• Title/Summary/Keyword: Cartesian

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Automatic Compensation for Cartesian Feedback Transmitter Imperfections Using the Binary Search Algorithm (이진 검색 알고리즘을 이용한 Cartesian Feedback 송신기 불완전성의 자동보상)

  • 임영희;이병로;임동민;이형수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.10A
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    • pp.1507-1516
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    • 1999
  • 본 논문에서는 전력증폭기 선형화를 위한 Cartesian feedback 방식의 궤환 경로에서 발생하는 DC offset과 이득 및 위상 불일치를 자동적으로 보상하는 개선된 방식을 제안한다. Cartesian feedback에 의한 비선형 전력증폭기 왜곡성분의 감쇠 정도는 시스템 루프의 이득, 대역폭, 시간지연에 의해 결정된다고 알려져 있다. 그러나 궤환 경로 각 소자에서 발생하는 DC offset과 이득 및 위상의 불일치로 인하여 송신기의 출력신호에 원하지 않는 반송파 성분과 이미지 신호가 발생하여 궤환보상의 효과가 반감되는 결과를 초래한다. 본 논문에서는 디지털 신호처리 시스템 구조에서 이진 검색 (binary search) 알고리즘을 이용하여 궤환 경로에서 발생하는 DC offset과 이득 및 위상 불일치를 자동적으로 보상하는 방식을 제안하고 컴퓨터 모의실험을 통하여 제안된 방식의 성능을 분석한다. 모의실험에서 고려된 방식에 비하여 동일한 정도의 DC offset과 이득 및 위상 불일치의 보상에 걸리는 시간을 평균적으로 40% 단축할 수 있었다.

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Free Vibration Analysis of Horizontally Sinusoidal Curved Beams in Cartesian Coordinates (직교 좌표계에 의한 정현형 수평 곡선보의 자유진동 해석)

  • Lee, Byoung-Koo;Lee, Tae-Eun;Kang, Hee-Jong;Kim, Kweon-Sik
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.11-16
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    • 2002
  • The differential equations governing free vibrations of the elastic, horizontally curved beams with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates, in which the effect of torsional inertia is included. Frequencies are computed numerically for the sinusoidal curved beams with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without torsional inertia, as functions of three non-dimensional system parameters: the horizontal rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio.

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Two-time Scale Controller Design for Vibration Reduction of High Speed Cartesian Manipulator (고속 직교 머니풀레이터의 진동 감소를 위한 Two-time scale 제어기 설계)

  • 강봉수
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.7
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    • pp.107-114
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    • 2004
  • This paper presents a two-time scale approach for vibration reduction of a high speed Cartesian manipulator. High speed manipulators would be subject to mechanical vibration due to high inertia forces acting on linkages. To achieve high throughput capability, such motion induced vibration would have to be damped quickly, to reduce settling time of the manipulator end-effector. This paper develops a two-time scale model fer a structurally-flexible Cartesian manipulator. Based on the two-time scale model, a composite controller consisting of a computed torque method for the slow time-scale rigid body subsystem, and a linear quadratic state-feedback regulator for the fast time-scale flexible subsystem, is designed. Simulation results show that the proposed two time-scale controller yields good performance in attenuating structural vibration arising due to excitation from inertial forces.

Effect of 2nd Axis Linear Motion Guide on Mechanical Performance of Robot in 2-Axis Cartesian Coordinate Robot (2축 직교좌표 로봇에서 2축 직선 운동 가이드가 로봇의 기계적 성능에 미치는 영향)

  • Lee, Jong Shin
    • Journal of the Korean Society of Mechanical Technology
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    • v.13 no.1
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    • pp.95-103
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    • 2011
  • Robots in various types carry and assemble parts through repeatedly and accurately moving to stored locations by combining linear motions. And, linear systems are used in orthogonal axes of robots and driven via ball screws, such as 2-axis cartesian coordinate robot in this paper. This paper presents the effect of the linear motion guide that is used in $2^{nd}$ axis in 2-axis cartesian coordinate robot. Some simulation results show that the linear motion guide influence greatly in robot performance such as the nominal life of linear guide. When use LM guide that have capacity near in $2^{nd}$ axis, this paper show that the nominal life on LM block of $1^{st}$ axis increases 37.4% and that the specification of $2^{nd}$ axis LM guide influences greatly the nominal life of $1^{st}$ axis LM block.

Numerical Method for Improving the Accuracy of Molten Metal Flow (주조유동의 정확도 개선을 위한 수치기법 연구)

  • Choi, Young-Sim;Hong, Jun-Ho;Hwang, Ho-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.3
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    • pp.253-258
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    • 2012
  • The Cartesian grid system has generally been used in casting simulations, even though it does not represent sloped and curved surfaces very well. These distorted boundaries cause several problems, and special treatment is necessary to resolve them. A cut cell method on a Cartesian grid has been developed for the simulation of threedimensional mold filling. Cut cells at a cast/mold interface are generated on Cartesian grids, and the governing equations are computed using the volume and areas of the cast at the cut cells. In this paper, we propose a new method based on the partial cell treatment (PCT) that can consider the cutting cells which are cut by the cast and the mold. This method provides a better representation of the surface geometry, and will be used in the computation of velocities that are defined on the cell boundaries in the Cartesian gird system. Various test examples for several casting process are computed and validated.

Development of a Numerical Model of Shallow-Water Flow using Cut-cell System (분할격자체계를 이용한 천수흐름 수치모형의 개발)

  • Kim, Hyung-Jun;Lee, Seung-Oh;Cho, Yong-Sik
    • Journal of the Korean Society of Hazard Mitigation
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    • v.8 no.4
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    • pp.91-100
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    • 2008
  • Numerical implementation with a Cartesian cut-cell method is conducted in this study. A Cartesian cut-cell method is an easy and efficient mesh generation methodology for complex geometries. In this method, a background Cartesian grid is employed for most of computational domain and a cut-cell grid is applied for the peculiar grids where the flow characteristics are changed such as solid boundary to enhance the accuracy, applicability and efficiency. Accurate representation of complex geometries can be obtained by using the cut-cell method. The cut-cell grids are constructed with irregular meshes which have various shape and size. Therefore, the finite volume method is applied to numerical discretization on a irregular domain. The HLLC approximate Riemann solver, a Godunov-type finite volume method, is employed to discretize the advection terms in the governing equations. The weighted average flux method applied on the Cartesian cut cell grid for stabilization of the numerical results. To validate the numerical model using the Cartesian cut-cell grids, the model is applied to the rectangular tank problem of which the exact solutions exist. As a comparison of numerical results with the analytical solutions, the numerical scheme well represents flow characteristics such as free surface elevation and velocities in x-and y-directions in a rectangular tank with the Cartesian and cut-cell grids.

FUZZY L-CONVERGENCE SPACE

  • Min, Kyung-Chan
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 1998.06a
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    • pp.95-100
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    • 1998
  • A notion of 'fuzzy' convergence of filters on a set is introduced. We show that the collection of fuzzy L-limit spaces forms a cartesian closed topological category and obtain an interesting relationship between the notions of 'fuzzy' convergence structure and convergence approach spaces.

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A Study on Linearity Improvement of Cartesian Vector Modulator Predistorter for WiMax Applications (모바일 WiMax용 카르테시안 벡터 모듈레이터 전치왜곡기의 선형성 개선에 관한 연구)

  • Chun, Sang-Hyun;Kim, Ji-Yeon;Kim, Jong-Heon
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.9 no.4
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    • pp.32-42
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    • 2010
  • In this paper, we represent considering parameters for design of a Cartesian vector modulator predistorter to maximize linearity improvement of the predistorter and propose an advanced Cartesian vector modulator predistrotrer with nonlinear starting point control circuit. In order to confirm the performance of the proposed predistorter, the predistorter is applied to power amplifier with 15 W output power for 2.5 GHz band mobile WiMax 1-FA signal. From the measured results, ACLR of -45.3 dBc with 4 dB improvement of ALCR compared with the previous predistorter is obtained and linearity improvement range is also extended.