• Journal of the Korean Institute of Intelligent Systems
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• v.20 no.4
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• pp.469-475
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• 2010

This paper presents controller design of a two wheeled mobile inverted pendulum robot for one man transportation vehicle. Since the overall mass is varying with different drivers, suitable controller gains are obtained through experimental studies. Variation of the center of gravity due to different masses also affects stable balancing control. Thus, the desired balancing angle si required to be modified with respect to different masses. To measure masses for different drivers, a weight scale is used and those data are used for balancing control through communication. The gain scheduling method of using data obtained from experimental studies allows the robot to have stable balancing performances.

• Journal of the Korean Society for Railway
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• v.11 no.5
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• pp.465-470
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• 2008

Sound transmission characteristics are investigated on the honeycomb panels used for railway vehicles. Equivalent orthotropic plate model and equivalent mass law are applied to predict the sound transmission loss (STL) of the honeycomb panels. The predicted values of the STL are compared with the measured values. The reliability and the limitation of the prediction models are investigated. Coincidence effect and local resonance effect on STL are considered. The result of the study shows that the equivalent orthotropic plate model can be used as a good prediction model, if the local resonance frequency is properly applied. finally, ways to improve the severe STL drop by local resonance are proposed and the effect on the sound insulation performance is analysed.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.535-546
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• 2010

Recently, the probability of collision accident between vehicles or vessels and infrastructures are increasing at alarming rate. Particularly, collision impact load can be detrimental to sub-structures such as piers and columns. The damaged pier from an impact load of a vehicle or a vessel can lead to member damages, which make the member more vulnerable to impact load due to other accidents which. In extreme case, may cause structural collapse. Therefore, in this study, the vehicle impact load on concrete compression member was considered to assess the quantitative design resistance capacity to improve, the existing design method and to setup the new damage assessment method. The case study was carried out using the LS-DYNA, an explicit finite element analysis program. The parameters for the case study were cross-section variation of pier, impact load angle, permanent axial load and axial load ratio, concrete strength, longitudinal and lateral rebar ratios, and slenderness ratio. Using the analysis results, the performance based resistance capacity evaluation method for impact load using satisfaction curve was developed using Bayesian probabilistic method, which can be applied to reinforced concrete column design for impact loads.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1131-1138
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• 2007

This paper studies experimentally on the building-up process for the amplitude of a commercial truck vibration induced by brake judder. A front axle drum equipped with a drum brake system is utilized for this experiment. A brake dynamo test, a real vehicle ride test and a real vehicle braking test are performed for the analysis of brake judder. The brake dynamo test measures judder by applying brake chamber pressures of 1, 2 and 3 bar at initial brake pad temperatures of $100^{\circ}C$ and $150^{\circ}C$. In order to assess the vertical acceleration at the front axle, the real vehicle ride test on a straight test road with velocities of 20, 40, 60 and 80 km/h is performed. The real vehicle braking test is carried out at the deceleration rate of 0.2g from a velocity of 90km/h for evaluating the vertical, lateral and longitudinal accelerations both at the front axle and at the cab floor under the driver's seat. The magnitudes and frequencies of the measured peak accelerations from the brake dynamo test, the real vehicle ride test and the real vehicle braking test are comparatively analyzed. This paper shows that the vibration produced by brake judder is built up due to the brake system's peak acceleration frequency being close to the vehicle ride mode's frequency.

• The Journal of the Acoustical Society of Korea
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• v.29 no.2
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• pp.118-124
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• 2010

In this paper, design parameters of dynamic vibration absorber, which is used to reduce bending vibrations of a vehicle drive line, is optimized. For obtaining the correct dynamic response characteristics, a flexible-body drive line is made by applying the flexibility data extracted from vibration analysis of propeller shafts to the drive line dynamic model. Inner tube mass, rubber stiffness and rubber damping coefficient of the dynamic vibration absorber are taken as design parameters for optimization. To minimize the vertical acceleration of the drive line, a second-order regression equation of the objective function is generated by performing the central composite experimental design with 3 factors, 2 levels and 15 test runs. And the design parameters of the dynamic vibration absorber are determined by using optimization program. The vehicle model with optimized dynamic vibration absorber reduces the vertical acceleration peak of the drive line by 17.1 % in compared with the initial model.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.32-38
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• 2020

This study examined the problems of existing vehicles to propose alternatives to improve the crashworthiness of railway freight cars through collision acceleration analysis using a one-dimensional collision analysis method. A collision scenario of railway shunting and crash accidents was selected from the collision accident cases and international standards. A one-dimensional collision simulation using LS-DYNA was performed according to those scenarios. As a result, the acceleration level of the freight wagon was calculated to be under 2g and was predicted to meet the EN 12663 standard in the shunting situation. On the other hand, the result of crash simulation with an impact velocity between 10 and 15 km/h revealed the shock absorber capacity of the railway coupler to be insufficient in a crash situation, resulting in increased acceleration, and carbody deformation could be predicted. As a method of improving the crashworthiness, a deformation tube-type energy absorber was applied to the coupler system, and collision analysis was performed again with new energy absorption strategy. Overall, the simulation showed that the acceleration level was decreased by 12% of the conventional freight-car energy absorption system.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.23-30
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• 2009

Crash cushions are protective devices that prevent errant vehicles from impacting on fixed objects. This function is accomplished by gradually decelerating a vehicle to a safe stop in a relatively short distance. Commonly used crash cushions generally employ one of two concepts to accomplish this function. The first concept involves the absorption of the kinetic energy of a moving vehicle by crushable or plastically deformable materials and the other one involves the transfer of the momentum of a moving vehicle to an expendable mass of material located in the vehicle's path. Crash cushions using the first concept are generally referred to as compression crash cushions and crash cushions using the other concept are generally referred to as inertial crash cushion. The objective of this research is the development of a compression-type crash cushion by employing the two concepts simultaneously. To minimize the number of full-scale crash tests for the development of the crash cushion, preliminary design guide considering inertial and frictional energy absorption was constructed and computer simulation was performed. LS-DYNA program, which is most widely used to analyze roadside safety features, was used for the computer simulation. The developed crash cushion satisfied the safety evaluation criteria for various impact conditions of CC2 performance level in the Korean design guide.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.1
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• pp.163-170
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• 2001

In this paper, a massless link model transmitting external forces is developed to achieve the numerical efficiency in simulation of vehicle suspension systems. Forces acting on links are resolved and transmitted to attached points with a quasi-static assumption. Also, a theoretical derivation and computer implementation of a massless link with bushing elements are proposed. In the massless link with bushing elements, one end is connected to the adjacent body with bushings and the other end is connected with a spherical joint. The deformation of a massless link with bushing elements is theoretically determined by minimizing the potential energy function with quasi-static equilibrium assumption at each time step. Several simulations with a full vehicle model are carried out to compare the efficiency of the developed massless link component. From the results, it is concluded that the proposed approach can reduce the computational time considerably.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.476-479
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• 2012

차량의 충돌에 따른 등유의 누출에 의한 화재와 항공기 충돌에 따른 항공유의 누출에 의한 화재 발생 시 격실의 개구부 크기에 따른 화염온도를 평가하기 위해 화원으로 등유와 Jet-A-1을 사용하고 개구부의 크기를 조절해 가며 격실화재시험을 수행하였으며, 가장 높게 측정된 시험결과의 조건으로 과도화재시험을 수행하여 금속저장용기가 화염온도에 미치는 영향을 평가하였다. 시험결과 등유보다 Jet-A-1의 열 방출속도 및 질량 연소유속이 크게 나타났으며, Jet-A-1에서의 화염온도가 높게 측정되었다. 연료 소모율은 개구부의 크기가 클 경우 작은 경우보다 크게 나타났으며, 개구부의 크기가 클 경우 화염온도가 높게 측정되었다. 격실 내에 금속저장용기가 저장되었을 때는 저장용기가 화염으로부터 받는 열량만큼 화염의 온도는 낮아지는 것으로 나타났다.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.433-435
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• 1999

전동차의 구동시스템 및 보조 전원장치 등의 제어가 고성능화되고 복잡해지면서 각 기기의 개별 시험이 아닌 조합시험을 통한 신뢰성의 확보가 점점 중요해지고 있다. 특히 구동시스템의 시험을 위해서는 실제 차량부하와 유사한 부하 특성을 조합시험장치가 제공하는 것이 중요하다. 전동차의 부하특성에서 가장 지배적인 역할을 하는 특성은 관성이다. 국내에 운용중인 조합시험장치들은 전동차의 직선 운동에 해당하는 등가 회전관성을 가지는 플라이휠(flywheel)을 이용하여 관성부하를 구현하고 있다. 본 논문에서는 이러한 관성부하를 기계적 질량이 아닌 서보시스템을 이용하여 구현할 경우의 장단점과 특성에 대해 알아보고, 그 적절한 구현방법을 제안하고자 한다. 또한 실험 및 실험 결과를 통해 그 타당성을 검증하고자 한다.