• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.609-614
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• 1998

A new small signal modeling of an average current mode control is proposed. In order to analyze the characteristics of the control scheme, the discrete and continuous time small signal models are derived. The derivation are mainly come from the analysis of the sampling effect presented in the current control loop. By the mathematical interpretation of practical sampler representing the sampling effect of a current control loop, the small signal models of an average current mode control can be easily derived. The instability of the current control loop, which gives rise to the subharmonic oscillation, can be identified by the proposed models. To show the usefulness of the proposed models, the simulation and experiment are carried out. The results show that the predicted results by the proposed model are much better agreed with the measured ones than that of the conventional model, even though the high gain of the compensation network of a current control loop is employed.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.1
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• pp.1-13
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• 2007

This study was carried out to evaluate the applicability of the odor source tracking using wind field and fingerprint as a solution tool. First of all, CALMET and HYSPLIT modeling system, and database of odor discharge companies were utilized to track odor from industrial complexes. Secondly, industrial odor fingerprint was made by listing on the 19 domestic industries, and compared with foreign data to assess the representative, and thus the similarity was 86.7%. On the modeling experiment, Sihwa industrial complex did not show any difference because the matching rates of day and night were 49.5% and 50.0%, respectively. However, the Banwol and Sihwa industrial complexes did show some differences due to odor facility density. Separately, in this study, odor samples were obtained from 10 odor discharging companies, located in the Sihwa and Banwol industrial complexes, They were compared with the results of odor tracking modeling. The matched companies were 4 of 10 by three cases of tracking, while the fingerprint and industry of odor monitoring networks and companies matched each other. Therefore, this study confirmed the approach applicability of source tracking system using the fingerprint.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.461-467
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• 2000

Mechanical problems are basically three dimensional nonlinear dynamic problems, which makes it difficult to solve. The difficulties are tried to overcome by modeling, i.e., simplifications of the system with the assumptions or negligence of minute effects. However, the correctness or usefulness of the model should be verified through the comparison with experimental results, which is the process of physical understanding of the system. The understanding of physics of the system make it possible to design or operation of the system. The effects of clearance and friction are always difficult problems in mechanical system due to its nonlinearity. The nonlinearity comes from piecewise-linear characteristics of the stiffness and damping of the system. The modeling of piecewise-linearity and the experimental result are discussed in this paper for impact and friction oscillator and rotor rubbing problem, which is the combination of impact and friction problems.

• Journal of information and communication convergence engineering
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• v.6 no.2
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• pp.207-212
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• 2008

There are several sensors in the liquid cargo ship. In the liquid cargo ship, we can get values from various sensors that are level sensor, temperature sensor, pressure sensor, oxygen sensor, VOCs sensor, high overfill sensor, etc. It is important to guarantee the reliability of sensors. In order to guarantee the reliability of sensors, we have to study the diagnosis of sensor fault. The technology of smart sensor is widely used. In this paper, the technology of smart sensor is applied to diagnosis of level sensor fault for liquid cargo ship. In order to diagnose sensor fault and find the sensor position, in this paper, we proposed algorithms of diagnosis of sensor fault using independent sensor diagnosis unit and self fault diagnosis using sensor modeling. Proposed methods are demonstrated by experiment and simulation. The results show that the proposed approach is useful. Proposed methods are useful to develop smart level sensor.

• Journal of KIBIM
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• v.9 no.2
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• pp.11-20
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• 2019

The use of drones and laser scanners have the potential to drastically reduce the time and costs of conventional techniques employed for field survey of cultural heritage buildings. Moreover, point cloud data can be utilized to create an as-built Building Information Model (BIM), providing a repository for consistent operations information. However, BIM creation is not a requisite for heritage buildings, and their technological possibilities and barriers have not been documented. This research explored the processes required to convert a heritage university building to a BIM model, using existing off-the-shelf software applications. Point cloud data was gathered from drones for the exterior, while a laser scanner was employed for the interior of the building. The point clouds were preprocessed and used as references for the geometry of the building elements, including walls, slabs, windows, doors, and staircases. The BIM model was subsequently created for the individual elements using existing and custom libraries. The model was used to extract 2D CAD drawings that met the requirements of Korea's heritage preservation specifications. The experiment showed that technical improvements were needed to overcome issues of occlusion, modeling errors due to modeler's subjective judgements and point cloud data cleaning and filtering techniques.

• Transactions of Materials Processing
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• v.32 no.3
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• pp.122-128
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• 2023

As electric vehicles (EV) have increasingly replaced the conventional vehicles with internal combustion engines (ICE), most of automotive makers are actively devoting to the technology development of EV parts. Accordingly, the manufacturing process for power source has been also shifting from engine/transmission to EV motor/reducer system. However, lack of experience in developing the EV motor still remains as a technical challenge. In this paper, we employed the forming simulation based on finite element modeling to solve this problem. In particular, in order to increase the accuracy of the forming simulation, we introduced the elastic-plastic constitutive model parameters for polymer-copper hybrid wire by investigating the individual strain-stress curves, and elastic modulus of polymer and copper. Then, the reliability of modeling procedure was confirmed by comparing the simulated results with experiments. Finally, the identified mechanical properties and finite element modeling were applied to a hairpin forming process, which involves multiple deformation paths such as bending, pressing, widening, and twisting. The proposed numerical approach can replace common experience or experiment based trials by reducing production time and cost in the future.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1253-1263
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• 2002

The control system design and modeling of an unmanned vehicle by means of a new concept for better performance through a tole-operation system is suggested by sensor fusion. But, the control of a real vehicle is very difficult, because the system identification of the vehicle is hard to find the unknown factors and the disturbances of the experimental environment. For the longitudinal and lateral controls, the traction system and steering system models are set up and a tuning method to find the gain of the controller by experiments is presented. In this research, mechanical and electronic parts are implemented to operate the unmanned vehicle and data reconstruction method of information about the environment data coming from several sensors is presented by data plot for the vehicle navigation. This paper focuses on the integration of tole-operated unmanned vehicle. This vehicle mainly controlled lateral and longitudinal directions with actuators for controlling vehicle movement and sensors for the closed-loop controlled system.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.87-90
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• 2002

This paper analyzes statistically the relationship between size and balance of text corpus by evaluation of the effect of interview sentences in language model for Korean broadcast news transcription system. Our Korean broadcast news transcription system's ultimate purpose is to recognize not interview speech, but the anchor's and reporter's speech in broadcast news show. But the gathered text corpus for constructing language model consists of interview sentences a portion of the whole, $15\%$ approximately. The characteristic of interview sentence is different from the anchor's and the reporter's in one thing or another. Therefore it disturbs the anchor and reporter oriented language modeling. In this paper, we evaluate the effect of interview sentences in language model for Korean broadcast news transcription system and analyze statistically the relationship between size and balance of text corpus by making an experiment as the same procedure according to varying the size of corpus.

• Korea-Australia Rheology Journal
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• v.18 no.3
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• pp.161-167
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• 2006

This study presents results on the numerical simulation of Newtonian and non-Newtonian flow in a channel obstructed by an asymmetric array of obstacles for clarifying the descriptive ability of current non-Newtonian constitutive equations. Jones and Walters (1989) have performed the corresponding experiment that clearly demonstrates the characteristic difference among the flow patterns of the various liquids. In order to appropriately account for flow properties, the Navier-Stokes, the Carreau viscous and the Leonov equations are employed for Newtonian, shear thinning and extension hardening liquids, respectively. Making use of the tensor-logarithmic formulation of the Leonov model in the computational scheme, we have obtained stable solutions up to relatively high Deborah numbers. The peculiar characteristics of the non-Newtonian liquids such as shear thinning and extension hardening seem to be properly illustrated by the flow modeling. In our opinion, the results show the possibility of current constitutive modeling to appropriately describe non-Newtonian flow phenomena at least qualitatively, even though the model parameters specified for the current computation do not precisely represent material characteristics.

• Transactions of the Korean Society of Automotive Engineers
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• v.3 no.3
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• pp.66-78
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• 1995

In this paper, we address vehicle modeling and dynamic analysis of four wheel steering systems (4WS). 4WS is one of the devices used for the improvement of vehicle maneuverability and stability. All research done here is based on a production vehicle from a manufacturer. To study actual system response, a three dimensional, full vehicle model was created. In past research of this type, simple, two dimensional, bicycle vehicle models were typically used. First, we modelled and performed a dynamic analysis on a conventional two wheel steering(2WS) vehicle. The modeling and analysis for this model and subsequent 4WS vehicles were performed using ADAMS(Automatic Dynamic Analysis of Mechanical Systems) software. After the original vehicle model was verified with actual experiment results, the rear steering mechanism for the 4WS vehicle was modelled and the rear suspension was changed to McPherson-type forming a four wheel independent suspension system. Three different 4WS systems were analyzed. The first system applied a mechanical linkage between the front and rear steering mechanisms. The second and third systems used, simple control logic based on the speed and yaw rate of the vehicle. 4WS vehicle proved dynamic results through double lane change test.