A method for damping identification using piecewise integral

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Journal of Vibration and Shock ›› 2015, Vol. 34 ›› Issue (20) : 109-114.

ZHAO Xiao-dan，XU Jun-jie，WANG Xi-fu

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Abstract

A method using piecewise integral to identify damping ratios is proposed. Natural frequency of response signal is calculated by the application of Fast Fourier Transform plus Continuous Fourier Transform (FFT-FT). Construct a complex exponential function with the calculated natural frequency, and two inner product which have different integral time were conducted between response signal and the constructed exponential function. Control the time of inner product to be integer time semi-period of the response signal, and the formula of attenuation coefficient was derived. Accordingly, the damping ratio can be determined. Feature of this method is that interference of negative frequency item was eliminated by controlling the time of inner product. This method is not restricted by the size of damping ratios and the length of sample, and it has high precision. Damping ratios of closely spaced modes can be identified by this method combined with iterative algorithm. Digital simulations and experiment show that this method is effective. In Crankshaft experiment, small changes of damping ratios were identified. This method is practical in engineering.

Key words

piecewise integral / attenuation coefficient / damping ratio / crankshaft

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ZHAO Xiao-dan，XU Jun-jie，WANG Xi-fu. A method for damping identification using piecewise integral[J]. Journal of Vibration and Shock, 2015, 34(20): 109-114

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