• Title/Summary/Keyword: Measurement position

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Quantification of Acoustic Pressure Estimation Error due to Sensor and Position Mismatch in Planar Acoustic Holography (평면 음향 홀로그래피에서 센서간 특성 차이와 측정 위치의 부정확성에 의한 음압 추정 오차의 정량화)

  • 남경욱;김양한
    • Journal of KSNVE
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    • v.8 no.6
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    • pp.1023-1029
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    • 1998
  • When one attempts to construct a hologram. one finds that there are many sources of measurement errors. These errors are even amplified if one predicts the pressures close to the sources. The pressure estimation errors depend on the following parameters: the measurement spacing on the hologram plane. the prediction spacing on the prediction plane. and the distance between the hologram and the prediction plane. This raper analyzes quantitatively the errors when these are distributed irregularly on the hologram plane The sensor mismatch and inaccurate measurement location. position mismatch. are mainly addressed. In these cases. one can assume that the measurement is a sample of many measurement events. The bias and random error are derived theoretically. Then the relationship between the random error amplification ratio and the parameters mentioned above is examined quantitatively in terms of energy.

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Finite Element Analysis of Wheel-set for Derailment Coefficient Measurement that have Plane Plate Shape (평면 플레이트 형상을 가진 탈선계수 측정용 윤축의 구조해석)

  • 함영삼;오택열
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.119-122
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    • 2004
  • Since a derailment of rolling stocks results in huge losses in properties and lives, the measurement of a derailment coefficient is a very important test item to estimate the running safety of rolling stocks. For a measurement of the derailment measurement of forces between the wheel and rail a measuring wheel-set should be made first. The process to make a measuring wheel-set has some stages for correct measurement. They are as follows; a finite element analysis of a wheel to find a position of holes at which vertical force shall be measured, a finite element analysis for the position of strain gauges.

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Double Electro-Magnetic Force Compensation Method for the Micro Force Measurement (미소 힘 측정을 위한 이중 전자기힘 보상방법)

  • 최임묵;우삼용;김부식;김수현
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.2
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    • pp.104-111
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    • 2003
  • Micro force measurement is required more frequently for a precision manufacturing and investment in fields of precision industries such as semiconductor, chemistry and biology, and so forth. Null balance method has been introduced as an alternative of a loadcell. Loadcells have advantages in aspects of low cost and easy manufacturing, but have also the limitation in resolution and sensitivity to environment variations. In this paper, null balance method is explained and the dominant parameters related to system performances are mentioned. Null position sensor, electromagnetic system and controller are investigated. Also, the characteristic experiment is carried out in order to estimate the resolution and the measurement range. In order to overcome the limitation by the drift of position sensor and the performance of controller, double electromagnetic force compensation method is proposed and experimented. After controlling and filtering, the resolution under $\pm$ 1mg and measurement range over 300g could be obtained.

The Analysis of Motion Error in Scanning Type XY Stage (스캐닝 방식 XY 스테이지의 운동오차 분석)

  • 황주호;박천홍;이찬홍;김동익;김승우
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2004.10a
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    • pp.1380-1383
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    • 2004
  • The scanning type XY stage is frequently used these days as precision positioning system in equipment for semiconductor or display element. It is requested higher velocity and more precise accuracy for higher productivity and measuring performance. The position accuracy of general stage is primarily affected by the geometric errors caused by parasitic motion of stage, misalignments such as perpendicular error, and thermal expansion of structure. In the case of scanning type stage, H type frame is usually used as base stage which is driven by two actuators such as linear motor. In the point view of scanning process, the stage is used in moving motion. Therefore, dynamic variation is added as significant position error source with other parasitic motion error. Because the scanning axis is driven by two actuators with two position detectors, 2 dimensional position errors have different characteristic compared to general tacked type XY stage. In this study 2D position error of scanning stage is analyzed by 1D heterodyne interferometer calibrator, which can measure 1D linear position error, straightness error, yaw error and pitch error, and perpendicular error. The 2D position error is evaluated by diagonal measurement (ISO230-6). The yaw error and perpendicular error are compensated on the base stage of scanning axis. And, the horizontal straightness error is compensated by cross axis compensation. And, dynamic motion error in scanning motion is analyzed.

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Method for Measuring Absolute Position of a Yard Crane for Port Automation (항만 자동화를 위한 야드 크레인의 절대위치 측정 기법)

  • 전태원;유우종;이홍희;김흥근;노의철
    • The Transactions of the Korean Institute of Power Electronics
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    • v.9 no.2
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    • pp.163-170
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    • 2004
  • Since 1960s, a container shipping volume has increased dramatically and continuous on a trend of rapid growth, and so the number of containers handled at the port increases. The position measurement of the yard crane is very important for improving the operating efficiency of the port. This paper describes the method to measure the absolute position of yard crane accurately and rapidly, using both the output pulse of an encoder and infrared sensors. The crane position is calculated by counting the output pulse of an incremental encoder, which is mounted on the wheel in the crane. By the way, the wheel slippage on rail may cause some errors in the crane position information obtained from encoder pulse, and the infrared sensor is used to compensate for errors in the crane position information. The performance of proposed method is verified on experimental results with the simulator of yard crane, the size of which is about 1/10 with the real crane.

A hybrid navigation system of underwater vehicles using fuzzy inferrence algorithm (퍼지추론을 이용한 무인잠수정의 하이브리드 항법 시스템)

  • 이판묵;이종무;정성욱
    • Journal of Ocean Engineering and Technology
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    • v.11 no.3
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    • pp.170-179
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    • 1997
  • This paper presents a hybrid navigation system for AUV to locate its position precisely in rough sea. The tracking system is composed of various sensors such as an inclinometer, a tri-axis magnetometer, a flow meter, and a super short baseline(SSBL) acoustic position tracking system. Due to the inaccuracy of the attitude sensors, the heading sensor and the flowmeter, the predicted position slowly drifts and the estimation error of position becomes larger. On the other hand, the measured position is liable to change abruptly due to the corrupted data of the SSBL system in the case of low signal to noise ratio or large ship motions. By introducing a sensor fusion technique with the position data of the SSBL system and those of the attitude heading flowmeter reference system (AHFRS), the hybrid navigation system updates the three-dimensional position robustly. A Kalman filter algorithm is derived on the basis of the error models for the flowmeter dynamics with the use of the external measurement from the SSBL. A failure detection algorithm decides the confidence degree of external measurement signals by using a fuzzy inference. Simulation is included to demonstrate the validity of the hybrid navigation system.

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The Design and Implementation of Location Information System using Wireless Fidelity in Indoors (실내에서 Wi-Fi를 이용한 위치 정보 시스템의 설계 및 구현)

  • Kwon, O-Byung;Kim, Kyeong-Su
    • Journal of Digital Convergence
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    • v.11 no.4
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    • pp.243-249
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    • 2013
  • In this paper, GPS(Global Positioning System) that can be used outdoors and GPS(Global Positioning System) is not available for indoor Wi-Fi(Wireless Fidelity) using the Android-based location information system has been designed and implemented. Pedestrians in a room in order to estimate the location of the pedestrian's position, regardless of need to obtain the absolute position and relative position, depending on the movement of pedestrians in a row it is necessary to estimate. In order to estimate the initial position of the pedestrian Wi-Fi Fingerprinting was used. Most existing Wi-Fi Fingerprinting position error small WKNN(Weighted K Nearest Neighbor) algorithm shortcoming EWKNN (Enhanced Weighted K Nearest Neighbor) using the algorithm raised the accuracy of the position. And in order to estimate the relative position of the pedestrian, the smart phone is mounted on the IMUInertial Measurement Unit) because the use did not require additional equipment.

Study on Error Correction of Impact Sound Position Estimation Using Ray Tracing (음선 추적을 이용한 폭발음 위치추정 오차 보정에 대한 연구)

  • Choi, Donghun;Go, Yeong-Ju;Lee, Jaehyung;Na, Taeheum;Choi, Jong-Soo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.1
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    • pp.89-96
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    • 2016
  • TDOA(time delay of arrival) position estimate from acoustic measurement of artillery shell impact is studied in order to develop a targeting evaluation system. Impact position is calculated from the intersections of hyperbolic estimates based on the least square Taylor series method. The mathematical process of Taylor series estimation is known to be robust. However, the concern lays with the accuracy because it is sensitive to the bias caused by the randomness of measurement situation. The measurement error typically occurs from the distortion of waveform, change of travelling path, and sensor position error. For outdoor measurement, a consideration should be made on the atmospheric condition such as temperature and wind which can possibly change the trajectories of rays of sound. It produces wrong propagation time events accordingly. Ray tracing and optimization techniques are introduced in this study to minimize the bias induced by the ray of sound. The numerical simulation shows that the atmospheric correction improves the estimation accuracy.

A Study on Correlation of the Results VFA Measured by CT Position with VFA Measured by InBody (CT 측정 위치에 따른 내장지방 면적과 Inbody로 측정한 내장지방 면적의 상관성 연구)

  • Lee, Sang Heon;Im, In Chul;Lee, Hyo-Yeong
    • Journal of the Korean Society of Radiology
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    • v.13 no.5
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    • pp.691-698
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    • 2019
  • The patients who visited the Health Promotion Center were compared between the visceral fat area according to CT fat measurement position and the visceral fat area measured by Inbody. In the CT measurement, the visceral fat area measured at the L4-5 and CT Umbilicus positions was not different regardless of gender. In addition, there was no difference between CT visceral fat area and Inbody visceral fat area in the correlation between visceral fat area according to CT measurement position and visceral fat area measured by Inbody. The highly correlated CT measurement position were male L4-5, L5-S1, female L3-4, L4-5, L5-S1, and Umbilicus. In addition, when studying the relationship between the inbody visceral fat area and CT visceral fat area regardless of gender, it is suggested to compare the visceral fat area at the CT L4-5 position.

Position Estimation Technique of High Speed Vehicle Using TLM Timing Synchronization Signal (TLM 시각 동기 신호를 이용한 고속 이동체의 위치 추정)

  • Jin, Mi-Hyun;Koo, Ddeo-Ol-Ra;Kim, Bok-Ki
    • Journal of Advanced Navigation Technology
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    • v.26 no.5
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    • pp.319-324
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    • 2022
  • If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.