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Analysis on Triaxial Velocity induced by Wheel Off-loading of Geostationary Satellite (정지궤도위성의 휠모멘텀 제어에 의해 발생되는 3축 궤도병진 속도에 관한 분석)

  • Park, Young-Woong;Park, Keun-Joo;Kim, Dae-Kwan;Yang, Koon-Ho
    • Aerospace Engineering and Technology
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    • v.7 no.2
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    • pp.88-94
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    • 2008
  • In this study, triaxial velocity is analyzed for COMS(Communication, Ocean and Meteorological Satellite) configuration, which is generated when thrusters are used to dump wheel momentum. Since COMS is designed to periodically change the thruster set in order to uniformly decrease the performance of thrusters, triaxial velocity would be different during the change of thruster set. So, the triaxial velocity generated due to the change of thruster set is optimized.

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Rotordynamic Design and Analysis of the Rotor-Bearing System of a 500Wh Flywheel Energy Storage Device (플라이휠 에너지 저장장치 회전체계의 동역학적 설계및 해석)

  • 최상규;김영철;경진호
    • Journal of KSNVE
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    • v.8 no.1
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    • pp.81-86
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    • 1998
  • A 500Wh class high-speed Flywheel Energy Storage System (FESS) driven by a built-in BLDC motor/generator has been designed, which runs from 30000 to 60000rpm nominally. Due to the motor/generator inside, the flywheel rotor made of composites supported by PM/EM hybrid bearing system has a shape of bell or pendulum and thus requires accurate rotordynamic analysis and prediction of its dynamic behavior to secure the operating reliability. Rotordynamic analyses of the flywheel rotor-bearing system revealed that the bell shaped rotor has two conical rigid-body modes in the system operating range and the first conical mode, of which nodal point lies in the radial EM bearing position, can adversely affect the dynamic response of the rotor at the corresponding critical speed. To eliminate the possibility of wild behavior of the rotor, two guide bearings are adopted at the upper end of the rotor and motor/generator. It was also revealed that the EM bearing stiffness if 0.5~1.0E+6 N/m and damping of 2000 Ns/m are favirable for smooth operation of the system around the 2nd critical speed.

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A Study on the Compensating of the Dead-reckoning Based on SLAM Using the Inertial Sensor (관성센서를 이용한 SLAM 기반의 위치 오차 보정 기법에 관한 연구)

  • Kang, Shin-Hyuk;Jang, Mun-Suck;Lee, Dong-Kwang;Lee, Eung-Hyuk
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.46 no.2
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    • pp.28-35
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    • 2009
  • Positioning technology which a part technology of Mobile Robot is an essential technology to locate the position of Robot and navigate to wanted position. The Robot that based on wheel drive uses Odometry position. technology. But when using Odometry positioning technology, it's hard to find out constant error value because a slip phenomenon occurs as the Robot runs. In this paper, we present the way to minimize positioning error by using Odometry and Inertial sensor. Also, the way to reduce error with Inertial sensor on SLAM using image will be shown, too.

A Study of Wheel Guards for Reduction of High Frequency Road Noise (고주파수 소음 저감 휠가드 연구)

  • Kim, Hyungyung;Baik, Hongsun;Lee, Moonsuk;Kim, Donghyo;Kim, Dohyung
    • Transactions of the Korean Society of Automotive Engineers
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    • v.22 no.3
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    • pp.12-18
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    • 2014
  • This paper describes about the development of new concept's rear wheel guards for the reduction of Road Noise in the passenger vehicle using test. The new wheel guards are proposed by various frequency chamber concept and different textile layers concept. Two wheel guards were verified by small cabin resonance test and vehicle test. Through new developing process without vehicle test, Result of road noise will be expected when new concepts and materials of wheel guard is applied into automotive vehicle. As a result of the application of Aimed Helmholtz and Multi-layers concept, this paper classifies the road noise, cost and weight are reduced by new concepts and the solutions are adopted into the 2 cars.

Experimental Study of Driving Load Conditions for the Wheel Bearing Hub Unit of Passenger Car (승용차용 Wheel Bearing Hub Unit 설계를 위한 주행 하중조건의 실험적 연구)

  • 김기훈;유영면;임종순
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.2
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    • pp.166-173
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    • 2002
  • The wheel bearing hub unit is developed type of wheel bearing unified with the hub parts. It has advantage of reducing the weight and the number of components. And, it also improves uniformity of manufacturing quality, In order to design the wheel bearing hub units, many techniques are used such as load analysis, structure analysis and bearing characteristics analysis and so forth. These techniques need highly accurate load conditions founded on service conditions. In this study, to design the wheel bearing hub units used widespread in passenger cars, the service load was measured through driving tests on the public roads and in the special events. The public roads are classified into highway, intercity road, rural road, urban road, and unpaved road so as to know what the characteristics of the road loads are. The results of the tests showed that the wheel force was relative to the lateral acceleration, and also could be calculated from the lateral acceleration. The lateral acceleration was measured from 0.0G to 0.6G in general driving on the public roads, with different distributions in each road type. In special events, the maximum lateral acceleration was measured from 0.8G to 1.3G.

Improvement of Maldistributed Air Velocity in the Vane Wheel of a Bowl Type Pulverizer (바울형 미분기 베인휠에서의 유속 불균일 개선에 관한 연구)

  • Park, Deok-Bae;Hur, Jin-Huek;Moon, Seung-Jae
    • Plant Journal
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    • v.6 no.2
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    • pp.62-69
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    • 2010
  • The stability of coal pulverizer in the 800 MW coal-fired plants is vital to maintain their performance. Thus, this study analyzed the uneven abrasion of the deflector and coal spillage due to the air velocity maldistribution in the vane wheel of a bowl-type pulverizer as it is a possible cause for problems of facility using pulverized coal. In addition, air flow in the underbowl of a bowl-type pulverizer was studied to check air velocity maldistribution in the vane wheel using numerical method. In an attempt to correct the maldistribution of air velocity, air flow of the modified duct vane was studied as enlarging the length of the duct vanes installed at the air inlet duct of the pulverizer and increasing the angle of inclination. It was found that modified duct vane make the velocity distribution at the vane wheel uniform. formed by the duct vanes installed at the air inlet duct of the pulverizer and swirling flow is the major factor in making the velocity distribution of vane wheel exit uniform. This can prevent the uneven abrasion of the deflector, which is one of the components inside the pulverizer and coal spillage.

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Upgrading Filter Position Mechanism of SQUEAN

  • Lee, Hye-In;Pak, Soojong;Ji, Tae-Geun;Park, Woojin;An, Jongho;Kim, Sanghyuk;Im, Myungshin
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.1
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    • pp.74.1-74.1
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    • 2016
  • 미국 텍사스 주 맥도날드 천문대에 위치한 2.1m 망원경에 부착된 SQUEAN (SED Camera for QUasars in EArly uNiverse)은 2010년부터 운용되고 있는 CQUEAN을 바탕으로 개발된 적외선 영역 광학기기이다. 20개의 필터 장착이 가능한 필터 휠 제어 시스템을 가지고 있는 SQUEAN 시스템은 SMOP (SQUEAN Main Observation software package), KFC82 (KHU Filter wheel Control software package for McDonald 82 inch Telescope), KAP82 (KHU Auto-guiding software Package for McDonald 82 inch Telescope) 등으로 구성되어 있다. 그러나 대형 필터 휠을 제어하는 모터의 토크부족과 감속기의 백래시(Backlash)의 영향으로 오프셋의 오차가 커서 초기위치의 재설정 없이 하룻밤 이상 관측을 지속하는데 어려움이 있었다. 토크가 크고 인코더가 장착된 모터 교체와 제어 프로그램 등을 변경하고, 백래시의 영향을 최소화할 수 있도록 소프트웨어로 보정하였다. 또한, SMOP로부터 네트워크 통신을 통해 초기화용 필터 마스크(Initial Filter Mask:IFM)를 제작하여 돔 플랫 이미지에서 정확한 필터의 위치를 측정하는 기능을 도입하였다. 이 발표에서는, 개선된 하드웨어 및 소프트웨어의 내용과 테스트한 결과에 대해 보여준다.

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Evaluation of the Permanent Deformation Behavior on Geosynthetics-Reinforced Asphalt Pavement by using the Wheel Tracking Tests (휠트래킹 시험을 통한 토목섬유시트 보강 아스팔트포장의 소성변형 거동특성 평가)

  • Cho, Sam-Deok;Lee, Dae-Young;Kim, Jin-Hwan;Kim, Nam-Ho
    • Journal of the Korean Geosynthetics Society
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    • v.2 no.3
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    • pp.39-46
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    • 2003
  • The major pavement distress types found in the domestic roadways include rutting, fatigue cracking, and reflection cracking which are results of the environment and repeated traffic loads. These distresses usually occur before pavements approach their design life, and therefore, a significant amount of national budget is spent for maintenance of roadway pavements. The purpose of this study is to establish a geosynthetics-asphalt pavement system. For the study, wheel tracking tests are conducted to analyze the controlling effect of geosynthetics on rutting of asphalt pavement. On the basis of these works, the reinforcement effect of geosynthetics on the rutting of the asphalt pavement is clarified and deformation characteristics of geosynthetics-asphalt mixture is examined.

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A Study on the Wear Condition Diagnosis of Grinding Wheel in Micro Drill-bit Grinding System (마이크로 드릴비트 연마 시스템 연삭휠의 마모 진단 연구)

  • Kim, Min-Seop;Hur, Jang-Wook
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.3
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    • pp.77-85
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    • 2022
  • In this study, to diagnose the grinding state of a micro drill bit, a sensor attachment location was selected through random vibration analysis of the grinding unit of the micro drill-bit grinding system. In addition, the vibration data generated during the drill bit grinding were collected from the grinding unit for the grinding wheels under the steady and worn conditions, and data feature extraction and dimension reduction were performed. The wear of the micro-drill-bit grinding wheel was diagnosed by applying KNN, a machine-learning algorithm. The classification model showed excellent performance, with an accuracy of 99.2%. The precision, recall and f1-score were higher than 99% in both the steady and wear conditions.

Design Optimization for Automotive Wheel Bearings Considering Life and Stiffness (수명과 강성을 고려한 자동차용 휠 베어링의 설계 최적화)

  • Seungpyo Lee
    • Tribology and Lubricants
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    • v.39 no.3
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    • pp.94-101
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    • 2023
  • Automotive wheel bearings are a critical component of vehicles that support their weight and facilitate rotation. Life and stiffness are significant performance characteristics of wheel bearings. Designing wheel bearings involves finding optimal design variables that satisfy both performances. CO2 emission reduction and fuel efficiency regulations attribute to the recent increase in design requirements for lightweight and compact automotive parts while maintaining performance. However, achieving a design that maintains performance while reducing weight poses challenges, as performance and weight are generally inversely proportional. In this study, we perform design optimization of automotive wheel bearings considering life and stiffness. We develop a program that calculates the basic rated life and modified rated life based on international standards for evaluating the life of wheel bearings. We develop a regression equation using regression analysis to address the time-consuming stiffness analysis during repetitive analysis. We perform ANOVA and main effect analyses to understand the statistical characteristics of the developed regression equation. Furthermore, we verify its reliability by comparing the predicted and test results. We perform design optimization using the developed life prediction program, stiffness regression equation and weight regression equation. We select bearing specifications and geometry as design variables, weight as the cost function, and life and stiffness as constraints. Through design optimization, we investigate the influence of design variables on the cost function and constraints by comparing the initial and optimal design values.