• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.454-458
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• 2001

A new model utilizing a transfer function was proposed in the previous paper for analizing motion errors of hydrostatic tables. Validity of the proposed method was theoretically verified as the calculated motion errors were compared with the results by conventional multi pad method. In this paper, relationship between form error of rail and motion errors of hydrostatic table is analized theoretically in order to comprehand so-called 'averaging effect of oil film'. Experiments on the motion errors of hydrostatic table is conducted with 3 different rails, and the results are compared with the results calculated by Transfer Function Method. The results show good agreement. From the results, it is verified that TFM is very effective to analize the motion errors of hydrostatic table.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.10 no.6
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• pp.1-7
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• 2001

It is very important to test circular motion accuracy of NC machine tools as it affects all other machines machined by them in industries. In this paper, it has become possible to detect errors of linear displacement of radial directions for circle tar motion accuracy test using newly assembled magnetic type of linear scale so called Magnescale ball-bar system. It has also organized computer program systems using tick pulses come out from computer for getting error motion data at colt start time interval in circular motion test on NC lathe. Error data gotten from test is expressed to plots and analysed to numerics by various statistical treatments.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.5
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• pp.139-148
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• 2002

Motion errors of linear motion guideway are analyzed theoretically in this paper. For the analysis, an new algorithm predicting motion errors of bearing and guideway is proposed using the Hertz's elastic deformation theory. Accuracy averaging effect can be calculated quantitatively by analyzing relationship between motion errors of guideway and spatial frequency of rail form error. Influences of design parameters on the motion errors including the number of balls, preload, ball diameter, bearing length and the number of bearings are analyzed. As it is difficult to measure the rail form error, experimental results are compared with results analyzed by the equivalent analysis method which evaluate the motion errors of guideway using the measured errors of bearing. From the experimental results, it is confirmed that the proposed analysis method it effective lo analyze the motion errors of linear motion bearing and guideway.

• The KIPS Transactions:PartB
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• v.13B no.6 s.109
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• pp.607-614
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• 2006

In this paper, we propose an error resilience video coder which uses a hybrid error concealment algorithm. Firstly, the algorithm uses the error concealment with data hiding. If the hiding information is lost, the motion vector of lost macroblock is computed with adaptive selection of adjacent motion vectors and OBMC (Overlapped Block Motion Compensation) is applied with this motion vector. We know our algorithm is more effective in case of continuous GOB. The results show more significant improvement than many temporal concealment methods such as MVRI (Motion Vector Rational Interpolation) or existing error concealment using data hiding.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.257-263
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• 2003

Error control and concealment in video communication is becoming increasingly important because transmission errors can cause single or multiple loss of macroblocks in video delivery over unreliable channels such as wireless networks and the internet. This paper describes a temporal error concealment by postprocessing. Lost image blocks are overlapped block motion compensated (OBMC) using median of motion vectors from adjacent blocks at the decoder. The results show a significant improvement over zero motion error concealment and other temporal concealment methods such as Motion Vector Rational Interpolation or Side Match Criterion OBMC by 1.4 to 3.5㏈ gain in PSNR. We present experimental results showing improvements in PSNR and computational complexity.

• Journal of the Korea Institute of Military Science and Technology
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• v.22 no.5
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• pp.674-686
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• 2019

In this paper, we will discuss the absolute angular error control mode for the Gun/Turret driving system. The Gun/Turret driving controller receives absolute angular error calculated from the fire control system (FCS). Thus, the Gun/Turret driving controller is subjected to step command to cause residual vibration and system unstable. In order to reduce residual vibration and to ensure the system stability, we propose an error motion profile method with two types of trapezoidal and S-Curve. The validity of the proposed error motion profile method is confirmed via simulation by observing that the resulting position error, driving power, and power density satisfied the control performance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.566-573
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• 2019

In order to obtain high-quality images by motion compensation in the airborne synthetic aperture radar (SAR), accurate motion sensing in image acquisition section is necessary. Especially, reducing relative position error and discontinuity in motion sensing is important. To overcome the problem, we propose a pre-parametric error modeling (P-PEM) algorithm which is a real-time motion sensing algorithm for the airborne SAR in this paper. P-PEM is an extended version of parametric error modeling (PEM) method which is a motion sensing algorithm to mitigate the errors in the previous work. PEM estimates polynomial coefficients of INS error which can be assumed as a polynomial in the short term. Otherwise, P-PEM estimates polynomial coefficients in advance and uses at image acquisition section. Simulation results show that the P-PEM reduces relative position error and discontinuity effectively in real-time.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.380-384
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• 1997

For improving the motion accuracy of hydrostatic table, corrective machining algorithm is proposed in this paper. The algorithm consists of three main processes. Reverse analysis is performed firstly to estimate rail profile from measured linear and angular motion error, in the algorithm. For the next step, correctwe machining information is decided as referring to the estimating rail profile. Finally, motion errors on correctively machined rail are analized by using motion error analysls method proposed in the previous paper. These processes can be rtcrated if the analized motion errors are worse than target accuracy. In order to verify the validity of the algorithm theoretically, motion errors by the estimated rail after corrective machining are compared with motion errors by true rail assumed as the measured value. Estimated motion errors show good agreement with assumed values, and it is confirmed that the algorithm IS effective to acquire the corrective machming information to improve the accuracy of hydrostatic table.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.5
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• pp.124-130
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• 2000

For measuring out the submicron order straightness, a precision measuring device is developed in this paper. The device is constructed with a hydrostatic feed table and a capacitive type sensor which is mounted to the feed table. Straightness is acquired as substracting the motion error of feed table from the measured profile with probe. Motion error of feed table is simultaneously compensated upto 0.120${\mu}{\textrm}{m}$ of linear motion error and 0.20arcsec of angular motion error using the active controlled capillary. Reversal method and strai호t-edge is used fur estimating the measuring accuracy and from the experimental result, it is verified that the device has the measuring accuracy 0.030m. Also, through the practical application on the measurement of ground surface, it is confirmed that the device is very effective to measure the submicron order straightness.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.11-15
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• 2008

Metrology tools with the ability to measure spindle motion error on the order of a nanometer are required due to recent advances in nanotechnology. We propose a direct measurement method for the radial motion error of a precision spindle using a regular crystalline lattice and a scanning tunneling microscope (STM). A highly oriented pyrolytic graphite (HOPG) crystal combined with an STM is used as a two-dimensional reference scale. The measurement principle and the preliminary experimental results are discussed in this article. The preliminary experimental results demonstrated that the proposed method has the capability to incorporate a two-dimensional encoder to measure the spindle motion error.