• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.8 s.350
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• pp.35-46
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• 2006

When an RFID reader attempts to read the tags, interference might occur if the neighboring readers also attempt to communicate with the same tag at the same time or the neighboring readers use the same frequency simultaneously. These interferences cause the RFID reader collision. When the RFID reader collision occurs, either the command from the reader cannot be transmitted to the tags or the response of the tags cannot receive to the reader correctly, Therefore, the international standard for RFID and some papers proposed the methods to reduce the reader collision. Among those, Colorwave and Enhanced Colorwave is the reader anti-collision algorithm using the frame slotted ALOHA based a TDM(Time Division Multiplex) and are able to reduce the reader collision because theses change the frame size according to a collision probability. However, these can generate the reader collisions or interrupt the tag reading of other readers because the reader that collides with another reader randomly chooses a new slot in the frame. In this paper, we propose a new RFID reader anti-collision algorithm that each reader monitors the slots in the frame and chooses the slot having the minimum occupation probability when the reader collision occurs. Then we analyze the performance of the proposed algorithm using simulation tool.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.8 no.4
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• pp.41-47
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• 2009

This research deals with evaluation of machining accuracy for Parallel Kinematic Machine Tool(PKMT) applied parallel type robot system with high precision and stiffness. For this purpose, machine simulation is carried out to foreknow collision and interference between workpiece and tool. Furthermore, on the basis of machine simulation data, PKMT is manufactured. Machining accuracy such as cylindricity straightness, squareness, parallelism circularity, concentricity pitch error and yaw error, is measured by using coordinate measuring machine. Test piece for evaluation of machining accuracy is designed and manufactured under the standard of ISO 10791-7.

• Korean Journal of Computational Design and Engineering
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• v.9 no.1
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• pp.35-43
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• 2004

It is well known that the five-axis machining has advantages of tool accessibility and machined surface quality when compared with conventional three-axis machining. Traditional researches on the five-axis tool-path generation have addressed interferences such as cutter gouging, collision, machine kinematics and optimization of a CL(cutter location) or a cutter position. In the paper it is presented that optimal CL data for a face-milling cutter moving on a tool-path are obtained by incorporating TSS(tool swept surface) model. The TSS model from current CL position to the next CL position is constructed based on machine kinematics as well as cutter geometry, with which the deviation from the design surface can be computed. Then the next CC(cutter-contact) point should be adjusted such that the deviation conforms to given machining tolerance value. The proposed algorithm was implemented and applied to a marine propeller machining, which proved effective from a quantitative point of view. In addition, the algorithm using the TSS can also be applied to avoid cutter convex interferences in general three-axis NC machining.

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

• Journal of the Society of Naval Architects of Korea
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• v.55 no.2
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• pp.178-186
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• 2018

The scale effects on the permanent deformations and fractures of structures subjected to impact loadings have been aware by structural engineers for a long time. Experimental investigations have been performed with various structures to demonstrate the effects, but very few are directly related with marine structural elements. Furthermore, the causes of the scale effects have not clearly been answered yet. In this study, to quantify the scale effects on the permanent deflections, lateral collision tests were performed on steel unstiffened plates and the numerical analyses of the tested models were also conducted using a commercial package, Abaqus. After the substantiation of the numerical tool using the test results, a parametric study was carried out considering and neglecting the strain-rate hardening. Based upon the parametric study results, it may be concluded that the main cause of the scale effects on the permanent deflections of steel unstiffened plates subjected to lateral collision loads is the strain-rate effects.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.4 no.2
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• pp.16-23
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• 2005

This study is intended to find out the reason of interference phenomenon of a machine tool when it operates for 5-axises working. The researcher made a Virtual Machine which has same figures of the 5 axises machine tool and Virtual Manufacturing System which has both Software factors - controller and NC code data to manipulate the movement characteristics of the machine - and Hardware factors - fixtures, workpiece, tools, holders and so on. With these virtual tools, this study is designed to find out the relation between the movement and the interference or collision, and also intended to verify the simulation and work-processing. In this study, the researcher found out, in case of the vertical 5 axises type, that it has more chances to have interference between the fixture, the workpiece and the main spindle including the tool holder due to the tilting kinetics of the main spindle. In case of the horizontal 5 axises type, on the other hand, the researcher found out that it has more possibility to have the interference between the main spindle and the rotary shaft.

• Journal of the Korean Society of Safety
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• v.32 no.3
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• pp.136-140
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• 2017

The physical tool for analyzing collision accidents narrows down to the conservation law of momentum. The conservation law of momentum which is also utilized to investigate or to analyze a traffic accident is essential to Newton mechanics. This paper suggests an alternative analytical tool based on the conservation law of momentum. Simply put, the tool is a alternative qualitative method of analyzing a car's direction to find out whether it is driving over the centerline This paper proposes a deduction theory that use qualitative information to make a qualitative analysis of which car drove over the center line.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.29-39
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• 1998

A conversational programming system for turning processes was studied to enhance the user friendliness of a NC Lathe by adopting man-machine interface functions through Delphi programming tool under the Windows 95 environment. Functions of tool collision checking were developed through zone limitation algorithms. Final shape of workpiece was generated by means of tree structure algorithm. Shop floor programming performance was incorporated in the developed CAM module. In order to increase flexibility of the man-machine interface, graphic based programming tools have been developed. A NC turning machine equipped with an open architecture PCNC was used as a test bed of the system. Performance of the system was verified through case studies.

• Korean Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.293-303
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• 1998

The objective of this study is to develop a PC level freeform surface modeling system which explicitly represents information of part geometry. Surface modeler uses nonuniform rational B-spline (NURBS) function with nonuniform knot vector for the flexible modeling work. The results of this study are as follows. 1) By implementation surface modeler through applying representation scheme proposed to represent free-form surface explicity, the technical foundation to develop free-from surface modeling system using parametric method. 2) Besides the role to model geometric shape of a surface, geometric modeler is developed to model arbitrary geometric shape. By doing this, the availability of the modeling system is improved. Geometric modeler can be utilized application fields such as collision test of tool and fixture, and tool path generation for NC machine tool.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.6
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• pp.95-101
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• 2011

Micro-abrasive jet machining(${\mu}AJM$) using mask is a fine machining technology which can carve a figure on a material. The mask should have holes exactly same as the required figure. Abrasive particles are jetted into the holes of the mask and it collide with the material. The collision break off small portion of the material. And the ${\mu}AJM$ nozzle should move all over the machining area. However, in general the carving shape is modeled as in a bitmap figure, because it often contains characters. And the mask model is also often modeled from the bitmap image. Therefore, the machining path of the ${\mu}AJM$ also efficient if it can be generated from the bitmap image. This paper suggest an algorithm which can generate ${\mu}AJM$ tool path directly from the bitmap image of the carving figure. And shows some test results and applications.