• 시스템엔지니어링학술지
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• 제12권2호
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• pp.19-27
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• 2016

Many countries concentrated on the space developments to enhance the national security and the people's quality of life. A space launch vehicle for accessing the space is a typical large complex system that is composed of the high-technology like high-performance, high-reliability, superhigh-pressure, etc. The project developing large complex system like space launcher is mostly conducted in the uncertain environment. To achieve a goal of the project, its success probability should be enhanced consistently by reducing its uncertainty during the life cycle: it's possible to reduce the project's uncertainty by performing the risk management (RM) that is a method for identifying and tracing potential risk factors in order to eliminate the risks of the project. In this paper, we introduce the risk management (RM) process applied for a Space Launch Vehicle R&D Project.

• 한국자동차공학회논문집
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• 제14권2호
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• pp.158-165
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• 2006

In this paper, a new uni-axial bushing model for vehicle dynamics analysis is proposed. Bushing components of a vehicle suspension system are tested to capture the nonlinear and hysteric behavior of the typical rubber bushing elements using the MTS machine. The results of the tests are used to develop the Bouc-Wen bushing model. The Bouc-Wen model is employed to represent the hysteretic characteristics of the bushing. ADAMS program is used for the identification process and VisualDOC program is also used to find the optimal coefficients of the model. Genetic algorithm is employed to carry out the optimal design. A numerical example is suggested to verify the performance of the proposed model.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.1420-1425
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• 2008

This study is to examine the sound transmission loss of a railway vehicle floor. To this end, a semi-reverberation room was constructed. The semi-reverberation room was made of a railway vehicle floor between the sound radiating chamber and the sound receiving chamber. To block the sound, the wall was made of acryl, urethane foam, wood, and glass fiber. The test followed the KS F 2808 standard, and a typical reverberation room was used to verify the performance of the semi-reverberation room. As a result, comparison of the measurements showed that the test results of the semi-reverberation room had the same tendency as those of the reverberation room. Consequently it was possible to measure the sound transmission loss of railway vehicle structures using the semi-reverberation room.

• 대한인간공학회지
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• 제26권4호
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• pp.127-133
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• 2007

The purpose of this study is to apply WDA (Work Domain Analysis) for the development of EID (Ecological Interface Design) of vehicle control display. At first, a work domain model on the automobile operation was developed using the AH (Abstraction Hierarchy) which is one of WDA tools. Secondly, information requirements that should be included in vehicle control displays were extracted on the basis of the completed model. The vehicle control information that typical automobiles interface displays currently provide occurred on the low level of the work domain model. This implies that current control displays impose too heavy cognitive workload on automobile drivers. Information requirements that can be included new vehicle control display are also discovered in the high level of the work domain model. The detailed information for EID was not proposed in this study. In the further study, the development of vehicle control display will be deeply conducted, using the results of this study.

• 자동차안전학회지
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• 제9권2호
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• pp.13-19
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• 2017

This paper presents safety assessment scenarios for cyclist autonomous emergency braking(AEB) system. To assess the safety performance of AEB in real traffic situation with limited number of scenarios, scenario should reflect the characteristics of real traffic collision cases. For this, statistic data of real traffic car-to-cyclist collision in Korea are analyzed. Many types of accidents are listed and categorized based on the movement of vehicle and cycle just before the collision. Then, the characteristics, main issues and limitations of each scenarios are discussed. Not only the test scenario itself but also the cost and time for the test are very important issues for the test scenarios to actually repeat the test for various systems. Also, the performance of AEB can be effected by the algorithm of AEB and the technical limitation of the sensors and hardwares. Therefore, required number of tests, possibility of dummy destruction and other technical issues are discussed for each scenarios. Based on these information, typical scenarios are selected. Also, using this information, vehicle speed range, cyclist speed and collision point are established. Proposed scenarios are verified and modified based on the vehicle test results. vehicle test was evaluated 5 times for each scenarios. Based on this results, final test scenarios are modified and proposed.

• 자동차안전학회지
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• 제5권2호
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• pp.17-23
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• 2013

This paper describes an algorithm for Advanced Emergency Braking(AEB) with tire-road friction coefficient estimation. The AEB is a system to avoid a collision or mitigate a collision impact by decelerating the car automatically when forward collision is imminent. Typical AEB system is operated by Time-to-collision(TTC), which considers only relative velocity and clearance from control vehicle to preceding vehicle. AEB operation by TTC has a limit that tire-road friction coefficient is not considered. In this paper, Tire-road friction coefficient is also considered to achieve more safe operation of AEB. Interacting Multiple Model method(IMM) is used for Tire-road friction coefficient estimation. The AEB algorithm consists of friction coefficient estimator and upper level controller and lower level controller. The numerical simulation has been conducted to demonstrate the control performance of the proposed AEB algorithm. The simulation study has been conducted with a closed-loop driver-controller-vehicle system using using MATLAB-Simulink software and CarSim Vehicle model.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.35-44
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• 2017

Supercavitation is one of the most attractive technologies to achieve high speed for underwater vehicles. However, the multiphase flow with high-speed around the supercavitating vehicle (SCV) is difficult to simulate accurately. In this paper, we use modified the turbulent viscosity formula in the Standard K-Epsilon (SKE) turbulent model to simulate the supercavitating flow. The numerical results of flow over several typical cavitators are in agreement with the experimental data and theoretical prediction. In the last part, a flying SCV was studied by unsteady numerical simulation. The selected computation setup corresponds to an outdoor supercavitating experiment. Only very limited experimental data was recorded due to the difficulties under the circumstance of high-speed underwater condition. However, the numerical simulation recovers the whole scenario, the results are qualitatively reasonable by comparing to the experimental observations. The drag reduction capacity of supercavitation is evaluated by comparing with a moving vehicle launching at the same speed but without supercavitation. The results show that the supercavitation reduces the drag of the vehicle dramatically.

• Interaction and multiscale mechanics
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• 제5권2호
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• pp.145-155
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• 2012

The thin-plate structure and the box-beam structure are two typical welded structures in railway vehicles. Because of their structure complexity, bigger size and multi-seams, welding residual distortion which occur in welding process bring unfavorable effect on the quality of welding products manufacturing and service. As a result, welding distortion forecasting and control become an important and urgent research topic in railway vehicles. In this paper, three different numerical methods are presented corresponding to three typical types of welded structures of railway vehicles and welding deformation are simulated. Consistence of numerical results and experimental data proves the correctness of models and feasibility of simulation methods.

• 전자공학회논문지SC
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• 제48권6호
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• pp.71-81
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• 2011

일반적인 내연기관 자동차와는 달리, 전기자동차는 파워트레인을 구성하는 배터리, 인버터, 모터 등의 전기 동력 시스템들이 차량의 주행성능과 동역학 특성에 직접적인 영향을 준다. 따라서 전기 차량의 최종 운동 및 동특성을 예측하기 위해서, 기계 및 전기전자 복합 시스템을 세부적으로 모델링하고 이를 통한 전체 파워트레인의 해석이 필요하다. 본 논문에서는 전기자동차의 최종 출력 성능을 예측하고 분석하기 위한 전기자동차의 파워트레인 시스템의 동적 모델을 유도하였다. 전기적인 신호로부터 최종 기계 동력 시스템으로 전달되는 입출력 변수의 상관관계를 수학적으로 모델링하여 개발하였다. 또한, 전기자동차의 동특성을 시뮬레이션 할 수 있는 기준모델을 Matlab/Simulink 플랫폼 기반으로 개발하였으며, 이를 이용하여 유도된 수학적 분석 모델을 검증하였다. 이를 통하여 속도, 가속도, 추진력 등의 주요 차량 주행성능을 비교 분석하였다.

• 산업경영시스템학회지
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• 제30권3호
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• pp.165-173
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• 2007

A space launch vehicle system represents a typical example of large-scale multi-disciplinary systems, consisting of subsystems such as mechanical structure, electronics, control, telecommunication, propulsion, material engineering etc. A lot of cost is required to develop the launch vehicle system. A precise planning of R&D cost is very essential to make a success of the launch vehicle development program. Especially in the early development phase of a new space launch vehicle system, cost estimation techniques and analogy from past similar development data are very useful methods to estimate a development cost of the launch vehicle system. Now Korea Aerospace Research Institute is in charge of the KSLV-I (Korea Space Launch Vehicle-I) Program that is a part of Korea National Space program. KSLV-I Program is a national undertaking to develop launch capabilities to deliver science satellites of a 100kg-class into a low earth orbit. It is hereafter, going to plan to develop a new korean space launch vehicle. In this paper, first the development costs of well-known launch vehicles in the world are presented to provide a reference to make a development plan of a new launch vehicle. Second this paper introduces the present status of cost estimation applications at NASA. Finally this paper presents the results from application of a TRANSCOST, a parametric cost model, to derive a cost estimate of a new launch vehicle development, as an example.