Research On The Key Technology Of Leakage Fault Diagnosis Of Hydraulic Cylinder By Acoustic Emission And Vibration

Hydraulic system be widespread application in the field of engineering machinery with its low cost, stable operation and a wide range of the adjustable-speed. Cause it often provide power, there are serious accidents and huge economic losses when it has broken. The hydraulic cylinder plays an important role and status as the key component in the cylinder hydraulic system. It has impressed the entire equipment work and life directly. The most common fault of hydraulic cylinder is leakage, it can due to the damage of parts or seal, pollution to the environment, reduction of pressure, or even serious accidents. In this paper, the detection and fault diagnosis of cylinder is based on the analysis of AE, vibration signals and feature of leakage.The object of this thesis is research of hydraulic cylinder inner leakage fault by the technology of acoustic emission and vibration. The AE and vibration signals processing method and FFT as the theoretical basis, the empirical mode decomposition as the method, the differences of the pressure signal as reference resources, the advantage and the validity of the method has been verified. The main work and achievements include:(1)A detailed analysis of the excitation source, the vibration characteristics and fault mechanism of hydraulic cylinder of extruder is founded. A mathematical model of leakage fault is established. An affection of the cylinder pressure rise or drop rate by the spill is explained. All above, the theory of research is founded.(2)By introducing of the research status of fault diagnosis methods of hydraulic system and signal processing, describing of the progress of leakage fault diagnosis and the inner leakage acoustic emission signal theory, the fault diagnosis method of empirical mode decomposition for hydraulic system is put forward. The adaptability of the empirical mode decomposition method and preprocessing method of AE signal are discussed which is the basis of this study.(3)Through the study of the actual detection of extruder, the acoustic emission andvibration signals have been collected by professional acquisition system and instrument.By using the empirical mode decomposition method and MATAB software, the countinganalysis, amplitude analysis, kurtosis analysis and energy analysis are used. The treatmentof the data normalization guide to the practical engineering application.(4)The research of the characteristics of vibration and pressure signals verify theeffect and significance of the fault vibration and AE signals’ detection method.