• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.660-671
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• 2008

The suspension bridge between Myodo and Gwangyang is located in the main navigation channel to Gwangyang Harbor. So, there is need for the collision protection against large vessels. As ship collision protection, artificial island with concrete block quay wall is planned. The risk analysis and non-linear numerical analysis are introduced to consider the ship collision effects. In the Gwangyang bay area, there are some different sedimental conditions in clayey stratums. For a desirable design, we classify into four zones and 2 layers in each zone, and then determine suitable soil properties considering these zones. As a ground improvement under artificial island, DCM and SCP methods are Planned.

• Journal of Biosystems Engineering
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• 제3권1호
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• pp.1-19
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• 1978

Power tiller is a major unit of agricultural machinery being used on farms in Korea. About 180.000 units are introduced by 1977 and the demand for power tiller is continuously increasing as the farm mechanization progress. Major farming operations done by power tiller are the tillage, pumping, spraying, threshing, and hauling by exchanging the corresponding implements. In addition to their use on a relatively mild slope ground at present, it is also expected that many of power tillers could be operated on much inclined land to be developed by upland enlargement programmed. Therefore, research should be undertaken to solve many problems related to an effective untilization of power tillers on slope ground. The major objective of this study was to find out the travelling and tractive characteristics of power tillers being operated on general slope ground.In order to find out the critical travelling velocity and stability limit of slope ground for the side sliding and the dynamic side overturn of the tiller and tiller-trailer system, the mathematical model was developed based on a simplified physical model. The results analyzed through the model may be summarized as follows; (1) In case of no collision with an obstacle on ground, the equation of the dynamic side overturn developed was: $$\sum_n^{i=1}W_ia_s(cos\alpha cos\phi-{\frac {C_1V^2sin\phi}{gRcos\beta})-I_{AB}\frac {v^2}{Rr}}=0$$ In case of collision with an obstacle on ground, the equation was: $$\sum_n^{i=1}W_ia_s\{cos\alpha(1-sin\phi_1)-{\frac {C_1V^2sin\phi}{gRcos\beta}\}-\frac {1}{2}I_{TP} \( {\frac {2kV_2} {d_1+d_2}\)-I_{AB}{\frac{V^2}{Rr}} \( \frac {\pi}{2}-\frac {\pi}{180}\phi_2 \} = 0 $$ (2) As the angle of steering direction was increased, the critical travelling veloc\ulcornerities of side sliding and dynamic side overturn were decreased. (3) The critical travelling velocity was influenced by both the side slope angle .and the direct angle. In case of no collision with an obstacle, the critical velocity $V_c$ was 2.76-4.83m/sec at $\alpha=0^\circ$, $\beta=20^\circ$ ; and in case of collision with an obstacle, the critical velocity $V_{cc}$ was 1.39-1.5m/sec at $\alpha=0^\circ$, $\beta=20^\circ$ (4) In case of no collision with an obstacle, the dynamic side overturn was stimu\ulcornerlated by the carrying load but in case of collision with an obstacle, the danger of the dynamic side overturn was decreased by the carrying load. (5) When the system travels downward with the first set of high speed the limit {)f slope angle of side sliding was $\beta=5^\circ-10^\circ$ and when travels upward with the first set of high speed, the limit of angle of side sliding was $\beta=10^\circ-17.4^\circ$ (6) In case of running downward with the first set of high speed and collision with an obstacle, the limit of slope angle of the dynamic side overturn was = $12^\circ-17^\circ$ and in case of running upward with the first set of high speed and collision <>f upper wheels with an obstacle, the limit of slope angle of dynamic side overturn collision of upper wheels against an obstacle was $\beta=22^\circ-33^\circ$ at $\alpha=0^\circ -17.4^\circ$, respectively. (7) In case of running up and downward with the first set of high speed and no collision with an obstacle, the limit of slope angle of dynamic side overturn was $\beta=30^\circ-35^\circ$ (8) When the power tiller without implement attached travels up and down on the general slope ground with first set of high speed, the limit of slope angle of dynamic side overturn was $\beta=32^\circ-39^\circ$ in case of no collision with an obstacle, and $\beta=11^\circ-22^\circ$ in case of collision with an obstacle, respectively.

• 대한임베디드공학회논문지
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• 제17권2호
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• pp.115-121
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• 2022

This paper proposes a distributed model predictive formation control algorithm for a group of unmanned ground vehicles (UGVs) with guaranteeing collision avoidance between UGVs. Generally, the model predictive control based formation control has a disadvantage in that it takes a long time to compute control inputs when considering collision avoidance between UGVs. In this paper, in order to overcome this problem, the formation control algorithm is implemented in a distributed manner so that it could be individually controlled. Also, a collision-avoidance method considering real-time is proposed. The proposed formation control algorithm is implemented based on robot operating system (ROS), open source-based middleware. Through the various simulation tests, it is confirmed that the formation control of five UGVs is successfully performed while avoiding collisions between UGVs.

• 한국항공우주학회지
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• 제40권6호
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• pp.515-522
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• 2012

항공기 사고 중에서 주요 원인 중 하나인 조종상태 지상충돌(Controlled Flight Into Terrain, CFIT)을 해결하기 위하여 대지 접근 경고 장치(Ground Proximity Warning System, GPWS)를 사용하여 항공기 아랫부분의 지형에 대해서 지형충돌 경고를 출력한다. 이러한 대지 접근 경고 장치도 적시에 경고가 발생하지 않아 많은 문제가 있었다. 본 논문에서는 비행 상태와 지형정보를 이용하여 속도가 빠르고, 고기동을 하는 전투기에 대해서 보다 효율적인 지형/장애물 충돌 회피 경고 알고리듬을 개발하였다. 이 알고리듬에는 조종사의 반응시간을 포함하여 항공기의 지연시간을 고려하였고, 일련의 검증을 통해 실제 탑재 가능한 알고리듬을 제시하였다.

• Earthquakes and Structures
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• 제3권5호
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• pp.675-694
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• 2012

The 2008 Iwate-Miyagi Nairiku earthquake ($M_w$ 6.9, $M_{jma}$ 7.2) occurred on 14 June 2008 in Japan. The amplification and asymmetric waveform of the vertical acceleration at the ground surface recorded by accelerometers at station IWTH25, situated 3 km from the source, were remarkable in two ways. First, the vertical acceleration was extremely large (PGA = 38.66 $m/s^2$ for the vertical component, PGA = 42.78 $m/s^2$ for the sum of the three components). Second, an unusual asymmetric waveform, which is too far above the zero acceleration axis, as well as large upward spikes were observed. Using a multidegree-of-freedom (MDF) system consisting of a one-dimensional continuum subjected to vertical acceleration recorded at a depth of 260 m below ground level, the present paper clarifies numerically that these singular phenomena in the surface vertical acceleration records occurred as a result of the jumping and collision of a layer in vertical motion. We herein propose a new mechanism for such jumping and collision of ground layers. The unexpected extensive landslides that occurred in the area around the epicenter are believed to have been produced by such jumping under the influence of vertical acceleration.

• 한국정밀공학회지
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• 제30권1호
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• pp.53-58
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• 2013

In this paper, we present a framework for collision avoidance of UGVs by vision-based control. On the image plane which is created by perspective camera rigidly attached to UAV hovering stationarily, image features of UGVs are to be controlled by our control framework so that they proceed to desired locations while avoiding collision. UGVs are assumed as unicycle wheeled mobile robots with nonholonomic constraint and they follow the image feature's movement on the ground plane with low-level controller. We used potential function method to guarantee collision prevention, and showed its stability. Simulation results are presented to validate capability and stability of the proposed framework.

• 대한기계학회논문집A
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• 제40권5호
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• pp.469-481
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• 2016

본 논문에서는 강체 간 충돌에 의해 발생하는 충격력을 얻는 수학적 방법이 이론적으로 연구되었다. 이 이론적 방법은 사고로 지면에 추락낙하 하는 고준위폐기물 처분용기에 가해지는 충격력을 구하는 데에 적용되었다. 이 연구로부터 고준위폐기물 처분용기의 구조 안전성 설계에 요구되는 충격력이 이론적으로 유도되었다. 이론연구의 주된 내용은 두 강체의 충돌 시 강체운동학과 운동방정식에 관한 것이다. 이를 토대로 두 물체 간 충돌 시 발생하는 충격력을 구하는 일반적인 충격이론이 개발되었다. 이 충격이론을 처분장에서 처분용기 운송 시 운반차량에서 사고로 추락낙하 하여 지면과 충돌하는 처분용기에 발생하는 충격력을 구하는 문제에 적용하여 충격력에 대한 수학적 근사해를 이론적으로 구하였다. 동시에 컴퓨터코드를 이용한 수치해석을 수행하여 구한 수치해를 수학적 근사해와 비교하였다.

• 한국전산구조공학회논문집
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• 제33권1호
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• pp.17-23
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• 2020

본 논문에서는 인공섬 형식의 방호공을 구성하는 수중사면에 선박이 충돌하는 경우 발생하는 선박과 지반의 거동을 해석하기 위한 모델을 Coupled Eulerian-Lagrangian(CEL) 기법을 이용하여 구성하였다. 충돌에서 발생하는 지반의 전단파괴를 포함하는 대변형을 고려하기 위하여 지반과 해수는 Eulerian 영역으로 구성하고 충돌체를 Lagrangian 영역으로 구성되었다. 해석의 효율성을 향상시키기 위해서 mass scali기법을 충돌체의 모델링에 도입하였으며, 지반은 Eulerian영역에서 Eulerian Volume Fraction(EVF)값을 설정하여 구성하였다. 작성된 모델의 적용성을 검증하기 위하여 동적관입앵커에 대한 해석을 수행하였다. 또한 컨테이너선의 외부형상에 따라 고체요소로 모델링된 선수가 수중사면에 충돌하는 경우의 해석을 수행하고, 그 때 발생하는 변위, 속도, 소산에너지 등의 거동을 평가하였다. 그 결과로 매개변수해석에 대한 추가적인 연구 필요성이 도출되었다.

• 한국군사과학기술학회지
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• 제11권2호
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• pp.53-65
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• 2008

This paper proposes the qualitative method for planning the operation of multi-AUVs with environmental disturbances, which is considered to be a very difficult task. In this paper we use an extension collision map as a collision free motion planner. The tool was originally developed for the multiple ground vehicles with no internal/external disturbance. In order to apply the method to a water environment where there are tides and waves, and currents, we analyze the path deviation error of AUVs caused by external disturbances. And we calculate safety margin for the collision avoidance on the extension collision map. Finally, the simulation result proves that the suggested method in this paper make multi-AUVs navigate to the goal point effectively with no collision among them.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.82-91
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• 2011

In this paper, a planar model for mechanics of a vehicle/pedestrian collision incorporating road gradient is derived to evaluate the pre-collision speed of vehicle. It takes into account a few physical variables and parameters of popular wrap and forward projection collisions, which include horizontal distance traveled between primary and secondary impacts with the vehicle, launch angle, center-of-gravity height at launch, distance from launch to rest, pedestrian-ground drag factor, the pre-collision vehicle speed and road gradient. The model including road gradient is derived analytically for reconstruction of pedestrian collision accidents, and evaluates the vehicle speed from the pedestrian throw distance. The model coefficients have physical interpretations and are determined through direct calculation. This work shows that the road gradient has a significant effect on the evaluation of the vehicle speed and must be considered in accident cases with inclined road. In additions, foreign/domestic empirical cases and multibody dynamic simulation results are used to construct a least-squares fitted model that has the same structure of the analytical one that provides an estimate of the vehicle speed based on the pedestrian throw distance and the band within which the vehicle speed would be expected to be in 95% of cases.