Applied Mathematics and Mechanics (English Edition) ›› 2013, Vol. 34 ›› Issue (7): 801-810.doi: https://doi.org/10.1007/s10483-013-1708-9

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Separation of closely spaced modes by combining complex envelope displacement analysis with method of generating intrinsic mode functions through filtering algorithm based on wavelet packet decomposition

Y. S. KIM1,2, 陈立群1,3,4   

  1. 1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, P. R. China;
    2. Department of Mechanics, Kim II Sung University, Pyongyang, D. P. R. Korea;
    3. Department of Mechanics, College of Sciences, Shanghai University, Shanghai 200444, P. R. China;
    4. Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai University, Shanghai 200072, P. R. China
  • 出版日期:2013-07-03 发布日期:2013-07-03
  • 通讯作者: Li-qun CHEN E-mail:lqchen@staff.shu.edu.cn

Separation of closely spaced modes by combining complex envelope displacement analysis with method of generating intrinsic mode functions through filtering algorithm based on wavelet packet decomposition

Y. S. KIM1,2, Li-qun CHEN1,3,4   

  1. 1. Shanghai Institute of Applied Mathematics and Mechanics, Shanghai 200072, P. R. China;
    2. Department of Mechanics, Kim II Sung University, Pyongyang, D. P. R. Korea;
    3. Department of Mechanics, College of Sciences, Shanghai University, Shanghai 200444, P. R. China;
    4. Shanghai Key Laboratory of Mechanics in Energy Engineering, Shanghai University, Shanghai 200072, P. R. China
  • Online:2013-07-03 Published:2013-07-03
  • Contact: Li-qun CHEN E-mail:lqchen@staff.shu.edu.cn

摘要: One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the modal identification by the empirical mode decomposition (EMD) method, because of the separating capability of the method, it is still a challenge to consistently and reliably identify the parameters of structures of which modes are not well separated. A new method is introduced to generate the intrinsic mode functions (IMFs) through the filtering algorithm based on the wavelet packet decomposition (GIFWPD). In this paper, it is demonstrated that the GIFWPD method alone has a good capability of separating close modes, even under the severe condition beyond the critical frequency ratio limit which makes it impossible to separate two closely spaced harmonics by the EMD method. However, the GIFWPD-only based method is impelled to use a very fine sampling frequency with consequent prohibitive computational costs. Therefore, in order to decrease the computational load by reducing the amount of samples and improve the effectiveness of separation by increasing the frequency ratio, the present paper uses a combination of the complex envelope displacement analysis (CEDA) and the GIFWPD method. For the validation, two examples from the previous works are taken to show the results obtained by the GIFWPD-only based method and by combining the CEDA with the GIFWPD method.

关键词: 自旋姿态动力学, TVC飞行器, 非线性解耦控制, empirical mode decomposition (EMD), wavelet packet decomposition, complex envelope displacement analysis (CEDA), closely spaced modes, modal identification

Abstract: One of the important issues in the system identification and the spectrum analysis is the frequency resolution, i.e., the capability of distinguishing between two or more closely spaced frequency components. In the modal identification by the empirical mode decomposition (EMD) method, because of the separating capability of the method, it is still a challenge to consistently and reliably identify the parameters of structures of which modes are not well separated. A new method is introduced to generate the intrinsic mode functions (IMFs) through the filtering algorithm based on the wavelet packet decomposition (GIFWPD). In this paper, it is demonstrated that the GIFWPD method alone has a good capability of separating close modes, even under the severe condition beyond the critical frequency ratio limit which makes it impossible to separate two closely spaced harmonics by the EMD method. However, the GIFWPD-only based method is impelled to use a very fine sampling frequency with consequent prohibitive computational costs. Therefore, in order to decrease the computational load by reducing the amount of samples and improve the effectiveness of separation by increasing the frequency ratio, the present paper uses a combination of the complex envelope displacement analysis (CEDA) and the GIFWPD method. For the validation, two examples from the previous works are taken to show the results obtained by the GIFWPD-only based method and by combining the CEDA with the GIFWPD method.

Key words: TVC vehicle, spinning attitude dynamics,nonlinear uncoupled control, empirical mode decomposition (EMD), wavelet packet decomposition, complex envelope displacement analysis (CEDA), closely spaced modes, modal identification

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