• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.1
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• pp.53-58
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• 2011

Ultra-precision miniaturized machine tools essential for manufacturing accurate machine components in micro/meso-scale have been developed. To realize high accuracy using mMTs, geometric errors, which are considered as the main sources of inaccuracy should be identified and compensated. The conventional systems for measuring geometric errors, such as a laser interferometer, can measure only one geometric error in a single setup and they involve complicated measurement procedures. A measurement system using PSDs is a promising alternative but the measurable range of such systems is limited to the active range of the PSDs. The proposed measurement system using PSDs can overcome the limit of small measurable range. Further, the mounting errors that could occur during set-up process can be avoided. In this paper, an algorithm corresponding to the system was analyzed and experiments were carried out.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1832-1835
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• 1997

Off-line programming systems are widely spread in assembly lines of minute electronic products to huge offshore structures. Any OLP system has to be calibrated before the on-line robot tasks are performed because there are inherent differences between the CAD model on OLP and the real robot workspace. This paper uses simple geometric expressions to propose a calibration method applicable to an OLP for SCARA robots. A positioning task on the two-dimensional horizontal surface was used in the error analysis of a SCARA robot and the anaysis shows that the inaccuracy results from the two error sources non-zero offset angles of two rotational joints at the zero return and differences in link lengths. Pen marks on a sheet of plotting paper are used to determine the accurate data on the joint centers and link dimensions. The calculated offset angles and link lengths are fed back to the OLP for the calibration of the CAD model of the robot and task environments.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.226-232
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• 2003

Difficulties in the finite element modeling of human spine are evaded by using a stiffness matrix element whose properties can be characterized from experimentally measured stiffness of functional spinal units. Relative easiness is in that inter-vertebral discs, ligaments, and soft tissues connecting vertebrae do not need to be modeled as they are. The remarkable coupling effect between distinct degrees of freedom induced by the geometric complexity can be accommodated without much effort. An idealized block model with simple geometry for vertebra is employed to assess the feasibility of this method. Analyses are performed in both levels of motion segment and spinal column, and the result is compared with that from detail model. As far as the global behavior of spine is concerned, the simplification is found not to aggravate inaccuracy only if sufficient experimental data is provided and interpreted properly.

• Journal of the Ergonomics Society of Korea
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• v.8 no.2
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• pp.19-26
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• 1989

This study, as a part of integrated human-robot ergonomics, improves the robot motion control on the robot task in the TOES/WCS whose purpose is improving the teaching task constructed in the previous study. First, the updated combined fuzzy process using a new membership function with Weber's law is constructed for the purpose of coordinate reading of the end points in the macro motion control. Second, an algorithm using the geometric analysis is desinged in order to calculate position values and posture values of the robot joints. Third, the MGSLM method is designed to remove unnecessary the robot motion control caused by the GSLM method in the micro motion control. Consequently, proposed methods in this study lessen burdcn of a human of an improvement of the robot motion control and reduce the teaching time of a human operator and inaccuracy of the teaching task, which contribute to the integrated human-robot ergonomics.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.322-327
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• 2003

It is important to know the accurate radionuclide inventory of radioactive waste for the reliable management. However, estimation of radionuclide concentrations in drummed radioactive waste is difficult and unreliable because of difficulties of direct detection, high cost, and radiation exposure of sampling personnel. In order to overcome these difficulties, scaling factors (SFs) have been used to assess the activities of radionuclides that could not be directly analyzed. A radionuclide assay system has been operated at KORI site since 1996 and consolidated scaling factor method has played a dominant role in determination of radionuclides concentrations. However, some problems are still remained such as uncertainty of estimated scaling factor values, inaccuracy of analyzed sample values, and disparity between the actual and ideal correlation pairs and the others. Therefore, it needs to improve the accuracy of scaling factor values. The scope of this paper is focused on the improvement of accuracy and representativeness of calculated scaling factor values based on statistical techniques. For the selection of reliable activity determination method, the accuracy of estimated SF values for each activity determination method is compared. From the comparison of each activity determination methods, it is recommended that SF determination method should be changed from the arithmetic mean to the geometrical mean for more reliable estimation of radionuclide activity. Arithmetic mean method and geometric mean method are compared based on the data set in KORI system.