• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.1
• /
• pp.1-8
• /
• 2012

Recently, the needs of system performances such as working speed and processing accuracy in machine tools have been increased. Especially, the speed increment generates harmful heat at both moving part of the machine tools and handicrafts. The heat is a main drawback to progress accuracy of the processing. Hence, a cooler system to control temperature is inevitable for the machine tools. In general, two representative control schemes, hot-gas bypass and variable speed control of a compressor, have been adopted in the water cooler system. In this paper, comparisons of system performances according to the control schemes in a cooler for machine tools were conducted in detail. Each proportional-integral feedback controller for the two different control systems is designed. The system performances, especially the temperature control accuracy and coefficient of performance which is a criterion of energy saving, were mainly analyzed through various experiments using 1RT water cooler system with different two types of control scheme. These evaluations will provide useful information to choose suitable water cooler system for the engineers who design controllers of the cooler system for machine tools.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.30 no.6_1
• /
• pp.511-518
• /
• 2012

It is well-known that non-metric digital cameras have to be calibrated for the close-range photogrammetry. But, the self-calibration is still not an easy task because it requires rather a large calibration site of accurate control points, multiple image acquisitions in different positions, and accurate image point measurements that are quite labor-intensive and time-consuming. Based on the premise, this study carried out check point accuracy analysis from self-calibration of different control point designs and photo combinations. The test results showed that the calibration using three photos covering three-dimensional control points produced high accuracy, but control points on a plane could attain the comparable accuracy with four photos including a 90-degree rotated photo. We then compared the target accuracy of on-site self-calibration using flat control points to that of laboratory-self calibration and observed comparable results.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.3
• /
• pp.408-413
• /
• 2013

Micro-features such as grooves and lenses, which perform optical functions in flat displays, should be manufactured with a good form accuracy because this is directly related to their optical performance. As the size of the display increases, it is very difficult to maintain a high relative accuracy because of the inherent geometric errors such as the waviness of a large-area plate. In this paper, the optical effect of these geometric errors is investigated, and surface-referenced micro-grooving to measure and compensate for such geometric errors on line is proposed to improve the form accuracy of the micro-grooves. A PZT-based fast depth adjustment servo system is implemented in the tool holder to maintain a uniform groove depth in reference to the wavy surface. Through experiments, the proposed method is shown to be an efficient way to produce high-quality micro- grooves on a wavy die surface.

• Journal of Institute of Control, Robotics and Systems
• /
• v.8 no.7
• /
• pp.573-577
• /
• 2002

A tape feeder of a SMD(Surface Mount Device) mounter is a device that sequentially feeds electronic components on a tape reel to the pick-up system of the mounter. As components are getting much smaller, feeding accuracy of a feeder becomes one of the most important factors for successful component pick-up. Therefore, it is critical to keep the feeding accuracy to a specified level in the assembly and production of tape feeders. This paper describes a tape feeder inspection system that was developed to automatically measure and inspect feeding accuracy using machine vision. It consists of a feeder base, an image acquisition system, and a personal computer. The image acquisition system is composed of CCD cameras with lens, LED illumination systems, and a frame grabber inside the PC. This system loads up to six feeders at a time and inspects them automatically and sequentially. The inspection software was implemented using Visual C++on Windows NT with easily usable GUI. Using this system, we can automatically measure and inspect the quality of all feeders in production process by analyzing the measurement results statistically.

• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.12
• /
• pp.163-170
• /
• 2002

The quality of a precision product, in general, relies on the accuracy and precision of its manufacturing and inspection process. In many cases, the level of precision in the manufacturing and inspection system is also dependent on the positioning capability of tool with respect to the work piece in the process. Recently the positioning accuracy level has reached to the level of submicron and long range of motion is required. For example, for 1 GDARM lithography, 20nm accuracy and 300mm stroke needs. This paper refers to the lithography stage especially to fine stage. In this study, for long stroke and high accuracy, the dual servo system is proposed. For the coarse actuator, LDM (Linear DC Motor) is used and for fine one VCM is used. In this study, we propose the new structure of VCM for the fine actuator. It is 3 axis precision positioning stage for an aligner system. After we perform the optimal design of the stage to obtain the maximum force, which is related to the acceleration of the stage to accomplish throughput of product. And we controlled this fine stage with TDC. So we obtained 50nm resolution. So later more works will be done to obtain better accuracy.

• Journal of Korean Academy of Nursing
• /
• v.37 no.1
• /
• pp.125-134
• /
• 2007

Purpose: The study aimed to identify the effects of a newborn care education program on newborn care confidence and behavioral accuracy of primiparas in a postpartum care center. Method: This was a quasi-experimental study with a non-equivalent control group non-synchronized design. Subjects were 29 primiparas selected from a postpartum care center in D and P hospitals in Ulsan. The intervention was a newborn care education program which was composed of education with a booklet, demonstration, watching a video, and verbal encouragement. The outcome variables were newborn care confidence and behavioral accuracy. Data was collected from Feb. 1 to Mar 22 in 2005 with self-administered questionnaires and observation by researchers. Data was analyzed using the $X^2-test$, Fisher's exact test, t-test and ANCOVA. Result: The experimental group showed significantly higher score changes between the pre-test and post-test in confidence and behavioral accuracy than the control group. Conclusion: The newborn care education program showed positive effects on newborn care confidence and behavioral accuracy of primiparas in a postpartum care center. Therefore, we recommend that this program should be applied in postpartum care centers.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.17 no.2
• /
• pp.90-96
• /
• 2008

A pneumatic system was proposed to evaluate displacement accuracy of the pneumatic actuator without external load and to analyze capability of integration of the proposed valve system. The proposed pneumatic system consisted of a combination of pneumatic valves, two proximity sensors, and a programmable logic controller(PLC). The position controller is based on the PLC controller connected with the proximity sensors. Displacement accuracy of the pneumatic cylinder stroke was tested by varying air pressures of the supply and discharge-side and strokes of the pneumatic cylinder. The displacement accuracy of the pneumatic cylinder stroke increased as the supply and discharge side of air pressure increased at the stroke length of 133mm. Also the displacement accuracy increased as the stroke length increased with a fixed supply and discharge side of air pressure of the pneumatic cylinder as 3.5 and $4.5kg/cm^2$, respectively. The most accurate displacement of the pneumatic cylinder(i.e., standard deviation of 0.01 mm) was obtained at the supply and discharge side of air pressure of 4.0 and $5.0kg/cm^2$, respectively, and strokes of 170 and 190 mm among arbitrarily selected supply and discharge side air pressures and strokes.

• Journal of Institute of Control, Robotics and Systems
• /
• v.18 no.8
• /
• pp.713-718
• /
• 2012

Lumber spine range of motion has been used to measure of physical and functional impairment by various tools from a ruler to 3D kinematic devices. However, pre-existing tools have problems in either movement or accuracy and reliability limitations. Accurate devices are limited by fixed space whereas simple devices are limited in measuring complex movements with less accuracy. In order to solve the location, movement and accuracy limitations at once, we have developed a novice measurement device equipped with accelerometer sensor and gyroscope sensor for getting three-dimensional information of motion. Furthermore, Kalman filter was applied to the algorithm to improve accuracy. In addition, RF wireless communication was added for the user to conveniently check measured data in real time. Finally, the measurement method was improved by considering the movement by a reference point. An experiment was conducted to test the accuracy and reliability of the device by conducting a test-retest reliability test. Further modification will be conducted to used the device in various joints range of motion in clinical settings in the future.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.29 no.2
• /
• pp.123-130
• /
• 2016

With the development of fast construction mode in shipbuilding market, the demand on accuracy management of hull is becoming higher and higher in shipbuilding industry. In order to enhance production efficiency and reduce manufacturing cycle time in shipbuilding industry, it is important for shipyards to have the accuracy of ship components evaluated efficiently during the whole manufacturing cycle time. In accurate shipbuilding process, block accuracy is the key part, which has significant meaning in shortening the period of shipbuilding process, decreasing cost and improving the quality of ship. The key of block accuracy control is to create a integrate block accuracy controlling system, which makes great sense in implementing comprehensive accuracy controlling, increasing block accuracy, standardization of proceeding of accuracy controlling, realizing "zero-defect transferring" and advancing non-allowance shipbuilding. Generally, managers of accuracy control measure the vital points at section surface of block by using the heavy total station, which is inconvenient and time-consuming for measurement of vital points. In this paper, a new measurement method based on point clouds technique has been proposed. This method is to measure the 3D coordinates values of vital points at section surface of block by using 3D scanner, and then compare the measured point with design point based on ICP algorithm which has an allowable error check process that makes sure that whether or not the error between design point and measured point is within the margin of error.

• Spatial Information Research
• /
• v.16 no.4
• /
• pp.401-410
• /
• 2008

In this contribution, the renovation of the Korean geodetic control points is introduced. The renovation is described in terms of structure and accuracy. Mainly the establishment of the three-dimensional control points is the renovation on structure which leads many changes in accuracy, contents and hierarchy of the control points. The accuracy of the information is being improved based on the satellite positioning technology and precision geoid being developed. Diverse spatial information such as gravity and environmental elements are considered to be measured at the position of the control points so that the related research is enhanced through the analysis of combined information. In addition, an access to the information of control points and service to the public with spatial information will be faster and more efficient through RFID and CDMA communication. With all these efforts being made currently, the Korean geodetic network will provide the most accurate and diverse spatial information in an efficient way. We hope that these activities lead the trends, roles, and future direction of the geodetic control points.