• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.1121-1124
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• 1999

Linear motor is able to produce line movement without rotary-to-line converter at the system required line moving. Thus Linear motor has no gear, screw, belt for line movement. Therefore it has some advantage which decrease friction loss, noise, vibration, maintenance effort and prevent decay of control performance due to backlash. This paper proposes the estimation method of unknown parameters from the BLDC Linear motor and determine the PI controller gain through this estimation. Each control movement that is current, speed, position control, and PWM wave generation is performed on Processor, which is DSP(Digital Signal Processor), having high speed performance. PI theory is adopted to each for controller for control behavior More fast convergence to command position is accomplished by applying the new velocity locus which derived from position error.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.8
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• pp.60-70
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• 1998

A harmonic drive is compact torque transmission device with no backlash which is widely applied in industrial field to transmit torque precisely. However, one of the disadvantages of harmonic drives is the existence of mechanical flexibility caused by its structural properties, which imposes great limitation on designing precise controller This paper proposes a nonlinear controller for synchronous operation of DC servo-motors with harmonic drive, using Integrator Backstepping method. Furthermore, an alternative algorithm for serial type synchronous operation of multiple DC servo-motors is proposed. Simulation results by SIMULINK for proposed controller shows considerably small error and rapid approach to reference input, which can be adapted to industrial applications.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.9-16
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• 2002

In this paper, we intend to demonstrate a new intuitive force-feedback device for advanced VR applications. Force feed-back for the device is tension based and is characterized by 7 degrees of freedom (DOF); 3 DOF for translation, 3 DOF for rotation, and 1 DOF for grasp). The SPIDAR-G (Space Interface Device for Artificial Reality with Grip) will allow users to interact with virtual objects naturally by manipulating two hemispherical grips located in the center of the device frame. We will show how to connect the strings between each vertex of grip and each extremity of the frame in order to achieve force feedback. In addition, methodologies will be discussed for calculating translation, orientation and grasp using the length of 8 strings connected to the motors and encoders on the frame. The SPIDAR-G exhibits smooth force feedback, minimized inertia, no backlash, scalability and safety. Such features are attributed to strategic string arrangement and control that results in stable haptic rendering. The design and control of the SPIDAR-G will be described in detail and the Space Graphic User Interface system based on the proposed SPIDAR-G system will be demonstrated. Experimental results validate the feasibility of the proposed device and reveal its application to virtual reality.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.2
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• pp.138-143
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• 1999

A new control method for the precision robust position control of a brushless DC(BLDC) motor for direct drive m motor(BLDDM) system using the asymptotically stable adaptive load torque observer is presented. A precision position c control is obtained for the BLDD motor system appro성mately linearized using the fieldlongrightarroworientation method. Many of t these motor systems have BLDD motor to obtain no backlashes. On the other hand, it has disadvantages such as the h high cost and more complex controller caused by the nonlinear characteristics. And the load torque disturbance is d directly affected to a motor shaft. To r밍ect this problem, stability analysis is calTied out using Lyapunov stability t theorem. Using this results, the stability is proved and load disturbance detected by the asymptotically stable adaptive observer is compensated by feedforwarding the equivalent CUlTent having the fast response.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.1-6
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• 2017

In this paper, we present a study concerning the design of a 400 N class side thruster for small ships. The side thrusters used in Korea are imported from abroad. The performance and durability of the imported products employed in Korea are not adequate, therefore the side thrusters which will be suitable for Korean domestic needs to be re-designed. The strength calculation of the side thruster was performed by KS standard. Strength calculation and design were made to meet design requirements. Structural analysis and safety factor analysis were carried out to confirm the validity of strength calculations and design. After manufacturing the bevel gear, a back lash test was conducted. We also conducted a no-load test, a rated load, and an overload test for a performance test and a durability test of the design while satisfying the design conditions.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.68-76
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• 2005

We propose a new type of stereoscopic camera system with a zoom lens module to overcome the backlash for the stability of picture matching and the difficulty of zoom control. This system is designed to control a pair of zoom lens with a rotation lever. In this paper, we present the structural characteristics of our proposed system, and verify that there are no image mismatching at acquired stereo images and the zoom in$\cdot$out is easy to control. In our experiments, we achieve good results that a convergence control is very simple and distortion of images is decreased.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.10a
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• pp.375-381
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• 2004

Recently, the evolution in production techniques (e.g. high-speed milling) and the complex shapes involved in modem production design has been increasingly popular. The key to the achievement is a drastic improvement of the dynamic behavior of the machine tool axes used in production machinery. The more complex these tool paths the higher the speed and acceleration requirements. But it is very difficult to reach the target for high speed machine tool because of the limitations of servo system and motion control system. However 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, more mechanical simplicity and very higher acceleration and velocity comparing to the traditional system. This paper focused on the performance tests of the high speed horizontal machine tool based on linear motor. Especially, dynamic characteristics were investigated through circular test and circular form machining test is carried out considering many important parameter. Therefore these several experiments is used to be evaluated the model for prediction of circular motion error and circular machined error.

• Journal of Welding and Joining
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• v.24 no.1
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• pp.43-49
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• 2006

This paper describes the friction surface modification which has been successfully developed with the friction stir welding recently There are several problems including just position control and backlash in conventional friction surface modification system. Therefore it has been developed the friction surface modification system which has been controlled precisely both position and force by driving hydraulic cylinder in this paper. The mechtrode rotation speed(N) and feeding speed(Vz), travel speed(Vx,y) are of critical importance for the width and thickness of the coating in friction surfacing process. But there is no theoretical method of determining interrelations between process parameters affect the coating width and thickness. As a result of DOE(design of experiment) with developed system, the coating thickness and width seemed to decrease according to increase the mechtrode rotation speed(N) and traveling speed(Vx,y), to decrease feeding speed(Vz) apparently. However as the result of regression analysis the main effect was only the mechtrode rotation speed in the coating thickness.

• 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.

• Clinical and Experimental Pediatrics
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• v.61 no.4
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• pp.108-113
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• 2018

Purpose: This study aimed to investigate the clinical and socioenvironmental characteristics of sudden cardiorespiratory arrest after venipuncture in children. Methods: We conducted a retrospective email-based survey of all members of the Korean Pediatric Society. The questionnaire included items on patient demographics, socioenvironmental circumstances of the venipuncture, type of cardiorespiratory arrest, symptoms and signs, treatment, prognosis, and presumed cause of the arrest. Results: Fourteen patients were identified. Of these, 13 were young children (<2 years old), and 1 was 14 years old. All patients had been previously healthy and had no specific risk factors for sudden cardiorespiratory arrest. Most cases (n=11, 79%) were defined as cardiac or cardiorespiratory arrest, while the remaining cases (n=3, 21%) were defined as respiratory arrest. Aspiration (n=3), acute myocarditis (n=2), and laryngeal chemoreflex (n=1) were presumed as the causes; however, the exact causes were unclear. The overall prognosis was poor (death, n=7; morbidity, n=5; full recovery, n=2). The medical institutions faced severe backlash because of these incidents (out-of-court settlement, n=5; medical lawsuit, n=5; continuous harassment, n=3). Conclusion: Cardiorespiratory arrest after venipuncture is unpredictable and the probable cause of most cases is a vasovagal reaction. Medical personnel must be aware of the risk of unexpected cardiorespiratory arrest during routine intravenous procedures.