• ETRI Journal
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• v.34 no.2
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• pp.175-183
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• 2012

Conventional synchronization algorithms for impulse radio require high-speed sampling and a precise local clock. Here, a phase-locked loop (PLL) scheme is introduced to acquire and track periodical impulses. The proposed impulse PLL (iPLL) is analyzed under an ideal Gaussian noise channel and multipath environment. The timing synchronization can be recovered directly from the locked frequency and phase. To make full use of the high harmonics of the received impulses efficiently in synchronization, the switching phase detector is applied in iPLL. It is capable of obtaining higher loop gain without a rise in timing errors. In different environments, simulations verify our analysis and show about one-tenth of the root mean square errors of conventional impulse synchronizations. The developed iPLL prototype applied in a high-speed ultra-wideband transceiver shows its feasibility, low complexity, and high precision.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.537-542
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• 2004

Machinble Ceramics have some excellent properties as the material for the mechanical components. It is, however, very difficult to grind ceramics with high efficiency because of their high strength, hardness and brittleness. Lapping used diamond slurry and lapping by in-process electrolytic dressing is developed to solve this problem. On this paper, a comparative study of processing ability of lapping used diamond slurry and lapping by in-process electrolytic dressing.

• Journal of the Korean Society for Precision Engineering
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• v.29 no.2
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• pp.161-169
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• 2012

Recently, a study for the functional surface production of super hydrophobic of natural and biomimetic artificial has attracted much attention. To make process methods of super hydrophobic surface has a variety of ways such as lithography, etching, and laser ablation. However, we were used ultra-shot pulse laser ablation process which has the virtue of more environmental friendliness and simple process. In this paper, we were fabricated a multiplicity of super hydrophobic patterns on mold surface(NAK80) using by optimizing the laser processing conditions and it was transferred on PDMS. Also, we measured contact angle super hydrophobic patterns on PDMS. The result showed there is no patterns on PDMS were measured 94 degrees, by contrast, optimized super hydrophobic patterns on PDMS was 157 degrees. Therefore we fabricated super hydrophobic surface on mold. Based on these experimental results, it is possible to mass production using ultra shot pulse laser ablation of super hydrophobic pattern and to be applied for a variety of industries.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.3
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• pp.70-76
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• 2022

Recently, the demand for ultra-precision processing has increased owing to the increase in the demand for high-performance ultra-precision optical parts in the fields of information technology (IT), bio, healthcare, aerospace, and future automobiles. In this study, a performance improvement of a multi-stage pump was achieved by improving the pump casing structure rather than using the existing performance improvement method. To verify the performance improvement, the CFD analysis reliability of the existing pump, Pump A, was verified using the FLUENT app in the analysis software ANSYS, and the pump casing was improved through the verified CFD analysis of Pump B. Therefore, we want to analyze the performance improvement.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.198-202
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• 2002

In this paper, stability of ultra precisio unit is analyzed, this unit is the kernel unit precision processing machine. According alteration of shape and material about stability investigation is performed. Through this stability investigation, trial is reduced in design and manufacture, at the time, we are accumulated foundation data for control.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.20-26
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• 2003

This study proposes the construction of attractor quadrant method for high-precision cutting characteristics evaluation of non-ferrous metals. Also this paper aims to find the optimal cutting conditions of diamond turning machine by measuring surface form and roughness to perform the cutting experiment of non-ferrous metals, which are aluminum, with diamond tool. As well, according to change cutting conditions such as feed rate, using diamond turning machine to Perform cutting Processing, by measuring cutting force and surface roughness and according to cutting conditions the aluminum about cutting properties. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics and attractor quadrant characteristics. In quantitative quadrant feature extraction, 1,309 point in the case of A17075 (one quadrant) and 1,406 point (one quadrant) in the case of brass were proposed on the basis of attractor reconstruction. Proposed attractor quadrant method can be used for high-precision cutting characteristics evaluation of non-ferrous metals.

• Journal of Digital Contents Society
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• v.18 no.6
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• pp.1175-1182
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• 2017

Recent trend in the manufacturing industry is focused on the convergence with IoT and Big Data, by emergence of the 4th Industrial Revolution. To realize a smart factory, the proposed system based on MTConnect technology collects and integrates various status information of machines from many production facilities including heterogeneous devices. Also it can distribute the acquisited status of heterogeneous manufacturing machines to the remote devices. As a key technology of a flexible automated production line, the proposed system can provide much possibility to manage important information such as error detection and processing state management in the unmanned automation line.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1468-1471
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• 2005

This Paper is to find out a solution for the full-coverage algorithm requiring the real-time processing such as mobile home service robots and vacuum cleaner robots. Previous methods are used by adopting based grid approach method. They used lots of sensors, a high speed CPU, expensive ranger sensors and huge memory. Besides, most full-coverage algorithms should have a map before obstacle avoidance. However, if a robot able to recognize the tangent vector of obstacles, it is able to bring the same result with less sensors and simplified hardware. Therefore, this study suggests a topological based approach and a local obstacle voidance method using a few of PSD sensors and ultra sonic sensors. The simulation results are presented to prove its applicability.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1475-1478
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• 2004

This paper describes map building for the path planning to avoid obstacles with vision sensor and ultrasonic sensor. We get the 2 dimensional information from the processed images of CCD sensor and 1 dimensional range information from ultrasonic sensor. I proposed a way to generate the map which contains these two kinds of information in the program. And we made the biped robot which have 20 DOF with these sensors and get good experimental result to prove the validity of the proposed method.

• Transactions of Materials Processing
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• v.21 no.2
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• pp.138-143
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• 2012

A polishing method using magnetorheological (MR) fluid has been developed as a new precision technique to obtain a fine surface. The process uses a MR fluid that consists of magnetic carbonyl iron (CI) particles, nonmagnetic polishing abrasives, water and stabilizers. But the CI particles in MR fluids cause a severe corrosion problem. When coated with Xanthan gum, the CI particles showed long-term stability in corrosive aqueous environment. The surface roughness obtained from the MR polishing process was evaluated. A series of experiments were performed on fused silica glass using prepared slurries and various process conditions, including different polishing times. Outstanding surface roughness of Ra=2.27nm was obtained on the fused silica glass. The present polishing method could be used to produce ultra-precision micro parts.