Fault Diagnosis For Hydraulic Screw Down System Based On Data Fusion

Hydraulic automatic gauge control system (HAGC) is a typical servo control systemgathering electrical and hydraulic pressure technique, and it is a key part of the modernlarge-scale strip rolling mill thickness control. Faults that may occur in addition to theusual mechanical failures of abrasion and deformation, there are also the hydraulic failuresof Oil pollution and leakage, and the electrical failures of electrical disconnection andservo stuck, and sometimes even occur in mechanism, electric, and hydraulic couplingfaults. These faults directly threaten the normal production and product quality issues. Soit is necessary and versatile to do fault diagnosis technology research.In this paper, we propose the establishment of the strip mill thickness control systemdynamic simulation model of three degrees of freedom and change some of the physicalcharacteristic parameters of the model to simulate some of the common faults that mayoccur in the actual production engineering of the strip mill. Then processing and analysisof these data for fault diagnosis research; For time-domain characteristics signal of thestep response that the strip mill HAGC system output, this paper pick up the fourcharacteristic parameters of the rise time, peak time, adjustment time and the maximumovershoot to characterize the fault phenomenon of the HAGC system. Respectively fittingcurve equation of each fault characteristic parameters and physical characteristicsparameters. According to the fault characteristic parameters to obtain the physicalcharacteristic parameters when making the fault diagnosis, and then determine the typeof fault according to certain rules; Depending on different faults, HAGC system havedifferent input and output data, this paper proposes the establishment of autoregressionergodic model (ARX) of the input voltage signal and the output strength signal and extractthe model’s modulusb1,b2,b3as characteristic parameters to characterize the system’sfault. Finally fitting curve equation of each fault characteristic parameters and physicalcharacteristics parameters, and determine the type of fault according to certain rules.Based on the above two fault diagnosis methods and the subjective experience,application of data fusion theory to fuse the diagnostic results, thereby overcome the limitations and the instability caused by single diagnostic method, make the diagnosticresults more reliable. And on this basis develop fault diagnosis system with interactiveinterface.In the end, the experimental data are based on300four-high cold rolling mill testplatform of national cold-rolled strip equipment and process engineering technologyresearch center of Yanshan University, providing some experimental basis for researchwork of this thesis.