Kineziologija, Vol. 26 No. 1-2, 1994.
Stručni rad
Application of spectral analysis in processing of kinematic signals of movement
Mladen Mejovšek
; Fakultet za fizičku kulturu, Sveučilište u Zagrebu, Zagreb
Sažetak
Kinematic measurement of sport movements is realized by a particular technique that makes it possible to record this movement kinematically (e. g. video, film), and by a digitizer, thus attaining the transition from the continuous amplitude and the continuous time into the discrete form. Different problems appear during such a process. These problems are connected to the time resolution in the collection of signals and to the accidental error in measurement- this error appears because of the visual identification and manual mapping of anatomy locations during digitalization. Because the insufficient sampling (time resolution) and measurement error have drastic influence on the results of differentiation (derivations of linear and angular displacements) it is necessary to analyze the amplitude and phase spectrum of signals by means of the Discrete Fourier Transform (DFT). The results of the spectral analysis provide data about sufficient sampling (sampling theorem) and about the cut-off frequency of kinematic signals, that is used in order to select significant spectral components (separating the information of the signal from the measurement error). Together with the known part of the spectra, that is connected to the measurement errors, the reconstruction of the kinematic signal is being done by means of the Inverse Discrete Fourier Transformation (IDFT), summing up only the frequency components that are lower than the cut-off frequency. This means that the inverse transformation is going to low-pass filter the original signal, and that the reconstructed signal will be freed from measurement errors. Only the signal that has been prepared in such a way will be suitable for differentiating in the time domain, i.e. for calculating the required kinematic values.
Ključne riječi
biomechanics, spectral analysis, kinematic measurement of movements
Hrčak ID:
253486
URI
Datum izdavanja:
10.3.1994.
Posjeta: 674 *