• Title, Summary, Keyword: Mode Truncation Method

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Mode Truncation Method in Frequency Response Analysis (주파수 응답해석의 모드 축약법)

  • 조태민;이은경;임경화
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • pp.91-94
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    • 2001
  • In the frequency response analysis using a modal method, it is very important to determine the number of modes involved with the formulation of a frequency response function. Most engineers are inclined to determine mode truncation with their experience. But it is difficult for non-experts to decide the mode truncation reasonably in many problems of dynamic analyses. In this study, fuzzy theory is used to standardize the empirical determination of mode truncation so that not only the experts but also non-experts can decide a proper mode truncation easily. Fuzzy rule base is based on the simulation results using finite element method. Numerical simulations show that the developed mode truncation method is a very effective method to choose the number of the considered modes.

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Mode Truncation Method in Frequency Response Analysis (주파수 응답해석의 모드 축약법)

  • Cho, Tae-Min;Lee, Eun-Kyoung;Seo, Hwa-Il;Rim, Kyung-Hwa
    • Journal of Korean Institute of Intelligent Systems
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    • v.12 no.1
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    • pp.39-43
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    • 2002
  • In the frequency response analysis using a modal method, it is very important to determine the number of modes involved with the formulation of a frequency response function. Most engineers are inclined to determine mode truncation with their experience. But it is difficult for non-experts to decide the mode truncation reasonably in many problems of dynamic analyses. In this study, fuzzy theory is used to standardize the empirical determination of mode truncation so that not only the experts but also non-experts can decide a Proper mode truncation easily. Fuzzy rule base is based on the simulation results using finite element method. Numerical simulations show that the developed mode truncation method is a very effective method to choose the number of the considered modes.

Efficient Mode Superposition Method for Non-Classically Damped Systems (비비례 감쇠시스템의 해석을 위한 효율적인 모드 중첩법)

  • Cho, Sang-Won;Cho, Ji-Seong;Park, Sun-Kyu;Lee, In-Won
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.549-555
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    • 2000
  • The improved mode superposition methods for non-classically damped systems are presented in this paper. Generally, the mode superposition method uses a relatively small subset of the normal modes of structures. The mode acceleration method and the modal truncation augmentation method improve the results of the mode superposition method by considering effects of truncated high modes. For using these methods to analyze non-classically damped systems, the systems are approximated to the classically damped systems and thereby the errors are induced. In this paper, the mode acceleration method and the modal truncation augmentation method are expanded to analyze the non-classically damped systems. The applicability of the expanded methods is verified by closed form solutions and numerical examples. The expanded modal truncation augmentation method is conditionally stable depending on the pattern of the external loading in the non-classically damped systems whereas the expanded mode acceleration method is stable for the all cases of loading. In the stable case, the results are the same with those of the expanded mode acceleration method.

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A Study on the Block Truncation Coding Using the Bit-plane Reduction (비트평면 감축을 이용한 블록 절단부호화에 관한 연구)

  • 이형호;박래홍
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.24 no.5
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    • pp.833-840
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    • 1987
  • A new Block Truncation Coding(BTC) technique reducing the bit-plane and using differential pulse code modulation (DPCM) is proposed and compared with the conventional BTC methods. A new technique decides whether the subblock can be approximated to be uniform or not. If the subblock can be approximated to be uniform(merge mode), we transmit only the gray-level informantion. It not (split mode), we transmity both the bit-plane and the gray-level information. DPCM method is proposed to the encoding of gray-level information when the subblock can be approximated to be uniform. Also modified quantization method is presented to the encoding of gray-level information when the subblock is not uniform. This technique shows the results of coding 256 level images at the average data rate of about 0.75 bits/pel.

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Multi-Mode BTC Image Compression Algorithm for LCD Overdriving (LCD 오버드라이브를 위한 다중 모드 BTC 영상 압축 알고리즘)

  • Cho, Moonki;Yoon, Yungsup
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.3
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    • pp.67-74
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    • 2015
  • BTC (Block Truncation Coding) image compression is simple to implement by hardware and has excellent edge retention capability of image, image compression techniques are widely used in LCD overdrive. In this paper, to maintain high visual quality and has high compression rate, Multi-Mode BTC (MM-BTC) algorithm is proposed. The MM-BTC has high compression rate using advanced Y-based BTC method and has high visual quality using improved 2-level and 4-level BTC method in this paper. As shown in simulation results, MM-BTC improves still image PSNR (Peak Signal to Noise Ratio) up to 2.34 dB as compared with other algorithms. When the MM-BTC is applied to LCD overdrive, MM-BTC improves moving picture PSNR up to 2.33 dB as compared with other algorithms in literature.

Active vibration robust control for FGM beams with piezoelectric layers

  • Xu, Yalan;Li, Zhousu;Guo, Kongming
    • Structural Engineering and Mechanics
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    • v.67 no.1
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    • pp.33-43
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    • 2018
  • The dynamic output-feedback robust control method based on linear matrix inequality (LMI) method is presented for suppressing vibration response of a functionally graded material (FGM) beam with piezoelectric actuator/sensor layers in this paper. Based on the reduced model obtained by using direct mode truncation, the linear fractional state space representation of a piezoelectric FGM beam with material properties varying through the thickness is developed by considering both the inherent uncertainties in constitution material properties as well as material distribution and the model error due to mode truncation. The dynamic output-feedback robust H-infinity control law is implemented to suppress the vibration response of the piezoelectric FGM beam and the LMI method is utilized to convert control problem into convex optimization problem for efficient computation. In numerical studies, the flexural vibration control of a cantilever piezoelectric FGM beam is considered to investigate the accuracy and efficiency of the proposed control method. Compared with the efficient linear quadratic regulator (LQR) widely employed in literatures, the proposed robust control method requires less control voltage applied to the piezoelectric actuator in the case of same control performance for the controlled closed-loop system.

Model Reduction Considering Both Resonances and Antiresonances (공진과 반공진 특성을 동시고려한 모델 축소)

  • 허진석;이시복;이창일
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.985-990
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    • 2001
  • The Frequency Response Function(FRF)s of FE Model reduced by SEREP methods accurately estimate the full model at resonance frequencies, However these FRFs are not accurate at antiresonance frequencies, Additionally, the truncation errors may he significant in the reduction mode1. So this paper considers the possibility of SERFP method through a numerical method to preserve dynamic behavior at antiresonance and appliers the static or dynamic compensation methods for truncation errors to the reduction model. This compensated reduction model is redesigned for pole-zero cancellation methods the objective of reducing a resonance frequency.

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Automatic Variable Block Truncation Coding Technique (자동 가변 블록절단 부호화 기법)

  • 김태균;박래홍
    • Journal of the Korean Institute of Telematics and Electronics B
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    • v.30B no.12
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    • pp.73-86
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    • 1993
  • This paper proposes an automatic variable block truncation coding (BTC) method. It selects the block size automatically based on the mode of the discontinutiy measure of blocks. The combination of an automatic block-size determination scheme and the conventional BTC results in the proposed automatic variable BTC techniques. For color images, subsampling in I and Q chrominance components is adopted along with the variable BTC. To show the effectiveness of the proposed algorithm, its simulation results are compared to those of the several conventional BTC algorithms for monochrome and color test images. Computer simulation shows that the proposed algorithm gives better performance than the conventional ones based on the subjective and objective performance evaluation.

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Modal transformation tools in structural dynamics and wind engineering

  • Solari, Giovanni;Carassale, Luigi
    • Wind and Structures
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    • v.3 no.4
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    • pp.221-241
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    • 2000
  • Structural dynamics usually applies modal transformation rules aimed at de-coupling and/or minimizing the equations of motion. Proper orthogonal decomposition provides mathematical and conceptual tools to define suitable transformed spaces where a multi-variate and/or multi-dimensional random process is represented as a linear combination of one-variate and one-dimensional uncorrelated processes. Double modal transformation is the joint application of modal analysis and proper orthogonal decomposition applied to the loading process. By adopting this method the structural response is expressed as a double series expansion in which structural and loading mode contributions are superimposed. The simultaneous use of the structural modal truncation, the loading modal truncation and the cross-modal orthogonality property leads to efficient solutions that take into account only a few structural and loading modes. In addition the physical mechanisms of the dynamic response are clarified and interpreted.

Efficient Mode Superposition Method or Non-classically Damped Systems (비비례 감쇠시스템의 해석을 위한 효율적인 모드 중첩법)

  • 조상원;조지성;이인원
    • Journal of the Earthquake Engineering Society of Korea
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    • v.4 no.1
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    • pp.89-98
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    • 2000
  • 본 연구에서는 비비례 감쇠시스템을 효율적으로 해석할 수 있도록 모드 가속도법(mode acceleration method)과 모드 절삭 보강법(modal truncation augmentation method)을 확장하고 그 사용성을 검증하였다,. 비례 감쇠시스템의 동응답해서에 널리 사용되는 모드 가속도법과 모드 절삭보강법은 누락된 고차모드의 영향을 보정하여 모드 중첩법의 결과를 개선하는 방법이다. 기존의 방법들로 비비례 감쇠시스템을 해석하는 경우 비비례 감쇠특성을 무시하지 않으며 정확하고 효율적으로 해석할 수 있도록 모드 가속도법과 모드 절삭보강법을 확장하였다. 비례 감쇠시스템에서는 모드 가속도법보다 모드 절삭보강법이 더 효율적인 반면에 비비례 감쇠시스템에서는 대부분의 경우에 있어서 확장된 두 방법의 효율성이 동일하다. 그러나 수치적 안정성은 확장된 모드 가속도법이 모드절삭 보강법보다 우수하다. 이와 같은 확장된 모드 가속도법과 모드 절삭보강법의 사용성 검?을 위해서 이론적 방법과 수치예제를 수행하였다.

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