Research On The Method Relate To The Envelope Of EMD

Almost all the signal is nonlinear,non-stationary in real life.The time-frequency analysis method has been pay more attention to study. for processing non-linear and non-stationary signal.Hilbert huang transform is a new method of time-frequency analysis after Fourier transform, wavelet transform. The core idea of hilbert huang transform is the empirical mode decomposition.Empirical Mode Decomposition (EMD) is a local digital signal processing method, fully based on adaptive data, is very suitable for analyzing nonstationary and nonlinear properties, multi-component signal. The method breaks through the conventional ideas of traditional signal processing, the processing method is simple, and can more accurate analysis instantaneous characteristics of the nonlinear signal.The method has good application prospect in nonlinear nonstationary signal processing direction, thus won the attention of academic circles. At present, many scholars has carried on the improvement of related research in view of the defects and disadvantages of the EMD, has achieved great achievement,make the flaws of the EMD are well improved, has provided a broad platform for the engineering application of the EMD.This paper mainly study the EMD theory method. The specific work content of the paper as follows:First, This paper detail elaborated the standard empirical mode decomposition algorithm which by N.E.Huang put forward. Second, according to the standard EMD has the incomplete envelope situation when structure the envelope in cubic spline interpolation method.The problem is the envelope will cutting signal line. Improve the envelope algorithm tto improve the standards EMD algorithm,and the effectiveness of the improve method is verified by experiment. Third, the optimal mean envelope, the orthogonality stopping criteria of the inverse EMD algorithm process was introduced in this paper. The author test and compared the orthogonality index and energy leak index of the standard EMD, before of the improved inverse EMD, and the improved inverse EMD, analysed and compared the advantages of optimal envelope mean and other envelope mean, studied the effect of EMD decomposition by enhance sampling rate. Fourth, this paper introduces the fast band-pass filter intrinsic mode function decomposition method [3]that put forward by li-zhen zhang. The fast filtering method can effectively overcome the modal aliasing phenomenon is verified by an example. The innovation of the paper as follows:First, through the point of tangency to fitting envelope instead of the conventional method of extreme value point to fitting envelope in the envelope fitting process, can avoid appearring overshoot and undershoot phenomenon when fitting envelope near the extreme value point. the effectiveness of the improveing the EMD algorithm is verified by experiment.Second, the second order optimal envelope method is proposed in reverse screening of the EMD algorithm. to avoid excessive screening out the other component which of without physical meaning,this paper use improving envelope method in the EMD algorithm what second order optimal envelope and reverse screening. The author test the orthogonality index and energy leak index by experiment. the effectiveness of the method is verified.Third,by drawing on the ideas of signal decomposition of the most broad band intrinsic mode function that put forward by li-zhen zhang,this article proposes a moderate signal bandwidth bandpass filter decomposition method. The method than the broad band obtained intrinsic mode function is more accurate, this conclusion is verified by the simulation. Examples show that this method is able to overcome the modal aliasing phenomenon...