryload of the geostationary satellite COMS(Communication, Ocean and Meteological Satellite) for ocean monitoring. It is scheduled to be launched at the end of 2008. GOCI observes ocean color around the Korean Peninsula over $2500km\times2500km$ area. It used tilted two-axis scan mechanism to observe entire field of view. In this work, the pointing stability of the tilted two-axis method is analyzed and compared with that of gimbal method. The analysis results show that tilted two-axis method gives great stability and it is adequate for geostationary payload. The results can also be used to determine and analyze the mechanism specifications.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.4
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• pp.93-98
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• 2019

On today, optical system are the next generation weapon systems being studied in many countries, starting from USA. One of the most important technologies in optical system is a high-speed automatic target tracking system that can continuously track high-speed moving small targets. This paper designs an automatic target tracking system based on a correlated trekker that is robust against rapid shape changes for fast moving targets and small targets at a distance. The proposed system showed about 98% success rate in response to the targets that are under a complex background such as drone, ranger, etc.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.82-82
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• 2023

홍수기 하천에서 유량측정은 예산, 인력, 안전 및 측정 시 편의성 등의 이유로 측정에 제한이 많다. 특히, 태풍 등으로 인한 호우사상 발생 시 위와 같은 문제로 홍수량 측정에 어려움이 따른다. 이러한 문제점을 개선하기 위해 Lee et al.(2021)은 드론과 전자파표면유속계의 기능을 융합한 DSVM(Dron and Surface Veloctity Meter using doppler radar) 측정방법을 개발하였다. 전자파표면유속계 측정의 제한 요소인 진동을 감소시키기 위해 댐퍼플레이트를 개발하였고 금강의 지류인 봉황천에 현장 적용을 통해 DSVM 측정방법의 실용성을 확인하였다. 기존 연구에서 DSVM 방법은 드론의 각 측선 이동을 위한 조종과 전자파표면유속계 측정의 제어를 측정자가 수행하였는데 본 연구에서는 통합 드론측정시스템(IDMS, Integrated Drone Measurement System) 개발을 통해 측정자의 조종 의존도를 줄임과 동시에 안전하고 정확한 유량측정을 위해 노력하였다. 기존 댐퍼플레이트의 상하 진동 흡수 기능뿐만 아니라 전자파표면유속계의 흔들림 현상 등 자세 제어 기능을 보완하기 3축 모터를 적용한 방수짐벌을 개발하여 측정 정확도를 향상시켰다. 미션컴퓨터 개발로 측정지점의 측정 임무정보를 DB화하여 각 측선별 헤딩, 고도, 이동 등 자동항법 기능과 기체의 안정화 이후 전자파표면유속계를 자동으로 제어하여 측정을 실시하는 기능을 구현하였다. 또한 통합 GCS(Ground Control System)를 통해 비행 및 측정에 대한 모든 정보를 확인하고 컨트롤 할 수 있게 하였다. 2022년 금산군(제원대교), 무주군(취수장), 경주시(서천교) 지점에서 홍수기 유량측정에 도입하여 중간단면적법, 지표유속법을 적용하여 통합드론측정시스템의 실용성을 검증 완료하였다. 2023년 현장에 18대의 통합 드론측정시스템을 도입하여 홍수기 유량측정에 활용할 계획이다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.21-30
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• 2022

This paper describes the design, manufacture, and testing of servos applicable to small tracking radars. First, Chapter 1 describes the necessity of this study. Chapter 2 describes the development of servos applicable to future tracking radars in small missile systems. Chapter 3 describes the design and test results for current control of brushed DC motors, brushless DC motors, and permanent magnet synchronous motors. And Chapter 4 describes the design and test results for speed control of the test wheel. And in Chapter 5, the results of the previous tests are summarized. In this paper, some pictures were intentionally blurred for security reasons, and the control result of test wheel was described, not the test with the developed gimbals.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.119-119
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• 2021

최근 국내에서는 이상기후변화로 인해 수환경 변화가 일어나고 있으며, 이로인해 하천이나 저수지에 조류의 과대성장이 빈번히 발생되고 있다. 조류의 과대성장으로 인해 조류가 생산하는 독성물질, 이취미 물질은 수질을 악화 및 생태계에 큰영향을 미치는 실정이다. 또한, 조류는 하천, 저수지에 넓은 분포로 발생하게 되며, 현재 조류 조사방법은 다양한 계측장비를 통해 조사를 진행하고 있으나, 조류를 직접 채취하여 검경하거나, 보트 또는 조사선에 센서를 부착하여 측정하기 때문에, 점 또는 선단위의 간혈적 조사가 진행된다. 따라 많은 인력과 시간이 소요된다. 국내에선 인력과 시간을 줄이기 위해 최근 위성영상과 드론을 활용한 조류 원격탐사 모니터링에 대한 연구가 많이 진행되고 있다. 본 연구에서는 안동댐 인근 예안교에서 드론과 초분광센서를 이용하여 초분광데이터를 수집 및 조류 맵핑을 진행하였다. 사용된 드론은 DJI사의 RGB드론과 M-600Pro를 사용하였으며, 초분광 센서는 CORNING사의 microHSITM 410 SHARK를 이용하였으며, 파장 400-1000 nm에서 NIR(visNIR)파장을 분석할 수 있다. 드론에 짐벌을 장착하여 초분광센서를 수표면과 평행하게 두고 촬영 및 영상을 수집하였다. 방사보정을 하기위해 영상을 촬영 구간에 방사 보정용 반사천을 두고 동시간에 같이 촬영 하여 방사보정을 진행하였다. 본 연구에서는 초분광센서와 드론을 활용하여 조류 맵핑에 대한 연구를 하기위해 시료를 채취하여 검경결과와 비교분석을 하였으며, 초분광영상 분석을 통해 조류 최적밴드비를 산정하고 조류 맵핑을 진행하여 촬영구간에 대한 2차원 조류 맵핑 제시하여 하천에 적용하고자 한다.

• Journal of Aerospace System Engineering
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• v.17 no.6
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• pp.9-15
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• 2023

In order to effectively prevent and respond to disasters, several techniques have been developed in which the pilot wearing a see-through Head Mounted Display (HMD) performs disaster-related rescue activities using images transmitted from an Unmanned Aerial Vehicle (UAV). However, these techniques have limitations in quickly determining and executing tasks appropriate to the on-site situation because the pilot cannot recognize the entire field in an integrated manner. In order to overcome these problems, we propose an AR based-interface technique that allows the rescuer wearing a see-through HMD to operate a UAV efficiently. Simulation results show that the proposed interface technique allows the rescuer wearing a see-through HMD to control the gimbal and flight of the UAV at a high speed based on finger gestures in a visibility situation.