• Title/Summary/Keyword: Series expansion

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Natural Frequency of Two Rectangular Plates Coupled with Fluid (유체로 연성된 두 사각평판의 고유진동수)

  • Jeong, Kyeong-Hoon;Park, Keun-Bae
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.908-913
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    • 2002
  • An analytical study is presented on the hydroelastic vibration of two rectangular identical plates coupled with a bounded fluid by using the finite Fourier series expansion method. It is observed that the two contrastive modes, the so called the out-of-phase and in-phase modes appear. The proposed analytical method is verified by observing a good agreement to three dimensional finite element analysis results. All natural frequency of the in-phase modes can be predicted well by the combination of the dry beam modes. The theoretical prediction for the out-of-phase mode can be improved by using the polynomial functions satisfying the plate boundary conditions and fluid volume conservation instead of using dry beam modes.

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The Semi-Analytic Structural Sensitivity Using Pade Approximation (Pade근사를 이용한 준해석 구조 민감도의 해석)

  • Dan, Ho-Jin;Lee, Byung-Chai
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.12
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    • pp.2631-2635
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    • 2002
  • The semi-analytic sensitivity analysis using Pade approximation is presented for linear elastic structures. Although the semi-analytic method has several advantages, accuracy of the method prevents it from practical application. One of promising remedies is the use of geometric series for the matrix inversion. Though series expansion of order three has been successfully applied to the calculation of the structural sensitivity in the most range of the design perturbation, it is prone to have a slow convergence for large perturbation. To overcome this shortage, Pade approximation is introduced so that it can broaden the trust region of the perturbation without adding expansion terms. Numerical results show that the confident sensitivity can be obtained with tiny expenses of computation effort.

An Experimental Study on the Performance Improvement of Industrial Blower Silencer (산업용 송풍기 소음기의 성능개선을 위한 실험적 연구)

  • Kim, B.S.;Kim, Yong-woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.9 s.102
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    • pp.1060-1069
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    • 2005
  • Silencers are engineering devices that are designed to attenuate sound waves propagating in a flowing medium. The muffler type silencer has a series of chambers in parallel or series utilizing the reflection and expansion characteristics of the expansion chambers, sidetubes, branch resonators, and tailpipes to attenuate the sound. To Improve the performance of industrial blower silencer of muffler type which is employed in petrochemical plant, this paper seeks its optimal arrangement of buffs by experimental method and suggests optimal arrangement of buffs. Experimental results show that the optimal one suggested can reduce the noise level as much as 14 dB (or 18 dB(A)) in the laboratory and as much as 4 dB(A) compared to that of the existing silencer on the ground.

Implementation of a PWM Controlled Active AC Power Filter Using a Fast PWM Control Method (PWM 제어 능동 교류 전력 필터의 개발 및 속도 개선)

  • Kim, Jae-Hyun;Park, In-Gyu;Park, Jong-Keun
    • Proceedings of the KIEE Conference
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    • 1987.11a
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    • pp.457-462
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    • 1987
  • This paper deals with the PWM controlled active AC power filter. A new PWM control method from the viewpoint of speed and simplicity is proposed. And a microprocessor-based controller is used to realize the active AC power filter. The existing PWM control methods are primarily based on Fourier series expansion and these methods need FFT calculation and solving nonlinear harmonic equations, which are heavy burden to real-time control. The proposed method is based upon generalized pulse series expansion and needs only definite integrals of harmonic signal. So, computational effort can be reduced by a large margin. The digital circuit using 16-bit microprocessor is designed to implement the actual active power filler.

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Fourier Series Expansion Method for Free Vibration Analysis of a Fully Liquid-Filled Circular Cylindrical Shell (Fourier 급수전개를 이용한 유체로 가득 채워진 원통형 셸의 고유진동 해석)

  • 정경훈;이성철
    • Journal of KSNVE
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    • v.4 no.2
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    • pp.137-146
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    • 1994
  • An analytical method for linear free vibration of fully liquid-filled circular cylindrical shell with various boundary conditions is developed by the Fourier series expansion based on the Stokes' transformation. A set of modal displacement functions and their derivatives of a circular cylindrical shell is substituted into the Sanders' shell equations in order to explicitily represent the Fourier coefficients as functions of the end point displacements, forces, and moments. For the vibration relevant to the liquid motion, the velocity potential of liquid is assumed as a sum of linear combination of suitable harmonic functions in the axial directions. The unknown parameter of the velocity potential is selected to satisfy the boundary condition along the wetted shell surface. An explicit expression of the natural frequency equation can be obtained for any kind of classical boundary conditions. The natural frequencies of the liquid-filled cylindrical shells with the clamped-free, the clamped-clamped, and the simply supported-simply supported boundary conditions examined in the previous works, are obtained by the analytical method. The results are compared with the previous works, and excellent agreement is found for the natural frequencies of the shells.

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Evaluation of Analytical Vibration Characteristics for Triple Cylindrical Shells Filled with Fluid (유체로 채워진 삼중 원통셸의 해석적 진동 특성 평가)

  • 지용관;이영신
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.12 no.2
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    • pp.150-160
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    • 2002
  • The free vibration characteristics of the triple cylindrical shells filled with fluid are investigated. The triple cylindrical shells are filled with compressible fluid. The boundary condition is clamped at both ends. Analytical method is developed to evaluate natural frequencies of triple cylindrical shells using Sanders' shell theory and courier series expansion by Stokes' transformation. Their results are compared with those of finite element method to verify the validation of the method developed. The modal characteristics of shells filled with fluid at region 1, 2 and 3 are evaluated.

Free Vibration Analysis of a Circular Plate Submerged in a Fluid-filled Rigid Cylinder (유체로 채워진 강체 실린더에 잠긴 원판의 고유진동 해석)

  • Jeong, Kyeong-Hoon;Choi, Suhn;Jhung, Myung-Jo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2003.05a
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    • pp.921-925
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    • 2003
  • An analytical method for the free vibration of single circular plate submerged in a fluid-filled rigid cylindrical vessel was developed by the Rayleigh-Ritz method based on the Fourier-Bessel series expansion. It was assumed that the plate is clamped at an offcentered location of the cylinder, and the non-viscous incompressible fluid contained in the cylinder is bisected by the plate. It was found that the theoretical results can predict well the fluid-coupled natural frequencies with excellent accuracy comparing with the finite element analysis results. The offcentered distance effect on the natural frequencies was also observed.

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Anti-Swing Control of Overhead Crane System using Sum of Squares Method (천정형 크레인의 흔들림 억제제어에 관한 SOS 접근법)

  • Hong, Jin-Hyun;Kim, Cheol-Joong;Chwa, Dongkyoung
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.62 no.3
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    • pp.407-413
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    • 2013
  • This paper proposes anti-swing control of overhead crane system using sum of squares method. The dynamic equations of overhead crane include nonlinear terms, which are transformed into polynomials by using Taylor series expansion. Therefore the dynamic equation of overhead crane can be changed to the system of polynomial equation. On the basis of polynomial dynamics of crane system, we propose the Sum of Squares (SOS) conditions considering the input constraints. In addition, control gains are obtained by numerical tool which is called by SOSTOOL. The effectiveness of the proposed method is demonstrated by numerical simulation.

Development of Visual Servo Control System for the Tracking and Grabbing of Moving Object (이동 물체 포착을 위한 비젼 서보 제어 시스템 개발)

  • Choi, G.J.;Cho, W.S.;Ahn, D.S.
    • Journal of Power System Engineering
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    • v.6 no.1
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    • pp.96-101
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    • 2002
  • In this paper, we address the problem of controlling an end-effector to track and grab a moving target using the visual servoing technique. A visual servo mechanism based on the image-based servoing principle, is proposed by using visual feedback to control an end-effector without calibrated robot and camera models. Firstly, we consider the control problem as a nonlinear least squares optimization and update the joint angles through the Taylor Series Expansion. And to track a moving target in real time, the Jacobian estimation scheme(Dynamic Broyden's Method) is used to estimate the combined robot and image Jacobian. Using this algorithm, we can drive the objective function value to a neighborhood of zero. To show the effectiveness of the proposed algorithm, simulation results for a six degree of freedom robot are presented.

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Time Discretization of Nonlinear Systems with Variable Time-Delayed Inputs using a Taylor Series Expansion

  • Choi Hyung-Jo;Chong Kil-To
    • Journal of Mechanical Science and Technology
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    • v.20 no.6
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    • pp.759-769
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    • 2006
  • This paper proposes a new method of discretization for nonlinear systems using a Taylor series expansion and the zero-order hold assumption. The method is applied to sampled-data representations of nonlinear systems with input time delays. The delayed input varies in time and its amplitude is bounded. The maximum time-delayed input is assumed to be two sampling periods. The mathematical expressions of the discretization method are presented and the ability of the algorithm is tested using several examples. A computer simulation is used to demonstrate that the proposed algorithm accurately discretizes nonlinear systems with variable time-delayed inputs.