• Journal of the Korean Society for Marine Environment & Energy
• /
• v.9 no.4
• /
• pp.253-262
• /
• 2006

In this paper, collision analysis is carried out between two FRP fishing boats. A computer simulation with finite element method is used to accomplish this objective. At first, a detailed geometric model of the boat is constructed using 3-D CAD program. The formation of a finite element from a geometric data of the boats is carried out using HYPERMESH that is the commercial software for mesh generation and post processing. Twelve collision configurations are established by combining two kinds of contact angle($90^{\circ},\;135^{\circ}$) and three different speed(5, 10, 15knot) for small and large boats. Collision analysis is accomplished using DYNA3D. Stress distribution and deformation shape are investigated for each collision condition. In general, $90^{\circ}$ collision angle generate larger stress than $135^{\circ}$ case and the collision for two moving boats showed larger maximum stress than the case that one is moving and the other is stationary. When analysis is carried out until 150ms contact parts of two boats are broken for 10 and 15knot collision speed, in which maximum stress is larger than ultimate strength of the material.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.10
• /
• pp.5963-5967
• /
• 2014

Reducing the impact of collisions of cars is a major issue for reducing the injury and death of passengers. According to the statistical data of the Road Traffic Authority, the deaths from side collision accidents caused by the collision of passenger cars is greater than the deaths from head-on collision accidents. To accommodate this, vehicle designers have added a reinforcing material called the impact frame and impact beam on the inside of the door. Many experiments are needed to develop the door impact beam. These reinforcements to develop a collision experiment is essential. Collision experiments are costly and time consuming. This study used a drop Impactor to obtain the impulse and a strain experimental device was developed for this purpose. The economic costs were reduced and the ideal experiment device configuration was determined. A comparison of the experimental results with numerical value analysis revealed $3.5{\tiimes}10-3sec$ strain ranging from $3.49{\tiimes}10-3$ to $3.99{\tiimes}10-3$.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2019.05a
• /
• pp.267-267
• /
• 2019

Driftwood is one of serious problems in a river environment. In several countries, such as Indonesia, Japan, and Italy, the driftwood frequently appears in a river basin, and it can alter the channel bed, flow configuration by wood deposition and jam formation. Therefore, the studies related to driftwood have been actively conducted by many researchers to understand the mechanism of driftwood dynamics. In particular, wood motion by collision is one of the difficult issues in the numerical simulation because the calculation for wood collision requires significantly expensive calculation time due to small time step. Thus, this study conducted the numerical simulation in consideration of the wood motion by water flow and wood collision to understand the wood dynamics in terms of computation. We used the 2D (two-dimensional) depth-averaged velocity model, Nays2DH, which is a Eulerian model to calculate the water flow on the generalized coordinate. A Lagrangian type driftwood model, which expresses the driftwood as connected sphere shape particles, was employed to Nays2DH. In addition, the present study considered root wad effect by using larger diameter for a particle at a head of driftwood. An anisotropic bed friction was considered for the sliding motion dependent on stemwise, streamwise and motion directions. We particularly considered changeable draft at each particle and projection area by an angle between stemwise and flow directions to precisely reproduce the wood motions. The simulation results were compared with experimental results to verify the model. As a result, the simulation results showed good agreement with experimental results. Through this study, it would be expected that this model is a useful tool to predict the driftwood effect in the river flow.

• 제어로봇시스템학회:학술대회논문집
• /
• 1995.10a
• /
• pp.530-533
• /
• 1995

This paper deals with the problem of motion planning for a unicycle-like robot. We present a simple local planner for unicycle model, based on an approximation of the desired configuration generated by local holonomic planner that ignores motion constraints. To guarantee a collision avoidance, we propose an inequality constraint, based on the motion analysis with the constant control input and time interval. Consequently, we formulate our problem as the constrained optimization problem and a feedback scheme based on local sensor information is established by simply solving this problem. Through simulations, we confirm the validity and effectiveness of our algorithm.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.20 no.2
• /
• pp.169-173
• /
• 2011

Crash box is introduced to vehicle design to improve the impact performance and reduce the damage of vehicle body at impact speed. The crash box behind bumper can absorb impact energy effectively to improve vehicle safety. Repair cost at collision accident can be cut down by use of this box. The configuration of car body must be designed by considering the characteristic of material due to the deformation of car body happened at impact. Many papers have been published about material of crash box all over the world. The study of crash box with tube expansion type has been going on Korea. This study is done by the simulation analysis about front collisions against 5 kinds of aluminum crash boxes with the basic structure of square section.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.4
• /
• pp.213-220
• /
• 2023

This paper presents a model simulating the folding process and collision dynamics of "ddakji", a traditional Korean game played using paper tiles (which are also referred to as ddakji). The model uses two A4 sheets as the base materials for ddakji. The folding process involves a series of boundary conditions that transform the wing part of the paper structure into a twisted configuration. A rigid plate boundary condition is also adopted for squeezing, establishing the shape and stress state of the game-ready ddakji through dynamic relaxation analysis. The gaming process analysis involves a forced displacement of the striking ddakji to a predetermined collision position. Collision analysis then follows at a given speed, with the objective of overturning the struck ddakji--a winning condition. A genetic algorithm-based optimization analysis identifies the optimal collision conditions that result in the overturning of the struck ddakji. For efficiency, the collision analysis is divided into two stages, with the second stage carried out only if the first stage predicts a possible overturn. The fitness function for the genetic algorithm during the first stage is the direction cosine of the struck ddakji, whereas in the second stage, it is the inverse of the speed, thus targeting the lowest overall collision speed. Consequently, this analysis provides optimal collision conditions for various compression thicknesses.

• Journal of the Korean Mathematical Society
• /
• v.61 no.3
• /
• pp.565-602
• /
• 2024

We study the collective behaviors of two second-order nonlinear consensus models with a bonding force, namely the Kuramoto model and the Cucker-Smale model with inter-particle bonding force. The proposed models contain feedback control terms which induce collision avoidance and emergent consensus dynamics in a suitable framework. Through the cooperative interplays between feedback controls, initial state configuration tends to an ordered configuration asymptotically under suitable frameworks which are formulated in terms of system parameters and initial configurations. For a two-particle system on the real line, we show that the relative state tends to the preassigned value asymptotically, and we also provide several numerical examples to analyze the possible nonlinear dynamics of the proposed models, and compare them with analytical results.

• Journal of computational fluids engineering
• /
• v.16 no.2
• /
• pp.66-74
• /
• 2011

The SCR catalyst in coal-fired power plant is eroded by the collision of fly ash on the catalyst surface. However the erosion of SCR catalyst by the collision of fly ash has not been fully studied, especially in terms of fluid dynamics. Hence, in the present study, we focus on the gas and solid flows inside the SCR catalyst duct and their consequent effect on the erosion characteristics. For this purpose, computational fluid dynamics is applied to investigate the two-phase flows and to evaluate the erosion rate for different flow and particle injection conditions. Also, the erosion rate and pressure drop of commonly used square shape are compared with equilateral triangle and hexagon shapes. The pressure drop of SCR catalyst is increased when SCR catalyst surface area per unit volume increases. The erosion rate of SCR catalyst is enhanced when the particle velocity, mass flow rate of particle, particle diameter and cell density of SCR catalyst are increased. From the results, the pressure drop and erosion rate at the catalyst surface can be minimized by reducing cell density of SCR catalyst to decrease particle velocity and number of particle impacts.

• International Journal of Control, Automation, and Systems
• /
• v.5 no.6
• /
• pp.674-680
• /
• 2007

The probabilistic roadmap (PRM) method, which is a popular path planning scheme, for a manipulator, can find a collision-free path by connecting the start and goal poses through a roadmap constructed by drawing random nodes in the free configuration space. PRM exhibits robust performance for static environments, but its performance is poor for dynamic environments. On the other hand, reinforcement learning, a behavior-based control technique, can deal with uncertainties in the environment. The reinforcement learning agent can establish a policy that maximizes the sum of rewards by selecting the optimal actions in any state through iterative interactions with the environment. In this paper, we propose efficient real-time path planning by combining PRM and reinforcement learning to deal with uncertain dynamic environments and similar environments. A series of experiments demonstrate that the proposed hybrid path planner can generate a collision-free path even for dynamic environments in which objects block the pre-planned global path. It is also shown that the hybrid path planner can adapt to the similar, previously learned environments without significant additional learning.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.51 no.3
• /
• pp.155-160
• /
• 2002

This paper focuses on the problem of local obstacle avoidance of mobile robots. To solve this problem, the safety direction section search algorithm is suggested. This concept is mainly composed with non-collision section and collision section from the detecting area of laser scanning sensor. Then, we will search for the most suitable direction in these sections. The proposed local motion planning method is simple and requires less computation than others. An environment model is developed using the vector space concept to determine robot motion direction taking the target direction, obstacle configuration, and robot trajectory into account. Since the motion command is obtained considering motion dynamics, it results in smooth and fast as well as safe movement. Using the mobile base, the proposed obstacle avoidance method is tested, especially in the environment with pillar, wall and some doors. Also, the proposed autonomous motion planning and control algorithm are tested extensively. The experimental results show the proposed method yields safe and stable robot motion through the motion speed is not so fast.