• The Journal of Korea Robotics Society
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• v.18 no.3
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• pp.299-307
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• 2023

In the midst of accelerating wars around the world, unmanned robot technology that can guarantee the safety of human life is emerging. ERP-42 is a modular platform that can be used according to the application. In the field of defense, it can be used for transporting supplies, reconnaissance and surveillance, and medical evacuation in conflict areas. Due to the nature of the military environment, atypical environments are predominant, and in such environments, the platform's path followability is an important part of mission performance. This paper focuses on reducing the minimum turning radius in terms of improving path followability. The minimum turning radius of the existing 2WS/2WD in-wheel platform was reduced by increasing the torque of the independent driving in-wheel motor on the rear wheel to generate oversteer. To determine the degree of oversteer, two GPS were attached to the center of the front and rear wheelbases and measured. A closed-loop speed control method was used to maintain a constant rotational speed of each wheel despite changes in load or torque.

• Journal of Energy Engineering
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• v.11 no.2
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• pp.160-165
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• 2002

The heavy-duty LPG-fueled single cylinder engine was designed and developed as a fundamental equipment for analyzing combustion processes and emission performances. The cylinder head and the piston crown were modified to fire the LPG in the engine. The flywheel was also fabricated to minimize the vibration of the single cylinder engine. The size of bore and stroke of the tested engine are 130 mm and 140 mm, respectively. Compression ratios were varied 8 to 9 with different piston crown shapes. The developed single cylinder engine operates at 1,000 rpm for this work. The major conclusions of this work are; (1) the power of the developed engine was peaked at the condition of equivalence ratio 1.0 at three different compression ratios; (2) the power is slightly increased with the increase of compression ratio; (3) the optimum ignition timing is retarded with the increase of compression ratio ranged 2 to 10 crank angle.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.1
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• pp.32-43
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• 1999

In this paper, the transformed QMSA to load a capacitor without limitation of the electric force on QMSA(Quarter-wavelength Microstrip Antenna) is designed. Bandwidth of the designed and manufactured antenna is 5.7% at the resonant frequency of 2.0 GHz and the resonant frequency and bandwidth versus change of any arbitrary feed point is observed. Since the size of wide slot width between the left and right parallel plate to load a capacitor is very wide bandwidth, will be suitable for very wide bandwidth communication. The radiation pattern characteristics of the designed antenna based on the dipole structure and the aperture structure analysis method. As calculation results, relative backward radation is - 5 dB.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.163.2-163.2
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• 2012

다목적실용위성 3호는 2012년 5월 발사되어, 위성 기능점검을 위한 시험을 성공적으로 완료하였다. 위성이 발사체로부터 분리된 이후 임무궤도(고도 685km, 승교점 지방시 13시 30분을 갖는 태양동기궤도)를 획득하기 위해서는 궤도조정이 필요하다. 본 논문에서는 다목적실용위성 3호의 초기운영 기간 동안 수행한 총 10번의 궤도조정 계획 및 결과에 대해 기술하였다. 궤도조정 1 단계에서는 궤도조정 절차 및 기능을 점검하기 위해 6번의 시험 궤도조정을 순차적으로 수행하였고 이후 2 단계에서는 임무궤도 진입을 위해 4번의 궤도조정을 실시하였다. 궤도조정을 위해서는 원하는 추력분사 방향을 맞추기 위해 롤 방향 또는 피치 방향의 자세제어가 필요한데, 추력기를 사용하여 자세를 기동하는 모드(Del-V Mode)와 휠을 사용하여 자세를 기동하는 모드(Fine Del-V Mode)로 구분된다. 시험 궤도조정에서는 우선적으로 두 가지 모드에 대한 모드전환 시험을 실시하여 위성체 및 지상국 운영절차에 대한 이상 유무를 점검하였고, 이후 추력기 분사량을 10초로 설정하여 예측 대비 실제 궤도변경 결과값을 확인하였다. 시험 궤도조정의 결과를 토대로 본 궤도조정에서는 임무궤도를 획득하기 위한 경사각 조정 및 고도 조정을 수행하였다. 경사각 조정 시에는 승교점 지방시의 변화량을 줄이고, 이후 자연 교란력에 의한 궤도변화를 고려하여 목표궤도를 계획하였다. 또한, 고도 조정 단계에서는 연료 사용량 및 이심률 변화를 최소화 할 수 있도록 전형적인 호만 궤도천이 방식을 적용하였다. 궤도조정 결과 당초 목표한 값을 정확하게 달성하였고, 궤도조정 이후 궤도변화도 장기간 동안 임무궤도 범위를 유지함을 확인할 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.497-505
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• 2017

TDF (Tire derived fuel) Fly ash is an industrial by-product when scraped tire was used a fuel source at the power plant. TDF Fly ash has been classified as domestic waste at the workplace so far and has not been appropriately utilized. We conducted a fundamental physical property test of asphalt mixture to investigate the possibility of using TDF Fly ash as a mineral filler of asphalt mixture for exploring new usage strategies. TDF Fly ash meets KS F 3501 asphalt mixture mineral filler criteria. And the optimal asphalt binder amount was determined to be 4.5% by Marshall design. Mineral filler content was determined at 3% and analyzed by comparing using mineral filler as stone powder. The basic physical property test of the asphalt mixture was evaluated to the provision indicated in "Production and Construction Guidelines for Asphalt Mixture" published by the Ministry of Land, Infrastructure and Transport. In the test, Marshall stability test, dynamic immersion test, tensile strength ratio test, wheel tracking test were carried out. As a result of the experiment, Marshall stability and dynamic stability satisfied the standards, and confirmed the stability and Dynamic immersion and tensile strength ratio test that TDF Fly ash is more effective for scaling and moisture resistance than stone dust. Therefore, in this research, it is expected that multilateral utilization of TDF Fly ash, and a positive effect can be also expected.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.1-13
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• 2004

This study dealt with size effect of specimen in measuring deformation strength and estimating rut resistance of asphalt concretes under static loading using Kim test. Two aggregates, a normal asphalt (pen 60-80) and 6 polymer-modified asphalt (PMA) binders were used for preparation of 14 dense-graded mixtures. Mixtures were prepared based on optimum asphalt content by Marshall compactor (S= 10cm) and gyratory compactor (S= 15cm) for Kim test and for wheel tracking test. In statistical analysis by general linear model (GLM) procedure of SAS, the diameter of specimen was found not to be a significant factor that affect the Kim test result. Therefore, it was found that either loom-diameter or 15cm-diameter of specimen gave no significant difference in deformation strength ($K_D$) values in Kim test for any aggregate mixture. However, the thickness of specimen was found to be a significant factor in determining $K_D$. It is estimated that $K_D$ is a function of y, vertical deformation, and y has something to do with thickness of specimen. Therefore, it is suggested that the thickness of specimen should not be higher than 6.6cm, and the correction factor depending on the thickness value should be developed in the future study.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.45-53
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• 2004

This study dealt with correlation analysis between deformation strength and rut resistance of asphalt concretes based on binder grade in Superpave specification with changing submerging time. Currently, Mashall mix design is known to have little correlation with rutting related performance. Therefore, some agencies started to use the Superpave method for asphalt mix design. But this method has a weak point in that it can not distinct mechanical property of the asphalt mixtures designed. For solution of these problem, this study used deformation strength, $S_D$, of Kim test which is a new approach under development for finding property which represents rut resistance characteristics of asphalt mixtures under static loading. This study used two aggregates from two regions and five PG asphalt binders. Final rut depth (DR) and dynamic stability (DS) from wheel tracking (WT) test were obtained. and $S_D$ value of the same mixture specimen which was made by gyratory compactor was obtained using loading head [4(1.0)]. Three submerging times 30min, 40min, 50min were used as a test variable at $60^{\circ}C$. Correlation analysis of DR and DS with $S_D$ were performed based on PG grade. It was found out that the $S_D$ has a high correlation with DR and DS of superpave mixtures. The highest $R^2$ was found from the $S_D$ values of 30min. submerged specimen.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.166.2-166.2
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• 2012

국내에서 개발한 고기동 저궤도 위성이 일본 다네가시마 우주센터에서 2012년 5월 18일 발사되었다. 자세제어계는 위성의 임무수행을 완수할 수 있도록 발사 후부터 위성 수명 기간 동안 자세명령을 생성하고 제어 및 결정을 하며, 궤도 조정과 모멘텀 덤핑등의 임무를 수행한다. 이러한 임무 수행을 가능하게 하기 위해 자세제어계는 적절한 센서와 구동기 조합을 사용하여 추력기 기반 안전모드, 궤도 조정을 위한 Del-V Burn 기동 모드, 태양지향 서브모드 및 목표지향 서브모드 등을 설계했다. 고기동 위성의 초기 운용 중 자세제어계는 자세제어계 하드웨어의 초기 구동 및 점검을 수행하고 설계한 각 모드의 기능과 성능 확인을 수행하게 된다. 본 연구는 성공적으로 완료한 자세제어계 하드웨어의 초기 점검 결과를 소개하는 것이 목적이다. 초기 운용은 위성이 발사된 직후 탑재컴퓨터가 깨어나면서부터 시작되는데, 발사 후 최초 접속시 추력기 기반 안전모드에서 태양 획득 성능 및 제어 성능을 확인한 후 정상 상태 모드인 태양지향 자세로 전환하기 위해 자세제어계 하드웨어인 별 추적기, 자기토커, 반작용휠의 초기 구동 및 점검을 수행하였다. 본 연구에서는 각 하드웨어의 초기 구동 점검과 성능 및 기능 요구조건 만족에 대한 성능 분석 결과를 정리하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.36-42
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• 1997

A prototype of 500Wh class flywheel energy storage device was designed and manufactured to check the previously predicted system performance. The system was intentionally designed to show rigid body behavior up to the maximum operating speed of 60000Tpm and to have its 2nd rigid critical mode, of which nodal point lies on the flywheel center of mass, around 4000 to 6000rpm with radial magnetic bearing stiffness of l.e+6 N/m. Numerous experiments an the system behavior showed that the PM axial bearing, designed utilizing a commercial code, acts as resonably as predicted and, most importantly, the system becomes stable after the 2nd critical speed. The EM radial bearing, however, was found out to have orthotropic property with much less radial stiffness values than expected, so that it was observed that the 2nd forward and backward critical modes were excited at 310 and 590rpm respectively with larger vibration amplitudes. Thus, in order to improve the system dynamic behavior, the EM radial bearing is currently being re designed so as to get bigger stiffness and, in turn, smoother operation of the system.

• Journal of Drive and Control
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• v.11 no.2
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• pp.22-29
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• 2014

This paper presents simulation-based analysis of energy flow of a wheel loader. The objective of this study is to analyze the energy flow of a wheel loader during driving and working. Because the wheel loader powertrain consists of a mechanical and hydraulic powertrain, the generated power from the engine is divided into 2 powertrains. Further, a virtual prediction of energy flow in the powertrains is a key factor in terms of optimal design. Accordingly, the simulation model that is able to predict the virtual energy flow is developed and analyzed in this study. The proposed wheel loader simulation model has been constructed in the Matlab/Simulink environment. It is expected that the developed simulation model will analyze the energy flow and efficiency in the design stage.