Dae-Woo Lee

Autonomous flight test using angle of UAV’s velocity vector

This paper describes the result of the guidance using the heading angle from the magnetic heading vector and velocity vector when autonomous flight is performed by the point navigation guidance. The guidance logic makes difference between the line of sight angle and UAVpsilas heading angle as an error using PD controller. In fixed-wing, the accuracy of convergence is influenced by perturbation like the crosswind, and the flight path to the next waypoint affected also by the states of approach. Therefore, the robust guidance is needed at autonomous flight. When flight using magnetic heading vector, the result is shown that the vehicle does not follow a expected path even though heading vector of UAV is pointing at waypoint. Moreover, the vehicle does not pass the waypoint but the UAV has circular flight path sometimes. When flight using velocity vector, from the result of flight, the flight performed with smaller radius at waypoint, even if side slip was occurred. Considering the UAVpsilas usage and ability, the flight path is significantly influenced by perturbation in windy area or closed to each waypoint. It causes a lot of losses in mission performance or operation of UAV, so autonomous flight needed using guidance performed by velocity vector based on flight path in UAV.

A Study on the Dynamic Characteristics of Airship Through the Flight Test

Nowadays, many kinds of research for airship have being studied with increase of interests in airship. But these make little progress even now. In flight test, the data acquisition from the actual flight test has lots of difficulties because the airship dynamic response is slow and sensitive to external environment. In this paper, through the actual flight test, appropriateness of the mathematical dynamic model was presented by showing the test results in various conditions. The turning, the acceleration, and the deceleration motions were tested and analyzed.

Fitness Change of Mission Scheduling Algorithm Using Genetic Theory According to the Control Constants

In this paper, the final fitness results of the satellite mission scheduling algorithm, which is designed by using the genetic algorithm, are simulated and compared with respect to the control constants. Heuristic algorithms, including the genetic algorithm, are good to find global optima, however, we have to find the optimal control constants before its application to a problem, because the algorithm is strongly effected by the control constants. In this research, the satellite mission scheduling algorithm is simulated with different crossover probability and mutation probability, which is major control constant of the genetic algorithm.

Optimization of the Satellite Mission Scheduling Using Genetic Algorithms

A mission scheduling optimization algorithm according to the purpose of satellite operations is developed using genetic algorithm. Satellite mission scheduling is making a timetable of missions which are slated to be performed. It is essential to make an optimized timetable considering related conditions and parameters for effective mission performance. Thus, as important criterions and parameters related to scheduling vary with the purpose of satellite operation, those factors should be fully considered and reflected when the satellite mission scheduling algorithm is developed. The developed algorithm in this study is implemented and verified through a comprehensive simulation study. As a result, it is shown that the algorithm can be applied into various type of the satellite mission operations.

Re-entry Survivability and On-Ground Risk Analysis of Low Earth Orbit Satellite

LEO(Low Earth Orbit) Satellite which is discarded should be reentered to atmosphere in 25 years by `25 years rule` of IADC(Inter-Agency Space Debris Coordination Committee) Guidelines. If the parts of satellite are survived from severe aerothermodynamic condition, it could damage to human and property. South Korea operates KOMPSAT-2 and STSAT series as LEO satellite. It is necessary to dispose of them by reentering atmosphere. Therefore this paper analyze the trajectory, survivability, casualty area and casualty probability of a virtual LEO satellite using ESA(European Space Agency)`s DRAMA(Debris Risk Assesment and Mitigation Analysis) tool. As a result, it is noted that casuality area is and casualty probability is 5.9614E-03 then will be survived 198.831kg.

3D depth estimation for target region using optical flow and mean-shift algorithm

Tracking in the image is important to get information in many difference sides. Also, we can get more useful information using only image. However, 2D image isnpsilat enough for getting more information. The purpose of this study is realization the 3D virtual target and surround environment models using 3D locate information. In the image, itpsilas hard to distinguish between target and surround. Mean-shift algorithm for target tracking sets ROI and indicates the target from surround. Subspace method and another method which uses optical flow and camera motion give 3D information. The same thing of both methods is that optical flow used for depth estimation. Subspace method uses residual function from least square method. In the other side, another method using region optical flow has formulas so easier to apply. This paper presents the first step of getting 3D locate information and also, paper includes comparing algorithms.

Vision Based Estimation of 3-D Position of Target for Target Following Guidance/Control of UAV

This paper describes methods to estimate 3-D position of target with respect to reference frame through monocular image from unmanned aerial vehicle (UAV). 3-D position of target is used as information for surveillance, recognition and attack. In this paper. 3-D position of target is estimated to make guidance and control law, which can follow target, user interested. It is necessary that position of target is measured in image to solve 3-D position of target. In this paper, kalman filter is used to track and output position of target in image. Estimation of target`s 3-D position is possible using result of image tracking and information of UAV and camera. To estimate this, two algorithms are used. One is methode from arithmetic derivation of dynamics between UAV, carmer, and target. The other is LPV (Linear Parametric Varying). These methods have been run on simulation, and compared in this paper.

Cerebrospinal fluid rhinorrhoea as a complication of endoscopic endonasal reduction of blowout fractures.

BACKGROUND Unless the orbital contents are supported, the insertion of nasal packing material during endoscopic endonasal surgery may cause serious intracranial complications such as cerebrospinal fluid leakage. METHODS Case report and literature review. RESULTS We report a patient with iatrogenic cerebrospinal fluid rhinorrhoea caused by intracranial entry of a Silastic sheet inserted into the nasal cavity. This skull defect and the surrounding skull base were successfully reconstructed in a multilayer fashion via an endoscopic endonasal approach. CONCLUSION This case highlights the need for caution when inserting nasal packing material. During endoscopic endonasal reduction of blowout fractures, great care must be taken to support the orbital contents, in order to avoid serious intracranial complications such as cerebrospinal fluid leakage.

Analysis of the Collision Probability and Mission Environment for GEO

The increasing number of orbital debris objects is a risk for satellite operations due to space activities over past 50 years since launched Sputnik. The GEO (Geostationary Earth Orbit), where COMS-1 is being operated since last June 2010, has more and more risks that collide with space debris or another satellites. In this paper, as a preliminary study about GEO satellite collision probability and operations environment, collision probability between COMS-1 and RADUGA 1-7 that is one of Russian military communication satellites is investigated and analyzed. Indeed, the space environment including space debris of COMS-1 is presented. As a result, it is noted that collision probability between two satellites using NORAD TLEs on 14th Jan. 2011 was 2.8753E-07 in case that position uncertainty was assumed 10km. Particularly, the largest proportion of space debris around COMS-1`s mission orbit is meteoroids.The increasing number of orbital debris objects is a risk for satellite operations due to space activities over past 50 years since launched Sputnik. The GEO (Geostationary Earth Orbit), where COMS-1 is being operated since last June 2010, has more and more risks that collide with space debris or another satellites. In this paper, as a preliminary study about GEO satellite collision probability and operations environment, collision probability between COMS-1 and RADUGA 1-7 that is one of Russian military communication satellites is investigated and analyzed. Indeed, the space environment including space debris of COMS-1 is presented. As a result, it is noted that collision probability between two satellites using NORAD TLEs on 14th Jan. 2011 was 2.8753E-07 in case that position uncertainty was assumed 10㎞. Particularly, the largest proportion of space debris around COMS-1’s mission orbit is meteoroids.

Analysis of the Collision Probability and Mission Environment for Space debris

The increasing number of orbital debris objects is a risk for satellites because of past 50 years space activities. The LEO (low earth orbit) where KOMPSAT-2 and KOMPSAT-5 are operated is including about 84% of the total space debris. Thus, the space missions need to consider the space debris. In this paper, we analysis the orbit characteristics and spatial density of space debris about KOMPSAT-2 that is in activity and KOMPSAT-5 that will be launched in 2010. Analyzed probability damage and collision with space debris are also performed. ESA MASTER2005 and of NASA DAS2.0 are used to analysis KOMPSAT mission environment. As a result, it is noted that KOMPSAT-2`s collision probability was far more than KOMPSAT-5 because KOMPSAT-2`s orbit has high density composed space debris.