摘要：Boundary effects are caused by incomplete data in the boundary regions when the analysis window gets closer to the edge of a signal. Various extension schemes have been developed to handle the boundaries of finite length signals to reduce the boundary effects. Zero padding, periodic extension, and symmetric extension are some basic extension methods. However, these solutions have drawbacks. In this paper, we consider the problem of handling the boundary effects due to improper extension methods in the wavelet transform for the application of fault diagnosis of rotating machine. An extension algorithm based on curve fitting with properties that make it more suitable for boundary effects reduction is presented. This extension algorithm could preserve the time-varying characteristics of the signals and be effective to reduce distortions appearing at the boundary. Then, an interpolation approach is used in the boundary effects region to further alleviate the distortions. Procedures for realization of these two algorithms and relative issues are presented. Several experimental tests show that the proposed algorithms are efficient to alleviate the boundary effects in comparison to the existing extension methods.
