A New Method for Vibration Modal Analysis

INTRODUCTION This paper is about a new method for vibration modal analysis, which is called the smooth orthogonal decomposition (SOD) based modal analysis method. The proper orthogonal decomposition (POD) based modal analysis method, which was first proposed by Feeny et.al in 1998, indicates an exciting method for extracting the modal shapes of a vibration system by using only the output displacement signal. However, that method requires to know the mass distribution of the system in advance, which is not always available for real applications. Also there is trouble of identifying the modes when two proper orthogonal values are close to each other. In this paper, we present the SOD-based modal analysis method which could overcome those limitations of the POD-based method, in addition, this method can provide not only the mode shapes but also the natural frequencies of the system. We start with the theory of the SOD and then give the mathematical justification for its application in modal analysis. Several simulation results are followed to show the performances of this method, in the meantime, the results from the POD-based modal analysis method are also provided to do the comparison. The conclusion is reached in the last.