• Design & Manufacturing
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• v.16 no.4
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• pp.7-16
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• 2022

A helmet is essential for safety when operating personal mobility. However, user's actual helmet wear rate is low due to the inconvenience of wearing and poor ventilation. In this study, a new helmet structure with improved ventilation for personal mobility devices was designed. To design a new structure with improved breathability compared to the existing helmet while satisfying the safety regulations for the helmet, a generative design method was applied to the shock-absorbing liner of the helmet. In addition, other materials were applied to create a structure with improved ventilation while maintaining safety. The generated design result was verified for shock absorption through simulation. As a result of the study, EPS, the current material was replaced with CFRP and Kevlar, and the structure was changed. This design was judged to satisfy safety regulations against impact. The new helmet structure is expected to improve the helmet usability for personal mobility and increase the helmet wear rate of users.

• Journal of the Korea Convergence Society
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• v.2 no.2
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• pp.27-34
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• 2011

This study is making a product for the development of one process worm wheel of making a shape for gear for worm wheel without hobbing manufacturing process. Because of removing a hobbing process, plastic worm wheel for increased productivity and equivalent quality is produced in the result. As the result, this product is selling to Hyundai Mobis, Mando, TRW, KOYO/NSK/Showa(Japan), Delphai(America). The core technology and different strategy are as follows. The technology protection for molding of worm whee is currently patent process "Molding process of helical gear(No. 10-2008-0105908). Further patent procedure for "molding system for positioning decision of inserting boss is currently prepared. As gear molding procedure in hobbing machine without gear machining procedure, most of all, core development technology which is making a gear tooth is main topic. So that, in case of currently developed worm wheel, because core and mold base are not developed in the first procedure, gear is machining in hobbing M/C as the second procedure. In the later, patent for mold base structure will be prepared in this study results.

• International Journal of Aeronautical and Space Sciences
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• v.1 no.2
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• pp.50-67
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• 2000

The spacecraft simulator is used for command validation, operational check of the Satellite Operation Subsystem (SOS), spacecraft anomaly analysis support, satellite operator training etc. In this paper, S/W design features and modeling characteristics of the KOMPSAT Spacecraft Simulator Subsystem (SIM) are described. Validation procedures and simulation results are also provided. The SIM provides extensive simulation capabilities by including models for most of the spacecraft subsystems. The software structure of the SIM was designed and implemented so as to support operations not only in real-time but also in non real-time by utilizing the Hewlett Packard (HP) UNIX functions. The SIM incorporates as many user-friendly Man Machine Interface (MMI) windows as possible so that all the SIM normal operations can be executed through the MMI windows.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.7
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• pp.105-116
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• 2004

The design of pico-/nano-satellites is particularly challenging due to constraints in mass, volume, power, and surface area. An efficient low-cost picosatellite HAUSAT-1 Electrical Power Subsystem (EPS) is developed to supply the power for various loads during the full mission life. This paper addresses design and analysis results of solar arrays, batteries, power conditioning and distribution units. The component selection, manufacturing and test results are presented by considering appropriate development cost and performance. The simulation results of power system are also illustrated, according to operational modes, through energy balance analysis. Finally, the EFS design feasibility is verified by comparing analysis results with functional and environmental test results at the system and component levels, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.175-180
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• 2008

The objective of this study was to investigate biosorption of organic matter on EPS(Extracellular Polymeric Substances) at different SRT(Sludge Retention Time) in a SBR(Sequencing Batch Reactor) process, which was operated with the following operation steps : Fill-React-Settle-Decant-Idle. The hydraulic retention time was set to be 24 hours. The results obtained from this study showed that the organic removal efficiency per unit microbial biomass decreased with increasing SRT, and the corresponding EPS amount also did. The percent removal of organic by biosorption increased with SRT, and it reached to 53.2% at SRT of 30 days. However, the highest biosorption per microbial biomass(48.6 mgCOD/gVSS) was found at SRT of 2 days. The EPS analysis was performed by measuring TSS, TCOD$_{Cr}$, and TKN. The EPS production per unit microbial biomass was observed to be high at a low SRT. Due to the above result, the floc formation was hindered and therefore poor settlement of sludge resulted in decreasing the COD removal efficiency. It was therefore concluded that the consideration of the system design should include the characteristic of EPS as well as other factors such as SRT, MLSS, and organic loading.

• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.309-311
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• 2006

A train having a system which tilts the train body to reduce the lateral acceleration experienced by passengers when operating around curves, allowing the train to run at higher speeds through curves than non-tilting trains. A tilting train may have a maximum design service cant deficiency of up to $8^{\circ}$. In this case there is, at worst, a margin of only $6^{\circ}$ cant deficiency between a train travelling at enhanced permissible speed and its roll-over resistance. This is a significant reduction in the margin against overturning compared to that offered at permissible speeds. Particular consideration therefore needs to be given to the adequacy of the margin and the additional controls against overturning required when trains travel at enhanced permissible speeds. This paper deals with the speed supervision system of tilting train through curves.

• Journal of Astronomy and Space Sciences
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• v.24 no.2
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• pp.179-194
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• 2007

The design and analysis of satellite power subsystem is an important driver for the mass, size, and capability of the satellite. Every other satellite subsystem is affected by the power subsystem, and in particular, important issues such as launch vehicle selection, thermal design, and structural design are largely influenced by the capabilities and limitations of the power system. This paper introduces a new electrical power subsystem design program for the rapid development of LEO satellite and shows an example of design results using other LEO satellite design data. The results shows that the proposed design program can be used the optimum sizing and the analytical prediction of the on-orbit performance of satellite electrical power subsystem.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1183-1185
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• 2005

This paper describes the optimal design and performance characteristics of the BLDC Motor for Electrical Power Steering System. To develope the optimal dimension within a given volume, BLDC Motor with the low cogging torque is designed and analyzed by FEM analysis. The prototype BLDC Motor has 4 poles rotor and 24 slots stator. To estimate the prototype machine, this paper gives the comparison between the FEM results and the experiment ones.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1930-1935
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• 2009

This paper deals with the torque ripple reduction of permanent magnet synchronous motor using harmonic current injection. Torque ripple of electric motor reduces system stability and performances, therefore efforts to reduce torque ripple are exerted in the design process. Torque ripple can be reduced by appropriate pole/slot combination, skew of rotor or stator, design of magnetic circuit, etc. In addition, torque ripple can be also reduced by input voltage and current, and many researches have been conducted to reduce torque ripple for six-step drive. Torque ripple reduction for current vector controlled permanent magnet synchronous motor also have been conducted and verified by investigating back emf wave form. Torque ripple reduction in this paper started from getting torque profile according to input current and electrical angle calculated by FEA, then instantaneous currents at each electrical angles for constant torque are calculated and applied to experiments. Therefore, 0% of torque ripple can be obtained theoretically with harmonic current injection. In order to maximize the effect of torque ripple reduction, a BLDC motor having high harmonic component of back emf is chosen. With sinusoidal current drive, over 100% of torque ripple is obtained initially, then 0.5 % of torque ripple is obtained by FEA using harmonic current injection. The effect is verified by experiment and the presented method can be effectively applicable to Electric Power Steering(EPS).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.38-43
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• 2002

A study on the test, design and fabrication of wind tunnel model for measurement of air load distribution on wing surfaces is presented. 447 pressure taps are installed normal to the wing surfaces, and measured by PSI-8400 system using total 8 ESPs modules installed in the model. The test was performed at 50 m/sec constant speed in the low speed wind tunnel of Agency for Defense Development. Tests were carried out to determine effects of angle of attack, angle of sideslip and flap and stores for the load distribution of wing. The test results in this paper can be applied to the design optimization of structure and validation of computational fluid dynamics.