Research On Fault Diagnosis And Fault Tolerance Control Of EHA Hydraulic Cylinder Internal Leakage

Electric hydrostatic actuators(EHA)have many advantages as a pump-controlled closed hydraulic system,such as low weight,simple and compact structure,easy maintenance,high reliability and so on in aircraft,active suspension systems,automotive and other fields have a wide range of engineering applications.However,EHA also has problems in the work.For example,the EHA actuator will cause internal seal wear of the actuator under continuous operation for a long time,which will lead to internal leakage failure and deteriorate the system performance.At the same time,the system contains a large number of Certainty,the existence of such uncertainty will greatly affect the control performance of the system.The research object of this thesis is EHA test bench,which can simulate the leakage fault in hydraulic cylinder.The research content is the oil leakage diagnosis of EHA symmetrical cylinder and the system uncertainty for many system uncertainties including internal leakage fault.To perform fault-tolerant position control,the specific work is as follows:(1)The theoretical background of wavelet analysis and empirical mode decomposition is studied.The signal processing methods of wavelet decomposition and empirical mode decomposition are expounded from the principle and process.The advantages and disadvantages of the two methods are summarized.Limitations are discussed in depth.(2)From the perspective of the electrical system and hydraulic system principle of the EHA test bench,the various components of the test bench are fully introduced.Simulate the internal leakage fault of the hydraulic cylinder,collect the pressure signal of the corresponding chamber,and use the wavelet analysis and the empirical mode decomposition to decompose the pressure signal to complete the feature extraction,and compare the characteristic changes under the fault and healthy operation mode to confirm Both methods can be used to judge the fault and the fault level,and compare the diagnostic effects of the two.(3)The mathematical model of the EHA experimental platform is established.The determination and uncertainty parameters of the experimental platform and its variation range are measured according to the actual situation.The quantitative feedback theory is used to design the QFT fault-tolerant controller for system uncertainty and internal leakage fault.And with the PID controller for fault-tolerant control effect step response simulation comparison.(4)Using QFT controller to verify the simulation effect,using MATLAB/Simulink software to build the controller module,control the servo motor by the Quarc software embedded in it to realize the operation of the hydraulic cylinder,simulate the adjustment of the internal leakage fault to verify the The actual control effect of the designed QFT controller.The results show that the internal leakage fault and fault level can be judged by wavelet analysis and empirical mode decomposition according to the pressure signal in the EHA double-rod chamber.The designed QFT fault-tolerant controller simulation is almost the same as the experimental results,which can meet the performance requirements of the system.