Dymamic Model And Diagnosis Research For The Secondary Double Nozzle Baffle Elrctro-hydraulic Servo Valve

Secondary double nozzle baffle electro-hydraulic servo valve(hereinafter referred to as the servo valve) is the thickness of the rolling mill hydraulic automatic control(hydraulic automatic gauge control system, referred to as the HAGC) is a key part, the servo valve failure will directly affect the HAGC system of plate mill thickness accuracy. In addition to electrical failures, such as, valve stuck and the larger coil current, the possible forms of failure also include hydraulic failures, such as, oil pollution and leaking and mechanical failures, such as, valve core wear etc. So it is necessary and versatile to do failure diagnosis researches.First by the method of theoretical analysis, on the dynamic analysis of each part of the servo valve, and the use of modern control theory method to analyze the mathematical model of the secondary double nozzle flapper electro-hydraulic servo valve, and has set up the dynamic model of whole.Secondly, based on the analysis of the above servo valve dynamics, the simulation model of the servo valve is built by AMESIM, and the parameters of the modules are set up. By changing the parameters of the module, the characteristic curves of different fault forms of servo valve are simulated, and the fault characteristics of the fault characteristic curve can be extracted.By analyzing the degree of distortion simulation curve shape, the theoretical knowledge of servo valve and some experts’ experience in this field, the relation matrix structure between the servo valve fault symptoms and failures’ causes are found. According to the principles of diagnosis under fuzzy theory(the maximum membership principle) the main hydraulic servo valve failures are identified, solve servo valve failure’s multi-results and multi-causes, on which a failure diagnosis expert system with human-machine interface are developed.All in all, the thesis creates a failure diagnosis expert system for secondary double nozzle flapper electro-hydraulic servo valve. By using this system to diagnose all failures easily happening in electro-hydraulic servo valve system, its stability and dependability can be proved.