Analysis of center of pressure signals using Empirical Mode Decomposition and Fourier-Bessel expansion

Center of pressure (COP) measurements are often used to identify balance problems. A new method for analysis of COP signals using empirical mode decomposition (EMD) and Fourier-Bessel (FB) expansion is proposed in this paper. The EMD decomposes a COP signal into a finite set of band-limited signals termed intrinsic mode functions (IMFs), before FB expansion is applied on each IMF to compute mean frequency. The FB expansion based representation is suitable for use in non-stationary and very short duration signals. Seventeen subjects were tested under eyes open (EO) and eyes closed (EC) conditions, with different vibration frequencies applied for EC condition to further perturb sensory information. Mean frequency as calculated by FB expansion for the first three IMFs was able to distinguish between EO and EC conditions (p < 0.05), while only first IMF was able to detect a vibration effect.