Comparison study of two commonly used methods for envelope fitting of empirical mode decomposition

Empirical mode decomposition (EMD) developed by professor Huang N E of NASA is an advanced method for signal analysis and its application scope is extremely widespread. Envelope fitting is a key step of EMD. Therefore, several approaches have been proposed for it and cubic spline interpolation (CSI) and piecewise cubic Hermite interpolation (PCHI) are the two most popular methods. However, it is a lack of a systemic and accurate evaluation for the performance of them. In this paper, they are evaluated by studying the end points effect, the signal reconstruction ability and the computing complexity comparatively. The production of the paper can provide some guidance for the envelope fitting method selection in practical application and the exploitation of new methods in the EMD algorithm.