• Proceedings of the KIEE Conference
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• 1997.07b
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• pp.474-477
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• 1997

In this paper, an efficient attitude determination algorithm based on the Kalman Filter which combines earth/sun sensor data with gyro data in a mutually compensating manner is presented. Quaternion is used as the attitude state to save computation time and to prevent the gimbal-lock situation associated with Euler angles. Gyro data allows the use of the kinematic equation instead of space vehicle's dynamic equation which is usually based on approximation of the actual dynamics and inaccurate torque information. The gyro data are used to propagate the attitude through kinematic equation and the earth/sun sensor data are used to update the attitude and estimate the gyro bias. Simulation results for the KOMPSAT attitude determination system are presented.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.303-304
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• 2007

항공기, 차량, 유도탄 둥과 같은 동적인 플랫폼에서 표적을 추적하기 위해서 시선을 안정화하는 외부의 추적 루프와 내부의 안정화 루프(또는 속도 루프)가 있고, 또한 표적을 추적하기 전 표적을 지향하고 포착하기 위해 김발을 동체에 대해 일정한 각도로 유지하기 위한 위치 루프도가지고 있다. 일반적으로 안정화 루프는 각속도를 측정하기 위한 검출기로 자이로를 사용하고, 위치 루프는 김발각을 제어하기 위한 위치 검출기를 사용한다. 그러나 안정화 루프에 사용되는 자이로는 루프 성능을 최적으로 하기 위해서 고성능/고가의 자이로가 사용되는 단점이 있다. 따라서 본 논문에서는 위치 루프에 사용되는 위치 센서인 리졸버를 사용하여 고성능/고가의 자이로 센서 없이 안정화 루프를 설계하였고, 리졸버를 사용하여 설계된 안정화 루프가 동적인 플랫폼에 사용될 수 있는지 시뮬레이션 결과와 실험 결과를 통해 분석하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.99-100
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• 2016

드론이나 이동형 촬영장비에 장착된 카메라로부터 깨끗하고 안정된 영상을 획득하기 위해서는 짐벌시스템의 안정화기 설계가 필요하다. 짐벌시스템은 카메라 모듈을 지지하는 구조와 외부로 부터의 진동을 차단하면서 정확한 각도를 추종하는 안정화기로 구성된다. 이동형 촬영장비나, 비행중인 드론에는 매우 다양한 주파수 성분의 진동이 발생되는데, 이러한 진동을 제어하기 위하여 6자유도 운동방정식을 유도하고, 이 중에서 본 논문에서는 일반적으로 rolling, pitching, yawing 운동에 대해서는 PID 제어기를 사용하여 안정화를 제어하기만, 카메라종류나 짐벌시스템 구조가 바뀔 때 마다 PID 파라미터를 변경해야 되는 경우가 빈번하다. 본 논문에서는 이런 문제점을 개선하기 새로이 제기된 제어 기법인 지적 PID(intelligent PID) 제어를 통하여 진동제어를 수행하여 짐벌시스템의 안정화를 위한 제어기법을 제안하고자 한다.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.2
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• pp.13-22
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• 1997

Strapdown inertial navigation system(SDINS) is a navigational instruments necessary to guide and con- trol a free vehicle. In this study, an error analysis of mechanical parts is carried out for manufacturing a dynamically tuned gyroscope. The errors usually come from the tolerance in machining and assembly. In the error analysis, a criterion to be considered during designing and manufacturing is proposed by quanti- tatively analyzing the effect of DTG performance by tolerances. The theory of dynamic balancing is deduced and unbalance is reduced through experiment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.648-653
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• 2014

Fly-wheel, gimbal antenna, mechanical gyro and cryocooler with moving parts generate a micro-vibration during their on-orbit operation. For the acquisition of high quality image of observation satellite, additional technical efforts are required to reduce the micro-vibration level from the vibration sources. In this study, we proposed a passive isolation system combined with a tuned mass damper-type energy harvester to generate electrical energy from the micro-vibration which has always been subjected to useless isolation objectives. The feasibility of the system has been investigated through the numerical simulation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.85-92
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• 2020

Applications for the unmanned aerial vehicle (UAV) have expanded enormously in recent years. Of all its various technologies, the UAV's ability to take off and land in a moving environment is particularly required for military or oceanic usage. In this study, we develop a novel leveling platform that allows the UAV to stably take off and land even on uneven terrains or in moving environments. The leveling platform is composed of an upper pad and a lower mobile base. The upper pad, from which the UAV can take off or land, is designed in the form of a 2 degrees of freedom (DOF) gimbal mechanism that generates the leveling function. The lower mobile base has a four-wheel drive structure that can be operated remotely. We evaluate the developed leveling platform by performing extensive experiments on both the horizontal terrain and the 5-degree ramped terrain, and confirm that the leveling platform successfully maintains the horizontal pose on both terrains. This allows the UAV to stably take off and land in moving environments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.3
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• pp.323-330
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• 2016

This paper describes real-time unbalance moment compensation method for line of sight(LOS) stabilization control systems. The factors of system inertia, frictions and unbalance moment affect the control accuracy of drive systems that are equipped to on the move(OTM) platforms requiring LOS stabilization function. In case of the unbalance moment among those factors is continuously changed as variation of relative angle between gravity vector and drive torque vector. Then, consideration of the effect in real-time is very complicate. Therefore, its effect should be designed to be minimized, however, designing it almost zero is impossible in real condition. In other words, it is hard to achieve target performance overcoming stability issue of highly unbalanced systems. To solve these problems, this paper proposes calculation method of unbalance moment by using measured sensor data for LOS stabilization control and its use for control compensation. Also, kinematical converting process and control structure for compensation are explained. The effectiveness of the proposed method as variation of unbalance moment is verified under simulation circumstance modeled by assuming LOS control system with 2-axis gimbal structure.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.391-400
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• 2016

In satellite operations, stable maneuvering of a satellite's onboard antenna to prevent undesirable vibrations to the satellite body is required for high-quality high-resolution images. For this reason, the onboard antenna's angular rate is typically minimized while still satisfying the system requirement that limits the speed of the onboard antenna. In this study, a simple yet effective method, called the ground station searching method, is proposed to reduce the angular rate of a satellite's onboard antenna. The performance of the proposed method is tested using real flight data from the KOMPSAT-3 satellite. Approximately 83% of arbitrarily selected real flight scenarios from 66 test cases show reductions in the onboard antenna's azimuth angular rates. Additionally, reliable solutions were consistently obtained within a reasonably acceptable computation time while generating an onboard antenna tracking profile. The obtained results indicate that the proposed method can be used in real satellite operations and can reduce the operational loads on a ground operator. Although the current work only considers the KOMPSAT-3 satellite as a test case, the proposed method can be easily modified and applied to other satellites that have similar operational characteristics.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.639-646
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• 2022

Landing site searching algorithms are developed for a quadrotor using a depth map in unknown environment. Guidance and control system of Unmanned Aerial Vehicle (UAV) consists of a trajectory planner, a position and an attitude controller. Landing site is selected based on the information of the depth map which is acquired by a stereo vision sensor attached on the gimbal system pointing downwards. Flatness information is obtained by the maximum depth difference of a predefined depth map region, and the distance from the UAV is also considered. This study proposes three landing methods and compares their performance using various indices such as UAV travel distance, map accuracy, obstacle response time etc.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.9
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• pp.1312-1319
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• 2022

This paper defines an effectiveness index for optical continuous observation of unknown space objects and presents a range of design variables combinations that can satisfy the effectiveness index from a telescope/mount control system perspective using integrated simulation. The overall system-level simulation was implemented and the tracking performance was analyzed by considering design variables such as target position prediction and frame rate, image processing time and measurement error, target trajectory characteristics, and maneuver performance of mount gimbal. As a result of the analysis, it was confirmed that the continuous tracking performance of the optical observation system is dependent on the combination of frame rate and mount maneuver performance. In a situation where an optical observation system is designed or a similar system is implemented using COTS, an appropriate combination of parameters between design variables can be found through effectiveness analysis simulation as in this study.