• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.11
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• pp.21-30
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• 1998

In this paper, a digital current control system using a FPGA(Field Programmable Gate Array) was implemented, and the system was applied to an induction motor widely used as an industrial driving machine. The FPGA designed by VHDL(VHSIC Hardware Description Language) consists of a PWM(Pulse Width Modulation) generation block, a PWM protection block, a speed measuring block, a watch dog timer block, an interrupt control block, a decoder logic block, a wait control block and digital input and output blocks respectively. Dedicated clock inputs on the FPGA were used for high-speed execution, and an up-down counter and a latch block were designed in parallel, in order that the triangle wave could be operated at 40 MHz clock. When triangle wave is compared with many registers respectively, gate delay occurs from excessive fan-outs. To reduce the delay, two triangle wave registers were implemented in parallel. Amplitude and frequency of the triangle wave, and dead time of PWM could be changed by software. This FPGA was synthesized by pASIC 2SpDE and Synplify-Lite synthesis tool of Quick Logic company. The final simulation for worst cases was successfully performed under a Verilog HDL simulation environment. And the FPGA programmed for an 84 pin PLCC package was applied to digital current control system for 3-phase induction motor. The digital current control system of the 3 phase induction motor was configured using the DSP(TMS320C31-40 MHz), FPGA, A/D converter and Hall CT etc., and experimental results showed the effectiveness of the digital current control system.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.2
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• pp.120-130
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• 1999

In this paper, we show that the instantaneous phase current of the bifiler-wound hybrid stepping motor is dependent of lead angle and that the information of motor position is obtained from the instantaneous phase current at ${\pi}/2$ by the theoretical formular and its computer simulation results. From the facts, we design the microcontroller-based motor position sensorless controller of optimal lead angle, which generates the excitation pulses for the closed-loop drives. The controller is consist of microcontroller which has the function of A/D converter, programmable input/output timer, and the transfer table which has the values of optimal lead angle depending on motor velocity, and ROM which has the transfer table of the values of lead angle depending on velocity of motor and the values of instantaneous phase current at ${\pi}/2$. From the design of microcontroller-based controller, we minimize the external interface circuit and obtain flexibility by changing the contents of ROM transfer tables and the control software. We confirm that the designed controller drives the bifilar-wound hybrid stepping motor is the mode of optimal lead angle by comparing the instananeous phase current experimental results and computer simulation results.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.75-87
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• 1998

KARES (KAIST Rehabilitation Engineering System) is the rehabilitation robot system in the type of the 6 degrees of freedom robot arm mounted on the wheelchair, in order to assist the independent livelihood of the disabled and the elderly. The interface device for programming and controlling of the robot arm is essential in the rehabilitation robotic system. Specially, in the case of the manual operation of the robot arm, the user has the burden of cognition and the difficulty for the operation of the robot arm. As a remedy, color vision system for the autonomous performance of jobs is proposed, and four basic desired jobs are specified. By mounting the camera in eye-in-hand type, color vision system for KARES is set up. The desired jobs for picking up the target and moving it to the user's face for drinking are successfully performed in real-time at the indoor environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.5
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• pp.383-388
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• 2018

This paper presents a 1.8 GHz six-port-based impedance modulator using CMOS technology, which can select an arbitrary load impedance with switch control. The proposed 1.8-GHz impedance modulator comprises a Wilkinson power divider, three quadrature hybrid couplers, and four SP3T switches for each load impedance selection. The measured insertion loss of -13 dB and the input/output return losses of >10 dB are achieved in the range of 1.4~2.2 GHz. The low drop output regulator for a stable 3.3 V DC power and the serial peripheral interface(SPI) for an easy digital control are integrated. The chip size, including the pads, is $1.7{\times}1.8mm^2$.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.69-69
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• 2010

최근 컨테이너 선박의 초대형화로 극후물 고장력 강재인 항복응력 460MPa급 고장력강인 EH47이 개발되었다. 두께 80mm의 극후물 용접에서 용접생산성 향상을 위하여 EGW/FCAW로 양면 용접이 검토되고, 입열량은 최대 300kJ/cm의 대입열 용접이 요구된다. 이를 위해서는 강재 및 용접재료 모두 300kJ/cm 용접부 성능이 선급 규격을 만족하여야 함은 물론 마지막 조립단계에서 적용되기 때문에 용접재료의 용접작업성도 매우 크게 요구되고 있다. 먼저 대입열 용접금속에서 요구되는 저온 충격인성($vE_{-20^{\circ}C}{\geq}57J$)을 만족하기 위하여는 용접금속의 미세조직 제어가 필요하며, 특히 조대한 입계페라이트 생성을 억제하고 미세한 입내 페라이트를 균일 분포하는 것이 중요하지만, 이를 위해 용접금속의 소입성이 지나치게 높이면 경화조직인 베이나이트 분율이 증가하여 오히려 용접금속 저온 충격인성을 저하시키므로, 적절한 용접금속의 성분 제어가 중요하다. 한편 용접부는 선급에서 요구하는 최소 강도인 570MPa를 만족하기 위하여 용접금속의 소성구속 현상을 활용하여 용접부 인장강도를 확보 할 수 있음을 확인했다. 이를 위해서는 용접금속의 적정한 경화도 확보가 필요하였다. 전술한 바와 같이 대입열 용접금속 저온 충격인성 확보와 용접부 강도 측면을 고려하여 용접금속 최적의 탄소당량 범위를 제시코자 하였다. 한편 용접재료의 용접작업성은 EGW용접의 용적이행 현상은 자유비행이행으로 이루어지고 있으며 특성상 용접중 용적과 용융지 사이에 많은 순간단락 현상을 동반하고 있으며, 슬래그 유동이 불안정하면 아크 꺼짐 현상도 관찰되고 있다. 따라서, 현장용접시 원할한 용접작업성을 확보할 수 있는 평가 기준으로써 아크 전류 및 전압의 변동 정도를 설정하고, 용접재료의 용접작업성 확보 기준을 제시코자 하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.9
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• pp.863-871
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• 2013

Flow characteristics of velocity-control trim in a valve is investigated numerically with high pressure drop. A basic trim widely used for a valve in domestic powerplants is selected and designed for a baseline of velocity-control trim. The numerical analysis is focused on flow rate and cavitation with the basic trim. For a condition of high-pressure drop, pressure drop between inlet and outlet and fluid temperature are selected to be 18.1 MPa and $160^{\circ}C$, respectively, which are typical ones considering operating conditions adopted in powerplants. With this baseline model and condition, design changes are made for improvement of flow rate and cavitation phenomenon. For re-design, trim is divided into three zones in radial direction and design parameters of flow area, stage, and flow direction are considered in each zone. With these combined parameters applied to each zone, 4 models with design changes are proposed and their flow rates and cavitation areas are investigated. From comparison with those in the baseline model of a basic trim, proposed models show better performance in both flow rate and cavitation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1239-1247
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• 2012

In this paper, design and fabrication of solid state power amplifier(SSPA) using GaN HEMT chip for X-band frequency are presented. The SSPA consists of the power supply for stable power and the control unit for communication and controlling the internal module, the RF Part to amplify RF signal, In particular the adopted active device for the RF Parts is GaN HEMT Bare chip of TriQuint company, the RF parts consists of pre-stage, drive-stage, main power-stage and each amplifier is designed with input and out matching circuit. The developed power amplifier demonstrated more than 300 W peak output power in condition of 26 % duty, max. pulse width 100us for the X-band frequency( 500 MHz bandwidth) and can apply to marine radar systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1575-1580
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• 2011

A key factor in the study of hybrid vehicle is to enhance the usability of energy. The paper introduces the monitor and controlling technology of hybrid vehicle that can process the relevant information considering the structure of power system and driving strategies simultaneously, and can monitor its results. This technology, so called HEV algorithm analysis, has been applied to PRIUS THS made by Toyota Co. LTD. This model is adapted to parallel hybrid type. It has a somewhat comlex structure, but has several merits. It's energy loss is lower when conversing. and also it is easily applied to the conventional vehicle having a gasoline engine without any overall changing of its structure, and so on. This monitor and controlling technology is very useful to study on the various driving strategies of hybrid vehicle for maximizing the usability between engine and electric motor.

• Journal of Internet Computing and Services
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• v.15 no.2
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• pp.9-18
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• 2014

The sensors attached on/in a person are moved since human body frequency changes their activity, therefore in wireless body area networks, nodal mobility and non-line-of-sight condition will impact on performance of networks such as energy efficiency and reliable communication. We then proposed schemes which study on forwarding decisions against frequent change of topology and channel conditions to increase reliable connections and improve energy efficiency. In this work, we control the size of packets, forwarding rate based on ratio of input links and output links at each node. We also robust the network topology by extending the peer to peer IEEE 802.15.4-based. The adaptive topology from chain-based to grid-based can optimal our schemes. The simulation shows that these approaches are not only extending network lifetime to 48.2 percent but also increase around 6.08 percent the packet delivery ratio. The "hot spots" problem is also resolved with this approach.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.264-269
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• 2008

For the synthesis of lead chromate pigments, we investigated the characteristics of particle growth with reacting conditions in the synthetic process, the effect of additives, and its micro-capsulation. The more tiny and uniform dispersion particles could be obtained at a lower pH and diluter intial concentration. The variation range of average pigment size was increased with the agitating speed. The pigment size could be controlled by adding aluminum sulfate as an additive, which maintained the optimum particle dispersion. It was found that the optimum micro-capsulation conditions were pH 9~10 and above $90^{\circ}C$ during the micro-capsulation of lead chromate pigment, and below 0.5% humidity after micro-capsulation.