• Title/Summary/Keyword: Direct method

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Lead-Lag Controller Design of Direct Drive Servo Valve Using Complex Method (컴플렉스법에 의한 직접구동형서보밸브의 진상-지상 제어기 설계)

  • Lee, Seong-Rae
    • Proceedings of the KSME Conference
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    • 2003.11a
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    • pp.1590-1595
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    • 2003
  • Direct drive servovalve(DDV) is a kind of one-stage valve since the rotary motion of DC motor is directly transferred to the linear motion of valve spool through the link. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

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Lead-Lag Controller Design of Direct Drive Servo Valve Using Complex Method (컴플렉스법에 의한 직접구동형서보밸브의 진상-지상 제어기 설계)

  • Lee, Seong-Rae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.11
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    • pp.1719-1726
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    • 2004
  • Direct drive servovalve(DDV) is a kind of one-stage valve because the main spool valve is directly driven by the DC motor. Since the structure of DDV is simple, it is less expensive, more reliable and offers reduced internal leakage and reduced sensitivity to fluid contamination. However, the flow force effect on the spool motion is significant such that it induces large steady-state error in a step response. If the proportional control gain is increased to reduce the steady-state error, the system becomes unstable. In order to satisfy the system design requirements, the lead-lag controller is designed using the complex method that is one kind of constrained direct search method.

A study on comparative analysis of direct current control in A.C.-D.C. interconnected power system (교류-직류 연계계통에 있어서 직류제어방식의 비교연구)

  • 정형환;왕용필;안병철;이광우
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.45 no.4
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    • pp.474-483
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    • 1996
  • In this paper, as a part of the method improving stability, the load-flow calculation in D.C. power system and the models for stability analysis are studied with A.C-D.C. interconnected power systems transmission performed. Moreover, the theory is established in relation to each control method of D.C. power systems. Then the stability of A.C-D.C.interconnected power systems is compared and considered by the way of dividing the operating control method of the rectifier inverter converter into ACR-AVR, APR-A.gamma.R, A.alpha.R-ACR. The dynamics characteristic of terminal voltage, frequency, active-reactive power and rotor angle of the generator with disturbances and load fluctuations is considered. In addition, the characteristic of direct voltage, direct current, power and control systems. From this the comparative analysis of the direct current control method, the possibility of the stability analysis of A.C.-D.C. interconnected power system is considered. (author). refs., figs., tabs.

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A Study on Common Module Modeling Method of Game Software based on DirectX/C++ (DirectX/C++ 기반 게임 소프트웨어의 공통 모듈 모형화 기법에 관한 연구)

  • Byun, Jung-Won;Rhew, Sung-Yul
    • Journal of Korea Game Society
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    • v.9 no.2
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    • pp.95-104
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    • 2009
  • The windows games and the console games that use DirectX occupied 20% or more of world game market and that are developed by C++ Language occupied 75% or more of the market. This study proposed that commonality and variability for code of the 20 projects based on DirectX and C++ is analysed and patternized, that common modules are created, and that modules are modeled. As a result of applying a case study, it is verified that the proposed model reduces effort in game development.

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A Study on the Effective Scattering Center Analysis for Radar Cross Section Reduction of Complex Structures (복합구조물의 RCS 저감을 위한 효율적 산란중심 해석에 관한 연구)

  • Kim, Kook-Hyun;Kim, Jin-Hyeong;Cho, Dae-Seung
    • Journal of the Society of Naval Architects of Korea
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    • v.42 no.4 s.142
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    • pp.421-426
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    • 2005
  • Scattering center extraction schemes for radar cross section reduction of large complex targets, like warships, was developed, which are an 1-D radar image method(range profile), and a direct analysis based on an object precision method. The analysis result of partial dihedral model shows that the presented direct analysis method is more efficient than the 1-D radar image method for scattering center extraction of interested targets, in terms of radar cross section reduction design, not signal processing. In order to verify the accuracy of the direct analysis method, a scattering center analysis of an naval weapon system was carried out, and the result was coincident with that of another well-known RCS analysis program. Finally, an analysis result of RCS and its scattering center of an 120m class warship-like model presented that the direct analysis method can be an efficient and powerful tools for radar cross section reduction of large complex targets.

Actuator and sensor failure detection using direct approach

  • Li, Zhiling;Nagarajaiah, Satish
    • Structural Monitoring and Maintenance
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    • v.1 no.2
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    • pp.213-230
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    • 2014
  • A novel real-time actuator failure detection algorithm is developed in this paper. Actuator fails when the input to the structure is different from the commanded one. Previous research has shown that one error function can be formulated for each actuator through interaction matrix method. For output without noise, non-zero values in the actuator functions indicate the instant failure of the actuator regardless the working status of other actuators. In this paper, it is further demonstrated that the actuator's error function coefficients will be directly calculated from the healthy input of the examined actuator and all outputs. Hence, the need for structural information is no longer needed. This approach is termed as direct method. Experimental results from a NASA eight bay truss show the successful application of the direct method for isolating and identifying the real-time actuator failure. Further, it is shown that the developed method can be used for real-time sensor failure detection.

Contingency Severity Ranking Using Direct Method in Power Systems (전력계통에 있어서 직접법을 활용한 상정사고 위험순위 결정)

  • Lee, Sang-Keun
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.54 no.2
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    • pp.67-72
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    • 2005
  • This paper presents a method to select contingency ranking considering voltage security problems in power systems. Direct method which needs not the detailed knowledge of the post contingency voltage at each bus is used. Based on system operator's experience and knowledge, the membership functions for the MVAR mismatch and allowable voltage violation are justified describing linguistic representation with heuristic rules. Rule base is used for the computation of severity index for each contingency by fuzzy inference. Contingency ranking harmful to the system is formed by the index for security evaluation. Compared with 1P-1Q iteration, this algorithm using direct method and fuzzy inference shows higher computation speed and almost the same accuracy. The proposed method is applied to model system and KEPCO pratical system which consists of 311 buses and 609 lines to show its effectiveness.

A New Refinement Method for Structure from Stereo Motion (스테레오 연속 영상을 이용한 구조 복원의 정제)

  • 박성기;권인소
    • Journal of Institute of Control, Robotics and Systems
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    • v.8 no.11
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    • pp.935-940
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    • 2002
  • For robot navigation and visual reconstruction, structure from motion (SFM) is an active issue in computer vision community and its properties arc also becoming well understood. In this paper, when using stereo image sequence and direct method as a tool for SFM, we present a new method for overcoming bas-relief ambiguity. We first show that the direct methods, based on optical flow constraint equation, are also intrinsically exposed to such ambiguity although they introduce robust methods. Therefore, regarding the motion and depth estimation by the robust and direct method as approximated ones. we suggest a method that refines both stereo displacement and motion displacement with sub-pixel accuracy, which is the central process f3r improving its ambiguity. Experiments with real image sequences have been executed and we show that the proposed algorithm has improved the estimation accuracy.

Transmission Electron Microscopy Specimen Preparation for Layer-area Graphene by a Direct Transfer Method

  • Cho, Youngji;Yang, Jun-Mo;Lam, Do Van;Lee, Seung-Mo;Kim, Jae-Hyun;Han, Kwan-Young;Chang, Jiho
    • Applied Microscopy
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    • v.44 no.4
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    • pp.133-137
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    • 2014
  • We suggest a facile transmission electron microscopy (TEM) specimen preparation method for the direct (polymer-free) transfer of layer-area graphene from Cu substrates to a TEM grid. The standard (polymer-based) method and direct transfer method were by TEM, high-resolution TEM, and energy dispersive X-ray spectroscopy (EDS). The folds and crystalline particles were formed in a graphene specimen by the standard method, while the graphene specimen by the direct method with a new etchant solution exhibited clean and full coverage of the graphene surface, which reduced several wet chemical steps and accompanying mechanical stresses and avoided formation of the oxide metal.

Enhancement of Data Flow for Multimedia Platform (멀티미디어 플랫폼의 데이터 흐름 개선)

  • 정하재
    • Proceedings of the IEEK Conference
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    • 1998.10a
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    • pp.515-518
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    • 1998
  • This paper describes a direct transfer method of multimedia data stream between multimedia processor and network device without using system memory. The hardware architecture and functions for direct transfer, the method to transfer multimedia data to and from the multimedia processor and etc are described. Comparing the proposed method with general methods, I show that the direct transfer method can decrease number of bus accesses and bus cycles.

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