• Title/Summary/Keyword: vibration modes

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Design of Single-Input Single-Output Positive Position Feedback Controller For the Control of Multiple Modes (다중모드제어를 위한 단일 입출력 양변위 되먹임제어기의 설계)

  • Jeong, Moon-San;Kwak, Moon-K.;Lee, Myung-Il
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.11a
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    • pp.310-313
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    • 2005
  • This paper is concerned with the active vibration control of beam equipped with piezoceramic sensors and actuators. The single-input and single-output positive position feedback controller is considered as an active vibration controller for the beam. The proposed single-input and single-output positive position feedback controller can cope with many modes of interest by summing each positive position feedback controller designed for each mode. In this paper, theoretical formulation is first explained in detail. We discuss how to design the single-input and single-output positive position feedback controller for a target structure by considering Euler-Bemoulli beam. It is found that the theories developed in this study are capable of predicting the control system characteristics and its performance.

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Shaking Table Test of Steel Cylindrical Liquid Storage Tank Considering the Roof Characteristics

  • Bae, Doobyong;Park, Jang Ho
    • International journal of steel structures
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    • v.18 no.4
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    • pp.1167-1176
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    • 2018
  • Steel cylindrical tanks are widely used for the storage of hazardous substances of which leakage must be prevented under any circumstances. However, the dynamic response of the steel cylindrical liquid storage tank depends sensitively on the fluid-structure interaction and the vibration of the tank structure and necessitates clarification for the safety of the tank structure. This paper presents the results of shaking table tests performed to examine the dynamic behavior of a scaled cylindrical steel tank model considering the presence or not of fixed roof and added mass at the top of the tank for various fluid levels. The test results confirm the occurrence of both beam-type and oval-type vibration modes and show that the larger content of liquid inside the container amplified the acceleration along the height of the cylindrical tank. The oval-type vibration modes are seen to be more dominant in case of large water-to-structure mass ratio.

Reproduction of vibration patterns of elastic structures by block-wise modal expansion method (BMEM)

  • Jung, B.K.;Cho, J.R.;Jeong, W.B.
    • Smart Structures and Systems
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    • v.18 no.4
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    • pp.819-837
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    • 2016
  • The quality of vibration pattern reproduction of elastic structures by the modal expansion method is influenced by the modal expansion method and the sensor placement as well as the accuracy of measured natural modes and the total number of vibration sensors. In this context, this paper presents an improved numerical method for reproducing the vibration patterns by introducing a block-wise modal expansion method (BMEM), together with the genetic algorithm (GA). For a given number of vibration sensors, the sensor positions are determined by an evolutionary optimization using GA and the modal assurance criterion (MAC). Meanwhile, for the proposed block-wise modal expansion, a whole frequency range of interest is divided into several overlapped frequency blocks and the vibration field reproduction is made block by block with different natural modes and different modal participation factors. A hollow cylindrical tank is taken to illustrate the proposed improved modal expansion method. Through the numerical experiments, the proposed method is compared with several conventional methods to justify that the proposed method provides the improved results.

A Study on Vibration Characteristics of Moisture Separator for APR1400 Steam Generator (APR1400 증기발생기 습분분리기 진동 특성에 관한 연구)

  • Cho, Minki;Park, Taejung;Ha, Changhoon;Park, Luke
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2014.10a
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    • pp.99-101
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    • 2014
  • A Comprehensive Vibration Assessment Program (CVAP) for steam generator internals (SGI) of Advanced Power Reactor 1400 (APR1400) is being performed in accordance with the United States Nuclear Regulatory Commission (U.S. NRC) Regulatory Guide 1.20 (RG 1.20) revision 3. This paper studies the vibration characteristics of moisture separator assembly as part of the vibration and stress analysis program for APR1400 SGI CVAP. The natural frequencies, mode shapes, and structural behavior of moisture separator assembly were investigated through modal analysis using finite element method and experimental measurement. Since the moisture separator consists of several items with complicated shape, an idealized shell model was used in the finite element analysis. Group of local modes caused by moisture separators and significant modes of shroud and separator support plate were identified. The results of this paper are to be utilized in the structural response analysis of moisture separator assembly.

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Vibration Control of Membrane with Tension Gradient Using Multiple Dynamic Absorber (다중 동흡진기를 이용한 장력구배를 갖는 박판의 진동 제어)

  • Park, Chong-Hyun;Kim, Sung-Dae;Kim, Won-Jin
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.15 no.5 s.98
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    • pp.595-603
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    • 2005
  • In this work, the multiple dynamic absorber( MDA ) is introduced to reduce several vibration modes of shadow mask simultaneously and its design method is developed from the theory of the simple dynamic absorber. When designing the dynamic absorber, there are three significant design parameters such as mass, damping ratio and tuning frequency. Therefore the sensitivity analysis for those parameters has been executed in order to find out the design criteria of multiple dynamic absorber using the finite element model of shadow mask. The multiple dynamic absorber(MDA) designed by the proposed method is tested theoretically and experimentally to estimate the efficiency of vibration reduction. From the results, it is verified that the method is feasible to apply the system having the multiple nitration modes and more efficient than the thin wire-type damper used commercially to reduce the vibration of shadow mask.

Design of Modal Transducer in 2D Structure Using Multi-Layered PVDF Films Based on Electrode Pattern Optimization (다층 압전 필름의 전극 패턴 최적화를 통한 2차원 구조물에서의 모달 변환기 구현)

  • 유정규;김지철;김승조
    • Journal of KSNVE
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    • v.8 no.4
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    • pp.632-642
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    • 1998
  • A method based on finite element discretization is developed for optimizing the polarization profile of PVDF film to create the modal transducer for specific modes. Using this concept, one can design the modal transducer in two-dimensional structure having arbitrary geometry and boundary conditions. As a practical means for implementing this polarization profile without repoling the PVDF film the polarization profile is approximated by optimizing electrode patterns, lamination angles, and poling directions of the multi-layered PVDF transducer. This corresponds to the approximation of a continuous function using discrete values. The electrode pattern of each PVDF layer is optimized by deciding the electrode of each finite element to be used or not. Genetic algorithm, suitable for discrete problems, is used as an optimization scheme. For the optimization of each layers lamination angle, the continuous lamination angle is encoded into discrete value using binary 5 bit string. For the experimental demonstration, a modal sensor for first and second modes of cantilevered composite plate is designed using two layers of PVDF films. The actuator is designed based on the criterion of minimizing the system energy in the control modes under a given initial condition. Experimental results show that the signals from residual modes are successfully reduced using the optimized multi-layered PVDF sensor. Using discrete LQG control law, the modal peaks of first and second modes are reduced in the amount of 12 dB and 4 dB, resepctively.

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Evaluation of Ride Comfort Considering Seat and Ride Vibration Modes (주행 진동 모드와 시트 진동을 고려한 추행 안락감 분석)

  • 김명규;유완석;김정훈
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.4
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    • pp.93-99
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    • 2002
  • Ride comfort, one of the most important performances of a car, is affected by vibration, noise, dynamic movement, and ergonomic factors. Among these factors, ride comfort vibration is heavily affected by the seat system, tire, suspension, and body structure. In this study, vibration characteristics of seat, tire, suspension, and body structure are analyzed. The vibration transfer function from the road input to the human body is also investigated.