• Journal of Power Electronics
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• v.18 no.1
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• pp.251-265
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• 2018

To enable a master-slave control independent microgrid system (MSCIMGS) to supply electricity continuously, the microgrid inverter should perform mode transfer between grid-connected and islanding operations. Transient oscillations should be reduced during transfer to effectively conduct a seamless mode transfer. This study uses a typical MSCIMGS as an example and improves the mode transfer strategy in three aspects: (1) adopts a status-tracking algorithm to improve the switching strategy of the outer loop, (2) uses the voltage magnitude and phase pre-synchronization algorithm to reduce transient shock at the time of grid connection, and (3) applies the hybrid-sensitivity $H_{\infty}$ robust controller instead of the current inner loop to improve the robustness of the controller. Simulations and experiments show that the proposed strategy is more practical than the traditional proportional-derivative control mode transfer and effective in reducing voltage and current oscillations during the transfer period.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.37-50
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• 2009

In this paper, we proposed a mechanism for effective cooperation in sensor network. There are a few mechanism like RBS, TPSN, FPSN for sensor network. However these are supporting synchronization among nodes without global state. Therefore, we proposed SGSM(Simple Global State Management) to maintain global state among sensor nodes. As experimental results, we confirmed loss rate is within 1% as maintaining global state with SGSM mechanism. In this paper, we defined global state in sensor network and introduced SGSM for improving timming accuracy in sensor environment.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.1
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• pp.36-44
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• 2000

In this paper, we describe the developing of a tool which supports both multimedia presentation with user's participation through a high speed network and authoring of various media using a single authoring tool. To support real-time synchronous multimedia presentation, we adopt dynamic synchronization method and adaptive transmission algorithm for synchronizing data transfer rate between sender and receiver using buffer management algorithm based on QoS parameters. And we also allow user's participation in the presentation using TRSG(Temporal Relationship Specification Graph) model. Finally, the proposed tool supports the minimal level of QoS and its continuous play-out using event auditing threads which control the current state of a multimedia presentation continuously by monitoring of negative factors effecting on QoS, and synchronization.

• International Journal of Precision Engineering and Manufacturing-Green Technology
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• v.9
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• pp.1563-1573
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• 2021

The impinging jet technique is a critical process for enhancing mechanical properties. Sensors for the precise diagnosis of the nozzle status are necessary to maintain product quality and reduce cost. The application of commercial sensors for this purpose is difficult because sensors in the casting, rolling, and reheating processes should provide sensitivity to small impact variations, durability, anticorrosion, waterproofing, and high-temperature endurance. We developed a sensor module to satisfy these engineering requirements. The sensor monitored impact pressures based on the reduction in the collision force caused by abnormal impinging jet flows. Smart signal filtering based on a low-pass filter was employed to achieve a short CPU time, noise discrimination, and the preservation of signal characteristics. A method for nozzle position synchronization and a new performance index for impinging jets for multiple-nozzle sensing in practical applications were also developed. The developed sensor module was validated using artificial abnormal nozzles and tested in the field. The validations showed that the developed sensor with the smart filter and nozzle synchronization method could provide an individual jet status with a high precision. The developed sensor is expected to contribute to the improvement of machine health monitoring technology in various fields with jet nozzles.

• Journal of the Korea Society for Simulation
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• v.18 no.3
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• pp.73-82
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• 2009

Due to the many advantages including low price, low power consumption, and miniaturization, the CMOS camera has been utilized in many applications, including mobile phones, the automotive industry, medical sciences and sensoring, robotic controls, and research in the security field. In particular, the 360 degree omni-directional camera when utilized in multi-camera applications has displayed issues of software nature, interface communication management, delays, and a complicated image display control. Other issues include energy management problems, and miniaturization of a multi-camera in the hardware field. Traditional CMOS camera systems are comprised of an embedded system that consists of a high-performance MCU enabling a camera to send and receive images and a multi-layer system similar to an individual control system that consists of the camera's high performance Micro Controller Unit. We proposed the SL-AVS (Small Size/Low power Around-View System) to be able to control a camera while collecting image data using a high speed synchronization technique on the foundation of a single layer low performance MCU. It is an initial model of the omni-directional camera that takes images from a 360 view drawing from several CMOS camera utilizing a 110 degree view. We then connected a single MCU with four low-power CMOS cameras and implemented controls that include synchronization, controlling, and transmit/receive functions of individual camera compared with the traditional system. The synchronization of the respective cameras were controlled and then memorized by handling each interrupt through the MCU. We were able to improve the efficiency of data transmission that minimizes re-synchronization amongst a target, the CMOS camera, and the MCU. Further, depending on the choice of users, respective or groups of images divided into 4 domains were then provided with a target. We finally analyzed and compared the performance of the developed camera system including the synchronization and time of data transfer and image data loss, etc.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.430-432
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• 2002

가상현실 기반 실시간 원격교육 시스템에서는 오디오와 비디오 그리고 Presentation Slide외에 3D VRML Data를 이용하여 강의를 구성한다. 강사의 음성과 화상 외에 텍스트와 2D, 3D Graphics를 이용함으로써 강의의 효율을 높이고 있다. 이러한 실시간 강의 시스템에서 발생하는 각 미디어간의 동기화를 위해 본 논문에서는 Synchronization Event Model(SEM)을 정의하고, 이것을 기반으로 한 가상현실 기반 실시간 원격 교육 시스템에서의 멀티미디어 통합 브라우저를 설계하고 있다.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.179-180
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• 2008

• Proceedings of the Korean Information Science Society Conference
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• 2007.06a
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• pp.161-162
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• 2007

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1480-1483
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• 1996

A set of approaches suggested to control the eccentricity is discussed in this paper. Among these, filter-integrator method is used to design the controller, which also includes the input signal synchronization, stabilizing filter and eccentricity source discrimination. Using the S/W that is coded for real time application of that controller, we simulated the operations of that one. The simulation results show the characteristics of eccentricity compensation and eccentricity discrimination. However, from these results, we can see that only proper stabilization strategy certificates the safe eccentricity control.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.799-803
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• 1991

This study proposes a CIM shell that is consisted with computers connected by a LAN. Since this system excludes production hardwares, physical movements of devices are represented by computer simulation. On the other hand, softwares that dictate system operation are real, and consu- me physical time. Thus the shell becomes half-real-half-simulation that requires events synchronization mechanism. This study shows the building procedure of such shell as well as an example of application of the shell.