On Lyapunov Exponent Analysis-Based Hydraulic Pump Fault Diagnosis Aproach And Experience

Hydraulic system has been extensively used by its excellence such as high power and quick response in engineering area and it plays an essential role in control and transmission of many equipments. The pump is the"heart"of the hydraulic system, and it has the severest working condition. So the condition monitoring and fault diagnosis of the pump is crucial for the hydraulic system. In recent years, the chaotic engineering is becoming the subject being paid attention abroad and the research on chaos and Lyapunov exponents can help to find out the internal regularity of system. In this paper, the analysis of the largest Lyapunov exponent is applied in fault diagnosis of the pump and the largest Lyapunov exponent of pump pressure signal is calculated. The results of experiment show that there is different the largest Lyapunov exponent in different working state, which can be a proof of whether fault occurs or not.The main works in this dissertation are showed as follows.(1)The feature of chaos is described in detail. New development of chaos and Lyapunov exponent in fault diagnosis field is summarized. The algorithm of Lyapunov exponents (QR decompose algorithm) is expatiated and applied to calculate Lyapunov exponents of Duffing equation.(2)The chaos character of Duffing equation and the nature character of Lyapunov exponents are expatiated. Lyapunov exponents analysis method is used in the process of state signal of hydraulic pump. Through calculating the largest Lyapunov exponent of Duffing equation, the critical value of system from chaos to periods is ascertained effectively.(3)The feathers of virtual instrument and its development tool LabVIEW are summarized systematically. The interface of LabVIEW and MATLAB is programmed. This mixed programming extends the function of LabVIEW. The virtual chaos character shower is developed through which the chaos character isanalyzed and identified.(4)LabVIEW is used to design the data acquisition software of hydraulic pump. With the soft the NI DAQ card is driven and the pressure signal of hydraulic pump is measured.(5)The obtained pressure signal of pump outlet is merged into Duffing equation and analyzed with the largest Lyapunov exponent. The calculated results show that the largest Lyapunov exponent of fault signal is smaller than that of normal signal. This conclusion can be a good quantitative evidence of whether fault occurs or not.