• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.5
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• pp.416-422
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• 2016

This paper presents preliminary performance analysis of a satellite formation flying testbed, which is under development by Astrodynamics and Control Laboratory, Department of Astronomy, Yonsei University. A model reference adaptive controller (MRAC) with a first-order reference model is chosen to enhance the response of reaction wheel system which is subject to uncertainties caused by unmodelled dynamics and measurement noise. In addition, an on-line parameter estimation (OPE) technique based on the least square is combined to eliminate the effect of angular measurement noise by estimating the moment of inertia. Both numerical simulations and hardware experiments with MRAC support the effectiveness and applicability of the adaptive control scheme, which maintains the tracking error below $0.25^{\circ}$ for the entire time span. However, the high frequency control input generated in hardware experiment strongly suggests design modifications to reduce the effect of deadzone.

• Journal of Convergence for Information Technology
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• v.7 no.5
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• pp.137-148
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• 2017

Recently, researchers are actively addressed to utilize Unmanned Aerial Vehicles(UAV) for military and industry applications. One of these applications is to trace the preceding flight when it is necessary to track the route of the suspicious reconnaissance aircraft in secret, and it is necessary to estimate the attitude of the target flight such as Roll, Yaw, and Pitch angles in each instant. In this paper, we propose a method for estimating in real time the attitude of a target aircraft using the video information that is provide by an external camera of a following aircraft. Various image processing methods such as color space division, template matching, and statistical methods such as linear regression were applied to detect and estimate key points and Euler angles. As a result of comparing the X-plane flight data with the estimated flight data through the simulation experiment, it is shown that the proposed method can be an effective method to estimate the flight attitude information of the previous flight.

• The KIPS Transactions:PartB
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• v.17B no.5
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• pp.355-362
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• 2010

Face tracking is to estimate the motion of a non-rigid face together with a rigid head in 3D, and plays important roles in higher levels such as face/facial expression/emotion recognition. In this paper, we propose an AAM-based face tracking algorithm. AAM has been widely used to segment and track deformable objects, but there are still many difficulties. Particularly, it often tends to diverge or converge into local minima when a target object is self-occluded, partially or completely occluded. To address this problem, we utilize the scale invariant feature transform (SIFT). SIFT is an effective method for self and partial occlusion because it is able to find correspondence between feature points under partial loss. And it enables an AAM to continue to track without re-initialization in complete occlusions thanks to the good performance of global matching. We also register and use the SIFT features extracted from multi-view face images during tracking to effectively track a face across large pose changes. Our proposed algorithm is validated by comparing other algorithms under the above 3 kinds of occlusions.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.04a
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• pp.562-565
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• 2010

시각기반 증강현실 시스템의 구현을 위해서는 입력되는 카메라영상의 프레임을 매번 특징점을 추출하고 패턴 매칭 과정을 반복하는 것은 저 사양의 모바일 기기에서는 적합하지 않다. 본 논문에서는 이러한 문제점을 해결 하고자 카메라영상에서 패턴이 한번 인식되게 되면 그 이후의 영상에 대해서는 패턴 인식과정을 생략하고 이전 영상에서 매칭된 특징점을 광류 기반 추적기법을 사용하여 추적하도록 한다. 또한 패턴 추적 절차의 수행 중 추적이 실패하여 생기는 특징점 소실 문제는 정확한 호모그래피 행렬과 카메라 자세 추정을 어렵게 하는데 이러한 문제를 해결하도록 하는 패턴 추적의 성공 또는 실패는 판단하는 기준을 세워 모바일 기기에서 빠르게 동작하도록 하는 광류 추적 기법을 사용한 자연 특징 추적 기반 증강현실 시스템을 제안한다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.6
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• pp.75-83
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• 2007

A model based approach of tracking the limbs of a walking human subject is proposed in this paper. The tracking process begins by building a data base composed of conditional probabilities of motions between the limbs of a walking subject. With a suitable amount of video footage from various human subjects included in the database, a probabilistic model characterizing the relationships between motions of limbs is developed. The motion tracking of a test subject begins with identifying and tracking limbs from the surveillance video image using the edge and silhouette detection methods. When occlusion occurs in any of the limbs being tracked, the approach uses the probabilistic motion model in conjunction with the minimum cost based edge and silhouette tracking model to determine the motion of the limb occluded in the image. The method has shown promising results of tracking occluded limbs in the validation tests.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.166.2-166.2
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• 2012

국내에서 개발한 고기동 저궤도 위성이 일본 다네가시마 우주센터에서 2012년 5월 18일 발사되었다. 자세제어계는 위성의 임무수행을 완수할 수 있도록 발사 후부터 위성 수명 기간 동안 자세명령을 생성하고 제어 및 결정을 하며, 궤도 조정과 모멘텀 덤핑등의 임무를 수행한다. 이러한 임무 수행을 가능하게 하기 위해 자세제어계는 적절한 센서와 구동기 조합을 사용하여 추력기 기반 안전모드, 궤도 조정을 위한 Del-V Burn 기동 모드, 태양지향 서브모드 및 목표지향 서브모드 등을 설계했다. 고기동 위성의 초기 운용 중 자세제어계는 자세제어계 하드웨어의 초기 구동 및 점검을 수행하고 설계한 각 모드의 기능과 성능 확인을 수행하게 된다. 본 연구는 성공적으로 완료한 자세제어계 하드웨어의 초기 점검 결과를 소개하는 것이 목적이다. 초기 운용은 위성이 발사된 직후 탑재컴퓨터가 깨어나면서부터 시작되는데, 발사 후 최초 접속시 추력기 기반 안전모드에서 태양 획득 성능 및 제어 성능을 확인한 후 정상 상태 모드인 태양지향 자세로 전환하기 위해 자세제어계 하드웨어인 별 추적기, 자기토커, 반작용휠의 초기 구동 및 점검을 수행하였다. 본 연구에서는 각 하드웨어의 초기 구동 점검과 성능 및 기능 요구조건 만족에 대한 성능 분석 결과를 정리하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.4
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• pp.327-334
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• 2013

In August 2012 the first CanSat competition was hosted by the Satellite Research Center of KAIST under auspice of the Ministry of Education, Science and Technology. The present authors team won the first prize in the university session. In this paper the overall procedure of the CanSat project presented from the conceptual design stage to the final launch test. As the compulsory mission CanSat should send GPS data and attitude information to the ground station which in practice was performed via Bluetooth channel. In addition our CanSat is designed to trace the sun for the solar panels supplying electric power of satellite. IMU and servo motors are used for the attitude control in order that the solar sensor of the CanSat is always direct towards the sun. Launching of CanSat was simulated by dropping from a balloon at the height of around 150m via parachute. Launching test results showed that the attitude control of the CanSat and its solar sensing function were successful.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.217.1-217.1
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• 2012

현존하는 저궤도위성의 S-Band 관제채널은 대부분 RH 또는 LH 편파를 사용한다. 그러나 다목적실용위성 3호와 같이 RH와 LH 편파를 동시에 사용하는 위성의 경우 위성추적을 위해 사용되어지는 지상안테나는 RH와 LH 편파를 동시에 수신하여야할 뿐만 아니라 편파변경시점에 따라 송신출력의 편파가 변경되어야하기 때문에 지상에서 위성으로 명령을 전송할 수 있는 송신가능시간(Command Window)에 영향을 미친다. 이러한 저궤도위성의 RH와 LH 편파의 신호세기는 위성체의 자세 및 운영방법에 따라 결정되어지기 때문에 다양한 형태의 편파수신경향성을 나타낸다. 따라서 이러한 영향을 최소화하기 위하여 지상안테나는 RH 및 LH 편파에 대하여 자동추적기능을 수행하여 위성을 추적하게 된다. 지상안테나의 자동추적기능은 수신되는 신호세기를 순간적으로 비교하여 가장 큰 세기의 신호가 수신될 수 있도록 제어하는 기술로서 수신신호의 형태에 따라 영향을 받으며 이 때 발생하는 오차는 위성추적에 지대한 영향을 미친다. 또한 편파가 변경되는 시점에서는 자동추적오차가 증가하게 되는 경향을 나타나게 된다. 따라서 본 논문에서는 다양한 형태로 동시 수신되는 RH 및 LH 편파의 자동추적오차를 분석하여 송신가능시간(Command Window) 및 수신신호에 어느 정도 영향을 미치는지에 대하여 분석하였으며 본 영향을 최소화할 수 있는 방법에 대하여 기술하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.537-538
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• 2016

Recently, modern people a lot of frequency of work and seat life by academic is increased, addictive spine for the wrong attitude and the wrong habits are many pelvic disease occurrence. Therefore, in order to induce continuous correct posture to prevent this, the system that can be induced to determine the posture information based on the seating information is requested. In this paper, when the development and inappropriate attitude of the device that is capable of tracking measurement in order to evaluate the attitude stability is detected, let your users know, to correct their attitude through the real-time monitoring It was implemented of categorize to help application.

• KIPS Transactions on Computer and Communication Systems
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• v.11 no.5
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• pp.157-166
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• 2022

Exercise is necessary for a healthy life, but it is recommended that it be conducted in a non-face-to-face environment in the context of an epidemic such as COVID-19. However, in the existing non-face-to-face exercise content, it is possible to recognize exercise movements, but the process of interpreting and providing feedback information is not automated. Therefore, in this paper, to solve this problem, we propose a method of creating a formalized rule to track the contents of exercise and the motions that constitute it. To make such a rule, first make a rule for the overall exercise content, and then create a tracking rule for the motions that make up the exercise. A motion tracking rule can be created by dividing the motion into steps and defining a key frame pose that divides the steps, and creating a transition rule between states and states represented by the key frame poses. The rules created in this way are premised on the use of posture and motion recognition technology using motion capture equipment, and are used for logical development for automation of application of these technologies. By using the rules proposed in this paper, not only recognizing the motions appearing in the exercise process, but also automating the interpretation of the entire motion process, making it possible to produce more advanced contents such as an artificial intelligence training system. Accordingly, the quality of feedback on the exercise process can be improved.