• 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.28 no.3
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• pp.292-300
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• 2011

Control systems in machinery equipment provide correction signals to motion units in order to reduce or cancel out the mismatches between sensor feedback signals and command or desired values. In this paper, we introduce a simulator for control characteristics of machinery equipment. The purpose of the simulator development is to provide mechanical system designers with the ability to estimate how much dynamic performance can be achieved from their design parameters and selected devices at the designing phase. The simulator has a database for commercial parts, so that the designers can choose appropriate components for servo controllers, motors, motor drives, and guide ways, etc. and then tune governing parameters such as controller gains and friction coefficients. The simulator simulates the closed-loop control system which is built and parameter-tuned by the designer and shows dynamic responses of the control system. The simulator treats the moving table as a 6 degrees-of-freedom rigid body and considers the motion guide blocks stiffness, damping and their locations as well as sensor locations. The simulator has been under development for one and a half years and has a few years to go before the public release. The primary achievements and features will be presented in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.177-178
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• 2006

Many authors issued the feature-preserving averaging technique according to positioning and scaling process using landmarks, which represent the geometric characteristics of three dimensional surface models. Such a technique should be done by manual procedure, choosing and marking the landmarks on each bone surface before averaging process. In this study, we produced another averaging technique without having to use such manual procedure, and made averaging models from three dimensional surface data that were reconstructed from computerized tomography images of Digital Korean Project. The bone models were subjected to orthogonal coordinator system. These models were transformed to coincide mass center and to align principal axis. Then, bone models were scaled according to average length data of sample bone models on all axis(x, y, z). After establishing voxellar hexahedron space which contain all sample bone models, we counted the number of overlapping for each voxel. We generated the three dimensional average surface by displaying the yokels that have more overlapping number than boundary number. The boundary number was decided when the average volume of each bone equal to the volume of bone that would be averaged. Using this technique, we can make a feature-preserving averaging volume of bones.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.4 s.193
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• pp.138-146
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• 2007

Some biodegradable polymers and other materials such as hydrogels have shown the promising potential for surgical applications. Post surgical adhesion caused by the natural consequence of surgical wound healing results in repeated surgery and harmful effects. Recently, scientists have developed absorbable anti-adhesion barriers that can protect a tissue from adhesion in case they are in use; however, they are dissolved when no longer needed. Although these approaches have been attempted to fulfill the criteria for adhesion prevention, none can perfectly prevent adhesions in all situations. Overall, we developed a new method to fabricate an anti-adhesion membrane using biodegradable polymer and hydrogel. It employed a highly accurate three-dimensional positioning system with pressure-controlled syringe to deposit biopolymer solution. The pressure-activated microsyringe was equipped with fine-bore nozzles of various inner-diameters. This process allowed that inner and outer shapes could be controlled arbitrarily when it was applied to a surgical region with arbitrary shapes. In order to fulfill the properties of the ideal barriers f3r preventing postoperative adhesion, we adopted the pre-mentioned method combined with surface modification with the hydrogel coating by which anti-adhesion property was improved.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.174-185
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• 2005

This paper presents the design, fabrication, and testing results of a dual stage actuator system for a fine positioning of magnetic heads in magnetic disk drives. A novel rotary microactuator which is electrostatically driven and utilized as a secondary actuator was designed. The stator and rotor electrodes in the microactuator was revised to have the optimal shapes and hence produces much higher rotational torque compared with the conventional comb-shape electrodes. The microactuators were successfully fabricated using SoG(silicon on glass) processing technology, which is known as being cost-effective. The fabricated microactuator has the structural thickness of $45{\mu}m$ with the gap width of approximately $3{\mu}m$. The dynamic characteristic of microactuator/slider assembly was investigated, and its natural frequency and DC gain were measured to be 3.4kHz and 32nm/V, respectively. The microactuator/slider assembly was integrated into a HDD model V10 of Samsung Electronics Co. and a dual servo algorithm was tested to explore the tracking performance of dual stage actuator system where the LDV signals instead of magnetic head signals were used. Experimental results indicate that this system achieves the tracking accuracy of 30nm. This value corresponds to a track density of 85,000 track per inch(TPI), which is about 3 times greater than that of current hard disk drives.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.1
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• pp.71-78
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• 2016

In the paper, we predict the number of multi-GNSS satellites and visible satellites with the navigation satellite launch plans and their nominal orbit parameters. Based on the methodology, the multi-GNSS navigation performance and DOP (Dilution of Precision) variation from 2015 to 2020 were forecasted by the Matlab simulation. To calculate the position using the multi-GNSS constellation, we determined the time-offset between the two different systems. Two different algorithms were considered for the sake of time-offset determination; that of each was applied to system level and user side. Also, the results from two algorithms were compared for evaluating each performance. For the reality, we applied the 3D map information to the simulation, which is expected to contribute for predicting the future navigation performance in urban canyon.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.9
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• pp.1069-1080
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• 2016

TDOA(Time Difference Of Arrival)-based localization system such as the passive surveillance system performs the time synchronization between the receivers after separated installing multiple receivers to set the same clock for all receivers. And it estimates 2D(or 3D) location of the target by solving intersection of the multiple hyperbola(or hyperboloid) using TDOA. To perform time synchronization, one receiver must be set to the master, and it provide the reference data to compensate the clock of the rest of the slaves. The positioning accuracy of TDOA-based localization system is changed in accordance with the master that is selected among multiple receivers. So, the optimum receiver which is selected among multiple receivers must be set to master to get best performance in the considered deployment of receivers. In this paper, we propose a selection scheme of master receiver for time synchronization using DOP(Dilution Of Precision) which is based on location of the target and the multiple receivers. The proposed scheme has low complexity and short processing time, and it is easy to automate in the TDOA-based localization systems.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.144-148
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• 2005

The goal of this work is to develop and test a robot-assisted surgery system for spinal fusion. The system is composed of a robot, a surgical planning system, and a navigation system. It plays the role of assisting surgeons for inserting a pedicle screw in the spinal fusion procedure. Compared to conventional methods fer spinal fusion, the proposed surgical procedure ensures minimum invasion and better accuracy by using robot and image information. The robot plays the role of positioning and guiding needles, drills, and other surgical instruments or conducts automatic boring and screwing. Pre-operative CT images and intra-operative fluoroscopic images are integrated to provide the surgeon with information for surgical planning. Several experiments employing the developed robotic surgery system are conducted. The experimental results confirmed that the system is not only able to guide the surgical tools by accurately pointing and orienting the specified location, but also successfully compensate the movement of the patient due to his/her respiration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.456-463
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• 2005

This paper describes a design process of end-milling cutters: solid model of the designed cutter is constructed along with computation of cutter geometry, and the wheel geometry as well as wheel positioning data fur fabricating end-mills with required cutter geometry is calculated. In the process, the main idea is to use the cutting simulation method by which the machined shape of an end-milling cutter is obtained via Boolean operation between a given grinding wheel and a cylindrical workpiece (raw stock). Major design parameters of a cutter such as rake angle, inner radius can be verified by interrogating the section profile of its solid model. We studied relations between various dimensional parameters and proposed an iterative approach to obtain the required geometry of a grinding wheel and the CL data fer machining an end-milling cutter satisfying the design parameters. This research has been implemented on a commercial CAD system by use of the API function programming, and is currently used by a tool maker in Korea. It can eliminate producing a physical prototype during the design stage, and it can be used fur virtual cutting test and analysis as well.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.6
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• pp.13-19
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• 1995

A dual purpose robot automation system is developed for both arc welding and spot welding by one robot within a cell. The need for automation of both arc welding and spot welding processes is urgent while the production volume is not so big as to accommodate separate stations for the two processes. Also, space is too narrow for separate stations to be settled down in the factory. A spot welding robot is chosen and the functions for arc welding are implemented in-house at cost of advanced functions. For the spot welding, a single pole type gun is used and the robot has to push down the plate to be wolded, which causes the robot positioning error. Therefore, position error compensation algorithm is developed. The basic functions for the arc welding processes are implemented using the digital I/O board of robot controller, PLC, and A/D conversion PCB. The weaving pattern is taught in meticulously by manual teach. A fixture unit is also developed for dual purpose. The main aspects of the system is presented in this paper especially in the design and implementation procedure. The signal diagrams and sequence logic diagrams are also included. The outcome of the dual purpose welding cell is the increased productivity and good production stability which is indispensable for production volume prediction. Also, it leads to reduction of manufacturing lead time.