• Journal of Drive and Control
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• v.21 no.3
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• pp.46-55
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• 2024

In the agricultural machinery field, load analysis is mostly done through field tests. However, field tests are time-consuming and costly. There are also limitations in test conditions due to weather conditions. To overcome these environmental limitations, research on load analysis through simulation in a virtual environment is actively being conducted. This study aimed to select the most appropriate soil particle size for modeling by analyzing the effect of soil particle size on the prediction of draft force of the implement using simulation and soil particle modeling in a virtual environment with the discrete element method (DEM) software. The accuracy was verified by simulating the draft force for the same moving speed by soil particle size. For soil particle modeling, DEM soil modeling was performed by designing soil property measurement procedure. Soil particle correction was performed with a virtual vane shear test. Average DEM simulation results showed an error of 27.39% (19.43~40.66%) compared to actual measured data. The possibility of improvement was confirmed through additional research. Results of this study provide useful information for selecting soil particle size in soil modeling using DEM from the perspective of agricultural machinery research.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.2660-2664
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• 2003

In this study, the concept of autonomous mobility is applied to a medical service robot. The aim of the development of the service robot is for the elderly assisting walking rehabilitation. This study aims that the service robot design parameter is proposed in ergonomic view. The walking assistant path pattern is derived from analyzing the elderly gait analysis. A lever is installed in the AMR in order to measure the pulling force and the leading force of the elderly. A lever mechanism is applied for walking assistant service of the AMR. This lever is designed for measuring the leading force of the elderly. The elderly adjusts the velocity of the robot by applying force to the lever. The action scope and the service mechanism of the robot are developed for considering and analyzing the elderly action patterns. The ergonomic design parameters, that is, dimensions, action scope and working space are determined based on the elderly moving scope. The gait information is acquired by measuring the guide lever force by load cells and working pattern by the electromyography signal.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2004.11a
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• pp.316-322
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• 2004

Wear volume was used generally to analyze the moving state of lubricated machine. But It is difficult of getting the correct wear volume because wear volume of it is progressed always unstably with a large amplitude on working condition. If correct analysis of wear volume on working condition for lubricated machine can be possible, it can be effect on diagnosis of failure condition. The purpose of this study is carried out to analysis friction factors affecting on wear volume for prediction of failure condition of alloy steel for machine structural use by design of experiment. The results show that the most important friction factors affecting on wear volume was applied load, neat sliding distance, sliding speed and materials.

• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.315-323
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• 2009

Pressure oscillations triggered by the unstable interaction of dynamic flow features of the hydraulic turbine with the hydraulic plant system - including the electrical design - can at times reach significant levels and could lead to damage of plant components or could reduce component lifetime significantly. Such a problem can arise for overload as well as for part load operation of the turbine. This paper discusses an approach to analyze the overload high pressure oscillation problem using computational fluid dynamic (CFD) modeling of the hydraulic machine combined with a network modeling technique of the hydraulic system. The key factor in this analysis is the determination of the overload vortex rope volume occurring within the turbine under the runner which is acting as an active element in the system. Two different modeling techniques to compute the flow field downstream of the runner will be presented in this paper. As a first approach, single phase flow simulations are used to evaluate the vortex rope volume before moving to more sophisticated modeling which incorporates two phase flow calculations employing cavitation modeling. The influence of these different modeling strategies on the simulated plant behavior will be discussed.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1422-1423
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• 2006

In our study, the PTFE nozzle ablation in the high-voltage self-blast type $SF_6$ gas circuit breaker was investigated. The test circuit breaker has the structure that the pin electrode is moving and the pressure reservoir volume and the dimension is almost same as commercial 145kv 40kA circuit breaker for similar result in real circuit breaker. The variation of current and arcing time was the range of $36kA_{rms}$(symmetry) - $40kA_{rms}$(asymmetry) and 10-16 ms. From the measured data the tendecy of the mass loss of the nozzle to current load and arc energy was estimated. In this process, the distance from the arc to nozzle(PTFE) surface, area which was exposed to arc and stroke contour was considered. These results will be used to enhance the accuracy of the computational fluid dynamics analysis in circuit breaker and estimate the residual life time of a circuit breaker.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.986-993
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• 2002

The equations of motion for an automated guide-way transit(AGT) system running on a path with roughness have been derived to investigate dynamic responses and wheel loads of moving vehicles of the AGT system. A vehicle of the AGT system is idealized as three-dimensional model with 11 degree-of-freedom. The computer program is developed to solve the dynamic equations, and anlatical results are verified by comparing the results with experimental oness. Parametric studies are carried out to investigate the dynamic responses of an AGT vehicle according to vehicle speeds, surface roughness, damping and stiffness of suspension systems. The parametric study demonstrates that amplitudes of dynamic responses and the wheel loads have a tendency to increase according to travel speeds, the stiffness of suspension system and surface roughness. On the other hand. those amplitudes tend to decrease according to increase of damping of the suspension system.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.6
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• pp.474-483
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• 2003

In this study, the dynamic characteristics of a catenary system and pantograph supplying electrical power to high-speed trains are investigated. One of the most important issues accompanied by increasing the speed of high-speed rail is stabilization of current collection. To stabilize current collection, it is necessary the contact force between the catenary and the pantograph to be kept continuous without loss of contact. The analytical model of a catenary and a pantograph is constructed to simulate the behavior of an actual system. The analysis of the catenary based on the Finite Element Method (FEM) is performed to develop a catenary model suitable for high speed operation. The reliability of the models is verified by the comparison of the excitation test with Fast Fourier Transform (FFT) data of the actual system. The static deflection of the catenary, stiffness variation in contact lines, dynamic response of the catenary undergoing constant moving load, contact force, and each state of the pantograph model were calculated. It is confirmed that a catenary and pantograph model are necessary for studying the dynamic behavior of the pantograph system.

• Journal of Drive and Control
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• v.16 no.2
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• pp.8-14
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• 2019

A typical gantry crane is generally used to lift and transport objects in various workplaces. Most of the supporting structures in a gantry crane are fixed on the ground while the moving hoist is running overhead along the girder. There are some disadvantages to its long installation time and high installation cost. Therefore, a hydraulic based gantry crane was studied to solve the issues of typical gantry cranes. The supporting structure of the proposed gantry crane consisted of a hydraulic cylinder and telescopic boom. The dimension of the proposed gantry crane can be decreased due to its simplified structure. The analytical and theoretical methods were used to verify the structural stability of the proposed crane. The most severe load condition was considered for the analysis, and the stress and deflection of the structure are analyzed. The simulation results were as expected from the theoretical analysis. Finally, the structural and dynamic safety of the proposed hydraulic based gantry crane was validated. The obtained results can be used as guidelines in the design process of the hydraulic based gantry crane.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.6_3
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• pp.1127-1133
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• 2022

Recently, the use of aircraft structures using Ti alloy (Ti-6Al-4V), a lightweight high-strength alloy material, is rapidly increasing due to the weight reduction of aircraft. However, high-strength materials such as Ti alloys require high energy for cutting and are classified as difficult-to-cut materials. Also, research on Laser Assisted Machining (hereinafter referred to as LAM), a cutting processing technology that utilizes improved machinability, is being actively researched. Therefore, in this paper, in order to confirm the proper temperature distribution using a laser, the finite element method is used to determine the temperature distribution according to the calorific value condition to derive the appropriate condition, and the thermal load generated at this time is used as a structural analysis. It is intended to be used as basic data for LAM processing conditions by measuring the amount of residual stress and thermal deformation caused by heat.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.101-108
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• 2011

In forest work, working conditions are very hard to improve. The proper distribution of work time and good posture is believed to bring about direct improvements such as accident prevention. On this, this study has analyzed forest workers' posture and their working hours in order to improve their working conditions in stone channel work. Authors has chosen several core elements of stone channel work to focus on, which include stone masonry, excavation of bed, moving stone, directing work, choosing stone, and breaking stone. The ratio of real working time over total working time was shown as 84.6%. As for the time ratio of each elemental work over the real working time, the stone masonry was 60.4%, the directing work was 15.1%, moving stone was 12.1%, choosing stone was 7.1%, breaking stone was 3.3%, and excavation of bed was 2.0%. According to the analytical results provided by OWAS, the ratio of category III (Work posture has a distinctly harmful effect on the musculoskeletal system) has shown that moving stone turned out 65.2%, choosing stone was 61.5%, stone masonry was 46.1%, breaking stone was 14.3%, excavation of bed was 12.5% and directing work was 6.8%. Furthermore, the ratio of category IV (Work posture with an extremely harmful effect on the musculoskeletal system) has shown that excavation of bed turned out 37.5%, breaking stone was 28.6%, stone masonry was 27.3%, choosing stone was 7.7%, moving stone was 6.1% and directing working was 4.5%. These results are expected to be utilized for the improvement with respect to both working methods in the stone channel work and the workers' working posture.