• Journal of Astronomy and Space Sciences
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• 제34권4호
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• pp.331-342
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• 2017

To ensure the successful launch of the Korea pathfinder lunar orbiter (KPLO) mission, the Korea Aerospace Research Institute (KARI) is now performing extensive trajectory design and analysis studies. From the trajectory design perspective, it is crucial to prepare contingency trajectory options for the failure of the first lunar brake or the failure of the first lunar orbit insertion (LOI) maneuver. As part of the early phase trajectory design and analysis activities, the required time of flight (TOF) and associated delta-V magnitudes for each recovery maneuver (RM) to recover the KPLO mission trajectory are analyzed. There are two typical trajectory recovery options, direct recovery and low energy recovery. The current work is focused on the direct recovery option. Results indicate that a quicker execution of the first RM after the failure of the first LOI plays a significant role in saving the magnitudes of the RMs. Under the conditions of the extremely tight delta-V budget that is currently allocated for the KPLO mission, it is found that the recovery of the KPLO without altering the originally planned mission orbit (a 100 km circular orbit) cannot be achieved via direct recovery options. However, feasible recovery options are suggested within the boundaries of the currently planned delta-V budget. By changing the shape and orientation of the recovered final mission orbit, it is expected that the KPLO mission may partially pursue its scientific mission after successful recovery, though it will be limited.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권1호
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• pp.358-377
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• 2015

In this paper, we propose a novel approach for trajectory recovery. Our system uses a triangulation procedure for skeletonization and graph theory to extract the trajectory. Skeletonization extracts the polyline skeleton according to the polygonal contours of the handwritten characters, and as a result, the junction becomes clear and the characters that are touching each other are separated. The approach for the trajectory recovery is based on graph theory to find the optimal path in the graph that has the best representation of the trajectory. An undirected graph model consisting of one or more strokes is constructed from a polyline skeleton. By using the polyline skeleton, our approach accelerates the process to search for an optimal path. In order to evaluate the performance, we built our own dataset, which includes testing and ground-truth. The dataset consist of thousands of handwritten characters and word images, which are extracted from five handwritten documents. To show the relative advantage of our skeletonization method, we first compare the results against those from Zhang-Suen, a state-of-the-art skeletonization method. For the trajectory recovery, we conduct a comparison using the Root Means Square Error (RMSE) and Dynamic Time Warping (DTW) in order to measure the error between the ground truth and the real output. The comparison reveals that our approach has better performance for both the skeletonization stage and the trajectory recovery stage. Moreover, the processing time comparison proves that our system is faster than the existing systems.

• 한국멀티미디어학회논문지
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• 제18권5호
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• pp.575-582
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• 2015

Obtaining the complete trajectory of the object is a very important task in computer vision applications, such as video surveillance. Previous studies to recover the trajectory between two disconnected trajectory segments, however, do not takes into account the object's motion characteristics and uncertainty of trajectory segments. In this paper, we present a novel approach to recover the trajectory between two disjoint but associated trajectory segments, called goal-directed tracking. To incorporate the object's motion characteristics and uncertainty, the goal-directed state equation is first introduced. Then the goal-directed tracking framework is constructed by integrating the equation to the object tracking and trajectory linking process pipeline. Evaluation on challenging dataset demonstrates that proposed method can accurately recover the missing trajectory between two disconnected trajectory segments as well as appropriately constrain a motion of the object to the its goal(or the target state) with uncertainty.

• Journal of Power Electronics
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• 제16권2호
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• pp.584-597
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• 2016

This paper focuses on an improvement in the transient performance of Boost converters when the load changes abruptly. This is achieved on the basis of the nature trajectory in Boost converters. Three key aspects of the transient performance are analyzed including the storage energy change law in the inductors and capacitors of converters during the transient process, the ideal minimum voltage deviation in the transient process, and the minimum voltage deviation control trajectory. The changing relationship curve between the voltage deviation and the recovery time is depicted through analysis and simulations when the load suddenly increases. In addition, the relationship curve between the current fluctuation and the recovery time is obtained when the load suddenly decreases. Considering the aspects of an increasing and decreasing load, this paper proposes the transient performance synthetic optimized trajectory and control laws. Through simulation and experimental results, the transient performances are compared with the other typical three control methods, and the ability of proposed synthetic trajectory and control law to achieve optimal transient performance is verified.

• Journal of Astronomy and Space Sciences
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• 제40권4호
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• pp.217-224
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• 2023

The Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, successfully entered its mission orbit on December 27, 2022 (UTC), and is currently performing its mission smoothly. To mitigate potential contingencies during the flight and to navigate the spacecraft into the desired lunar orbit, the KPLO flight dynamics (FD) team analyzed major trajectory-related contingencies that could lead to the violation of mission requirements and prepared operational procedures from the perspective of trajectory and FD. This paper presents the process of preparing contingency trajectory operations for the KPLO, including the identification of trajectory contingencies, prioritization results, and the development of recovery plans and operational procedures. The prepared plans were successfully applied to address minor contingencies encountered during actual operations. The results of this study will provide valuable insights to FD engineers preparing for space exploration mission operations.

• 한국정밀공학회지
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• 제29권4호
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• pp.417-425
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• 2012

This paper presents reference ZMP trajectory generation and implementation for a biped robot via linear inverted dumbbell model (LIDM), which can consider the effect of external momentum on the center of mass (COM) of robot. Based on a reference ZMP trajectory derived by using LIDM, a base trajectory is proposed not only to make the locomotion of robot similar to that of human but also to facilitate its implementation and tuning. In order to realize a dynamic walking using the proposed trajectory, compliance, impedance and ZMP tracking controllers are adopted together. Extensive experiments show that the proposed locomotion of a biped robot is stable and also, similar to that of human. Further researches on balance recovery of a biped robot will be carried out to guarantee its robust locomotion in combination with the proposed trajectory.

• Journal of Chest Surgery
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• 제32권5호
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• pp.422-427
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• 1999

배경: 빈맥을 이용하여 심부전을 만드는 방법은 확장성 심근증 모델 중에서 가장 좋은 방법으로 심장에 외과적 손상 혹은 약물의 독성을 최소화할 수 있고 사람의 심부전에 가장 가까우며 조작하기 쉬운 장점이 있다. 새로운 술식의 효과를 검증하기 위하여 심부전이 진행중인 모델에서 동물실험을 시행하는 것은 결과를 얻기 전에 실패할 가능성이 높다. 심부전의 진행을 중지시킨 회복궤도의 변화를 비교하는 방법은 심부전 악화에 의한 사망률을 줄일 수 있는 새로운 방법이지만 빈맥 조작 기술에 따라 저자마다 상당한 차이가 있어 이에대한 자료의 정립이 필요한 실정이다. 대상 및 방법: 21마리의 개(체중 25-35kg)를 대상으로 1)정상의 심장, 2) 심부전 심장, 3) 회복기 4주 4) 회복기 8주 등 4가지로 나누었다. 전신마취하에 우심실첨부에 박동기 전극을 삽입하여 빈맥은 처음 170회/분부터 매주 20회씩 프로그래머를 이용하여 증가시켰다. 4주 후 심부전이 발생하면 8주간의 회복기 동안 회복 궤도를 추적하였다. 심장의 크기와 혈역학적 변화를 관찰하고자 초음파는 2주마다, Swan-Ganz 도자와 열희석법은 4주마다 검사를 실시하여 이완기 말기 좌심실 체적, 수축기말기 좌심실 체적, 심박출율, 중심정맥압, 폐동맥압, 폐동맥 쐐기압, 우심실압, 일회박출량 등을 측정하였으며, 정상과 심부전 심장 상태에서 혈중 카테콜라민을 측정하였다. 그 외 심전도 및 대퇴동맥 도자를 넣어 맥박수, 혈압을 측정하였다. 정상심장, 심부전 심장, 회복기 4주 및 8주에서 측정한 값은 평균$\pm$표준편차로 표시하였다. 결과: 4마리(20%)가 심부전에 의한 합병증으로 사망하였다. 이완기 말기 좌심실 체적은 측정시기에 따라 40.8$\pm$7.4, 82.1$\pm$21.1, 59.9$\pm$7.7, 46.5$\pm$6.5ml로 수축기말기 좌심실 체적과 비슷한 변화양상을 보였으며 심박출율은 50.6$\pm$4.1, 17.5$\pm$5.8, 36.3$\pm$7.3, 41.5$\pm$2.4%였다. 혈압과 맥박은 의의 있는 양상을 보이지 않았으며 중심정맥압, 우심실압, 폐동맥압, 폐동맥 쐐기압 등은 심부전 시에 의의 있는 증가를 보이다가 회복기에는 감소하는 양상을 볼 수 있다. 일회박출량은 21.5$\pm$8.2, 12.3$\pm$3.5, 17.9$\pm$4.6, 15.5$\pm$3.4ml으로 회복기에 심부전 상태로부터 회복하는 경향을 볼 수 있었다. 혈중 카테콜라민은 정상 133.3$\pm$60.0pg/dL에서 심부전 시에는 479.4$\pm$327.3pg/dL로 증가를 보였다(p=0.008). 결론: 빈맥을 이용한 심부전 모델은 외과적손상이 적고, 병의 정도를 임의로 조절할 수 할 수 있는 간편한 방법이다. 회복기에는 심기능 및 심장비대가 회복하는 경향을 보이므로 향후 새로운 술식의 평가를 위하여 회복 궤도를 이용하는 경우 실험 동물의 심부전 악화에 의한 사망율을 줄일 수 있는 새로운 방법이다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1992년도 춘계학술대회 논문집
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• pp.369-373
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• 1992

Force control of a planar two-link structurally flexible robotic manipulator is considered in this study. The dynamic model is obtained by using the extended Hamilton's principle and the Galerkin criterion. A method is pressented toobtain the linearized equations of motion in Cartesian space for use in designing the control system. The approachto solving the control problem is to use feedforward and feedback control torques. The feedforward torques maneuver the flexible manipulatro along a nominal trajectory and the feedback torques minimize any deviations from the nominal trajectory. The linear quadratic Gaussian/loop transfer recovery (LQG/LTR) design methodology is explotied to design a robust feedback control system that can handle modeling errors and sensor noise, and operates on Cartesian space trajectory errors. The Lqg/LTR compenstaor together with a feedforward ollp is used to control the flexible manipulator. Simulated results are presented for a numerical example.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2006년도 추계 학술대회논문집
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• pp.89-92
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• 2006

Aerodynamic heating temperature shown in a NASA's sounding rocket test data was reproduced with CFD technique, comparing with those with analytical method CFD made heat transfer rates and recovery temperatures as the flight trajectory, which made it possible to calculate the wall temperature of rocket. The predicted wall temperature was compared with analytically predicted temperatures. Both the temperatures were compatible although their recovery temperature and heat transfer rates are a little different.

• International Journal of Contents
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• 제11권3호
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• pp.7-13
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• 2015

One of the biggest problems of skeletonization is the occurrence of distortions at the junction point of the final binary image. At the junction area, a single point usually becomes a small stroke, and the corresponding trajectory task, as well as the OCR, consequently becomes more complicated. We therefore propose an adaptive post-processing method that uses an adaptive threshold technique to correct the distortions. Our proposed method transforms the distorted segments into a single point so that they are as similar to the original image as possible, and this improves the static handwriting images after the skeletonization process. Further, we attained promising results regarding the usage of the enhanced skeletonized images in other applications, thereby proving the expediency and efficiency of the proposed method.