• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.367-372
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• 2000

Accuracy of a machined component is determined by the relative motion between the cutting tool and the workpiece. One of the important factors which affects the accuracy of this relative motion is the geometric error of machine tools. In this study, geometric error is modeled using form shaping motion of machine tool, where a form shaping function is derived from the homogeneous transformation matrix. Geometric errors are measured by laser interferometer. After that, the local positioning error can be estimated from the form shaping model and geometric error data base. From this information, we can remodel the part by shifting the design surface to the amount of positional error. By generating tool path to the redesigned surface, we can reduce the machining error.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.11a
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• pp.355-356
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• 2008

• The Journal of Korea Robotics Society
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• v.18 no.1
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• pp.99-109
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• 2023

In this paper, the cinch bag typed fruit harvesting gripper was proposed. This gripper is focused on preventing problems that we found from the related research and setting the breakthrough as a design condition according to the harvest failures of other related studies. The cover part is designed to overcome the surrounding obstacles of target fruits such as tomato, Korean melon, and sweet pepper. The measurement of maximum load showed that the well-grasped target object, such as a spherical object with 65 mm of diameter, is unable to slip in a range of 0 kg to 10 kg. The fact that the gripper allows from 4 cm to 6 cm of positional error was shown in the measurement of positional error tolerance. And the cover part of this gripper showed that the suggested gripper can grab a target object without being obstructed by leaves and stems. Finally, it was proved that the gripper satisfied the design conditions through the measurement of contacting force, which showed it is appropriate for grasping an actual fruit without damage.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.1
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• pp.31-37
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• 2011

Recently gantry-type robot with 3 axes rectangular coordinates have been studied in the many industrial production equipment and machinery fields. To acquire a good handling and motion performance of this robot, reducing the settling-time and securing the accurate-transfer positioning under high-speed conditions should be required. However when robot is moved in high-speed, the large inertia of robot can lead to serious vibration of robot's head. The time-delayed control characteristics of this robot can also lead to tracking error. In this research, the analysis of the effects of higher order positional-profile is carried out to assure high-speed performance and stiffness specifications. To remove the residual vibration caused by kinematic coupling effect of dual-servo gantry, we develop a dual-servo gantry of rotary type that moving frame of x-axis rotates about z-axis. In order to decrease the tracking error, the 3 type lead-filter through system identification was applied respectively. From the experimental results, it was shown that zero-order series leader-filter has the best performance about tracking error and settling time.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.26 no.5
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• pp.529-536
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• 2008

Researches about 3-D Positioning system using GPS were carried out many-sided by national organs, laboratories, the worlds of science. And most of researches were development of relative positioning algorithm and its applications. Relative positioning has a merit, which can eliminate error in received signals. But its error increase due to distance of baseline. GPS absolute positioning is a method that decides the position independently by the signals from the GPS satellites which are received by a receiver at a certain position. And it is necessary to correct various kinds of error(clock error, effect of ionosphere and troposphere, multi-path etc.). In this study, results of PPP(Precise Point Positioning) used Bernese GPS software was compared with notified coordinates by the NGII(National Geographic Information Institute) in order to analyze the positional accuracy of permanent GPS sites. And the results were compared with results of AUSPOS - Online GPS Processing Service for comparison with relative positioning.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.10
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• pp.1619-1625
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• 1997

This paper concerns a 2-axis PR type pneumatic manipulator system translating in vertical and rotating in horizontal directions. A simplified linear model is mathematically formulated similar to the pneumatic acturators in dynamic responses in order to devise an appropriate position control scheme. A PD controller preceding the on/off solenoid valve turns out not only economical but also effective in reducing rise time and amplitude of limit cycles, if its control gains are determined on the basis of frequency response. And, additional implementation of symmetric or asymmetric deadband at the PD controller output greatly helps minimize valve opening numbers, positional error, and undesirable direction-dependent property due to the gravitational load. Such a control concept is synthesized through numerical simulations and next applied to the experimental set-up, featuring enhanced positional servo characteristics.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.827-831
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• 2008

In this paper, kinematic analysis for a planar 3-DOF redundant stage which has four actuators is presented by using SimMechanics software package. SimMechanics is a block sets of the Matlab/Simulink package. The SimMechanics enables a simplified model for a complex kinematic mechanism, since kinematic relationship between joints and linkages for the kinematic chains are expressed as line vectors and block diagrams. Here, positional error and limit values of movement ranges of the stage are evaluated by using the SimMechanics. The validity of the kinematic characteristics model was compared with theoretical kinematic analyses for the 3-DOF stage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.383-386
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• 2002

It is very important to inspect color of printed texture in the textile process. To distinguish the color of the printed texture, RGB color values obtained from a scanner must be transformed to the standard colorimetric system used in the textile industry. It is XYZ color system that is defined by CIE(Commission Internationale do 1Eclairage). The mapping from RGB to XYZ color values is not simple and the scanner has even a positional deviation of RGB colors. In this paper an automatic color inspection method using a general scanning machine is presented. We used a U(neural network) model to map RGB to XYZ and compensate the positional error. In the real experiments, this inspection system shows to get very exact XYZ values from the traditional scanner regardless of the measuring position.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.123-127
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• 2002

In order to set up the design rule of micro optical bench, optical coupling efficiencies of two sets of test benches are calculated. Simple linear connections of incoming and outgoing optical fibers with and without ball lenses are designed. Positional errors that are possible in actual fabrication processes are considered in the calculations and their tolerances are determined from 3dB conditions. For a simple fiber-to-fiber connection, the working distance is limited to $2.7\mu\textrm{m}$ and tilt error $5.8^{\circ}$. When ball lenses are located in front of each fiber, the working distance can be extended over $60\mu\textrm{m}$ , but the positional errors have the strong interaction among position parameters and thus should be considered simultaneously for tolerance design.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.26 no.3
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• pp.250-257
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• 1993

The Global Positioning System(GPS) is a worldwide radio navigation system based on satellite technology. Signal availability and accuracy of GPS are subject to change due to an incomplete constellation and operational test activities. In order to analyze the signal availability and accuracy of GPS, we made an experiment on this system in Kunsan during April 6, 7, 9, 10, 1992. The results obtained are summarized as follows: 1. It was possible to avail the GPS system almost 24 hours per day, but sometimes it was impossible to obtain the GPS signal 2 or 3 times per day and its total time was at the most an hour. 2. By using satellite almanac, we also could calculate PDOP(HDOP) and forecast signal availability. And the mean positional error was $37.9{\sim}73.6m$ and standard deviation was $37.4{\sim}133.1m$. The positional error almost coincided with PDOP(HDOP). 3. The mean positional error of 3D was less than that of 2D. And the altitude error in 3D was about $56{\sim}74m$ and its standard deviation was about $65{\sim}93m$.