• Journal of Navigation and Port Research
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• v.29 no.3 s.99
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• pp.175-180
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• 2005

A mariner feels the shiphandling difficulty when the vessel onboard passes through breakwater. Until now, the shiphandling difficulty of the mariner has not been taken into account in the layout of a pair of breakwater. This paper reproduced such a situation that shiphandling is difficult enough by using marine traffic flow simulation, it is assessed by using ES Model which is a quantitative model for evaluating the difficulty of shiphandling arising from maneuvering a ship in the restricted or congested waters. The results are as follows. (1) The change in the layout of a pair of breakwaters has little influence on the shiphandling difficulty. (2) If the width between breakwaters is the same. the speed of a ship affects the shiphandling difficulty. (3) The increase of the width decreases the shiphandling difficulty.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.1
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• pp.22-30
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• 2008

This paper deals with the nonlinear optimal control approach to helicopter maneuver problems using the indirect method. We apply a penalty function to the deviation from a prescribed trajectory to convert the system optimality to an unconstrained optimal control problem. The resultant two-point boundary value problem has been solved by using the multiple-shooting method. This paper focuses on the effect of the number of shooting nodes and initialization methods on the numerical solution in order to define the minimum number of shooting nodes required for numerical convergence and to provide a method increasing convergence radius of the indirect method. The results of this study can provide an approach to improve numerical stability and convergence of the indirect method when we solve the optimal control problems of an inherently unstable helicopter system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.6
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• pp.126-133
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• 2004

MRE-1 Dual Thruster Module(DTM), which will be used in KOMPSAT(Korea Multi-Purpose Satellite), can provide reliable and cost-effective means for attitude and maneuvering control system. Thruster heat shield, one of the main components of DTM, is designed to prevent the critical radiative heat exchange between thruster and satellite during firing. To overcome the manufacturing difficulties, a electroforming process is preferred to classical welding process. In this case, an inner diameter of a new shield will be decreased a little due to the change of manufacturing process. Therefore, the interference problem between thruster nozzle and heat shield is investigated through structural analysis and their results are described in this paper.

• Proceedings of KOSOMES biannual meeting
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• 2006.11a
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• pp.277-282
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• 2006

The purpose in having a control surface on a ship is to control the motion of the ship. The control surface may be composed entirely of a single movable surface or of a combination of fixed and movable portion A control surface has one sole function to perform in meeting its purpose, and that is to develop a control force in consequence of its orientation and movement relative to the water. The forces and moments generated as a result of this rotation and angle of attack then determine the maneuvering characteristics of the ship. In this paper the study of flapped rudder's 2-dimensional section was accomplished. Model tests had been carried out with different angles of attack of a main foil and flap's deflection angles to predict the performance of the flapped rudder and the 2 frame particle tracking method had been used to obtain the velocity distribution in the flow field $Re=2.8\times10^4$ had been used during the whole experiments and measured results had been compared with each other.

• Proceedings of KOSOMES biannual meeting
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• 2004.11a
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• pp.57-62
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• 2004

A mariner feels the ship-handling difficulty when the vessel onboard passes through breakwater. Until now, there is no a layout design of breakwater to take into account the ship-handling difficulty for the mariner. 11Us paper reproduced this situation which ship-handling is difficult by using marine traffic flow simulation, and it applied to Environmental Stress Model as the assessment model which is a quantitative model for evaluating the difficulty of ship-handling arising from restriction in maneuvering water areas and arising from traffic congestion The results are as follows. (1) The layout change of breakwater has little influence for reduction of ship-handling difficulty in the areas of vessel traffic volume. (2) In the situation of same breakwater width, difference of ship speed has an effect on decrease of ship-handling difficulty. (3) Expansion of breakwater width decreases ship-handling difficulty quantitatively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.172-178
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• 2015

The control moment gyroscope(CMG) which is well known as an effective high-torque-generating device is applicable to space vehicles, airplanes, ships, automobiles, robotics, etc. for attitude stabilization and maneuver. This paper deals with the overall details of 100Nm-class CMG development for various industrial applications, and provides the activities and results associated with the CMG system-level requirement analysis, the motor subsystem design/manufacturing/integration, the construction of ground support equipment, and the performance test and evaluation. The performance test reveals that the CMG generates the torque output more than 120Nm in as-designed operation of spin motor and gimbal motor.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.2
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• pp.108-115
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• 2015

Electro-mechanical actuator installed on aircraft consists of a decelerator which magnifies the torque in order to rotate an axis connected with aircraft control surface, a control section which controls the motor assembly through receiving orders from cockpit and a motor assembly which rotates the decelerator. Electro-mechanical actuator controls aircraft altitude, position, landing, takeoff, etc. It is an important part of a aircraft. Aircraft maneuvering causes vibrations to electro-mechanical actuator. Vibrations may result in structural fatigue. For that reason, it is necessary to analyze the system structural safety. In order to analyze the system structural safety. It is needed reasonable finite element model and structural response stress closed to real value. In this paper, analytic model is derived by using the simplified finite element model, and damping ratio which is closely related to response stress is derived by using modal test. So, we developed analytic model in less than 10 % error rate, compared with modal test. Vibration response stress close to real value was estimated from analytic model modified with modal experimental damping ratio. Estimation method for damping ratio with empirical formula was suggested partly. Finally, It was proved that electro-mechanical actuator had reasonable structure margin of safety at environmental random $3{\sigma}$ stress during life cycle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.515-522
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• 2012

CFIT(Controlled Flight Into Terrain) is one of the major causes of aircraft accidents. In order to solve this problem, GPWS(Ground Proximity Warning System) is used to generate terrain collision warning using the distance between the aircraft and the underneath ground. Since the GPWS uses the vertical clearance only, it frequently generates false warnings. In this study, a terrain/obstacle collision avoidance warning algorithm was developed for fast flying and highly maneuvering fighters using the flight status and the geographic information. This algorithm condsiders the overall delay in the aircraft reactive motion including the pilot's reaction time. The paper presents a detailed logic and test methods.

• Journal of Auto-vehicle Safety Association
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• v.11 no.2
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• pp.35-43
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• 2019

This paper describes the improved environment recognition algorithms using some type of sensors like LiDAR and cameras. Additionally, integrated control algorithm for an autonomous vehicle is included. The integrated algorithm was based on C++ environment and supported the stability of the whole driving control algorithms. As to the improved vision algorithms, lane tracing and traffic sign recognition were mainly operated with three cameras. There are two algorithms developed for lane tracing, Improved Lane Tracing (ILT) and Histogram Extension (HIX). Two independent algorithms were combined into one algorithm - Enhanced Lane Tracing with Histogram Extension (ELIX). As for the enhanced traffic sign recognition algorithm, integrated Mutual Validation Procedure (MVP) by using three algorithms - Cascade, Reinforced DSIFT SVM and YOLO was developed. Comparing to the results for those, it is convincing that the precision of traffic sign recognition is substantially increased. With the LiDAR sensor, static and dynamic obstacle detection and obstacle avoidance algorithms were focused. Therefore, improved environment recognition algorithms, which are higher accuracy and faster processing speed than ones of the previous algorithms, were proposed. Moreover, by optimizing with integrated control algorithm, the memory issue of irregular system shutdown was prevented. Therefore, the maneuvering stability of the autonomous vehicle in severe environment were enhanced.

• Journal of the Korea Institute of Building Construction
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• v.23 no.5
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• pp.629-638
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• 2023

This study introduces an innovative approach to monitor the whereabouts of workers within indoor construction settings. While traditional modalities such as GPS and NTRIP have demonstrated efficacy for outdoor localizations, their precision dwindles in indoor environments. In response, this research advocates for the adoption of Aruco markers. Leveraging computer vision technology, these markers facilitate the quantification of the distance between a worker and the marker, subsequently pinpointing the worker's instantaneous location with heightened accuracy. The methodology's efficacy was rigorously evaluated in a real-world construction scenario. Parameters including system stability, the influence of lighting conditions, the extremity of measurable distances, and the breadth of recognition angles were methodically appraised. System stability was ascertained by maneuvering the camera at a uniform velocity, gauging its marker recognition prowess. The impact of varying luminosity on marker discernibility was scrutinized by modulating the ambient lighting. Furthermore, the camera's spatial movement ascertained both the upper threshold of distance until marker recognition waned and the maximal angle at which markers remained discernible.