• Title/Summary/Keyword: Bearing error

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A study in the Analysis of the GPS Error Pattern for the Realization of the Ship's GPS-Compass (선박용 GPS-Compass 구현을 위한 GPS 오차패턴 분석에 대한 연구)

  • 심영호;임정빈;임봉택;고광섭
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.2 no.S1
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    • pp.89-109
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    • 1996
  • The main information for a marine navigation is ship's bearing obtained from Gyro, Gyrocompass, Magneticcompass and electronic navigation systems such as LORAN, OMEGA and GPS. However, some of these systems have a disadvantage or restricted conditon involved critical problems in a war-ship and weapon system. In the work, we have done the basic resrarch, analysis of error pattern for GPS, for the development of the ship's seondary bearing sensor (GPS-Compass) to provide the back-up system of Gyro/Gyrocompass and a substitution way of Magneticcompass.

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Displacement Sensorless Active Magnetic Bearing Control by Current Measurement (전류신호를 이용한 능동 자기 베어링계의 제어)

  • 권계시;정호섭;이종원
    • Journal of KSNVE
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    • v.5 no.1
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    • pp.49-57
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    • 1995
  • An electronic circuit device is developed such that the displacement between an electromagnet and a moving target can be estimated from the coil current measurement, and then applied to an active magnetic bearing system. In order to levitate the shaft without using displacement sensor the stable control gains are obtained from the linearized model which includes the gap estimation circuit. Experimental results show that the shaft, by the estimated gap feedback, can be levitated within $\pm$6 ${\mu}m$ positioning error.

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An Analysis of Performance Error of Roundness Measuring Instrument -by phase different method- (眞圓度 測定器의 誤差特性에 대한 解析 -위상차법-)

  • 한응교;허문석;박익근
    • Journal of the korean Society of Automotive Engineers
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    • v.10 no.3
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    • pp.31-37
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    • 1988
  • A phase different method to evaluate the instrument error of roundness measuring instrument and the form error of specimens for the calibration of the instrument is used. An instrument with a rotary table supported by an air bearing was calibrated by using the standard balls as a standard. The calibration was carried out repeatedly by setting the same ball in 12 phase angles(per 30.deg.) on the table and by recording their roundness errors with a magnification of 100,000 times. As a result of data analysis of all the observations, readout at each of 144 orientations(per 2.5.deg.) from recorded data file, the error of performance of the instrument and the specimens are separated. In the particular instrument used in the present experiment, the error of the instrument was determined with the accuracy of 0.0164 (.mu.m) and the form error of the specimens was determined with the accuracy of 0.0264,0.0172(.mu.m), respectively. If the instrument was calibrated by using the above specimens, then the accuracy of the measurement of roundness error can be improved to about 0.017 (.mu.m).

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Study on Estimating the Shape of a Ship by Integrating Radar Images

  • Ishiwata, Junya;Fujisaka, Takahiko;Imazu, Hayama
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2006.10a
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    • pp.71-78
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    • 2006
  • The image of an object obtained by the radar is not corresponding to its true shape, because the image of an object observed by the radar is receiving an influence such as multiple-reflections and expanded in bearing because of the beam width of a radar. In addition, a radio wave does not hit the entire surface of an object. Therefore, the image of the front side of a ship facing a radar antenna corresponds to its true shape. In this paper, a method to estimate a ship's shape by means of the integration of the front parts of images obtained from radars is proposed. In addition, a matter, which is observation error of each radar, in using multi-radars, and the process included in the proposed method for solving the matter, are described. As a result of the experiment, the accuracy of about 3 degrees in ship's heading and about 14 meters in length and about 9 meters in beam was obtained.

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The Test-Retest Reliability and Criterion-Related Validity of a Trunk Stability Robot When Measuring Static Sitting and Standing Symmetry in Stroke Patients (뇌졸중 환자들을 위한 체간 안정화 로봇의 정적인 앉기와 서기 대칭성 평가의 검사-재검사간 신뢰도와 기준 관련 타당도)

  • An, Seung-Heon;Kim, Dong-Hoon;Jang, Young-Min
    • PNF and Movement
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    • v.16 no.3
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    • pp.405-414
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    • 2018
  • Purpose: The purpose of this study was to examine test-retest reliability and criterion-related validity of a trunk stability robot when measuring the weight-bearing symmetry static sitting and standing in stroke patients. Methods: For 27 stroke patients, weight-bearing symmetry was assessed twice, 7 days apart. The intraclass correlation coefficient (ICC2,1) and minimal detectable change (MDC) were used to examine the level of agreement between test and retest. The criterion-related validity of weight -bearing symmetry was demonstrated by Spearman correlation of modified Barthel index (MBI), the sit to stand test (STS), the timed up & go Test (TUG), and the function in sitting test (FIST). Results: the test-retest agreements were excellent for the weight-bearing symmetry of static sitting (ICC2,1: 0.90) and standing (ICC2,1: 0.89). It all showed that the acceptable MDC for the weight-bearing symmetry of static sitting and standing was 0.11 and 0.16, respectively (highest possible score<20 %), indicating that the measures had a small and acceptable degree of measurement error. The weight-bearing symmetry of static sitting was significantly correlated with the TUG(r=-0.45) and FIST(r=0.46)(p<0.05); the weight-bearing symmetry of static standing was also significantly correlated with MBI (r=0.65), TUG (r=-0.67), FIST (r=0.61)(p<0.01), and STS (r=-0.47)(p<0.05). Conclusion: The weight-bearing symmetry of static sitting and standing assessed by the trunk stability robot showed highly sufficient test-retest agreement and mild-to-moderate validity. It could also be useful for clinicians and researchers to evaluate balance performance and monitor functional change in stroke patients.

Influence of Ring Gear Boundary Conditions on the Static Characteristics of Epicyclic Gear Trains with Manufacturing Errors (링기어의 경계조건이 가공오차를 가지는 유성기어열의 정특성에 미치는 영향)

  • Cheon, Gill-Jeong;Oh, Jae-Kook
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1775-1780
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    • 2003
  • A hybrid finite element analysis was used to analyze the influence of ring gear rim thickness and spline number on the static properties of an epicyclic gear system with manufacturing errors. Both of these parameters affected the bearing force and critical stress. The effect of changes in the rim thickness on the load sharing between the gears depended on the type of manufacturing error. Ring flexibility improved the load sharing between planetary gears only in systems with planet tooth thickness or planet tangential errors; for other types of error, ring flexibility worsened the load sharing. To improve load sharing, rim thickness and spline number should be controlled within a specific range. The effect of the ring gear boundary condition was more apparent in a system with errors than in a normal system.

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Micropositioning of a Linear Motion Table with Magnetic Bearing Suspension (자기 베어링으로 지지 되는 직선운동 테이블의 초정밀 위치제어에 관한 연구)

  • 김의석;안형준;장인배;한동철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.466-469
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    • 1995
  • This paper presents a design and performance of the 6 D.O.F linear motion table with a magnetic bearing suspension. The linear positioning of the table with a 150mm stroke is driven by a brushless DC Linear motor and the other attitudes of the stage are controlled by the analog PD controller with magnetic bearing actuators. Each magnetic bearing unit which consists of 3 electromagnets, 3 capacitance probes and 3 backup bearings affords controlled forces by detecting the air gap between the probes and guideways. An integral type capacitance probe amplifier is equipped on the upper plate of the table so that the probe line to the probe amplifier can be shorter therefore the problems due to the stray capacitance and noise can be reduced. Form the pitch-yaw errormeasured by the autocollimator, the vertical and horizont straightness errors of the table are derived that they are maintained below 1.mu. m over 100mm stroke. The positioning accuracy of the linear motion is maintained below 2 .mu. m and the repeatability error is below 1 .mu. m

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A Study for the Development of Pile Design Method Considering Settlement and Compression (침하량과 압축량을 고려한 말뚝의 설계법 개발을 위한 연구)

  • Lim, Jong-Seok;Ha, Hyuk;Jung, Sang-Kyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2006.03a
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    • pp.1287-1294
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    • 2006
  • A pile is compressed with settlements when loading and bearing capacity is altered along relative displacement of pile/soil on settlement and compression. Settlements of pile displaying limit skin friction is different from displaying tip resistance. Therefore, it is an error in traditional method that bearing capacity of pile is estimated from the sum of limit skin fraction and tip resistance. Accordingly, development of design method considering behavior of load-settlement is needed. In this study, we would like to establish the base for development of design method considering bearing capacity altering along displacement on settlement and compression. For this, we established system and substance of design method. And in order to establish relationship of load-settlement of pile on the type of soil, we analyzed and arranged existing database and pile loading test. On design method, settlement is assumed gradually on each capacity level being assumed gradually. Bearing capacity developing on the pile is obtained on each settlement level. Until the obtained bearing capacity will be equal to assumed capacity, this process is continued with increasing settlement. Load-settlement curve for soil classification is sketched in the process computing settlement on assumed capacity. This design method will be materialized by computation program.

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Study of Dynamic Characteristics of 2.5-MW Wind Turbine Gearbox (2.5MW 풍력발전기 기어박스 동특성 연구)

  • Kimg, Jung-Su;Park, No-Gill;Han, Ki-Bong;Lee, Hyoung-Woo
    • Journal of Ocean Engineering and Technology
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    • v.28 no.4
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    • pp.314-323
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    • 2014
  • In this study, a gearbox and blade were modeled in the MASTA program, and the housing and carrier components were modeled using a finite element method. Using substructure synthesis, all the components were combined and used to establish a vibration model of a 2.5-MW wind turbine gearbox. In addition, the safety displacement factor was evaluated using an AGMA data sheet about bearing's outer race for the input shaft and output shaft. As a result, the bearing's outer race for the input shaft, and the radial and axial responses were satisfied by the $1^{st}$ and $2^{nd}$ planetary gears and the $3^{nd}$ helical gear transmission error(TE), respectively. However, the output shaft support bearing's outer race responses were not satisfied with the radial response by the $2^{nd}$ TE and axial response by the $3^{rd}$ TE. To reduce the vibration, tooth modification was needed. After profile tooth modification, at the outer race of the output shaft support bearing, the radial response was reduced by approximately $20{\mu}m$, and the axial response was reduced by approximately $6{\mu}m$.