Research On Fault Diagnosis For Hydraulic System Based On Fractal Theory

Fractal is a new subject which is especially suitable for the analysis of complex 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 operating 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 compared with fault files.Firstly, this paper generalizes and reviews state of art and development in the field of fault diagnosis for hydraulic system faults and, starting with fault signal identification, it raises a new method of hydraulic system fault diagnosis based on fractal. Then, it describes separately hydraulic system's complexity theory and fractal theory and analyzes all kinds of operating signals in hydraulic system. On these bases, it studies the method of fractal-based fault diagnosis of hydraulic system, puts forward its diagnosis model.Hydraulic pump is the research object in this paper. In this research, the simulation and experiment of fault diagnosis of hydraulic pump are established, including model establishing, data sampling, obtaining character parameters and so on. The results indicate that the different correlation dimensions of vibration and pressure signals of hydraulic pump under different operating states and the correlation dimension is sensitive to hydraulic pump faults. It reflects the dynamic characteristic of system. The method is simple, intuitionistic and feasible. It greatly overcomes the difficulty of characteristic identification in traditional methods.At last, the research is summarized and prospected in this paper.