Application of EMD method to friction signal processing

Due to measurement limitation, the measured friction signal often contains noise and other force components such as elastic forces. Traditional Fourier-based analysis methods are not suitable to process nonlinear and non-stationary signal. In this paper, the combination of median filter and empirical mode decomposition (EMD) method is used to analyze the measured friction signal. Median filter is a nonlinear process useful in reducing random noise, while EMD method has offered a powerful method for nonlinear and non-stationary data processing. The background noise and the noise arising from the measurement system in the measured friction signal are removed using median filter first. Then the other force components except the real friction force can be extracted from the measured friction signal using the EMD method. The residue after extracting can be taken as a relatively clean and real friction force. This method is compared with the traditional Fourier-based methods and wavelet decomposition method. The comparison results both in time domain and in Hilbert spectrum can show the superiority of the EMD method in dealing with the problem of friction signal processing.