Inspection for Roll Eccentricity Signal Based on Convolution Type of Wavelet Packet Transform

A multi-scale de-noising algorithm based on the convolution type of wavelet packet transformation is presented. This algorithm overcomes shortcomings of the classical wavelet packet transformation, in which the length of sequences obtained always decreases by decomposition scales. The new algorithm improves estimated method of white noise standard deviation at each scale and thus keeps the main edges of signal well. A new thresholding function is employed in this algorithm, which is simple in expression. A compensation algorithm based on the convolution type of wavelet packet transformation is presented to eliminate the fluctuation of rolling force caused by roll eccentricity. Simulation results show that the novel algorithm is superior to the Fourier algorithm.