• 한국자동차공학회논문집
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• 제25권3호
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• pp.360-366
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• 2017

In commercial vehicles such as frame-based mid-size trucks, it is easy to reduce vibration caused by driveline with the cab mount system. There are no critical driveline vibration problems associated with these vehicles up to now. However, in the case of a similar grade of monocoque type mini-bus, there are no effective vibration isolation components such as a cab mount. Vibration caused by driveline is quite a complex problem to understand in terms of which part governs the phenomenon and how the problem can be solved. Thus, we have to manage the design factor about the driveline and mount system strictly at the early stage of vehicle development. Low frequency vibration caused by the driveline system is investigated in this study. We created the CAE driveline model and analyze low frequency vibration. Then contribution analysis about each design factor of driveline and mount system is performed. Finally, we can obtain the optimized design factor for a driveline system of a mini-bus, which is verified by the vehicle test results.

• 수산해양기술연구
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• 제32권1호
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• pp.7-15
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• 1996

Full scale experiment was carried out in the southern sea of Korea to compare some important factors tested in the model experiment. The results obtained can be summarized as follows ; 1. The changing aspect of mouth performance of the full scale net was almost coincided with the results obtained by the model experiment. The vertical opening(H) and the opening area(S) can be expressed as a function of the towing velocity(V) as H=48.78. $e^0.38V$(unit: m, k't) S= 1,443 .$e^-0.25V$(unit: $m^2V$, k't) 2. The changing aspect of working depth of the full scale net was almost coincided with the results obtained by the model experiment. The depth(D) can be expressed as a function of the towing velocity(V) and the warp length(L) as D=92.49.$V^1.37$(unit: m, k't, L= 150m) D= 12.07+0.32. L (unit: m, V=2k't) [)= - 7.90+0.22 . L (unit: m, V=3k't) 3. Some problems were found to operate A - type full scale net by common bottom pair trawlers. The problems can be summarized as follows; (1) Entangling of wing and square head ropes while net casting.(2) Man power needed and time spent for net hauling by common bottom trawlers increased considerably.( 3) Tearing of nettings caused by over -load of tension and entangling of net pendant while net hauling. To solve these problems, the trawlers are favorable to be equipped with variable pitch propeller and llet drum. While the net is favorable to be constructed with trifurcated net pendant in stead of quadrifurcated net pendant used at present.

• 대한조선학회논문집
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• 제54권6호
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• pp.501-514
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• 2017

In the previous research, a study was carried out to estimate the actual performance such as the propeller Revolution Per Minute (RPM) and engine power of a Liquefied Natural Gas Carrier (LNGC) using the full-scale measurement data. After the predicted RPM and engine power were verified by comparing those with the measured values, the suggested method was regarded to be acceptable. However, there was a limitation to apply the method on the prediction of the RPM and engine power of a ship. Since the information of route, speed, and environmental conditions required for estimating the RPM and engine power is generally regarded as the intellectual property of a shipping company, it is difficult to secure the information on a shipyard. In this paper, the RPM and engine power of the 151K LNGC was estimated using the combination of Automatic Identification System (AIS) and European Centre for Medium-Range Weather Forecasts (ECMWF) database in order to replace the full-scale measurement. The simulation approach, which was suggested in the previous research, was identically applied to the prediction of RPM and engine power. After the results based on the AIS and ECMWF database were compared with those obtained from the full-scale measurement data, the feasibility was briefly reviewed.

• 로봇학회논문지
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• 제8권1호
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• pp.51-57
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• 2013

Recently, the number of jellyfish has been rapidly grown because of the global warming, the increase of marine structures, pollution, and etc. The increased jellyfish is a threat to the marine ecosystem and induces a huge damage to fishery industries, seaside power plants, and beach industries. To overcome this problem, a manual jellyfish dissecting device and pump system for jellyfish removal have been developed by researchers. However, the systems need too many human operators and their benefit to cost is not so good. Thus, in this paper, the design, implementation, and experiments of autonomous jellyfish removal robot system, named JEROS, have been presented. The JEROS consists of an unmanned surface vehicle (USV), a device for jellyfish removal, an electrical control system, an autonomous navigation system, and a vision-based jellyfish detection system. The USV was designed as a twin hull-type ship, and a jellyfish removal device consists of a net for gathering jellyfish and a blades-equipped propeller for dissecting jellyfish. The autonomous navigation system starts by generating an efficient path for jellyfish removal when the location of jellyfish is received from a remote server or recognized by a vision system. The location of JEROS is estimated by IMU (Inertial Measurement Unit) and GPS, and jellyfish is eliminated while tracking the path. The performance of the vision-based jellyfish recognition, navigation, and jellyfish removal was demonstrated through field tests in the Masan and Jindong harbors in the southern coast of Korea.

• 한국항공우주학회지
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• 제42권4호
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• pp.305-316
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• 2014

항공전자 장비들의 급속한 발전으로 인해 무인항공기의 크기가 소형화 되고 있으나, 무인항공기에 대해 주어지는 임무는 더욱 정확하고 복잡해지고 있다. 정지비행이 가능하고, 간단한 기계적 메커니즘을 가진 쿼드로터는 이 같은 환경에서 활동도가 점차 증가하고 있다. 그러나 쿼드로터는 구조 특성에 따라 출력의 개수보다 입력의 개수가 작은 under actuated 시스템이므로, 쿼드로터 제어에 큰 제약이 따른다. 본 논문에서는 이와 같은 쿼드로터의 단점을 해결하기 위해서 4개의 원동기 외에 2개의 추가적인 원동기를 더 부착한 모델을 제안하여, 입력의 개수와 출력의 개수가 같은 fully actuated 시스템을 구현하도록 한다. 제안한 쿼드로터 모델의 제어기를 설계하기 위해 궤환선형화 기법을 적용하였다. 수치 시뮬레이션을 수행하여 제안한 모델과 설계된 제어기의 성능을 검증하였다.

• 대한조선학회논문집
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• 제44권6호
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• pp.551-563
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• 2007

Numerical analysis for flow characteristics of a twin skeg container ship was carried out according to skeg vertical angles($0^{\circ}$, $10^{\circ}$, $20^{\circ}$) and skeg distances(16m, 20m, 24m) by using a commercial CFD code, FLUENT. Computed: pressure distributions, wake distributions and resistance coefficients have been compared with experimental and WAVIS results carried out by MOERI. Flow characteristics from numerical analysis such as nominal wake fractions, wake distribution and directions of the transverse vectors give good agreement with WAVIS results, even though there are quantitative discrepancy comparing with experimental measurements at the propeller plane. It is found that the better resistance performance can be obtained with the increase of the skeg vertical angle and the decrease of the skeg distance, which are mainly caused by viscous pressure resistance due to the skeg form and pressure recovery around the skeg. In addition, a vertical angle of the skeg gives more effect to the resistance coefficient comparing with the skeg distance. On the basis of results of the present study, it shows that numerical analysis using the commercial code, FLUENT, is useful and efficient tool for the evaluation of the complex stern hull form with twin-skegs.

• 한국음향학회지
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• 제21권5호
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• pp.446-454
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• 2002

본 연구는 이동 표적체에서 주파수가 서로 다른 신호가 서로 다른 위치에서 발생할 때 도플러 주파수 편이량을 추정하여 이들의 상대적인 신호 발생 위치를 추적하는 도플러 스캐닝 기법에 관한 연구이다. 예를 들어 선박의 발전기와 프로펠러 등과 같은 탑재 기계장치들의 진동에 의해 야기되는 기계적 소음의 각 특징 주파수들의 도플러 주파수 편이는 최단근접거리 (CPA: Closest Point of Approach)에 따라 유일한 시간 정보를 갖고 각 소음원들의 위치에 관련되는 함수이다. 따라서 도플러 스캐닝 기법을 적용하면 이동 선박의 각 기계적 소음원들간의 공간적인 상대 위치 추정이 가능하다. 그러나 일반적으로 기계류 소음의 주파수는 저주파수대역이므로 도플러 주파수 편이량을 추정하기 위해서는 주파수 분해능이 높아야 하고 아울러 탑재장치의 공간분해능을 높이기 위해서는 동시에 시간 분해능이 높아야 한다. 따라서 상호 역비례 관계에 있는 이들 분해능을 동시에 높이기 위해 확장 칼만 필터 알고리즘을 적용하여 특징 신호들의 도플러 주파수 편이량을 추정하여 기계류의 상대적인 탑재 위치를 규명할 수 있음을 보인다. 먼저 수치모의 실험으로 그 가능성을 검증하고 자동차에 탑재된 스피커 음원을 사용한 실험 결과를 통해 그 성능을 확인하도록 한다.

• 대한조선학회논문집
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• 제42권3호
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• pp.197-204
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• 2005

A waterjet propulsion system has many advantages compared with a conventional screw propeller especially for amphibious armored wheeled vehicles because of a good maneuverability at low speed, good operation ability at shallow water, high thrust at low speed to aid maneuverability and exit from water, etc. The POD type waterjet is adequate for the present wheeled vehicle because the weight is lighter and L/B is longer than the conventional armored amphibious vehicle. Resistance and self-propulsion tests with a 1/3.5-scale model are conducted at PNU towing tank. Based on these measurements, the performance is analyzed according to ITTC 96 standard analysis method and also according to the conventional propulsive factor analysis method. Based on these two methods, the full-scale effective and delivered powers of amphibious armored wheeled vehicle are estimated. This paper emphasizes the analysis method of model test of the waterjet propulsion system for a amphibious armored wheeled vehicle and the model test technique together with the comparison of the two analysis methods.

• 대한조선학회논문집
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• 제50권1호
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• pp.1-7
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• 2013

The high-skewed and/or composite propellers of current interests to reduce the ship vibration and to increase the acoustic performance are likely to be exposed to the unexpected structural problems. One typical example is that the added mass effect on the propellers working in the non-uniform wake field reduces the natural frequency of the propeller leading to the resonance with the low-frequency excitation of the external forces. To avoid this resonance problem during the design stage, the technique of fluid-structure interaction has been developed, but the higher-order effect of the blade geometry deformation is not yet considered in evaluating the added mass effects. In this paper the fluid boundary-value problem is formulated by the potential-based panel method in the inviscid fluid region with the velocity inflow due to the body deformation, and the structural response of the solid body under the hydrodynamic loading is solved by applying the finite element method which implements the 20-node iso-parametric element model. The fluid-structure problem is solved iteratively. A basic fluid-sturcture interaction study is performed with the simple rectangular plates of thin thickness with various planform submerged in the water of infinite extent. The computations show good correlation with the experimental results of Linholm, et al. (1965).

• 대한조선학회논문집
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• 제31권3호
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• pp.65-79
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• 1994

본 연구에서는 선미벌브의 채택이 유체력 특성 및 조종성능에 미치는 영향에 관해서 실험적으로 고찰하였다. 연구방법으로서는 일반선미 형상과 선미벌브 형상을 가지는 각각의 모형선을 공시선으로, 회류수조에서 조종성 관련 구속모형시험을 실시하여 양 선형의 차이에 기인하는 유체력 특성과 조종성능을 비교, 검토하였다. 연구 결과, 선미벌브를 채택함으로써 침로안정성은 나빠지지만 선회력이 향상됨을 확인하였고, 이러한 조종성능의 특성과 유체력 특성과의 상관관계를 규명하였다.