• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.158-161
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• 2003

Recently, the evolution in production techniques (e.g. high-speed milling), the complex shapes involved in modem production design, and the ever increasing pressure for higher productivity demand a drastic improvement of the dynamic behavior of the machine tool axes used in production machinery. And also machine tools of multi functional and minimized parts are increasingly required as demand of higher accurate in some fields such as electronic and optical components etc. The accuracy and the productivity of machined parts are natural to depend on the linear system of machine tools. The complex workpiece surfaces encountered in present-day products and generated by CAD systems are to be transformed into tool paths for machine tools. The more complex these tool paths and the higher the speed requirements, the higher the acceleration requirements are needed to the machine tool axes and the motion control system, and the more difficult it is to meet the requirements. The traditional indirect drive design for high speed machine tools, which consists of a rotary motor with a ball-screw transmission to the slide, is limited in speed, acceleration, and accuracy. The direct drive design of machine tool axes. which is based on linear motors and which recently appeared on the market. is a viable candidate to meet the ever increasing demands, because of these advantages such as no backlash, less friction, no mechanical limitations on acceleration and velocity and mechanical simplicity. Therefore performance tests were carried out to machine tool axes based on linear motor. Especially, dynamic characteristics were investigated through circular test.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.12
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• pp.185-193
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• 2002

Most of NC machines are operated by Is06983 standard called G-code, which was developed in the early days of machine tools. This G-code limits hardware performance of the currently developed high-performance hardware & machine tools. By describing only movements of tool, almost all of information of previous production departments is lost, and the machining department cannot exchange information with other departments. For adjusting new hardware environment and direct communication of CNC machines with CAD/CAM software, ISO 14649, STEP -NC is researched. This new standard stores CAD/CAM information as well as operation commands of CNC machines. In this research, the new CNC machine operated by STEP-NC was built and tested. Unlike other STEP-NC milling machines, this system uses the STEP-NC file in form of XML as data input. It makes possible for STEP-NC machines to exchange information to other databases using XML. The mentioned system of this paper loads the XML file, analyzes it, makes tool paths of two5D features with information of STEP-NC, and machines automatically without making G-code. All of software is programmed with Visual C＋＋, and the milling machine is made with table milling machine, step motors, and motion control board for PC that can be directly controlled by C＋＋ commands. All modules of software and hardware were independent, it allows convenient for substitution and expansion of the milling machine. The example 1 in ISP14649-11 that had all information about geometry and machining and the example 2 that has only geometry and tool information were used to test automatic machining by the open-architecture milling machine.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.3
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• pp.324-333
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• 2012

The conventional medium and large caliber gun, in general, utilize the hydro-pneumatic recoil mechanism to control the firing impulse and to return to the battery position. However, this kind of mechanism may cause the problems like the leakages and the property changes in oil and gas due to the temperature variations between low and high temperatures. Accordingly, the friction spring mechanism has recently been researched as an alternative system. The friction spring mechanism consists of a set of closed inner and outer rings with the concentric tapered contact surfaces assembled in the columnar form, and can only be used under the compression load. When the spring column is axially loaded, the tapered surfaces become overlapped, causing the outer rings to expand while the inner rings are being contracted in diameter allowing an axial displacement. Because of friction between tapered contact surfaces, much higher spring stiffness is obtained on the stroke at the increase in load than the stroke at the decrease. In this paper, the dynamic equations regarding the friction spring system and the design approach have been investigated. It is also tried for a dynamic model representing the recoil motion and the friction spring forces. And the model has been proved from firing test using a gun system with friction springs. All the results show that the recoil mechanism using friction springs can substitute for the classic hydro-pneumatic recoil system.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.12
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• pp.1434-1440
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• 2011

In this paper, we assessed muscular activities of lower limbs and foot pressure for car and bus drivers according to operating three electronic pedals that we developed. To analyze drivers' physical exhaustion, muscular fatigue of lower limbs was evaluated. Eleven car drivers and six urban bus drivers were participated in this experiment. The virtual driving system was used for the real driving environment. The virtual driving system was comprised of a spring seat, a steering wheel, pedals (clutch, excel and brake pedals), a manual transmission and a virtual driving simulation. For the real vibration like situation on the road, six degree of freedom motion base system was used. Measured muscles were rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA) and gastrocnemius (Gn) muscles. For the quantitative muscular activities, integrated electromyography (IEMG) was analyzed. Muscular fatigues also were analyzed through the analysis of the median frequency. In addition, foot pressures were analyzed and compared through the peak and averaged pressure during the operating three developed electronic pedals. The experiments are conducted with total 17 drivers, 11 general public and 6 drivers. As a result of the analysis, electromyogram and fatigue analysis through intermediate frequency reduction for pedal-1 more efficient than other pedals. And foot pressure also was decreased. Consequently, we suggested the most efficient pedal and method to minimize the amount of cumulative fatigue.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.1
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• pp.1-7
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• 2016

In the dentistry field, an ultrasonic surgery unit is widely used in bone cutting and scaling to reduce operation time and minimize hemorrhage. The purpose of this study was to evaluate bone cutting and the effect of a specimen's temperature on the two-type ultrasonic surgery unit using a handpiece moving system(HMS). A HMS, which can cut the bone, was developed to perform the experimental procedure with precision of motion control. Bone specimens were prepared from a combination of epoxy-hardener and cortical bone of bovine leg. Through the bone-cutting experiment, the cutting depth was evaluated by not only scanning electron microscopy, but also Vernier calipers. Also, the temperature distribution was measured by a thermo-graphic camera. This study may be applied methodically in various experimental evaluations on a performance test by a HMS.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2105-2114
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• 2006

In this paper, a simplified model is studied to predict analytically the vibration from the helical gear system due to an axial excitation of helical gears. The simplified model describes gear, shaft, bearing, and housing. In order to obtain the axial force of helical gears, the mesh stiffness is calculated in the load deflection relation. The axial force is obtained from the solution of the equation of motion, using the mesh stiffness. It is used as a longitudinal excitation of the shaft, which in turn drives the gear housing through the bearing. In this study, the shaft is modeled as a rod, while the bearing is modeled as a parallel spring and damper only supporting longitudinal forces. The gear housing is modeled as a clamped circular plate with viscous damping. For the modeling of this system, transfer matrices for the rod and bearing are used, using a spectral method with four pole parameters. The model is validated by finite element analysis. Using the model, parameter studies are carried out. As a result, the linearized dynamic shaft force due to the gear excitation in the frequency domain was proposed. Out-of-plan displacement from the forced vibrating circular plate and the renewed mode normalization constant of the circular plate were also proposed. In order to control the axial vibration of the helical gear system, the plate was more important than the shaft and the bearing. Finally, the effect of the dominant design parameters for the gear system can be investigated by this model.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.12
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• pp.3115-3123
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• 1993

This paper presents a real-time correction method of the movemont errors of a translatory precision machine axis. This method is a null-balances technique in which two plane mirrors are used to generate an interferometric fringe pattern utilizing the optical principles of TwymanGreen interferometry. One mirror is fixed on a reference frame, while the other is placed on the machine axis being supported by three piezoelectric actuators. From the fringe pattern, one translatory and two rotational error components of the machine axis are simultaneously detected by using CCD camera vision and image processing techniques. These errors are then independently suppressed by activating the peizoelectric actuators by real-time feedback control while the machine axis is moving. Experimental results demonstrate that a machine axis can be controlled with movement errors less than 10 nm in vertical straightness, 0.1 arcsec in pitch, and 0.06 arcsec in roll for 50mm travel by adopting the real-time correction method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4130-4135
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• 2013

This paper is a special-purpose machine studies for processing various patterns on the surface of the stone. We have developed a special-purpose machine that can be applied in various patterns upon the surface treatment of the stone with the water jet. The special-purpose machine is Configured of Transfer mechanism, motion controller, multi-nozzle mechanism, ultra high pressure water control system and S/W. We conducted a performance evaluation experiments of the pattern. We have developed a special-purpose machine with a precision of machining error ${\pm}0.5mm$ and pattern processing of various types.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1036-1043
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• 2022

This paper discusses about the development of a visual sensor that can be installed in an automatic mooring device to detect the berthing condition of a vessel. Despite controlling the ship's speed and confirming its location to prevent accidents while berthing a vessel, ship collision occurs at the pier every year, causing great economic and environmental damage. Therefore, it is important to develop a visual system that can quickly obtain the information on the speed and location of the vessel to ensure safety of the berthing vessel. In this study, a visual sensor was developed to observe a ship through an image while berthing, and to properly check the ship's status according to the surrounding environment. To obtain the adequacy of the visual sensor to be developed, the sensor characteristics were analyzed in terms of information provided from the existing sensors, that is, detection range, real-timeness, accuracy, and precision. Based on these analysis data, we developed a 3D visual module that can acquire information on objects in real time by conducting conceptual designs of LiDAR (Light Detection And Ranging) type 3D visual system, driving mechanism, and position and force controller for motion tilting system. Finally, performance evaluation of the control system and scan speed test were executed, and the effectiveness of the developed system was confirmed through experiments.

• Current Research on Agriculture and Life Sciences
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• v.31 no.2
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• pp.131-138
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• 2013

The precision aerial application of small farms, such as paddy, upland and orchard fields using agricultural unmanned helicopters became a new paradigm. The objective of this study was to evaluate the performance of a GPS module and algorithm, controlling drift of agricultural helicopter by the crosswind and maintaining the position for emergency landing. Purpose of the drift control, of which an algorithm works while hovering is related with the emergency sequence that coping with abnormal conditions of rotorcraft system. However, the inertial attitude control cannot detect a drifting motion of fuselage moving at the constant velocity, thus the crosswind takes the helicopter away from the landing position. Performance of the drift control module, based on the GPS that a hovering position did not deviate within 5m in diameter, were tested and evaluated. Initially, the reaction against a disturbing gust wind was sensitive, soon the helicopter maintained its locking position and azimuth within 5m in diameter. It was, however, difficult for the helicopter to recognize the swaying and nodding, the some deviation was expected due to the discrepancy characteristics of the GPS signal. The performance of the drift control proved the effectiveness of the module to maintain the position against an unintended drift during the emergency landing or hovering.