• Structural Engineering and Mechanics
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• 제54권6호
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• pp.1217-1244
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• 2015

In this research a theoretical and numerical study on a bridge damage detection procedure is presented based on vibration measurements collected from a set of accelerometers. This method, referred to as "Adjoint Variable Method", is a sensitivity-based finite element model updating method. The approach relies on minimizing a penalty function, which usually consists of the errors between the measured quantities and the corresponding predictions attained from the model. Moving mass is an interactive model and includes inertia effects between the model and mass. This interactive model is a time varying system and the proposed method is capable of detecting damage in this variable system. Robustness of the proposed method is illustrated by correct detection of the location and extension of predetermined single, multiple and random damages in all ranges of speed and mass ratio of moving vehicle. A comparative study on common sensitivity and the proposed method confirms its efficiency and performance improvement in sensitivity-based damage detection methods. In addition various possible sources of error, including the effects of measurement noise and initial assumption error in stability of method are also discussed.

• 보존과학연구
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• 통권20호
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• pp.121-137
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• 1999

Among pigment used at work of Dan-Chung, Emerald Green is specific illuminating fluorescent light of green. It is very difficult to change other organic or inorganic pigment. All of the internal high class pigment has rare light. But Emerald Green is superior to fresh color and stability out of industrial chemical products. It forms over 50% of quantity and importance of a pattern painting. Emerald Green prohibited to produce because of its toxicpollutants, so required to changing pigment development. It is characterized to excellent color, convenient work, economical, against-sunlight, against-air pollutant and durability. The result of a test is follows; 1. We are investigated into producing internal natural Emerald Green, import external pigment and industrial synthesis method etc. but unable to buy because of its toxic pollutant. 2. We are made six samples by yellowish and green is hpigment mixing. We tested on against sunlight and air pollutant. The best mixing ratio is follows. Titanium Dioxide R760 : 18g- Chalk, White Wash : 10g- Permanent Yellow : 7g- Cyanine Green : 8g- Chrome Yellow : 3g- Resin(Vehicle) : Acryl Emulsion(Styrene + 2-Ethyl HexylAcrylate + Methyl Meth Acrylate) 8%

• 대한기계학회논문집
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• 제11권3호
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• pp.437-443
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• 1987

본 연구에서는 승차감을 향상시키기 위해 원전석의 진동을 고려한 평면 5자 유도 모델을 사용하여 확정적 노면과 무작위 노면에 대한 시간영역, 주파수영역 해석 과 이에 따른 최적설계를 수행하였다. 최적설계시 목적함수는 주파수영역에서의 운 전석의 가속도 PSD를 구하여 여진동력(absorbed power)을 계산한 다음, 이를 최소화하 면서 차체의 안정성을 제한조건으로 하였다. 또 최적설계의 결과인 운전석의 가속도 rms값과 ISO경계값을 비교하였다. 시간영역에서는 결과를 해당된 운전석의 최대절대 가속도 및 상대변위에 대한 한계치와 비교하였다. 한편으로는 실제 노면 형상을 컴 퓨터로 시뮬레이션하고, 속도에 따른 최적치들 중에서 전체최적치 결정법을 제시하였 다.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.100-107
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• 2001

The main goals of the automotive suspension systems are to isolate roadway unevenness from the tire and to improve vehicle stability. To overcome the performance limitation of the passive systems the active systems which completely replace the passive spring and damper elements with a force generating actuator has been studied. However, application of the system has been limited because it has required a significant amount of power. Recently, alternative systems which retain passive elements but include active elements have been developed to reduce the power required. Those systems are mostly focused on the control system which compresses the spring-damper directly. In this study, a new type of power efficient control system which makes the spring-damper unit slide in side way is studied. After constructing the control system including dynamic modeling and motion control, two types of alternative control systems are compared in view of power consumption and dynamic attitudes such as roll responses as well as heave responses. Also, a half car bond graph model is developed to show clearly the significant differences in performances between two control systems.

• 로봇학회논문지
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• 제11권2호
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• pp.83-91
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• 2016

Most of outdoor mobile robots have a suspension on each wheel in order to relieve the shock by ground obstacles and to improve the driving stability. Typically, in the actual operations, the suspensions have been used under a given set of conditions as all the damping and spring coefficients of the suspensions are fixed. However, it is necessary to readjust the coefficients of the suspensions according to surface conditions that may cause the unstable shaking of a robot body at high speed driving. Therefore, this paper is focused on the mobility analysis of an outdoor robot when the coefficients of suspensions (in particular, damping coefficients) are changed while driving on an uneven road surface. In this paper, a semi-active suspension with twelve damping coefficient levels was used and a small sized vehicle with the suspensions was employed to analyze the mobility dependent on a change of the damping coefficient. And the mobility was evaluated through driving experiments on a bumped slope.

• International Journal of Aeronautical and Space Sciences
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• 제18권3호
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• pp.485-497
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• 2017

The pogo phenomenon refers to a type of multidiscipline-related instability found in space launch vehicles. It is caused by coupling between the fuselage structure and other structural propulsion components. To predict the pogo phenomenon, it is essential to undertake adequate structural modeling and to understand the characteristics of the feedlines and the propulsion system. To do this, a modal analysis is conducted using axisymmetric two-dimensional shell elements. The analysis is validated using examples of existing launch vehicles. Other applications and further plans for pogo analyses are suggested. In addition, research on the pogo phenomenon of Saturn V and the space shuttle is conducted in order to constitute a pogo stability analysis using the results of the present modal analysis.

• International Journal of Automotive Technology
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• 제6권5호
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• pp.545-554
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• 2005

Passive velocity field control (PVFC) was previously developed for fully mechanical systems, in which the motion task was specified by behaviors in terms of a velocity field and the closed-loop was passive with respect to the supply rate given by the environment input. However, the PVFC was only applied to a single manipulator. The proposed control law was derived geometrically and the geometric and robustness properties of the closed-loop system were also analyzed. In this paper, we propose a virtual passivity-based algorithm to apply decentralized control to multiple 3­wheeled mobile robotic systems whose subsystems are under nonholonomic constraints and convey a common rigid object in a horizontal plain. Moreover, it is shown that multiple robot systems ensure stability and the velocities of augmented systems converge to a scaled multiple of each desired velocity field for cooperative mobile robot systems. Finally, the application of proposed virtual passivity-based decentralized algorithm via system augmentation is applied to trace a circle and the simulation results is presented in order to show effectiveness for the decentralized control algorithm proposed in this research.

• 항공우주기술
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• 제7권1호
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• pp.151-160
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• 2008

본 논문에서는 발사체에 적용하는 전기-유압식 추력벡터제어 구동장치시스템의 합성공진 현상에 대한 해석 연구결과를 기술한다. 합성공진 현상은 위치서보 구동장치시스템을 유연한 발사체 기체구조체 지지부에 장착하였을 때 발생한다. 이는 관성부하를 갖는 전기-유압식 위치서보 시스템의 유압공진 현상과 유연한 기체구조체 지지부의 구조공진 현상의 합성에 의하여 발생한다. 합성공진 현상은 발사체 제어시스템에 의하여 되먹임 및 증폭되어 안정성을 악화시킬 수 있다. 이와 같은 현상을 정확하게 예측 및 분석할 수 있는 비선형 모델을 개발하였으며 이에 기반을 둔 합성공진 억제 특성이 우수한 동적 압력 되먹임(dynamic pressure feedback) 제어기법을 개발하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.183-188
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• 2009

The High speed electrical multiple train having a distributed electrical motor system has just been developing to aim the experimental maximum speed at 400km/h since August, 2007. This project comes in stage of basic design and so, it needs to take some review and analysis the characteristics of suspensions on the view of basic design. The vehicle model for dynamic analysis is made from the concept design model that used for the preliminary design review with Vampire program and it is modeled with three linear secondary dampers and two shear springs separated from the bush elements in previous model. The optimization technique is applied to search the proper range of linear characteristics for the suspension elements to satisfy the stability performance at speed 130m/s (about 460km/h). The results shows there are some optimum points according to the variation of primary and secondary suspension characteristics and it would be useful to make a decision to select the proper suspension elements in the precision design that will be done by the manufacturing company.

• Journal of the Optical Society of Korea
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• 제17권1호
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• pp.103-108
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• 2013

The operation of a Doppler wind LIDAR in a mobile environment is very sensitive to shocks and vibrations, which can cause critical failures such as misalignment of the optical path and damage to optical components. To be able to stabilize the LIDAR and to perform wind field measurements in motion, a shock absorption and vibration isolation system was designed and implemented. The performance of the vehicle-mounted Doppler wind LIDAR was tested in motion, first in a circular test route with a diameter of about 30 m and later in regular expressway traffic. The vibration isolation efficiency of the system was found to be higher than 82% in the main vibration area and shock dynamic deflection was smaller than maximal deflection of the isolator. The stability of the laser locking frequency in the same mobile environment before and after the vibration isolation system installation was also found to be greatly improved. The reliability of the vibration isolation system was confirmed by good results of the analysis of the LIDAR data, in particular the plane position indicator of the line of sight velocity and the wind profile.