• Journal of Drive and Control
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• v.13 no.3
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• pp.24-31
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• 2016

The performance characteristics of a dynamic control system are evaluated according to the transient and steady-state responses. The transient performance is the controllability of the output for the tracking of the reference or the ability to reduce or reject the effects of unwanted disturbances; alternatively, the steady-state performance is represented by the magnitude of the control error at the steady state. As the effects of the two performances on each other are reciprocal, a controller design that shows a zero steady-state error for the ramp input is uncommon because of the challenge regarding the achievement of an acceptable transient response. This paper proposes a PI+double-integral controller for the elimination of the steady-state error for the ramp input while a sound transient performance is maintained. The control-gain design procedure is described by the second-order response for the step input and the response of the error dynamics for the ramp input. The PI+double-integral controller is designed for the first-order transfer function that is derived from a system identification with the open-loop experiment data of the dc-motor. The simple structure of the proposed controller enables the adoption of a low-end microcontroller for the implementation of a real-time control. The experiment results show that the control performance is as effective as that of the simulation analysis for the operating point of linear system; furthermore, the PI+double-integral controller can be conveniently applied to the control system, which is desirable for the improvement of the steady-state error.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.53 no.3
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• pp.152-160
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• 2004

A novel UPQC(Unified Power Quality Conditioner), which consists of series inverter, shunt inverter, distributed generation system, is proposed. The proposing system can compensate reactive power, harmonics, voltage sag and swell, voltage interruption etc. through the change of paralleling operation mode and islanding operation mode. The control strategy for the proposing system was derived using the instantaneous power method. The performance of proposing system was analyzed by means of the PSCAD/EMTDC simulation and the experimental work with the hardware prototype. The proposing system has the ultimate capability of improving power quality at the point of installation on power distribution systems or Industrial power systems and can be utilized for the custom power device in th future distribution system.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.3
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• pp.75-78
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• 2008

Tire molds are manufactured by aluminum casting, direct five-axis machining, and electric discharging machining. Master models made of chemical wood are necessary if aluminum casting is used. They are designed with a three-dimensional computer-aided design system and milled by a five-axis machine. In this paper, a method for generating and machining a tire surface model is proposed and demonstrated. The groove surfaces, which are the main feature of the tire model, are created using a parametric design concept. An automatically programmed tool-like descriptive language is presented to implement the parametric design. Various groove geometries can be created by changing variables. For convenience, groove surfaces and raw cutter location (CL) data are generated in two-dimensional drawing space. The CL data are mapped to the tread surface to obtain five-axis CL data to machine the master model. The proposed method was tested by actual milling using the five-axis control machine. The results demonstrate that the method is useful for manufacturing a tire mold.

• International Journal of Precision Engineering and Manufacturing
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• v.2 no.3
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• pp.27-33
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• 2001

The aim of the present work is to propose a model for Computer Aided programming of numerical Control lathe. This model is based on the concept by features. It has been developed in an Artificial Intelligence environment, that offers a rapidity as well as a precision for NC code elaboration. In this study a pre-processor has been elaborated to study the geometry of turning workpiece. This pre-processor is a hybrid system which combine a module of design by features and a module of features recognition for a piece provided from an other CAD software. Then, we have conceived a processor that is the heart of the CAD/CAM software. The main functions are to study the fixture of the workpiece, to choose automatically manufacturing cycles, to choose automatically cutting tools (the most relevant), to simulate tool path of manufacturing and calculate cutting conditions, end to elaborate a typical manufacturing process. Finally, the system generates the NC program from information delivered by the processor.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1095-1096
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• 2006

Configuration management plays a key role in systems engineering process for any project from earlier stage of development. It consists of five major activities, ie., configuration management planing, configuration identification, configuration control, configuration status accounting and configuration verification and audit, and is essential to control system design development and operation throughout entire life cycle of the system development. And it is directly associated with other part of systems engineering management, ie., technical data management which provides traceability of important decisions and changes during development. In this paper, we describe how to apply CASE(Computer-aided Systems Engineering) tool-Cradle for the configuration management to achieve effectiveness of City Train Standard Specification Management process.

• Journal of Institute of Control, Robotics and Systems
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• v.7 no.8
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• pp.689-696
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• 2001

Large-scale Multi-disciplinary Systems(LMS) such as transportation, aerospace, defense etc. are complex systems in which there are many subsystems, interfaces, functions and demanding performance requirements. Because many contractors participate in the development, it is necessary to apply methods of sharing common objectives and communicating design status effectively among all of the stakeholders. The processes and methods of systems engineering which includes system requirement analysis; functional analysis; architecting; system analysis; interface control; and system specification development provide a success-oriented disciplined approach to the project. This paper shows not only the methodology and the results of model-based systems engineering to Automated Guided Transit(AGT) system as one of LMS systems, but also propose the extension of the model-based tool to help manage a project by linking WBS (Work Breakdown Structure), work organization, and PBS (Product Breakdown Structure). In performing the model-based functional analysis, the focus was on the operation concept of an example rail system at the top-level and the propulsion/braking function, a key function of the modern automated rail system. The model-based behavior analysis approach that applies a discrete-event simulation method facilitates the system functional definition and the test and verification activities. The first application of computer-aided tool, RDD-100, in the railway industry demonstrates the capability to model product design knowledge and decisions concerning key issues such as the rationale for architecting the top-level system. The model-based product design knowledge will be essential in integrating the follow-on life-cycle phase activities. production through operation and support, over the life of the AGT system. Additionally, when a new generation train system is required, the reuse of the model-based database can increase the system design productivity and effectiveness significantly.

• Journal of Drive and Control
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• v.15 no.3
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• pp.49-56
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• 2018

Construction machinery is used to improve productivity in civil engineering work and construction work, and it is a lengthy operation, and consumes considerable fuel to cope with large loads. As a result, productivity and fuel consumption of the construction machine become the main deciding factors. In the hydraulic system of the excavator, the main control valve is the most critical position for control. The flow distribution for control performance is achieved by the metering orifice, that causes critical energy loss. To improve this, we propose a combination of a three port proportional pressure reducing valve and a poppet type flow control valve as an IMV to replace the existing spool type MCV. To validate the proposal, we analyze static characteristics by modeling mathematically, and analyze dynamic characteristics. Simulation using the AMESim software on the regeneration circuit of the boom cylinder up-down operation, verifies the energy-saving effect compared to the existing MCV when IMV is used.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.10
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• pp.26-36
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• 2000

In this paper, we design the nonoverlapping multicarrier modulation (MCM) system for high rate paging system and evaluate the Performance by computer simulation. In conventional paging system, FSK was usually used, but we select QAM for high bandwidth efficiency. Transmitter structure adopts that of 4-16QAM of the iDEN$\^$TM/ and receiver consists of symbol timing recovery, carrier recovery and automatic gain control. In addition, pilot symbol aided modulation (PSAM) which can overcome the simulcast fading channel is considered and we also propose the optimum pilot symbol pattern. Finally, we show the performance of the overall 4-16QAM system by computer simulation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.5
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• pp.279-286
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• 2003

A new UPQC(unified power quality conditioner), which consists of series inverter, shunt inverter, dc/dc converter, and energy storage, is proposed. The proposing UPQC can compensate reactive power, harmonics, voltage sag and swell, voltage unbalance, and voltage interruption. The control strategy for the proposing UPWQC was derived using the instantaneous power method. The performance of proposing system was analyzed by means of the EMTDC/PSCAD simulation and the experimental work with the hardware prototype. The proposing UPQC has the ultimate capability of improving power quality at the point of installation on power distribution systems or industrial power systems and can be utilized for the custom power device in the future distribution system.

• The Journal of Korean Association of Computer Education
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• v.11 no.4
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• pp.71-83
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• 2008

The recent advances of the information technology have motivated lots of research efforts to develop new computer-aided teaching and learning methodologies on various computer science topics, such as data structures, operating system, computer networks, and computer architecture. However, there have been only few studies to educate the database subject although it is one of the most important topics in the computer science. Specifically, among the various issues in the database subject, a learner often suffers to understand the mechanism of the concurrency control and recovery of database transaction in the database because it highly interacts with other functions in the database. Obviously, an intelligent visualization tool can help a learner to understand the process of the concurrency control and the recovery of database transaction. The purpose of this study is to develop an efficient visualization tool which can help users understand the two phase locking protocol (2PLP)-based concurrency control. Specifically, this visualization tool is designed to encourage a users' participation and raise their interest by visualizing the process of transactions and allowing users to specify and manipulate their own transactions.