• Steel and Composite Structures
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• 제49권4호
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• pp.393-405
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• 2023

In this paper, the energy absorption capability of a novel cruciform composite lattice structure was evaluated through the simulation of compression tests. For this purpose, several test samples of Polylactic acid cellular reinforced with continuous glass fibers were prepared for compression testing using the additive manufacturing method of material extrusion. Using a conventional path design for material extrusion, multiple debonding is probable to be occurred at the joint regions of adjacent cells. Therefore, an innovative printing path design was proposed for the cruciform lattice structure. Afterwards, quasistatic compression tests were performed to evaluate the energy absorption behaviour of this structure. A finite element model based on local material property degradation was then developed to verify the experimental test and extend the virtual test method. Accordingly, different combinations of unit cells' dimensions using the design of the experiment were numerically proposed to obtain the optimal configuration in terms of the total absorbed energy. Having brilliant energy absorption properties, the studied cruciform lattice with its optimized unit cell dimensions can be used as an energy absorber in crashworthiness applications. Finally, a cellular structure will be suitable with optimal behavior in crush load efficiency and high energy absorption.

• 한국시뮬레이션학회논문지
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• 제21권4호
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• pp.65-73
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• 2012

함정 전투체계는 무기체계, 정보통신 등의 기술 발전으로 인한 복잡한 전장 환경에 따라 인간이 개입하여 다양한 전술을 운용해야 한다. 따라서 에이전트 기반의 국방 M&S 시스템의 연구가 최근 들어 활발히 진행되고 있다. 그러나 현존하는 에이전트 기반 M&S 시스템은 고정된 전술을 적용하여 분석하는데 그치고 있다. 본 논문에서는 함정 교전에서 보다 적합한 대응을 찾기 위해 환경변화에 능동적으로 대처할 수 있도록 강화 학습 기능을 갖으며, 또한 유전 알고리즘을 이용하여 세대별 진화 학습 기능을 갖는 에이전트 모델링 방법론을 제안하였다. 타당성 검증을 위해 서해상에서 벌어지는 가상의 1:1 함정교전 시뮬레이션을 수행하였고, 이를 통해 함정 교전에 있어 강화 및 진화 학습이 가능함을 검증하였다.

• 한국정밀공학회지
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• 제34권1호
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• pp.41-46
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• 2017

Magnetically levitated (Maglev) vehicles maintain a constant air gap between guideway and car bogie, and thereby achieves non-contact riding. Since the straightness and the flatness of the guideway directly affect the stability of levitation as well as the ride comfort, it is necessary to monitor the status of the guideway and to alert the train operators to any abnormal conditions. In order to develop a signal processing algorithm that extracts guideway irregularities from sensor data, virtual testing using a simulation model would be convenient for analyzing the exact effects of any input as long as the model describes the actual system accurately. Simulation model can also be used as an estimation model. In this paper, we develop a state-space dynamic model of a maglev vehicle system, running on the guideway that contains jumps. This model contains not only the dynamics of the vehicle, but also the descriptions of the power amplifier, the anti-aliasing filter and the sampling delay. A test rig is built for the validation of the model. The test rig consists of a small-scale maglev vehicle, tracks with artificial jumps, and various sensors measuring displacements, accelerations, and coil currents. The experimental data matches well with those from the simulation model, indicating the validity of the model.

• Smart Structures and Systems
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• 제26권3호
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• pp.373-390
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• 2020

Hybrid simulation (HS) is a versatile tool for structural performance evaluation under dynamic loads. Although real structural responses are often multiple-directional owing to an eccentric mass/stiffness of the structure and/or excitations not along structural major axes, few HS in this field takes into account structural responses in multiple directions. Multi-directional loading is more challenging than uni-directional loading as there is a nonlinear transformation between actuator and specimen coordinate systems, increasing the difficulty of suppressing loading error. Moreover, redundant actuators may exist in multi-directional hybrid simulations of large-scale structures, which requires the loading strategy to contain ineffective loading of multiple actuators. To address these issues, lately a new strategy was conceived for accurate reproduction of desired displacements in bi-directional hybrid simulations (BHS), which is characterized in two features, i.e., iterative displacement command updating based on the Jacobian matrix considering nonlinear geometric relationships, and force-based control for compensating ineffective forces of redundant actuators. This paper performs performance validation and application of this new mixed loading strategy. In particular, virtual BHS considering linear and nonlinear specimen models, and the diversity of actuator properties were carried out. A validation test was implemented with a steel frame specimen. A real application of this strategy to BHS on a full-scale 2-story frame specimen was performed. Studies showed that this strategy exhibited excellent tracking performance for the measured displacements of the control point and remarkable compensation for ineffective forces of the redundant actuator. This strategy was demonstrated to be capable of accurately and effectively reproducing the desired displacements in large-scale BHS.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.69-74
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• 2016

A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.

• 한국ITS학회 논문지
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• 제22권5호
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• pp.43-52
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• 2023

옐로카펫 보급된 이후 어린이 교통사고는 감소세이나 아직 옐로카펫 설치와 교통사고간의 인과관계에 대한 설명력은 부족한 상황이다. 기존의 실차조사연구에서 상황 구현의 어려움이나 위험성 등의 이유로 수행하지 못한 다양한 상황을 VR시뮬레이션 실험을 활용하여 옐로카펫 효과를 더욱 심도있게 분석하였다. 실제 옐로카펫이 설치되어있는 대상지를 선정하고, 가상환경으로 구현한 후 시선측정장비를 착용하고 시뮬레이터에 탑승하도록 하였다. 옐로카펫 설치 전·후의 시각/주행행태를 비교하였고, 통계적 검증을 위해 t-test 분석을 수행, 모두 통계적으로 유의한 수준인 것으로 나타났다.

• 한국BIM학회 논문집
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• 제10권4호
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• pp.1-10
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• 2020

While the importance of barrier-free and fire evacuation design is highlighted in architectural design education, systemic analysis, and examination on such performances are still challenging due to methodological lacks. The present study investigates the effectiveness of BIM-based human behavior simulation for architecture major students' analytical examinations to promote barrier-free and fire evacuation performances. To achieve such an aim, quasi-experiments were conducted, which compare 50 students' analysis and examination scores according to the use and non-use of the simulation, and the data were collected via participants' survey and interview. As a result, T-Test and MANOVA analyses indicate that, compared with its non-use counterpart, the use of human behavior simulation better facilitates the students' (1) examination of the physical properties and dimensions for the disabled's accessibility and evacuation, (2) understanding of the bodily capacity and handicap of the disabled, (3) examination on the spatial layouts and locations of exits, (4) understanding on evacuees' urgent behaviors, and (5) responsibility as an architect. Based on previous studies, the reasons of statistical results are interpreted as the explicit observation and analytical measures of multiple numbers of virtual-evacuees and direct-experience from body range of the disabled responding to the populated occupants as what they face in authentic reality.

• 한국소음진동공학회논문집
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• 제17권8호
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• pp.708-719
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• 2007

In case of indoor gymnastics training floor, in view of its characteristics, since it is simultaneously required the related smooth communication between the coach and the player, also the acoustic performance regarding to the clearness of music, besides the sport activity, the consideration about the acoustic character has entered the stage as an indispensable element. On such viewpoint, recently constructed dome-typed gymnastic training floor was optimized acoustic design with remodeling through acoustic simulation test. And acoustic satisfaction degree and reaction was attempted to investigate about the gymnastics training floor estimating value of human's psychological(sensual) degree using auralization that enables to experience the virtual sound field at the stage of design. As the result of investigation about the research on the space of object, it could be known that the valuation regarding to the acoustic performance of 'after-improvement' was distinctly more refined than that of 'before-improvement'. It is now considering that such result of the study can be utilized as the useful data which enables to improve the retrenchment effect of the construction cost as well as the acoustic capability, by means of the prediction control on the acoustic problem from the stage of design, for the occasion when the similar indoor sport gymnasium is planning to build for the near future.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.283-290
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• 2007

A bi-modal tram has been developed to offer an advanced transportation service compared with existing vehicles. The All-Wheel-Steering system is applied to the bi-modal tram to satisfy the required steering performance because the bi-modal tram has extended length and articulated mechanism. An ECU for the steering system is essential to steer wheels on 2nd and 3rd axles by the specific AWS algorithm with the prescribed driving condition. The Hardware-In-the-Loop Simulation(HILS) system is planned for the purpose of evaluating the steering system of the bi-modal tram. There are kinematic links with the hydraulic actuator to steer wheels on each 2nd and 3rd axles and also same steering mechanism as the actual vehicle is in the HILS system. Controlling the movement of hydraulic actuator which reflects the lateral steering reaction force on each wheel is the key to realize the HILS system, but the reaction force is continuously changed according to various driving conditions. Therefore, the simulation through the multi-body dynamics model is used to obtain the required forces.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.945-950
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• 2001

Vacuum interrupters that is used in various switchgear components such as circuit breakers, distribution switches, contactors, etc. spreads the arc uniformly over the surface of the contacts. The electrode of vacuum interrupters is used sintered Cu-Cr material satisfied with good electrical and mechanical characteristics. Because the closing velocity is 1-3m/s, the deformation of the material of electrodes depends on the strain rate and the dynamic behavior of the sintered Cu-Cr material is a key to investigate the impact characteristics of the electrodes. The dynamic response of the material at the high strain-rate is obtained from the split Hopkinson pressure bar test using cylinder type specimens. Experimental results from both quasi-static and dynamic compressive tests with the split Hopkinson pressure bar apparatus are interpolated to construct the Johnson-Cook equation as the constitutive relation that should be applied to simulation of the dynamic behavior of electrodes. To evaluate impact characteristic of a vacuum interrupter, simulation is carried out with five parameters such as initial velocity, added mass of a movable electrode, wipe spring constant, initial offset of a wipe spring and virtual fixed spring constant.