• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.583-585
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• 2004

In this paper we will deal with a calibration method for low cost motion capture system using psd(position sensitive detection) optical sensor. To measure the incident direction of the light from LED emitted marker, the PSD is used the output current ratio on the electrode of PSD is proportional with the incident position of the light focused by lens. In order to defect the direction of the light, the current output is converted into digital voltage value by opamp circuits peak detector and AD converter with the digital value the incident position is measured. Unfortunately, due to the non-linearly problem of the circuit poor position accuracy is shown. To overcome such problems, we compensated the non-linearly by using least-square fitting method. After compensated the non-linearly in the circuit, the system showed more enhanced position accuracy.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.184-189
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• 2013

This paper proposes a method for improving the performance of a position sensorless control system for a slotless surface permanent magnet synchronous motor (SPMSM) in a very low-speed region. In position sensorless control based on a motor model, accurate motor parameters are required because parameter errors would affect position estimation accuracy. Therefore, online parameter identification is applied in the proposed system. The error between the reference voltage and the voltage applied to the motor is also affect position estimation accuracy and stability, thus it is compensated to ensure accuracy and stability of the sensorless control system. In this study, two voltage error compensation methods are used, and the effects of the compensation methods are discussed. The performance of the proposed sensorless control method is evaluated by experimental results.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.63-73
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• 2008

The helicopter position, heading data and the direction finding data of ESM are essentially required to compensate the parallax and analyze the direction finding accuracy of heliborne ESM in flight test phase. In the case of the long test range compared with small platform like as LYNX helicopter and Jisim Island test site, the parallax compensation for direction finding accuracy calculation and GPS position error can be neglected. In this paper, the direction finding accuracy on the basis of helicopter propeller was calculated by coordinate changing between helicopter and transmitting antenna from WGS84 coordinate to navigation coordinate using helicopter position and direction finding data.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.1
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• pp.16-25
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• 1997

This paper shows the development of the high accuracy vehicle positioning algorithm using the differential technique in vehicle tracking systems form the existing vehicle position which is acquired from the global positioning system (GPS). The control center receives the satellite ephemerise data and pseudorange correction from the reference station, and vehicle position from the moving vehicle. The pseudorange is calculated with the satellite position and the vehicle position, and corrected by pseudorange correction. Using this corrected pseudorange and kalman filter, more improved vehicle positioning data were obtained.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.373-378
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• 2014

The technology of direction finding is very important to make high position fixing accuracy. TDOA(time difference of arrival) direction finding technology is a high accuracy technology and is used in RF system from 1990. The principle of TDOA is to receive an emitter signal with two antennas, measure the time difference of received signal and then convert the time differences to azimuth angle. For high DF(direction finding) accuracy long basis line and high SNR at receiving system are needed. The DF accuracy and position fixing accuracy are simulated with different SNRs and antenna base lines. We obtain the DF accuracy of $0.51^{\circ}$ at $0^{\circ}$ incident azimuth angle in case of 50m base line and 40dB SNR.

• Journal of Astronomy and Space Sciences
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• v.40 no.3
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• pp.113-122
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• 2023

Although the Relative Global Navigation Satellite System (GNSS) positioning technique provides high accuracy, it has several drawbacks. The scarcity of control points, the long baselines, and using of ultra-rabid and rabid products increased position errors. This study has designed a New MATLAB Program that helps users automatically select suitable IGS stations related to the baseline lengths and the azimuth between GNSS points and IGS stations. This study presented criteria for the length of the baselines used in Egypt and an advanced estimated accuracy before starting the project. The experimental test studies the performance of the position accuracy related to the relation between three factors: observation session, final, rabid, and ultrarabid products, and the baseline lengths. Ground control point mediates Egypt was selected as a test point. Nine surrounding IGS stations were selected as reference stations, and the coordinates of the tested point were calculated based on them. Baselines between the tested point and the IGS stations were classified regarding proposal criteria. The coordinates of the tested point were obtained in different observation sessions (0.5, 1, 2, 4, 5, 6, 7, 7.5 h). The results indicated that the lengths of the baseline in Egypt were classified short (less than 600 km), medium (600-1,200 km), and long (greater than 1,200 km) and required a minimum observation time of 4, 5, and 7 h to obtain accuracy 10, 19, 48 mm sequentially. The position accuracy was superior for the rapid and the final than the ultra-rapid products by 16%. A short baseline was at the best case; there was a performance in position accuracy with a 57% deduction in observation time compared with the long baseline.

• Journal of the Korean Institute of Navigation
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• v.22 no.3
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• pp.9-16
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• 1998

Loran C is a low frequently , pulsed. hyperbolic radio aid to navigation system, which operates in the 90 to 110 kHz frequency band. The position accuracy is not excellent but the repeatable and relative accuracy is very good, and it is very useful for fishing vessel in coastal waters. The operation of China north sea chain9GRI 7430) was begun on January, 1996, and in order to evaluate the accuracy of this chain, it was observed with Loran C receiver (LC-90, Furuno) in July 9 and December 30, 1997 at the fixed position of Kunsan national university. The obtained results were as follows : The time difference error of M-X, M-Y pair were $0.5{\mu}s$, $4.4{ \mu}s$ respectively and the mean time difference of M-X, M-Y pair were $15120.4{,\mu}s$ $32085.4{\mu}s$ respectively. The Loran C signals were received steadily and the daily fluctuation of time difference was very small. The longitudinal position error was very much than latitudinal position error, and the mean position error was about 1091.8m.

• 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.

• ETRI Journal
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• v.40 no.4
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• pp.531-536
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• 2018

The weighted K-nearest neighbor (WKNN) algorithm is used to reduce positioning accuracy, as it uses a fixed number of neighbors to estimate the position. In this paper, we propose a dynamic threshold location algorithm (DH-KNN) to improve positioning accuracy. The proposed algorithm is designed based on a dynamic threshold to determine the number of neighbors and filter out singular reference points (RPs). We compare its performance with the WKNN and Enhanced K-Nearest Neighbor (EKNN) algorithms in test spaces of networks with dimensions of $20m{\times}20m$, $30m{\times}30m$, $40m{\times}40m$ and $50m{\times}50m$. Simulation results show that the maximum position accuracy of DH-KNN improves by 31.1%, and its maximum position error decreases by 23.5%. The results demonstrate that our proposed method achieves better performance than other well-known algorithms.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.38-41
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• 1997

As the LPM is used for position accuracy decision device it is required that both the reason of posion error and the definition of position itself should be cleared. In this study, the precision of the position decision of LPM is affected by the geometrical shape such as tooth shape or processing accuracy. By using the analysis of magnetic circuit, we calculated the permeance come up with the gap. Once the thrust force has been obtained, the permeance due to the mechanical error of the pole pitch and the tooth pitch becomes the error of thrust force. We confirmed as well that it is being affected by the difference due to the variation of the airgap permeance.