• Journal of Ocean Engineering and Technology
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• v.33 no.1
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• pp.50-60
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• 2019

Recently, problems with excessive vibration of the radar masts of large bulk carriers and crude oil tankers have frequently been reported. This paper explores a design method to avoid the resonance of a radar mast installed on a large ship using various design of experiment (DOE) methods. A local vibration test was performed during an actual sea trial to determine the excitation sources of the vibration related to the resonant frequency of the radar mast. DOE methods such as the orthogonal array (OA) and Latin hypercube design (LHD) methods were used to analyze the Pareto effects on the radar mast vibration. In these DOE methods, the main vibration performances such as the natural frequency and weight of the radar mast were set as responses, while the shape and thickness of the main structural members of the radar mast were set as design factors. From the DOE-based Pareto effect results, we selected the significant structural members with the greatest influence on the vibration characteristics of the radar mast. Full factorial design (FFD) was applied to verify the Pareto effect results of the OA and LHD methods. The design of the main structural members of the radar mast to avoid resonance was reviewed, and a normal mode analysis was performed for each design using the finite element method. Based on the results of this normal mode analysis, we selected a design case that could avoid the resonance from the major excitation sources. In addition, a modal test was performed on the determined design to verify the normal mode analysis results.

• Journal of the Korea Society of Computer and Information
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• v.14 no.8
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• pp.59-64
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• 2009

This paper is intended to study how well the routing protocol supplied in wireless mesh networks can evade interference path along the applied routing metric. Wireless mesh networks, unlike existing network techniques, has the characteristics that node movement is less and energy effect is limited. Therefore. this type of network requires path configuring technique to reflect such network characteristics and new routing metric to determine proper path. Routing metric proposed recently is designed to produce link quality accurately, but it configures path not considering the traffic situation of adjacent nodes. Thus. this technique has the problems of reduced transfer rate and delay between terminals occurring due to frequent traffic chaos by the interference of adjacent nodes. Therefore, this paper proposes metric that configures routing path by finding like metric that can transfer data effectively by considering the traffic situation of adjacent nodes. We confirmed through simulation that the proposed routing metric reduces the delay between terminals via the path that evades the traffic interference of adjacent node.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.371-374
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• 2021

자율주행 기술이 급속도로 발전하고 있지만, 자율주행 레이싱 기술과 관련 산업은 전세계적으로 아직 걸음마 수준이다. 본 연구팀은 국내 자율주행차 대표기업인 (주)언맨드솔루션에서 지원하는 플랫폼을 사용하여 자율주행 레이싱 제어 모델 프레임워크를 설계하고 기초 실험을 진행하였다. 제안된 자율주행 레이싱 제어 모델은 GPS 신호처리부, LiDAR 신호처리부, 영상처리부, 차량제어부, 추월/회피 제어부, 컨트롤러 통신부 등으로 구성된다. 실험을 통해 각 구성요소에 대한 기본 성능을 검증하였고, 레이싱에 최적화된 인공지능(AI) 기반 추월/회피 제어 알고리즘 개발을 위한 중요한 토대를 마련하였다. 본 연구를 바탕으로 2021년 11월에 국내 최초로 개최되는 세계 AI 로보카레이스 대회에 출전하여 제안된 자율주행 레이싱 제어 모델 프레임워크의 성능을 검증할 계획이다.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.2
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• pp.218-224
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• 2012

Recently, as the needs of developing the micro autonomous underwater vehicle (AUV) are increasing, the acquisition of the elementary technology is urgent. While they mostly utilizes information of the forward looking sonar (FLS) in conventional studies of the local path control as an elementary technology, it is desirable to use the obstacle avoidance sonar (OAS) because the size of the FLS is not suitable for the micro AUV. In brief, the local path control system based on the OAS for the micro AUV operates with the following problems: the OAS offers low bearing resolution and local range information, it requires the system that has reduced power consumption to extend the mission execution time, and it requires an easy design procedure in terms of its structures and parameters. To solve these problems, an intelligent local path control algorithm based on the beam modeling of OAS with the evolution strategy (ES) and the fuzzy logic controller (FLC), is proposed. To verify the performance and analyze the characteristic of the proposed algorithm, the course control of the underwater flight vehicle (UFV) is performed in the horizontal plane. Simulation results show that the feasibility of real application and the necessity of additional work in the proposed algorithm.

• Journal of Environmental Policy
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• v.9 no.1
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• pp.83-107
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• 2010

Urbanized environments are constructed to estimate peak flow and cost savings in response to possible BMP allocation at a watershed scale. The main goal is to explore the proper allocation of sub-watershed level BMPs for peak flow attenuation at a watershed scale. Since several individual site scale BMPs work as a form of aggregated BMPs at a sub-watershed scale, it is a question as to how to properly allocate the sub-watershed level BMPs at a watershed scale. The Hydrological Simulation Program-FORTRAN (HSPF) is set up for a hypothetically urbanized watershed. A peak flow is determined to be the primary variable of interest and targeted to characterize the spatial distribution of aggregated BMPs. Construction cost of a regional pond forms the basis of the economic valuation. The results indicate that when total size of BMPs is constant in the entire watershed, (1) it is most effective to have aggregated BMPs in some upper sub-watersheds while the BMPs in either the mainstem sub-watershed or a single sub-watershed are the least effective choices for peak flow attenuation at a watershed scale; (2) savings exist between allocation differences and reduced peak flow increases cost savings. The largest saving is found in the strategy of aggregated BMPs in some upper sub-watersheds. These findings, however, call for follow-up site specific case studies revisiting the watershed scale impacts of BMP allocation. Then, it will be argued that location and extent of decentralization are considerable policy variables for an alternative stormwater management policy at a watershed scale.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.162-172
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• 2011

This paper proposes embedded System of two wheeled inverted pendulum robot designed by model based design method, using MATLAB/SIMULINK and LEGO NXT Mindstorms. At first, stability and performance of controller is verified through modeling and simulation. After that direct conversion from simulation model to C code is carried and effectiveness of controller is experimentally verified. Two wheeled inverted pendulum robot has basic function about autonomous balancing control using principle of inverted pedulum and it is also possible to arrive at destination. In this paper, state feedback controller designed by quadratic optimal control method is used. And quadratic optimal control uses state feedback control gain K to minimize performance index function J. Because it is easy to find gain, this control method can be used in the controller of two wheeled inverted pendulum robot. This proposed robot system is experimentally verified with following performances - balancing control, disturbance rejection, remote control, line following and obstacle avoidance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.208-211
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• 2005

This paper describes the development process of steering system for reduce idle vibration through the data level of frequency and sensitivity. High stiffness and light weight vehicle is a major target in the refinement of passenger cars to meet customers' contradictable requirements between NVH performance and fuel economy. The target frequency of the steering system is set by benchmarking of a competitive vehicle and the vibration mode map is used to separate steering column modes from resonance of body structure and engine idle rpm. This paper descirbes the analysis approach process for high stiffness of steering system and the design guideline is suggested about steering column and support system by using mother car at initial design stage. We used a patent map in order to analyze accurately a technical trend and suggested the design process using dynamic damper of steering system considering sensitivity. And we established techniques of analysis on steering system and evaluated the level of accuracy of analysis through correlating the test and analysis results. It makes possible to design the good NVH performance vehicle at initial design stage and save vehicles to be used in tests. These improvements can lead to shortening the time needed to develop better vehicles.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.11b
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• pp.705-708
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• 2003

본 논문에서는 무선 센서 네트워크의 특성을 고려한 미디어제어 프로토콜의 설계에 있어서의 고려사항 및 설계기법에 대해서 제안하고 있다. 무선 센서 네트워크는 제한된 에너지를 가지는 배터리를 에너지원으로 사용하는 센싱 디바이스들로 구성되어 있으며, 이러한 디바이스들로 구성된 네트워크는 하나 혹은 그 이상의 공통의 작업을 수행하는데 그 목적이 있다. 일반적으로 무선 센서네트워크는 ad hoc 헝태의 구조를 가지며, 각각의 노드들은 장시간동안 비활성화 상태에 머무르게 되며, 센싱을 하기 위한 특정 이벤트가 발생하였을 때만 활성 상태로 전이하게 된다. 이와 같은 센서 네트워크의 특성은 IEEE802.11 과 같은 기존의 무선 미디어 제어 프로토콜과는 차별성을 띄게 된다. 센서 네트워크는 노드별 미디어 접근 공정성이나 시간지연보다는 에너지절약과 위상자동설정에 더 중점을 두고 있기 때문에 이에 적합한 미디어 제어 기술이 필요한 것이다. 본 고에서는 에너지 소모를 최소화하고 위상 자동 설정을 지원하기 위한 3 가지의 기법들에 대해서 제안하고자 한다. 첫째로 이벤트 발생 여부에 따른 노드의 신호감지 및 Sleep 상태 전이 및 이웃 노드들과의 가상동기화기법을 이용한 에너지 절약 기법에 대해서 제안하고, 충돌회피 기법에 대해서 살펴보도록 하겠다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.6
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• pp.1141-1149
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• 1992

This paper presents a robust centralized control scheme for a magnetic bearing system which supports a rigid rotor at both shaft ends in the radial direction. The negative stiffness element and the inductive force associated with bearing magnetic field are considered in the dynamic model of the system. For this model, the controllability and observability are examined, and then a robust control theory is applied to design two types of multi-input multi-output servocontrollers. A general servocompensator is embedded in the first one and a centralized PID controller is suggested as a second one. By simulation study, the performance of two types of servocontrollers are compared in the aspects of disturbance rejection, reference tracking and the robustness limit.

• Journal of the Korean Institute of Intelligent Systems
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• v.23 no.2
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• pp.100-106
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• 2013

This paper presents design and control of an 'Omni-directional Cleaning Robot (OdCR)' which employs omni-wheels at three edges of its triangular configuration. Those omni-wheels enable the OdCR to move in any directions so that lateral movement is possible. For OdCR to be localized, a StarGazer sensor is used to provide accurate position and heading angle based on landmarks on the ceiling. In addition to that, ultrasonic sensors are installed to detect obstacles around OdCR's way. Experimental studies are conducted to test the functionality of the system.