• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.07a
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• pp.35-40
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• 2000

• Journal of the Korean Society for Precision Engineering
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• v.22 no.9 s.174
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• pp.147-154
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• 2005

A precision hi-directional actuator for a high precision leveling system with $Z{\Theta}_x{\Theta}_y$ motions is proposed and designed in this paper. The actuator is composed of a force generation structure, a guide mechanism, and a symmetric structure. At first, its driving force is generated by a change of flux in air gaps by permanent and changeable flux. The permanent flux is generated by a permanent magnet. The changeable flux is created by variable current flowing through coil. The combination of permanent and changeable flux makes various flux densities in air gaps between moving part and fixed yokes. And then, the difference between flux densities in lower and upper gaps creates forces fur the $bi-direction({\pm}z)$ motion. The guide mechanism of this actuator is composed of two circular plates and one shaft. Reducing motions generated by forces except z-motion, these circular plates endow the actuator with high stiffness for fast settling time. And the function of the shaft is to transfer motion to an object. At last, total body has a symmetric structure to be stable on thermal error. The actuator is designed by MAXWELL 2D and ProMECHANICA. The designed actuator is evaluated by 8nm laser doppler vibrometer, dynamic signal analyzer, and simple PID controller.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.264-268
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• 2016

Recently, various energy efficiency optimization activities are ongoing globally by integrating conventional grids with ICT (Information and Communication Technology). In this sense, various smart grid projects, which power suppliers and consumers exchange useful informations bilaterally in real time, have been being carried out. The electric vehicle diffusion program is one of the projects and it has been spotlighted because it could resolve green gas problem, fuel economy and tightening environmental regulations. In this paper, the economics of V2G system which consists of electric vehicles and the charging infrastructure is evaluated comparing electric vehicles for V2G with common electric vehicles. Additional benefits of V2G are analyzed in the viewpoint of load leveling, frequency regulation and operation reserve. To find this benefit, electricity sales is modeled mathematically considering depth of discharge, maximum capacity reduction, etc. Benefit and cost analysis methods with the modeling are proposed to decide whether the introduction of V2G systems. Additionally, the methods will contribute to derive the future production and the unit cost of electric vehicle and battery and to get the technical and economic analysis.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.4_2
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• pp.655-662
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• 2022

Recently, with the increase in the use of UAV(unmanned aerial vehicles), research on horizontal maintenance stations that can take off and land in various environments has been actively conducted. These stations can safely land UAV through multiple DOF(degrees of freedom) or at least 2-DOF-based actuator actuation. Among them, many researchers are dealing with the multi-DOF stewart platform due to its high safety. However, the stewart platform requires high-precision control technology because it requires a lot of torque to actuate according to the load action. Therefore, in this paper, to solve the mentioned problem, a bevel gear-based 2-DOF horizontal maintenance station system is proposed. The proposed system is configured to prevent damage due to air resistance when maintaining ships and to install it in a small space. Also, in terms of system configuration, the bevel gear-based horizontal maintenance system has the main advantage of being able to take off and land UAVs of various sizes through the replacement of station pads. The driving of the system consists of a simple form that can control the motor by adjusting the rotation speed of the motor according to the sea waveform.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.6
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• pp.139-144
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• 2019

For recent decades, Non-volatile Memory (NVM) technologies have been drawing a high attention both in industry and academia due to its high density and short latency comparable to that of DRAM. However, NVM devices has write endurance problem and thus the current data structures that have been built around DRAM-specific features including unlimited program cycles is inadequate for NVM, reducing the device lifetime significantly. In this paper, we revisit a red-black tree extensively adopted for data indexing across a wide range of applications, and make it to better fit for NVM. Specifically, we observe that the conventional red-black tree wears out the specific location of memory because of its rebalancing operation to ensure fast access time over a whole dataset. However, this rebalancing operation frequently updates the long-lived nodes, which leads to the skewed wear out across the NVM cells. To resolve this problem, we present a new swapping wear-leveling red-black tree that periodically moves data in the worn-out node into the young node. The performance study with real-world traces demonstrates the proposed red-black tree reduces the standard deviation of the write count across nodes by up to 12.5%.

• Journal of Drive and Control
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• v.12 no.4
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• pp.60-70
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• 2015

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1352-1355
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• 1997

This paper presents the algorithm for estimating the attitude of an underwater vehicle using EFK. The system model is designed by linerizing the nonlinear Euler angle differential equation and the measurements is a speed logger output. The simulation result shows that the estimation lagorithm is adequate for decreasing attitude errors that grow abruptly during the motion with acceleration and rotation. It also shows that we can adapt the algorithm for compensating initial attitude errors generated after initial leveling.

• The korean journal of orthodontics
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• v.23 no.2 s.41
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• pp.217-227
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• 1993

Preadjusted appliance, following the original concept of the Andrews Straight-Wire appliance, became increasingly common in the 1980s. In six phases of treatment, anchorage control, leveling and aligning, overbite control, overjet reduction, space closure, and finishing are very effective with using the preadjusted appliances. Space closure is the phase of treatment in which the difference between standard edgewise and preadjusted mechanics is most noticeable. Orthodontists have been able to reduce the use of closing loops and, because of the level slot lineup, enjoy the advantages of sliding mechanics. In 1990, Dr. John C. Bennett and Richard P. McLaughlin introduced the new space closure system, namely, elastic 'tiebacks'. They found an $.019'\times.025'$ working archwire most effective in an .022'-slot system. Hooks of .024' stainless steel or .028' brass wire are soldered to the upper and lower archwires. The force required for space closure is delivered by elastic 'tiebacks'. An elastic modulo stretched by 2-3mm(to twice its normal length) usually delivers 0.5-1.5mm of space closure per month. Group movement and sliding mechanics are combined for gentle, controlled space closure, so that about 0.5mm of incisor retraction and 0.5mm of mesial molar movement can be seen each month. The tiebacks are replaced every four to six weeks. By using the elastic 'tiebacks', the next two cases were treated during space closure. Even though we found some clinical problems of this mechanics, long treatment time, hard to control of vertical dimension and anchorage, the application method of this system is so simple that orthodontists can manage many patients during short chair time. But we must apply this mechanics after perfect understanding of the biomechanics in tooth movement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4D
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• pp.407-419
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• 2012

It is difficult to obtain the accurate and homogeneous height information over the whole Korea due to the effect of different vertical datums have been divided into land and sea part. In this study, we tried to unify the different vertical datums using the precise spirit leveling between TBM (tidal bench mark) and BM (bench mark) in order to solve the problems caused by different vertical datums. For this, the vertical datum offsets at observed points which were calculate from leveling results and then transformation model of vertical datum will be modelled using calculated offsets along the coastal line. For suggesting the precise modelling method to vertical datum transformation, we analyzed results from various interpolation methods such as Spline and LSC method. As the results from analysis, the LSC method combined with 4-parameters trend model is more suitable for modelling the offsets between vertical datums. The final transformation model of vertical datum using the combination of LSC and 4-parameter model which provides the transformation accuracies of ${\pm}10.4cm{\sim}14.8cm$ level. And, the software for vertical datum transformation that was also developed using the final model in order to convert the height information included in various spatial data effectively. Therefore, the transformation model between vertical datums of land and sea part, which is developed in this study, is expected to minimize the confusion caused by mismatch of height information in the use of spatial data, and it also can be minimize economic and time losses in various application fields such as coastal development project, coastal disaster prevention, etc.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.4
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• pp.71-81
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• 2010

In grid system, Task scheduling based on list scheduling models has showed low complexity and high efficiency in fully connected processor set environment. However, earlier schemes did not consider sufficiently the communication cost among tasks and the composition process of lightpath for communication in optical gird environment. In this thesis, we propose LSOG (Leveling Selection in Optical Grid) which sets task priority after forming a hierarchical directed acyclic graph (DAG) that is optimized in optical grid environment. To determine priorities of task assignment in the same level, proposed algorithm executes the task with biggest communication cost between itself and its predecessor. Then, it considers the shortest route for communication between tasks. This process improves communication cost in scheduling process through optimizing link resource usage in optical grid environment. We compared LSOG algorithm with conventional ELSA (Extended List Scheduling Algorithm) and SCP (Scheduled Critical Path) algorithm. We could see the enhancement in overall scheduling performance through increment in CCR value and smoothing network environment.