• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.3
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• pp.256-262
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• 2017

This paper presents the control algorithm of a single-phase AC/DC/AC PWM converter for the linear compressor of a refrigerator. The AC/DC/AC converter consists of a full-bridge PWM converter for the control of the input power factor and a half-bridge PWM inverter for the control of the single-phase linear compressor. At the DC-link of this topology, two capacitors are connected in series. These DC-link voltages must be balanced for safe operation. Thus, a new control method of DC voltage balancing for the half-bridge PWM inverter is proposed. The balancing algorithm uses the Integral-Proportional controller and inserts the DC-offset current at the Proportional-Resonant current controller of the inverter to solve the DC-link unbalanced voltages between the two capacitors. The proposed algorithm can be easily implemented without much computation and additional hardware circuit. The usefulness of the proposed algorithm is verified through several experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2265-2270
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• 2007

This paper discusses a tester of functionality and call processing performance, based on the MEGACO/H.248 protocol that both IETF and ITU-T recommend as a media gateway control protocol, of both a media gateway controller and an access gateway which constitute a next generation convergence network. Effective methods, a functional architecture and implementation for such testification are provided. Especially included are not only a virtual emulation function of analog subscriber lines connecting to an access gateway, but also a tester emulated as a counter system of the protocol for the testifying a media gateway controller and an access gateway system.

• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.5
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• pp.859-866
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• 2022

Active disturbance rejection control is a method in which the disturbance is removed from the controller by estimating the state variable using the Luenberger observer. The Luenberger observer is estimated by defining a nonlinear term including disturbance with constant characteristics in a steady state as a state variable. It can be shown that the speed tracking performance is improved by compensating the estimated state variable to the PI controller and the IP controller. The disturbance removal performance of the tracking control can be confirmed by observing that the estimated state error is within 1.9 [%] in the case of load fluctuation and the steady-state state tracking error converges to zero.

• Journal of Convergence for Information Technology
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• v.8 no.6
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• pp.149-157
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• 2018

In this paper, we propose an attack detection technology using SDN Controller to study security threats in IoT environment. The research methodology has been developed by applying IoT security threat management technology to the IoT layer and analyzing the research trend of applied security technology. The study results show that the effectiveness of the detection method using the sampling method is studied by adding OpenFlow based SDN Controller to the network switch equipment of the existing IoT network. This method can detect the monitoring and attack of the whole network by interworking with IDS and IPS without affecting the performance of existing IoT devices. By applying such improved security threat countermeasure technology, we expect to be able to relieve anxiety of IoT security threat and increase service reliability.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.1
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• pp.77-82
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• 2014

SD memory cards are widely used in portable digital devices, and most of them exploit NAND flash memory as their storage, so that they have a feature of storing users' important data safely with low costs. In case of using NAND flash memory as storage, however, there is no method to store users' data if memory capacity is insufficient when transferring a large volume of data. This paper proposes a virtual SD memory card system. It used a SD memory card device driver to process data requested from a host by exploiting external storage rather than by exploiting flash memory as a memory core for storing data to the SD memory card. For experiment, it used the FPGA-based SD card slave controller IP on the SMC controller with a S3C2450 ARM CPU to test.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.6
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• pp.1301-1306
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• 2015

This paper is to automate the intelligent and equipment to recycle the volatile organic compounds in various a gas stations and a laundry, in real life. In addition, based the ZigBee module and TCP/IP communications on ICT technologies, it's propose an integrated management system to monitor and manage an liquid at a remote location.Furthermore, it's propose a service model that can be freely managed from a remote location based on the app on android. In this paper, we present a communication protocol of the bridge modules and a liquefier of intelligent control system based ZigBee and MCU(Micro Controller Unit). Through the development of smart app based android mobile services in an integrated management system, it's represent for liquefier to a DB server for remote management(MS SQL 2012) and a web server (OS: Windows 2008).

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.3
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• pp.253-259
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• 2003

This paper aims at developing remote control system to control and monitor distributed various devices such as UPS through internet. TCP/IP(Transmission Control Protocol/Internet Protocol) and UPS operated in a row are adopted for the network management protocol and the application device, respectively. For controlling and monitoring distributed devices in realtime, java-environment software is constructed. Also, HelloDevice, general-use interface controller between network device and applied device is proposed. Finally, serial communication such as RS-232C is used between controller and applied device.

• The KIPS Transactions:PartC
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• v.18C no.6
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• pp.423-432
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• 2011

Recently, OpenFlow has been paid attention to as a fundamental technology which provides a function of virtualization and programmability in network. In Korea, deployment of OpenFlow networks in campuses and the interconnection between them through tunneling in layer 3 has been performed. However, the performance of the interconnected networks is decreased due to delay in IP layer. In this paper, we design and deploy nation-wide, not local, OpenFlow networks in a pure layer 2 environment over KREONET. After that, we do end-to-end Round-trip Time measurements and TCP/UDP performance tests in OpenFlow and normal networks, and do comparison and analysis on the test results. The results show that the nation-wide OpenFlow networks provide equal performance to normal networks except for the initial packet loss for UDP streaming. In regards to the performance decrease due to early UDP packet loss, we can mitigate it by implementing exceptional procedures in a controller which deal with the same continuous "Packet_in" events.

• Journal of KSNVE
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• v.8 no.5
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• pp.964-973
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• 1998

In this paper we propose a levitation and imbalance compensation controller design methodology of magnetic bearing system. In order to achieve levitation and elimination of unbalance vibartion in some operation speed we use the discrete-time Q-parameterization control. When rotor speed p = 0 there are no rotor unbalance, with frequency equals to the rotational speed. So in order to make levitatiom we choose the Q-parameterization controller free parameter Q such that the controller has poles on the unit circle at z = 1. However, when rotor speed p $\neq$ 0 there exist sinusoidal disturbance forces, with frequency equals to the rotational speed. So in order to achieve asymptotic rejection of these disturbance forces, the Q-parameterization controller free parameter Q is chosen such that the controller has poles on the unit circle at z = $exp^{ipTs}$ for a certain speed of rotation p ( $T_s$ is the sampling period). First, we introduce the experimental setup employed in this research. Second, we give a mathematical model for the magnetic bearing in difference equation form. Third, we explain the proposed discrete-time Q-parameterization controller design methodology. The controller free parameter Q is assumed to be a proper stable transfer function. Fourth, we show that the controller free parameter which satisfies the design objectives can be obtained by simply solving a set of linear equations rather than solving a complicated optimization problem. Finally, several simulation and experimental results are obtained to evaluate the proposed controller. The results obtained show the effectiveness of the proposed controller in eliminating the unbalance vibrations at the design speed of rotation.

• Journal of the Korean Institute of Intelligent Systems
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• v.12 no.4
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• pp.379-384
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• 2002

This paper represents the mobile robot system remote controlled by PDA(personal digital assistance). So far, owing to the development of internet technologies, lots of remote control methods through internet have been proposed. To control a mobile robot through internet and guide it under unknown environment, We propose a control method activated by PDA. In a proposed system, PDA acts as a user interface to communicate with notebook as a controller of the mobile robot system using TCP/IP protocol, and the notebook controls the mobile robot system. The information about the direction and velocity of the mobile robot feedbacks to the PDA and the PDA send new control method produced from the fuzzy inference engine.