Research On Fault Diagnosis Of The Damaged Hydraulic Cylinder And Piston Seal Ring For Construction Machinery

The hydraulic cylinder is the key component of the hydraulic system of the mechanical equipment such as machine tool and engineering machinery.The performance of the hydraulic cylinder directly affects the performance of the hydraulic system or even the whole machine,so it is of great significance to carry out performance testing and fault diagnosis for hydraulic cylinders.Internal leakage is the most common failure in the hydraulic cylinder.which is caused by the damaged hydraulic cylinder and the piston seal.With QY110 truck crane legs taken as the study object,this paper puts emphasis on studying the damage fault of the cylinder and sealing ring,diagnoses and evaluates the two kinds of faults.The main contents of this paper are as follows:Firstly,according to the method of field investigation and statistical data,the main reasons for the damage of the cylinder and seal ring as well as the influence on the performance of the hydraulic cylinder are summarized.On the basis of the hydraulic cylinder simulation test bench,a hydraulic cylinder comprehensive performance test system is developed based on LabVIEW software.Artificial simulation has prefabricated the damage fault of the cylinder and the seal ring,and collected the experimental data.Through the calculation results of the internal leakage in the hydraulic cylinder,change rules of internal leakage in the case ofload pressure and damage of the cylinder and seal ring are obtained.Secondly,utilizing wavelet transform to extract features of the pressure signal of hydraulic cylinder without rod when the cylinder and seal ring are in damage state.Wavelet root mean square wave,wavelet packet subband energy,wavelet packet entropy and wavelet packet energy variance as the four fault feature vectors are confirmed,the change rules of each eigenvector value are obtained when the cylinder and seal ring are in different damage degrees,the sensitivity of the four fault feature vectors to the damage of the cylinder and the seal is comparatively analyzed in addition.Thirdly,the basic structure and learning rules of the loose and compact wavelet neural networks are introduced.The two kinds of wavelet neural networks are applied separately to fault diagnosis of the hydraulic cylinders and the damaged sealing rings.Through making fault identification of the four states of the damaged hydraulic cylinder and three states of damaged sealing ring,the ideal recognition effect is achieved.The results show that the fault recognition accuracy of the compact wavelet neural network is higher than that of the loose wavelet neural network,and this method can be applied to the fault diagnosis of other equipment.