关键词: 局部均值分解（LMD）, 瞬态响应, 固有频率, 阻尼比

Abstract: This method, by adopting the LMD（Local Mean Decomposition）, identifies the inherent frequency and damping ratio of mechanical systems. The self-adapting Local Mean Composition（LMD） method can disintegrate a complex signal to several PF（Production Function） components. Using LMD method to decompose the acceleration response signal of a mechanical system with pulsed excitation gets some PF components with physical significance. With each PF component corresponding to the signal’s vibration response of one mode, the method is able to distinguish the inherent frequency and damping ratio of the signal in the modes, by matching the curves of instaneous frequency and magnitude. In this thesis, it analyses the experimental data of the transient response of a girder by adopting the simulating signal （method）, and by using LMD and EMD. The comparison of the results of the two methods shows that the LMD method is of more superiorities in analysing modes.

Key words: Local Mean Decomposition（LMD）, transient response, inherent frequency, damping ratio