Affiliations: State Key Laboratory of Mechanical System and
Vibration, Shanghai Jiao Tong University, Shanghai, 200240, P.R. China | Department of Precision Instruments, Tsinghua
University, Beijing 100084, P. R. China
Abstract: The present work carries out a comprehensive investigation into the
border distortion deficiency for the conventional scalogram and the reassigned
scalogram. The reasons for this deficiency are analyzed, and a simple way is
suggested to determine the border distortion ranges. New methods are proposed
to reduce the border distortions in both the scalograms. The practical meanings
of the border distortion improvement method are demonstrated by applying both
the scalograms with and without border distortion improvements to estimate the
modal parameters for a 2-DOF linear system. The estimation results indicate
that, in the presence of noise, which is inevitable in practice, for the mode
with weak amplitude, the reassigned scalogram can perform better than the
conventional scalogram in estimating the modal parameters. In addition, for the
mode with short effective duration, its frequency components at the border
distortion ranges are of great importance for the modal parameter estimation
purpose, and the border distortion improvement method can greatly increase the
estimation accuracy.
