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Research Papers

Self-Identification Experiments Using Variable Inertia Systems for Flexible Beam Structures

[+] Author and Article Information
Atsuhiko Senba

Department of Information Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603, Japansenba@nuae.nagoya-u.ac.jp

Hiroshi Furuya

Department of Built Environment, Tokyo Institute of Technology, 4259-G3-6, Nagatsuta, Midori-ku, Yokohama 226-8502, Japanfuruya@enveng.titech.ac.jp

J. Vib. Acoust 130(1), 011006 (Nov 12, 2007) (9 pages) doi:10.1115/1.2776343 History: Received August 25, 2006; Revised July 06, 2007; Published November 12, 2007

The concept of self-identification and its feasibility are experimentally investigated. The modal parameters changed by the variable inertia systems, which are controlled by control input, are used to obtain linear equations about unknown structural parameters to overcome the lack of modes in vibration testing. We derive the controllability of the modal parameters as the requested conditions for implementing self-identification using sensitivity analyses of the modal parameters with respect to the control input. Also, a criterion for the self-identification is proposed to measure the controllability. To examine the present method, the self-identification experiments are performed using a flexible cantilevered beam with controllable additional mass attached to the beam. In the experiments, we simulate the self-identification of a flexible structure with variable inertia systems, where lower vibration modes are changed by the variable inertia system adapting to the lack of modes in identification of unknown parameters. It is shown that the identification error of the bending stiffness and mass per unit length of the beam are ranging from about 8% to 12% and 1% to 7%, respectively, and they depend on the mode number because the mode shape estimation from strain sensors and cubic spline interpolation also depends on the mode. Furthermore, the factor for the identification error is discussed in detail through numerical analysis, and the results show the clear relationship between the present criterion and the identification accuracy in experiments.

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Figures

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Figure 6

Estimated second derivative of first mode shape of flexible beam with appendage mass

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Figure 7

Estimated second mode shape of flexible beam with appendage mass

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Figure 8

Estimated first derivative of second mode shape of flexible beam with appendage mass

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Figure 9

Estimated second derivative of second mode shape of flexible beam with appendage mass

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Figure 10

Measurement error of first mode due to spline interpolation

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Figure 11

Measurement error of second mode due to spline interpolation

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Figure 12

Measurement error of third mode due to spline interpolation

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Figure 1

Experimental setup for variable inertia system

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Figure 2

Time history of flexible beam with two appendage masses (j=3)

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Figure 3

Fourier spectrum amplitude of flexible beam with two appendage masses (j=3)

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Figure 4

Estimated first mode shape of flexible beam with appendage mass

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Figure 5

Estimated first derivative of first mode shape of flexible beam with appendage mass

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