Fractal Approach To Fault Diagnosis Of Hydraulic Equipment

Fractal is a new subject and it is especially fit for researching nonlinear system. Recently signal processing methods based on fractal have been applied to mechanical system fault diagnosis. The objective of the proposed research is to develop a method based on fractal theory for analyzing the nonlinear signals of mechanical system. This method will provide further useful information about the underlying dynamics. It is possible to implement mechanical system fault diagnosis by using this method combined with other signals analysis methods.The basic theory of mechanical system fault diagnosis based on fractal is firstly introduced. The correlation dimension reflects the attractor characteristic of complex mechanical system, so the signal processing methods based on fractal may be used to analyze complex mechanical system. In this research, the flow of mechanical system fault diagnosis is provided and the judgment principle of fractal characteristic of signals is also given.Hydraulic pumps are the important part of rolling mill and they are also the researched objects of this paper, hi this research, The experimentation project of fault diagnosis of hydraulic pump is established, including data sampling, obtaining character parameters, fault diagnosis method and so on. The correlation dimension is adopted as the character parameter of hydraulic pump dynamical system. The calculating method of correlation dimension and the principle of selecting parameters such as time delay and embedding dimension are discussed in this paper.In the application of hydraulic pump fault diagnosis by fractal method, this paper analyzes the correlation dimensions of vibration speed signals of hydraulic pump under different working states. The result shows that the correlation dimension is sensitive to hydraulic pump faults and it reflects the dynamic characteristic of dynamics system. The qualitative and quantitative conclusion can be gained by correlation dimension.The data analysis system based on fractal theory is developed during the research and it is introduced. At last, the research is summered and prospected in this paper.